RPM's drop and car dies when I take my foot off the gas

[Prius]

I have a 1999 Dodge Intrepid 2.7L V6 that dies every time I stop pressing the gas pedal. Sometimes it will idle for a few minutes while in park, but as soon as it's put into drive it'll die if I don't keep on the gas slightly. It will die no matter what speed I'm going. I've had it shut off on me while going 55mph on the highway. I have to drive with both feet so I can keep on the gas constantly to keep the RPM's up, even while I'm braking, while stopped, at highway speeds, and even while turning.

Originally, the oil pressure indicator light would come on and the RPM's would tank right before it died, then I replaced the oil pump and oil pressure sensor, thinking that would fix it, but the problem still occurs, only now the RPM's drop and the car dies WITHOUT the oil pressure warning light.

I've replaced the:

• idle air control valve
  
• the throttle position sensor
• oil pump
• oil pressure sensor
• PCV valve
• upstream O2 (oxygen) sensor
• engine air filter

And I've cleaned:

• (and checked the spacing on) all the spark plugs
• cleaned the throttle body
• cleaned and greased all the connections on the wiring harness
• used a Gumout brand fuel system cleaner (added into the gas tank)
• and cleaned all the fuel injectors

I can clearly hear the fuel pump kick on every time I turn the key into the ON position, so I'm sure that the pump is working correctly, although I can't speak for the condition of the filter.

I'm really stumped with this issue, guys. Any advice would be much appreciated.

Thanks in advance!

 

[Prius]

Also, a strange thing happened a while back that I think I should mention. This issue had been going on for a couple of weeks (give or take) every time I turned the car on, and so I changed the oil pump, thinking that would resolve the issue. After changing the pump the car drove like a dream for several days (maybe more than a week, I can't remember for sure). Eventually I drove it on a different road than I had been driving it up to that point, and ended up driving up one side and down the other of a somewhat steep hill, only to find that when I let off the gas to stop at the stop sign at the bottom of the hill, the RPM's tanked and the car stalled again, and the issue picked right back up where it had left off, with the RPM's bottoming out and the car dying every time I stopped applying the gas pedal. I thought it very strange, but haven't yet been able to connect the dots concerning the ongoing issue and whatever happened while climbing or descending that hill.

I had read a post a while back where someone was experiencing something similar with their car dying because the RPM's would drop (they were also driving with both feet to keep the car alive) and the guy said that he unplugged the battery, plugged it back in, and the car drove well for a period of time before going back to dying when he stopped giving it gas.

I mentioned this guy's post because I'm wondering if disconnecting my battery to do the oil pump replacement is what caused my car to run better for several days after. If that's the case, then what about going over that steep hill would have caused the issue with my car to return?

Could our problems be the same and does anyone have any ideas as to why disconnecting the battery could temporarily relieve the symptoms?

 

[boomerang]

You need to put a fuel pressure gauge on it, find out the specs and make sure it's putting out the pressure it's supposed to. I suspect that is your problem. The fuel pressure is too low.

It would be a good idea to replace the fuel filter. I would consider that basic maintenance but I would cease throwing any more parts at it until you can do some proper troubleshooting.

If disconnecting the battery temporarily makes the car run better it's because the learned parameters are cleared and then must be relearned. But you say drive well, is that the same as running normal?

Does the check engine light work? The light is not coming on and there are no codes stored?

Did the problems start at the same time as the oil pressure light starting coming on?

How much gas do you typically keep in the tank?

Please answer all questions.

 

[frozentundra123456]

My initial thought was the Throttle Position or Oxygen sensors, or as boomerang said, it could be fuel pump or filter related. Is the fuel injection throttle body or port injection? Could be a faulty injector. Does the car run smoothly when throttle is applied? Also as boomerang said, is the check engine light on? If it is, many auto parts stores will scan it and give you the diagnosis for free.

I once had a Saab with one of the early fuel injection engines that had a very similar problem, but it would stall at idle only when the outside temperature was below about 10 deg F. Unfortunately since I live in Minnesota, that is most of the time for several months of the year. I was never able to solve the problem, and eventually just traded the car in.

As boomerang also said, disconnecting the battery causes the engine management system to reprogram itself. While it is doing this, I believe it defaults to a richer than normal fuel mixture, so that is why it runs smoothly.

 

[Prius]

Yes, running normal. It ran and drove totally normally and the way it should after changing the oil pump. It idled normally and drove smoothly with no issues at all... until the issue reimmerged that is. I thought the problem had been fixed.

The check engine light does work and it had shown a few codes. It's been a few months since I've driven the car so I can't remember the exact code numbers that it was showing, but I believe there were 3 of them. One was for the system running rich, one was something about the EGR valve, and the other was for the O2 sensor. I replaced the sensor, cleared the codes, and test drove it, but the problem still persisted. I'll try to borrow a code reader and post the exact codes here in the next day or two.

The car was idling a little unevenly when I bought it (it would idle up on its own when in park). I drove it for a while like that, before I knew really anything about cars, but of course it soon started getting worse. Eventually it started reving itself up to around 2,000+ RPM's and holding it for up to a minute at a time. I did some research and learned that it was one of the sensors (I can't remember which one of the above mentioned sensors that it was) so I replaced it and that fixed that issue. Not long after that though the car started idling low occasionally. It would idle normally for a little while and then the idle would dip down and sometimes it would stay low for a minute, sometimes it would dip and then go right back up to normal. I think i remember that the oil pressure light would come on sometimes when it would idle really low. I did an amateur tune up on it, consisting of a new engine air filter, a fuel system additive, a spark plug cleaning and regapping, and a throttle body cleaning. That fixed the idling issue and it idles evenly and normally after that and that was the end of the oil pressure light for a while.

The oil pressure light didn't start coming on again until the current issue with the car started and it only illuminated right after the RPM's would drop and right before or as the car would die. After I changed the pump though the oil light hasn't come back on at all, even as the car is dying.

Typically I would fill the tank and then drive it down to around 1/8 - 1/4 tank and fill it up all the way again

 

[Prius]

Oh, and it's port injection.

 

[boomerang]

It's been a few months since I've driven the car so I can't remember the exact code numbers that it was showing, but I believe there were 3 of them. One was for the system running rich, one was something about the EGR valve, and the other was for the O2 sensor.

Find out what EGR related code or codes are being set. The valve should bleed a small amount of exhaust gas into the intake stream when called for. There is a temperature sensor downstream to let the computer know that has happened. Too much exhaust gas or exhaust gas at the wrong time will cause problems. If you have to drive the car to get codes to set, do so.

The following is food for thought. I say that because the paragraph above is your primary task and the one that needs to be investigated first.

You say you cleaned the injectors. How did you do this? Gas tank additives are good for peace of mind but injectors that are badly in need of cleaning are not going to be corrected that way.

I don't suppose you have access to an actual scan tool. Most of us don't. I am interested in whether the computer is getting the correct information regarding whether the car is in park or one of the drive gears. I am also interested in if the torque converter is unlocking as it should. Both of these could be related to your low idle and stalling.

You have issues that seem to be opposed to each other. High idle and low idle. Cutting out while driving. It almost seems like it's a vacuum leak problem but that explains everything but the low idle. Get those codes and report back. IMO it would still be a good thing to determine whether the fuel pressure is correct. Unless it's low at idle it may entail driving the car with the gauge visible. I would be curious what the pressure is when the car dies on you while cruising.

 

[frozentundra123456]

Yea, I thought about the torque converter solenoid as well. The oil pressure light could be unrelated actually. If it comes on as or just before the car stalls, it could be simply that the rpms have dropped too much. Could even be a head gasket (hopefully not).

 

[Prius]

The high idling hasn't happened since I replaced that sensor and the low idling wasn't happening either, after I did the tune up and before the RPM's started tanking while I'm driving. Currently the only issue the car has is that the RPM's bottom out when I don't keep feeding it a little bit of gas at all times.

I don't have a scan tool or a code reader. I usually end up borrowing one from AutoZone.

When I cleaned the fuel injectors I took them out one by one, hooked each one up to a can of carb cleaner (using a homemade attachment made of the straw that came with the cleaner and some heat shrink tubing) and then connected the negative port on the fuel injector to the negative side of a car battery. Then I connected the positive side of the injector to the battery using a quick and intermittent tapping motion to activate the injector in short, fast bursts. I followed the steps that I had learned from several "How to clean fuel injectors" videos on YouTube. None of the injectors seems to have been clogged. They all sprayed in a strong, uniform pattern. Then I put each injector back into the port that it had originally come out of.

 

[deadlyapp]

Something leads me to think this has something to do with your air fuel ratios and how your ECU is handling different things.

Have you checked/replaced your air flow sensor (is it a MAF or something else)? That would be a good first check. As another poster mentioned, unplugging the battery will put the ECU back into a learn / / fuel map mode where it follows specific fuel maps rather than going off of sensors. Over time, it can revert back to the original.

If you had a datalogger or similar, I would tell you to log the car during normal operation. More than likely you'll see that the car is dumping fuel or something similar when it notices the TPS go to zero, causing it to stall out.

 

[bruceb]

I second the idea of checking the Mass Air Flow Sensor. If it is the fuel injectors, a shop can run a proper cleaning by use of special solvents that connect right at the fuel rail schrader valve. It could also be a fuel pressure problem, either with the pump itself or the fuel pressure regulator, usually located at the fuel rail and typically has a vacuum hose on it. Possibly that hose is bad or the diaphragm inside the regulator went bad.

 

[boomerang]

Don't believe that engine has a MAF sensor guys. I see a MAP sensor listed at rockauto. And I see no listing for a fuel pressure regulator which leads me to believe that it's integrated into the pump which is why I have been harping on checking fuel pressure and asking about fuel levels, etc.

I've been also thinking if there could be a problem with the EVAP system in that instead of the valve opening to ingest vapors from the canister that the valve is opening and there is a damaged or missing hose, damaged canister itself, etc. that is causing a large vacuum leak to occur. I also am seeing a Vapor Leak Detection Pump listed at rockauto and I have never heard of that component and could only guess what its purpose is.

 

[deadlyapp]

Don't believe that engine has a MAF sensor guys. I see a MAP sensor listed at rockauto. And I see no listing for a fuel pressure regulator which leads me to believe that it's integrated into the pump which is why I have been harping on checking fuel pressure and asking about fuel levels, etc.

I've been also thinking if there could be a problem with the EVAP system in that instead of the valve opening to ingest vapors from the canister that the valve is opening and there is a damaged or missing hose, damaged canister itself, etc. that is causing a large vacuum leak to occur. I also am seeing a Vapor Leak Detection Pump listed at rockauto and I have never heard of that component and could only guess what its purpose is.

Looks like you're right. MAP sensor and an intake temperature sensor setup in speed-density. Could still be an issue.

An intermittent vacuum leak shouldn't cause a stall though in this format, as the airflow is measured directly in the intake (or slightly before the intake). Unless there is a vacuum source after the sensors (which I doubt) it shouldn't be an issue.

 

[Yuriman]

Any possibility it's only when in open loop? Does the car misbehave immediately upon starting, or is it only after it's been running for a few minutes? Could try doing something to force it to use maps instead of rely on sensors, such as unplugging O2 sensor, and see how it responds.

 

[bradly1101]

I had a similar issue on an older car. The mechanic said my EGR system needed to be "scrubbed." What ever he did, it was never rough or died at idle after. AC no longer affected idle.

If possible disengage any failed, unwanted system like ac belts.

 

[Prius]

Well... I can't get the Intrepid to start at all now. The battery was dead, so I jumped it, but it won't turn over. It just keeps cranking and there's a loud noise coming from the engine; sounds like the timing chain is banging against stuff as turns. I don't know how that could be possible, because when I changed the oil pump I inspected the chain (no issues that I could see) and replaced the timing chain tensioner. I've driven the car several times since the new chain tensioner and it definitely was not making that noise, or any noise at all. What could be causing this sound and causing the car not to start? What could have happened to it while it was just sitting there, not running?

Also, there are no codes stored in the car at the moment. I'll drive it and check the codes again after, if you guys can help me get the thing started.

This car is becoming a real pain in the butt, but I appreciate all your help so far guys. Thank you for all your advice.

 

[RLGL]

Time to admit defeat and take it to a REAL mechanic