91Reatta798 Posted June 2, 2006 Share Posted June 2, 2006 I'm looking for new suggestions to a frustrating problem. For over a year now my '91 has been stalling at stops (and idle), slow speeds in intersections, and any time the gas is released quickly. I've read old posts and tried most of the suggestions. I've put in a new IAC, a new TPS, air filter, I even took apart and cleaned the throttle body. I don't think it's related to a fuel pump or fuel line pressure because I would think the issue could occur at any speed, not slow or idle. I have become extremely frustrated and it poses a safety issue as it stalls in traffic. Link to comment Share on other sites More sharing options...
89REATTAJIM Posted June 2, 2006 Share Posted June 2, 2006 First thought: have you checked ALL of your vacuum lines?? 'specially pcv valve line & grommet? Good luck. Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 3, 2006 Author Share Posted June 3, 2006 Actually, I replaced the PCV a year ago not long after I got it. This past winter I had to replace a vacuum line and and some connectors. I'll have to check the other vacuum lines and see if that's the culprit. Thanks. Link to comment Share on other sites More sharing options...
Guest Motu 56 Posted June 3, 2006 Share Posted June 3, 2006 When you changed out the IAC did you clean the oriface that it goes into? This might sound strange but did you check the ECM. Try replacing it with one that you know that works.Same goes for the coil pak and ignition module. The afore mentioned parts can cause the strangest problems. I had what I thought was a transmission problem, turned out to be a coil pak. My friend's 3800 would not start in the cold, tried everything, changed coil pak, problem gone. You should have a spare coil pak and ignition module anyway. Good luck. Link to comment Share on other sites More sharing options...
Shelby Posted June 3, 2006 Share Posted June 3, 2006 Did you check the Fuel pressure on the rail. Link to comment Share on other sites More sharing options...
Guest Gomer Posted June 3, 2006 Share Posted June 3, 2006 Does it just die or does it seem to stumble then die? If it stumbles then dies i would suspect the EGR valve is stuck open. If you can get it to stay running for a few seconds (hopefully running badly) try tapping the base of the EGR. If it starts running better the EGR needs to be replaced. You could try cleaning it but i personally have never had any luck cleaning them. Good luck and i hope this helps. Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 3, 2006 Author Share Posted June 3, 2006 I have read that the fuel line pressure could be the issue, but if the pressure is low, wouldn't there be other problems even at higher speeds? I've never dealt w/ an EGR valve. I'll have to research the location and replacement of it. So, next week I will probably tackle the coil pack, EGR, and fuel pressure. I don't know if it's related, but my dash also displays 00 error almost every morning. I've had that problem before and cleaned the connections under the sterring column. After it's first trip from home to where ever, it works the rest of the day. Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 3, 2006 Author Share Posted June 3, 2006 Also, it does stumble, then die. The RPM's drop low, shoot up over 1000, drop again. At idle or stopped this repeats a couple times then stalls. At low speeds (i.e. starting into an intersection or quick release of the accelerator) it stalls immediately. Link to comment Share on other sites More sharing options...
Barney Eaton Posted June 3, 2006 Share Posted June 3, 2006 Without knowing the overall condition of the engine components, and what has already been replaced, it is very difficult to attempt to fix a problem long distance.The 3800 GM engine is a very common engine and any decent mechanic should be able to analize and fix the problem. Also with a shop manual and a little time you could go through the ECM diagnostics and verify that everything is within spec. Link to comment Share on other sites More sharing options...
alexhouston Posted June 3, 2006 Share Posted June 3, 2006 I am not an expert but when my Buicks did that, I have always had luck by replacing the oxygen sensor. I have never had luck with the other things suggested above. Link to comment Share on other sites More sharing options...
padgett Posted June 3, 2006 Share Posted June 3, 2006 Does sound like a classic "sticking IAC" problem but one question: does this happen when cold (approximately the first two minutes after starting) or only after in closed loop operation? Until in closed loop the O2 sensor reading is not used by the ECM. Link to comment Share on other sites More sharing options...
Rattaboy Posted June 4, 2006 Share Posted June 4, 2006 When I purchased my '90 convert it had a dying problem. It turned out that its air conditioner had been converted to R134 and had been over charged. The knowledgeable GM mechanic I took it to said it was not an unusual occurance. Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 5, 2006 Author Share Posted June 5, 2006 Padgett- It stalls any time, from 1st start up of the day or any time during a 20 min drive to work. In a nutshell, the factors I'll be narrowing down this week are between the ECM, EGR, coil pack, ignition module, fuel pressure, vacuum lines, and the O2 sensors. Good thing I've got some days off! Thanks for all the suggestions, I'll let everyone know how things turn out. Link to comment Share on other sites More sharing options...
Shelby Posted June 6, 2006 Share Posted June 6, 2006 I think it is fuel pump. Link to comment Share on other sites More sharing options...
Vincent Vega Posted June 6, 2006 Share Posted June 6, 2006 Check the fuel pressure. A bad regulator or pump could cause those symptoms. The regulator is very easy to replace. Review/perform the fuel pressure tests in the FSM to rule out fuel related problems. Link to comment Share on other sites More sharing options...
padgett Posted June 6, 2006 Share Posted June 6, 2006 O2 and EGR only come on line when in closed loop operation. If problem occurs at startup (during open loop) you can eliminate them. Certainly you want to check other things but if it runs well when your foot is pushing the accellerator and erratic/dies when not, that is classic IAC. Just about anything else will make the idle low or high but overshoots in both directions are almost always the IAC. Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 13, 2006 Author Share Posted June 13, 2006 Well, I didn't get to work on the car this past week, so I'll have my work cut out for me next week. Any way, one thing I forgot to mention, is that the exhaust seems to have a "rich" smell to it. Could that be related to my stalling and/or starting problem also? Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 17, 2006 Author Share Posted June 17, 2006 Padgett, you said the problem sounds like a classic sticking IAC. I've replaced the IAC twice in the last 3 months and cleaned the throttle body, including the housing for the IAC. If it is the IAC, what else could cause it to stick? Thanks. Link to comment Share on other sites More sharing options...
padgett Posted June 18, 2006 Share Posted June 18, 2006 Bad wiring to the IAC ? Failing IAC driver in the ECM ? Bad tach signal from the Ignition module (should see on instrument panel). If runs well when foot is on gas, it almost has to be the IAC or a stuck open EGR (but EGR will not cause high rpm excusions) Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 19, 2006 Author Share Posted June 19, 2006 After reading up on the the function of the EGR valve and the symptoms a bad one causes, I'd have to agree w/ Padgett on a bad EGR. I reviewed the '91 engine documents, but I haven't been able to locate the EGR. Can anyone point me in the right direction or refer me to the correct location in the service manual? Thanks. Link to comment Share on other sites More sharing options...
Guest crtnrds Posted June 20, 2006 Share Posted June 20, 2006 Padgett,I posted this on another topic but you apparently did not see it. In your article in cleaning the IAC you said not to turn/adjust it. I fiddled wiht it BEFORE I read your excellent article & now my '89 stalls only on initial start up unless I give it a little gas. It usually only does this once on initial start up, but is annoying. Is there a spec to adjust (re-adjust) the IAC? I couldn't find one in the manual. Link to comment Share on other sites More sharing options...
Guest F14CRAZY Posted June 20, 2006 Share Posted June 20, 2006 I don't remember the exact facts on it, but I know the IAC kind of resets itself by screwing in all the way, at some point Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 20, 2006 Author Share Posted June 20, 2006 Is anyone familiar w/ the location/removal of the EGR valve? Thanks. Link to comment Share on other sites More sharing options...
Duke Posted June 27, 2006 Share Posted June 27, 2006 If it runs at higher rpms, but dies at idle check out the cam position sensor. Mine would stumble and carry on at idle and die if left idle a bit, but as long as I gave it a bit of gas it would level out and run smoother. It also felt hesitant when accelerating. Think Padgett had a post on JB welding it. Hope that helps. Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 27, 2006 Author Share Posted June 27, 2006 Actually, I'm having a co-worker help me check the cam position sensor tomorrow. I more piece in a large puzzle. Thank again. Link to comment Share on other sites More sharing options...
Guest F14CRAZY Posted June 27, 2006 Share Posted June 27, 2006 Maybe you have a "Going Problem" instead.There's the cam sensor itself, and then inside, there's the interruptor that Padgett described fixing at his site, www.6007.us. I was thinking, however, that if the cam sensor or interruptor was faulty, there'd be a CEL. Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 27, 2006 Author Share Posted June 27, 2006 F-14, that's what I told my co-worker. His thought was that the sensor/interruptor is sending a reading (although incorrectly) that the reading would prevent the CEL. Any thoughts? Link to comment Share on other sites More sharing options...
Guest F14CRAZY Posted June 27, 2006 Share Posted June 27, 2006 CEL can be tricky though. An example is when my crankshaft position sensor went bad. The car wouldn't start at all, but no error codes were thrown. The Maui convertible we had had a code EO41, which was from a bad interruptor magnet. The car started and ran, but I'd say at about 80% power. I guess in this situation, my camshaft position sensor wasn't getting a signal from its magnet, so the sensor wasn't sending a signal to the engine computer, which improvised. The factory service manual says that the engine computer will pick "any old" plug to fire (or is it injector) with a 1-6 chance that it's right. At any rate, I'm thinking that the camshaft position sensor isn't your issue. Link to comment Share on other sites More sharing options...
Guest F14CRAZY Posted June 27, 2006 Share Posted June 27, 2006 Could the crankshaft position sensor be partially bad? I know for sure that it needs to be working to start the car, but may be intermittant. What I don't know, is if the engine would die if the signal is lost while it's running. Link to comment Share on other sites More sharing options...
padgett Posted June 27, 2006 Share Posted June 27, 2006 AFAIR (is in the FSM), driving over 38 mph for a few minutes will reset the IAC.BTW a bad cam sensor will set an error code 41 but a bad crank sensor won't (because usually the engine won't start). Secondary ignition will not set a code either.When the cam sesnsor goes, the engine will usually run (two opposing plugs fire at the same time so being 180 out does not matter) but the injectors fire in parallel instead of sequentially - if the pressure in the fuel rail is at all low, the engine will run lean and not be able to correct.Have seen crank sensors with part of one of the three magnets broken off. No telling what it will do then. Link to comment Share on other sites More sharing options...
91Reatta798 Posted June 27, 2006 Author Share Posted June 27, 2006 I changed my harmonic balancer this past March and at the time the sensors and magnets appeared to be in good shape. The car has been stalling for about a year now. Above anything else, I don't want to have to remove that balancer again to get to the sensors. I'll change everything else before I pull that apart again. Link to comment Share on other sites More sharing options...
Ames63 Posted July 25, 2006 Share Posted July 25, 2006 Add my name to the list, My car starts as long as I lay my foot on the gas pedal to open up the throttle valve (2000 rpm) when it falls below that the idle is rough and when I remove my foot, it flips over and does the dying cockroach. I will be going through this thread to resolve my issues. I will apprise my fellow experts of my progress. Link to comment Share on other sites More sharing options...
Shelby Posted July 25, 2006 Share Posted July 25, 2006 Have you check the fuel pressure yet? Link to comment Share on other sites More sharing options...
91Reatta798 Posted July 26, 2006 Author Share Posted July 26, 2006 I have not checked the fuel pressure yet for two reasons:First off, Autozone doesn't rent the pressure tester any more, they only sell it.Second, I've had this problem for over a year and a half and if my pump was going bad, it should've gotten there by now. I may possibly get the pressure tester just for the hell of it next week when I take a crack at replacing the vacuum lines. I'll let everyone know if I reap any benefits from that. Link to comment Share on other sites More sharing options...
Guest F14CRAZY Posted July 26, 2006 Share Posted July 26, 2006 Maybe you have a going problem.This is an odd one Link to comment Share on other sites More sharing options...
harry yarnell Posted July 26, 2006 Share Posted July 26, 2006 Don't forget about the PCV grommet in the plenum, behind the alternator. Have a habit of disintegrating, cauxing a massive vacuum leak. Link to comment Share on other sites More sharing options...
Roadster90 Posted July 26, 2006 Share Posted July 26, 2006 While attempting to cure another problem, I created a problem last week by "improperly installing the IAC" <img src="http://forums.aaca.org/images/graemlins/shocked.gif" alt="" />. If cocked when installing or not properly seating the IAC, it is easily possible to deform - pinch the O Ring causing a leak. While resolving the problem I also noticed that it is also possible to install the O Ring in the wrong location on the IAC .... Just trying to help - You might want to re check your IAC. Link to comment Share on other sites More sharing options...
Guest jcc3inc Posted July 26, 2006 Share Posted July 26, 2006 91Reatta978My '91 does not have an EGR. Maybe you don't have one either.Regards,Jack C. Link to comment Share on other sites More sharing options...
Shelby Posted July 26, 2006 Share Posted July 26, 2006 Take it some place a have them check the fuel pressure. Link to comment Share on other sites More sharing options...
Machiner 55 Posted July 27, 2006 Share Posted July 27, 2006 <div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> Maybe you have a going problem. </div></div> <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" /> <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" /> <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" /> <img src="http://forums.aaca.org/images/graemlins/blush.gif" alt="" /> <img src="http://forums.aaca.org/images/graemlins/laugh.gif" alt="" /> <img src="http://forums.aaca.org/images/graemlins/laugh.gif" alt="" /> <img src="http://forums.aaca.org/images/graemlins/laugh.gif" alt="" /> Link to comment Share on other sites More sharing options...
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