Cold Start: Engine dies immediately after start up

91StangGT5.0

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Oct 21, 2009
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Disclaimer: This has probably been discussed numerous times and yes I know I'm a noob for doing it, but nothing is making me comfortable believing that the solution given will fix my problem. So rather than searching and replacing everything that's brought up in a thread, I'm just going to ask my question and hopefully get something directed towards me and hopefully solve my problem.

Ok. I've just returned from being out of town for almost 2 months. I've replaced the ECT, ACT, and the IAC. The only code I get in KOER is 33 (EGR not opening properly). I get no codes on KOEO. When I start the engine, it starts up and right when the rpms start to go down it immediately stalls. Start it up a second time and the same thing. Third time, tap the gas and it acts like it's going to stall, dropping under 500 rpms, tries to catch itself, then stalls unless I give it gas. After numerous tries, I just give it gas and hold it at 2k for about 8-10 seconds, then it doesn't stall, but idles sort of rough (have a E303 cam). At this point, when I get it to idle, if I press the gas I feel hesitation under 2k. After 2k it goes away. After the engine has been running a bit, the engine will idle and rev normal without hesitation.....
 
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91StangGT5.0

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91StangGT5.0...have you checked for vacuum leaks?
I have to a certain extent. How would you go about checking for vacuum leaks? I've listened around for any signs of a leak, but don't notice anything which I'm sure some vacuum leaks aren't going to make a noise.
 

Three50won

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Jul 11, 2010
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Spray some brake cleaner around the engine while it is running. Spray one small section at a time. If you hear the engine rev up then that section is where the vacuum leak is.
 

91StangGT5.0

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Spray some brake cleaner around the engine while it is running. Spray one small section at a time. If you hear the engine rev up then that section is where the vacuum leak is.
Is there anything I should pay attention to as to not spray with brake cleaner? or is everything pretty much safe with the exception of the throttle body.
 

Three50won

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Don't spray the headers, haha!! You can spray the throttle body...that might be where the leak is. And look for cracks in the intake manifold, on the hoses, on the tubes...
 

Three50won

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Well there are several things that could be causing the problems you're having. Checking for vacuum leaks is probably one of the easier things to check. And it's only gonna cost you a few seconds and the price of a can of brake cleaner so do that first. Also If you're getting a code concerning the EGR valve not operating properly then that should be the first thing you replace...chances are thats what the problem is. If the problems persist then check your plugs, wires, distributor, fuel pump, MAF, etc. Always start with the easiest, cheapest, most obvious fixes first because it may be something simple.
 

91StangGT5.0

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How could a faulty EGR valve/position sensor cause this issue? It's main purpose is to route combusted gas exhaust back through the intake...unless I'm mistaken.
 

Three50won

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91StangGT5.0, sorry but I don't know how to answer your question. What I'm saying is that you're having issues with your car idling and running. Your ECU is telling you that the EGR is not operating properly. Now it might just be a coincidence that your EGR is bad while you're having problems that might be totally unrelated to it. But still you have to replace the EGR anyway...so replace that first and see what happens. Afterwards check for small cheap fix problems first. Maybe the IAC you bought was faulty...maybe the TPS voltage is off...check the timing...check the plugs...etc...but first, replace the EGR. The car is telling you that there is a problem with it so tackle that first. And reset the CEL while you're at it.
 

91StangGT5.0

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Oct 21, 2009
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91StangGT5.0, sorry but I don't know how to answer your question. What I'm saying is that you're having issues with your car idling and running. Your ECU is telling you that the EGR is not operating properly. Now it might just be a coincidence that your EGR is bad while you're having problems that might be totally unrelated to it. But still you have to replace the EGR anyway...so replace that first and see what happens. Afterwards check for small cheap fix problems first. Maybe the IAC you bought was faulty...maybe the TPS voltage is off...check the timing...check the plugs...etc...but first, replace the EGR. The car is telling you that there is a problem with it so tackle that first. And reset the CEL while you're at it.
The IAC isn't faulty, the TPS is new and the voltage read normal after testing it a few days ago, timing was set correctly (done it many times) yesterday, Plugs, wires, ignition coil are all new, and I just replaced the EGR valve, position sensor and vacuum solenoid for the EGR and problem still exists....
 

Three50won

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I will assume that you also checked for vacuum leaks since my first post...if not then you should just to rule it out. Maybe your FPR is faulty so check your fuel pressure. If the fuel pressure is fine then check the fuel injectors or just replace them if you have another set.
 

91StangGT5.0

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When it stops raining (Hopefully by tonight), I'm going to check for vacuum leaks. Someone pointed out in a different forum that the PCV valve could cause this since it operates by vacuum. Now about the same time this issue occured I noticed a leakage of motor oil coming from near the top of the engine....which I've suspected could be the PCV or a valve cover gasket. A leaking PCV could leak motor oil could it?
 

Noobz347

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Remove, clean the IAC and reinstall with a new gasket.

After install, leave it disconnected and start the car. Set the idle with the throttle stop screw to 800-900 rpm (this could vary depending on your mods).

Reconnect the IAC, allow the car to get cold, and try again.
 

Three50won

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bcam347, I don't really know why but I would think that the ECU tries to correct for it. I've noticed that whenever I've had vacuum leaks the engine would run rough and even stall out on initial start up. After running for a while tho (sometimes having to hold the pedal to keep the rpms up) it would stay considerably steady. So that in a nutshell is my only explanation...that the EFI adjusts for it after a while. And I've had leaks ranging from a small disconnected vacuum to a nickle sized hole on the underside of my upper intake manifold.
 

jrichker

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See the "Surging Idle Checklist for help with all your idle/stall problems. You can guess at the problem and throw parts at it, or you can use the checklist to help you find the problem quickly and inexpensively.

The quick and easy way to dump the codes is in there too, and all you need to do it is a paper clip! The first two posts contain all the fixes & updates. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.
 

91StangGT5.0

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Remove, clean the IAC and reinstall with a new gasket.

After install, leave it disconnected and start the car. Set the idle with the throttle stop screw to 800-900 rpm (this could vary depending on your mods).

Reconnect the IAC, allow the car to get cold, and try again.
I have a brand new one on there....no need to clean. Already set the idle to that rpm range.
 

Justin111

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Nov 28, 2011
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I have the same exact problem you have. I have replaced the fuel pump, pressure regulator, idle air. coolant temp, air temp, and tps. Same exact thing still. I have pulled my engine out over the weekend for a rebuild. If I find anything that has caused the problem I'll let you know.