Effects of Installing an Air Intake Temperature Sensor?

[BonzaiDuck]

Many times in the last week or so, I've reported my first ever encounter with a Mechanic-from-Hell. First, all I wanted was to troubleshoot the cause of a very minor transmission leak. I'm more concerned about the transmission than I am about engine oil leaks from the rear mainseal -- I never have to top up the crankcase oil level, and we're talking about maybe five drops on the garage drop pan -- each the diameter of a 50-cent coin -- over more than a week's time. But the Mechanic-from-Hell sold his manager on the idea that I needed new valve-cover-gaskets, which I had refused when his manager tried to sell me that service six months earlier. I succumbed, and the Mechanic-from-Hell broke one of the pipes on my car-interior heater-core when he removed the intake manifold and valve-covers. So he used a generic piece of unshaped hose to connect the engine fittings for the heater-core hoses in a "U-turn", thinking I wouldn't discover that I had no interior heater temperature control in several months -- or forever if we factor in So-Cal winter weather. Not only that, but he didn't secure a hose connection between the intake manifold and the pipe joining the upper radiator, leading to a bubble of air forming at the top of it. I would have to top up the anti-freeze every time the engine was cool enough to remove the radiator cap to check it.

Then, the Mechanic-from-Hell caused bad connections in the wiring harness, because he had to remove the dashboard (I told them to be careful!) for replacement of the heater-core -- for which they had to pay in addition to the labor. My fuse for the Windshield-wiper/washer had been blown, suggesting to me that the Mechanic from Hell was negligent about disconnecting the battery's negative terminal or reconnecting it, possibly leaving the wiper-washer switch to some operative position. My steering wheel horn buttons didn't work. I traced down the possible connections that needed attention, but the Mechanic-from-Hell insisted on installing a big-red-button horn switch on the dashboard and wiring it directly to ground and the Horn Relay -- not the "near-factory-configuration" and care that I had plainly explained when I first started using this new shop. You see, the Owner has decided at this point that the Mechanic-from Hell will never touch his beloved Trooper LS again -- never . . . nevernevernevernever---ev-er! The Owner still has a horn, and the Owner figures it's worth the trouble to do all that dashboard manipulation himself at least once. The Trooper will -- I SAY IT WILL! -- be road-worthy for another ten years, or whenever the Owner punches out and kicks the bucket. The leaks are gone, the wiper-washer works, the horn has a big red fuckstick button -- corrections that all required the Owner's intervention. We're cutting our losses here!

So "The Owner" had to correct a cooling problem. "The Owner" had to correct a blown fuse that caused all sorts of concern until he located it. "The Owner" either had to make the best of a kloodge wiring job by buying a standard switch that fit the most convenient dashboard blank, or he contemplates disabling the SRS driver-side airbag, following factory-manual short-cuts to remove a minimum of dashboard panels, and locating the loose horn connection himself. And "The Owner" had to copy and pass on to the Mechanic from Hell various pages of the PDF Factory Shop Manual, annotated, with comments and inviting reply comment. "With circles and arrows on each one!" if you're old enough to remember Arlo Guthrie's "Alice's Restaurant" song. Circles and arrows! The Mechanic from Hell didn't like this sort of customer behavior.

So the owner started looking into possible wear and tear on devices connected to this intake manifold -- maybe running a bit warm over 400 miles -- for an engine with 187,000 miles of use. And he did some reading about the Air Intake Temperature Sensor, which screws into the intake manifold opposite the throttle body.

The Air-Intake Temperature Sensor is discussed often with mention of its replacement operation as an easy, simple procedure: disconnect the sensor; unbolt it with a 14 or 15mm wrench; screw in the new one; torque it on with the wrench and reconnect the wires.. The Septuagenarian hardly has to bend over the engine with the hood up. He'd have more back pain from computer-gaming.

These sensors are cited for eventual wear, and mine has never been replaced as far as I know. But the engine idles smoothly; never hesitates at any temperature; never burns any oil and sails through bi-annual smog-testing with flying colors.

I suspect that the computer will reset itself or otherwise calibrate the new sensor. I don't know, though. There isn't much that can be tuned up on this 3.2L SOHC General Motors engine. [The Trooper was never a "real" rice-burner . . .]

What can I expect? What might need to be done as consequence? I'm hoping that a new sensor will improve performance and maybe show even better scores at the smog-test station.

PS The Air Intake Temperature Sensor is a cheap part. The RockAuto price ranges from $5 to $16, from manufacturers like "Standard Intermotor" and "Beck-Arnley" It appears that the factory OEM unit is really the same as the AX1 model from Standard, because there is variation in the appearance of these devices and I know "identical" when I see it.

 

[mindless1]

I'm in the don't fit it if it isn't broke, camp, and at most would take it out and spray some cleaner on it.

If you do get a new one, go major brand if not OEM, not a cheap generic. After installing it disconnect the battery to cause the ECU to go through its relearn process and drive around with the engine warmed up.

You'd probably get better improvements in emissions and fuel economy replacing the 02 sensors, but I wouldn't expect a lot there either if there's no OBD trouble codes.

Maybe you've already done that... there are tons of little things you can do to improve things by single-digital percentages if that, but ultimately an older vehicle is more desirable if it causes minimal expense and effort. Sometimes disturbing wiring or hoses or whatever, can break things and make a repair a lot more work than you intended.

 

[BonzaiDuck]

Please feel encouraged to continue with this discussion, Mindless1. I'm fishing for more information.

Thanks to you, I did considerable productive research today for what an HO2S looks like; how many there are (1 for a 95 Trooper); the symptoms of failing Air Intake Temp Sensor and the HO2S; the sources and prices for the Throttle or Air Intake unit, the HO2S and the MAP sensor.

The entire history of the Trooper beginning in its sixth year since model year, is in an Excel spreadsheet, with mileage dates for repairs, parts and maintenance. I bought the Trooper with 96,000 miles on the odometer; it now has in excess of 187,500 miles. The Check Engine Light has never -- ever -- appeared lit, and I'm pretty sure all the other idiot lights connected to what is either the ECU or PCM are working properly. Some things have more cryptic appearances for less common situations, as when the AC serpentine belt has been readjusted and the ECU has yet to recalibrate itself to work the magnetic clutch of the compressor -- two lights come on as the compressor clicks on and off with indecision, or the Brake light and Charging light go on and off with the compressor simultaneously.

I have no record for any of these three sensors -- IATS, HO2S, or MAP -- being replaced. If there was ever replacement, it was before 96,000 miles on the odometer. Therefore, as far as I know, these sensors have been on the car for 187,000+ miles.

Performance doesn't show any indications but one. No Check Engine. A smooth, purring idle; good emissions results -- the worst being an NO rating at 340+ and the state maximum for 2018 was 540+. I had previously come to the idea that catalytic converters, as they age and deteriorate, contribute to rising NO scores. The other scores are much closer to lower ranges of the state specs for CO, O2 and HC.

Acceleration is good in the lower gears. With the A/C turned on and climbing a moderate hill, acceleration seems a tad stunted at 50+ and 4th gear.

Owner's manual and Shop Manual indicate that the "fuel warning" light, which works on the same circuit and devices as the fuel gauge, may come on and go off sporadically as the vehicle may change its incline, tilt to the left or right, certainly more often at idle and often disappearing with acceleration. This latter item was my own observation, but it makes sense intuitively.

This was happening in the Trooper with a surge of frequency about 2 weeks ago. Then in recent days, it doesn't go on whether the fuel tank is full or only comfortably lower.

I run Premium gas 96/97 octane (as I recall), obviously unleaded. I've been running Lucas fuel-injector cleaner at about 1/2 bottle per tank -- full bottle per tank over two earlier months.

No hesitation, or indication that EGR valve needs replacement. Not after the Lucas treatment and just after I began to do it.

Wisdom says "If not broke, don't fix . . . " Milestone indications suggest that IATS and HO2S should be replaced every 90,000 miles. Either way, it looks either significantly or vastly overdue.

I also want to pay someone to run a state-standard smog-test without sending data to the state DMV for registration renewal. That's supposed to happen in January. I was steered to a particular garage/shop. I have no worries at all about passing in January, I just want to see the numbers sooner as I contemplate the parts replacements.

I have to kick my current repair shop. Let's say I'm "suspending" them. This recent serial cluster-f*** was phenomenal. Two careless mistakes when replacing the valve cover gaskets: broken heater-core and leak at throttle-body outflow radiator hose. The intake manifold had to be removed and then replaced twice, just to install the heater-hoses properly. Then, it seems the dashboard removal that was done for the heater-core replacement resulted in a blown window-wiper-washer fuse, and a non-functioning horn controlled from the original parallel-wired steering-wheel switches.

The horn problem is in the wiring harness and most likely across three possible connectors, complicated by the SRS airbag module sharing two different plugs with the horn circuit. The fuse could've been the original; never failed over 17 years; was working definitely in days before the dashboard removal, since I'd been washing the car windows and turned it on with the engine running.

My decision to stop taking the car to them is less a matter of resentment (of those other than the Mechanic-from-Hell), and more from a sense of risk and bad business.

I'm wondering if I should replace these sensors one at a time, or all at once. Or perhaps I should do IATS and HO2S replacement, and leave MAP alone.

But it's only going to cost me at most $100 in parts. Even the HO2S replacement can be done without removing the exhaust parts. I might only worry that removal of the very old HO2S could be damaging to a part connected to the exhaust manifold. Things get rusty; torqueing a bolt might just break off the whole fitting. IATS and MAP are the easiest to replace.

ONe could worry almost as easily for the parts causing worse smog-test results, but it seems less likely.

But with the car in its current condition, I could just as easily swear off the sensors for a year's time. Or I could merely install the IATS at the intake manifold. It's the only switch I've acquired, and it's probably the easiest to remove and install.

 

[mindless1]

As I get older my attention span decreases, something I've accused the younger generation of but now... you need to condense your posts.

I would not replace any sensors that don't cause a fault code unless you're about to put a large # of miles on it and want (hope for) a slight fuel economy improvement.

On the other hand, only you can assess the rust or muck buildup level. At some point, a sensor gets seized in and it's ideal to replace it before that happens, and if you are doing some other repair that makes certain sensors more accessible, go ahead and replace them then, BUT in some cases it may already be too late. You might think you're just going to pop the old pressure sensor off a plastic intake manifold or something, and the mount for it breaks off and the repair becomes much more time and money.

I drift towards enjoying the low cost of ownership. Save the money and spend it when necessary.

 

[JCH13]

What information are you fishing for? I don't have the patience to sift through your two super-long posts to try and figure out what you're interested in.

 

[BonzaiDuck]

As I get older my attention span decreases, something I've accused the younger generation of but now... you need to condense your posts.

I would not replace any sensors that don't cause a fault code unless you're about to put a large # of miles on it and want (hope for) a slight fuel economy improvement.

On the other hand, only you can assess the rust or muck buildup level. At some point, a sensor gets seized in and it's ideal to replace it before that happens, and if you are doing some other repair that makes certain sensors more accessible, go ahead and replace them then.

I drift towards enjoying the low cost of ownership. Save the money and spend it when necessary.

Also acknowledging JCH13's polite frustrations.

I have to take care of two elderly disabled people. We need total reliable mobility for serious reasons. I have a financial plan that minimizes impulse buying and unplanned outlays for two homes and three people. Everything works like clockwork. For the most part, savings only increases and we cover our expenses with the income flows, leaving the "stocks" or savings alone.

This is the "year of the cars". I budget $1,000/annum for each car, but hope to get by in some years -- or even a string of years -- only spending $80 each for oil changes. I'm looking to squeeze another five or ten years out of these "old" vehicles, hoping to avoid disruptions where I have to take a car to a repair shop for some number of days.

I'm "that close" to restoring my Trooper to a point where nothing is likely to go wrong for several years. So I'm obsessing about certain things.

The manual says the car is overdue for replacement of one or more sensors, whether or not "Check Engine" appears on the dashboard warning lights. Since the parts outlay is likely to be $100 or less, I'm trying to make up my mind about it before year's end.

Right now, I'm looking into the shop manual about the HO2 sensor, because that's the one subject to heat and exhaust crud. Recommendations insinuate the use of WD-40, etc. If it won't cause additional problems to remove and replace it, I might not hesitate.

PS and AFTERTHOUGHT: Yes -- it's "extra money" but we're not talking about having my engine overhauled. Right now, I'm getting ready to pull the string to buy a $120 OBD(1) data-link code-reader -- an "Actron" model from Summit Racing.

I went for 17 years just routinely delivering my Trooper to a mechanic once annually who knew what he was doing. After this troublesome summer working with "the Mechanic from Hell", I'm going to take a more active approach. Maybe, early next year, I might actually trust a repair shop enough to let them check and recharge my AC system. But I can take up to a year from now before I set aside a weekend to do "other maintenance" my (gdn) self . . .

 

[JCH13]

If a service is prescribed in maintenance schedule and you want to get maximum life out of the vehicles I would advise to follow the schedule.

If you have any bluetooth or wifi enabled device I suggest finding and OBDII dongle from Amazon or similar. They're $10-20 with the same reading/clearing capabilities as most dedicated devices.

I do not think that you should be running fuel system cleaner with every tank of fuel. I suspect that burning the extra chemicals would not be the best for your exhaust/emissions equipment. If you're using good quality fuels (sounds like you do) and don't let the vehicle sit (sounds like you drive it a lot) fuel system cleaner is not needed.

Hope this helps, and thanks for clarifying.

 

[mindless1]

Once you get it restored to perfect condition, some texting teen will plow into and total it.

It can happen in the blink of an eye, just a couple days ago I was not very far from my home, just driving up a hill and some idiot coming down the hill the other way veered into my lane to pass around some pedestrians, and would have ran head-on into me if I had not slammed on my brakes to give him more room.

Anyway, only you know what you've already done to the vehicle and what "I'm "that close" to restoring my Trooper to a point where nothing is likely to go wrong for several years.", means.

Things can go wrong with a 3 year old vehicle. Older vehicles tend to be a slow stream of continuing repairs because no matter how much you do, there are thousands of parts.

For example if the exhaust has a lot of miles on it, I might wait to do the O2 sensors with the exhaust replacement, but I have salted winter roads here so the exhaust is an expected wear item on my oldest SUV which I use in these conditions to save corrosion on other vehicles (and due to 4WD), particularly if using economical (less than 1/3rd the price) aluminumized steel pipes instead of stainless (except reasonably priced stainless mufflers are available).

Replacing an O2 sensor later is not necessarily more work than now, unless as I mentioned previously it has been on so long that it is seized in and yet that may have already happened. An O2 sensor is not vital, the vehicle should keep running if it failed entirely, just at a less fuel efficient ratio.

At the same time, as you mentioned it is not a great expense (for "most" vehicles) and if you need to get it over with to move on, that's one way to handle it, but in the long run it can be a losing proposition to try to restore more value into a vehicle than its bluebook value, unless you have special classic car type insurance to cover more than the usual book value which is now probably below $1000... and yet that is the other thing I like about older low value vehicles, that they are very inexpensive to keep going if you only have liability rather than collision or comprehensive insurance coverage.

I budget $1,000/annum for each car

This does not make sense to me for vehicles only worth $1K book value. I've done several repairs on my oldest SUV in recent years but aren't anywhere near $1k/year. Granted it doesn't get many miles put on per year, for all I know you might be spending no more per mile than I am.

 

[BonzaiDuck]

If a service is prescribed in maintenance schedule and you want to get maximum life out of the vehicles I would advise to follow the schedule.

If you have any bluetooth or wifi enabled device I suggest finding and OBDII dongle from Amazon or similar. They're $10-20 with the same reading/clearing capabilities as most dedicated devices.

I do not think that you should be running fuel system cleaner with every tank of fuel. I suspect that burning the extra chemicals would not be the best for your exhaust/emissions equipment. If you're using good quality fuels (sounds like you do) and don't let the vehicle sit (sounds like you drive it a lot) fuel system cleaner is not needed.

Hope this helps, and thanks for clarifying.

Last year, while the 3.2L engine was running smoothly, I noticed one thing consistently and occasionally. When the engine was hot, you could rev it, let off the gas to then see the tach needle drop below the spec 750RPM, sometimes "taking a dump" and stalling out. This was supposedly or possibly the result of a dirty EGR valve.

The EGR valve is inconveniently located between the firewall and the intake manifold. I can see how one might gingerly -- carefully -- cautiously -- remove the 10mm or 12 mm fixing bolts to remove and clean it, but it still looked like a PITA. I found web-links of advice on "Cleaning the EGR valve in place". Bardahl and SeaFoam make products to spray into the air intake and throttle body which will clean the EGR, and the web-sites touted pictures of "before" and "after" to show the remarkable result.

Instead, I decided on the regimen of fuel-injector-cleaner. Lucas recommends using it continuously -- one bottle per tank. I'm now using a half-bottle per tank.

The EGR-valve symptoms are long gone. I'm also expecting to see marginally better smog-test results, but we'll see . . . in January . . .

I think I'm going forward to order the Actron CP9670 code-reader. It's compatible with both the Nissan 95 pickup and the Trooper. some of those devices -- OBD2 mostly -- run $200 and more, but the Actron (OBD1) is about $115 before tax and shipping. Reviews are good. Probably a good investment for a 5-year time-horizon of keeping those vehicles.

Now -- to the remarks of mindless1 -- Yeah-- some teenager street-racing with a modified CRX. What are the odds? If you invest $5,000 in an old vehicle (forget about the Blue Book), your expectation of loss are the odds times the investment. The odds are lower if you're only putting 3,000/annum on the odometer. This is the calculation of the "used car strategy". You take the calculated risks, and if lightning strikes, you tell yourself "suffer, bitch!"

See, the other thing I did early in this year was to realize this desire I had when I first bought the vehicle in 2002. I was doing some "four-wheelin'" in the wildlife refuges with hiking trips in the North Cascades. I coveted those "bull-bars" or grill-guards. Kept putting it off. Then, I had a fender-bender in 2007 -- had to do smithy-work with one of the bumper "back bars", and regretted that I hadn't reinforced the front end. Maybe it's just a matter of "appearance" on an otherwise beautiful-as-is Trooper, but if I encounter the texting teenager, there's a better chance that I'll win out against his little lightweight CRX . . .

 

[mindless1]

Fuel system cleaner added to the gas tank shouldn't do anything to clean an EGR valve on a multi-port injected engine, because the fuel enters after the EGR. If the cleaner helped, I have to suspect the real problem was partially clogged injectors.

I'm sure the product manufacturer recommends using it as often as you can.

 

[BonzaiDuck]

Fuel system cleaner added to the gas tank shouldn't do anything to clean an EGR valve on a multi-port injected engine, because the fuel enters after the EGR. If the cleaner helped, I have to suspect the real problem was partially clogged injectors.

I'm sure the product manufacturer recommends using it as often as you can.

I would agree with that, but the EGR is the "Exhaust Gas Recirculation" Valve. I might be wrong, but I think the effect on the EGR valve involves the cleaner substances being recycled. It wouldn't be any different for spraying SeaFoam or Bardahl EGR Cleaner at the throttle body. So you could be right, but I couldn't see anything different as happening with the other substances. You don't spray them through the EGR valve; you merely spray them into the common chamber after pulling the rubber air intake duct a little bit away from the chamber's air intake opening. While that's being done, you're supposed to rev the engine to 3,000 RPM for about 30 minutes.

Either way -- it worked for me.

Now, as to the three sensors. I've only purchased one of them-- the IAT sensor, costing me about $15. The engine runs so damn smooth, cold or warm, that I have to look at the various symptoms documented for the IAT sensor as well as the HO2 sensor. The Trooper doesn't exhibit any of the symptoms described for either sensor. There's no "Check Engine" light. If some sources suggest that the IAT or HO2 sensors should be replaced after 90,000 miles, the current sensors are apparently working.

The only thing I could worry about at this point is whether the HO2 sensor is frozen in the "center exhaust pipe" of the exhaust system. This pipe has a common mating for two short pipes from the exhaust manifold at its intake side, and a single pipe connection to the pre-converter and catalytic converter behind it. I cannot find this part at RockAuto. I'm going to search a bit further to see if it's either available as a salvage part or a new one, and take note of the price.

I'm not going to attempt removing that HO2 sensor unless I have the proper tool, and I can be prepared with a backup part and a plan in the event this center exhaust pipe is damaged in the process.

 

[JCH13]

What does the manufacturer suggest for proactive replacement of those sensors? I would defer to the manufacturer rather than some mystery sources unless those mystery sources have some solid credentials.

If you're planning on replacing anything that might be seized I STRONGLY (I mean REALLY STRONGLY) recommend mixing up a batch of 90% ATF/10% Acetone and applying it to all threaded connections one or more times in advance of any work. An eyedropper or pipette works great. The amount of headache saved is huge. This mixture is an incredibly effective penetrating oil that's super inexpensive. When applied efficiently with a pipette it lasts almost indefinitely.

 

[mindless1]

I would agree with that, but the EGR is the "Exhaust Gas Recirculation" Valve. I might be wrong, but I think the effect on the EGR valve involves the cleaner substances being recycled. It wouldn't be any different for spraying SeaFoam or Bardahl EGR Cleaner at the throttle body. So you could be right, but I couldn't see anything different as happening with the other substances. You don't spray them through the EGR valve; you merely spray them into the common chamber after pulling the rubber air intake duct a little bit away from the chamber's air intake opening. While that's being done, you're supposed to rev the engine to 3,000 RPM for about 30 minutes.

When you spray a cleaner into the intake, it gets on everything between that point and the cylinders, including the EGR valve which is between these two points. The valve itself is upstream of the fuel injection so nothing in the fuel gets to the EGR valve because it's the opposite direction of airflow.

EGR exhaust "Gas" means the exhaust, that normally goes out your tailpipe. Unless cylinders are misfiring there is [ideally] no gasoline remaining in exhaust gas, so no additive to gasoline would make it to the EGR valve. I suppose it is possible that you could have a misfire causing fuel in the exhaust, then some would go through the EGR valve, but that would tend to clean some even without any fuel system cleaner in the fuel, and isn't a good strategy to try to (cause to) clean the valve because the unburnt fuel can harm the catalytic converter in the process.

The only thing I could worry about at this point is whether the HO2 sensor is frozen in the "center exhaust pipe" of the exhaust system. This pipe has a common mating for two short pipes from the exhaust manifold at its intake side, and a single pipe connection to the pre-converter and catalytic converter behind it. I cannot find this part at RockAuto. I'm going to search a bit further to see if it's either available as a salvage part or a new one, and take note of the price.

If you can get that pipe off intact, or safer still if you leave it on and take the vehicle to an exhaust shop, they should be able to weld together a replacement if it's just a (typical) Y-pipe, but they'll probably need to pull it off and check the new one for fit, and might have to destroy the old one, to weld the old mounting plates to the new pipe, not just make a new one for you to take home without disturbing it, at which point they might as well install the new one.

 

[BonzaiDuck]

JCH13 on "Proactive replacement" -- 20 years into retirement and after my edge began to dull, I sort of casually fish around for information. I should've done my word and phrase searches earlier on the Trooper Workshop Manual, which I've converted from PDF page images to PDF with searchable text.

I found a general diagnostic table. Guess what? The Factory Workshop Manual suggests only to give attention to these sensors after the appropriate warning light appears on the dashboard! At which time, you would either "correct" or replace the sensor. All three that I mentioned follow this procedure.

If I didn't say it already, I purchased a $115 Actron CP9670 OBD Code Scanner. I can come up to speed on this nifty little device in a few weeks, after I study the badly-written manual for it and read some reviews, which also contain information. I easily found a 2018 review, learning that the device's only shortcoming as a termination of firmware and software upgrades that might leave the new owner in the lurch for vehicles after maybe 2017. Apparently for being a 95 Trooper, it was prepared with forethought to be ready for OBD2, which took hold in 1996.

And I've had more sober thoughts about how to maintain this vehicle. At 3,000 or even 4,000 miles per year, four or five years should be a breeze. I shouldn't have to do more than change fluids and hoses -- in that regimen, I would still have 10,000 miles of reliability remaining in the timing belt. The AC seems to be working fine, even for being so old. I might have someone else check the refrigerant charge for it next year, or I might attend to learning how to do it myself (although you're apparently supposed to re-capture the old refrigerant and would need expensive equipment for that).

I'm going to replace the main radiator hoses and carefully flush the cooling system to add new coolant. No need for "water pump lubricant", now that I understand how that works. If corrosion has taken place since the Master Mechanic made his notes during 2017, it cannot be much. Figure the last water pump died at 158,000 miles -- 62,000 miles after I acquired the vehicle. It might be the original pump. I've only put about 29,000 miles on the new one.

I'll just freakin' drive the car. Five years could be easy without fretting about this other stuff. After that, we'll assess the possibility of another restoration cycle. I'd keep the car for specific reasons. Internal combustion is on its way out. So if I'm still driving, I'll want to catch the wave so to speak on a pre-owned mid- to upper-end electric.