My Fiero will stall once on cold start up, help please, I need advice.

My 86 four speed V-6 Fiero has in the last three weeks begun to stall out once on cold starts in the morning. I will restart and it will maybe sputter once more but then it runs fine. I've got good battery, grounds and CS alternator, I checked my spring tune up, replaced rotor and cap, cleaned IAC and TB, double checked for vacuum leaks and loose connectors just recently. The car runs like a top otherwise.

I am correct in thinking I have a fuel delivery problem?
I am not familar at all with the fuel system, any suggestions?

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jetman
Silver 86 SE 2M6 4-speed, with "check wallet light"

when you initally turn the key, do you hear the fuel pump run for a few seconds? if not it could be your relay, located on the firewall in front of the air cleaner are 2 relays, one is the a/c the other is the fuelpump. you can swap the plugs the relays to isolate.
the ecm will run the fuel pump for 3 seconds to prime the system for the cold start injector. after it sees ignition pulses, it turns it on full time. as a safety, the oil pressure sender has a direct feed to the fuel pump which will kick in at 6 psi.
if you have slow oil pressure and a bad relay you could get this symptom.

I have this same problem on my 86gt. I was thinking that the fuel pressure regulator could be the problem. Everything else is new on the car. And just like yours after it stalls or just comes close to stalling it runs like a top.

What tjm4fun was saying --you can run a leak down test to determine which compenent in the system would be causing a problem, also check/replace fuel filter, I have a hunch jetman --been following your posts for awhile on the idle issue (step down) ect, the wheather is getting colder, try checking the mat, in the airbox, I know doesnt make sense --but fixed one of mine doing that ...doesn`t hurt to check all avenues...

If yours is anything like mine (which is doing the exact same thing) and it is worse when its damp or raining, I would guess the coil. My assumption is that the coil is cracked and letting moisture in, which shorts it until it quickly burns off.

I am thinking mine is spark because sometimes when it is dogging I can hear it poping out the exaust like there is unburn fuel being passed through the cyls, which would not be happening if it wasnt getting fuel.

I just switched the fuel pump relay with the air conditioning relay from my other car, same results. The car will start and stall once, a restart and it will run fine. I did hear the fuel pump with the ignition on run for 3 seconds like I did before the relay switch. Thanks 86GT3.4DOHC, that makes perfect sense, can we rule that out since it has done this in all weather?

Fuel filter was swapped out in spring, think I should switch it out again?

Ok, the coil and relay appear fine, now the next step is the leak down test? Step by step, how do I do this? Tools needed?

The MAT sensor in the air cleaner housing or the ECM temp sensor above the water pump.
Don

And you might concider the map sensor also.
The temp sensors you can check out the resistance with a meter to see if they are close to spec.

Both temp sensors should read the following. You can adjust.guess in between temps.

At 70* should read 3,400 ohms.
At 100 should read 1800 ohms.

[This message has been edited by Dodgerunner (edited 09-10-2006).]

Thanks.
I just switched the MAT and will drive it to and from work. I can borrow the use of a "Scan 4000" engine analyzer from work and I will check the values on Monday. Meanwhile, I'm off to the archives to look up leak down tests and fuel systems.

Does it start right up or does it take about six or seven revolutions of the flywheel? If it takes a long time to start cold, check the cold start injector system!!!

[This message has been edited by 86soon3.4 (edited 09-10-2006).]

Mine still does it in all weather too, but its worse when wet. Im assuming even when its not raining condensation forms in there, especialy seeing as it usualy doesnt do it when its been sitting in the day, only over night.
Ive got a coil, but I rarely drive the car so I havent had the motovation to change it.

quote Originally posted by 86soon3.4: Does it start right up or does it take about six or seven revolutions of the flywheel? If it takes a long time to start cold, check the cold start injector system!!!

Starts right up, then stalls after 2 - 3 seconds, starts up and it runs fine, but I will double check to see if the cold start injector is flooding it out. Thanks.

The CSI does not have power after you release the key so should not be the problem unless the injector if leaking.

Update for everyone.
The car started right up and did not stall out but it did come real close, it caught itself and corrected. It did this both in the morning and after work with the different MAT sensor. I switched back to the original MAT sensor and will report my findings tomorrow. I cannot borrow the Scan-4000 until Wednesday. Thanks Dodgerunner for refreshing my memory about the CSI.
I will continue to post my findings so that everyone will be able to follow the progression of the trouble shooting.

The car has not stalled out in the morning in the last three weeks, here's what I did to improve it.

1) I ran a tap into the threads of the air cleaner housing where the MAT sensor goes to allow it protrude farther into the air stream of the intake air, almost touching the air cleaner element.

2) I cleaned the electrical connectors and used dielectric grease on all sensor components that I could get to. I still have to get to the engine (ECM) temp sensor though.

3) I did put a rubber cap directly onto the air cleaner outlet eliminating the rubber hose, metal tube and cracked rubber cap on the end (part of the recall IIRC) along the firewall. This was one of those out of sight/mind things that maybe everyone should check with their tune up. The cracked cap has been allowing some warmer air to enter the intake after the location of the MAT sensor.

4) I also put a fresh air filter in, old one only had a couple thousand but still, lets go with fresh.

5) I tightened up the alternator belt just a tad to insure that I wouldn't have any slippage on cold starts in the morning, you know, try to have full voltage imediately.

Results? Starts right up, goes to 600 - 700 RPM's catches itself nicely and does the cold idle of 1500. Not absolutely perfect but the car has over 100K on it, I can definitely live with it, and it maybe improved a tiny bit with the cooler fall weather.

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jetman
Silver 86 SE 2M6 4-speed, with "check wallet light"

jetman, I don`t understand what you are saying in # 3.

I had to re-read it a few times to get that also.
I think it sounds like the old recall pipe was still connected to the aircleaner and just capped behind the engine where it use to connect to the valve cover.

It's now totally disconnected.

At least that is what I read into it.

I am still experimenting with this problem and getting closer. Someone tell me why the fuel pump only runs for 5 seconds at startup and then quits. I know it is to prime the line for the cold start injector, but why can't it stay running until started. Why does it hurt anything for the fuel pump to run at all times the ignition switch is on. I am not going to say for sure, but I have jumped the fuel pump out so that it runs all the time when the ignition switch is turned on. So far I am getting good results, but will not brag to quick.
Don

quote Originally posted by Dodgerunner: I think it sounds like the old recall pipe was still connected to the aircleaner and just capped behind the engine where it use to connect to the valve cover.

Yes that is it, sorry I just could not articulate this clearly. In the past week the car has started and idled perfectly in the cooler fall weather.

ka4nkf, please keep us posted on your fuel pump jump. It is normal for the fuel pump to run for 2 seconds in initial key on position, I wonder if your fuel pump is about to croak since you have to jump it?

quote Originally posted by jetman: Yes that is it, sorry I just could not articulate this clearly. In the past week the car has started and idled perfectly in the cooler fall weather. ka4nkf, please keep us posted on your fuel pump jump. It is normal for the fuel pump to run for 2 seconds in initial key on position, I wonder if your fuel pump is about to croak since you have to jump it?

No I do not have to jump the fuel pump. I am just doing this as a experiment. My question is", why not have the fuel pump run all the time the switch is on. For example when you turn the ignition switch on the fuel pump runs for 5 seconds and then turns off. Now if it had 40 pounds when it came on and shut off. Then I would think that it lost some pressure from the cold start switch and there is a lapse time before the oil pressure starts it again. So maybe it dropped to 30 pounds when this happens and if the pump was running all the time while starting, then there would be no loss in pressure and it would start better ( I think). Someone else is going to have to chime in with me. Does all other cars operate this way? I don't think so. I think on most cars when you turn the ignition switch on that the fuel pump continues to run therefore loosing no pressure. This laps time in pressure is what I think is causing the problem. Like I said before what does it hurt to have the fuel pump running at all time when the engine is running, rather than have it come on and go off and then come on again. I know what I am thinking I just don't know how to explain it. Hang in there because we will get it solved.
Don

If you are having a time lapse because you are having to wait for the oil pressure to build, your problem is easily solved. Just replace the fuel pump relay. If you didn't already know, the fuel pump relay (located on the firewall behind the air cleaner) is what should be kicking on your fuel pump when you start the car. The oil pressure switch is just a backup in case the relay burns out.

I'm getting ahead of myself here. Since you said that your pump primes, your relay is fine. There shouldn't be any time lapse if you're starting the car normally. Now, if you're turning the key to run, packing the trunk, then starting the car; that's another story.

The reason is safety. The ecm runs the pump to prechare the fuel system for starting. Then goes into normal mode which it it has to see pulses from the ingnition to keep the pump running. If the ecm is not getting pulses or the oil pressure is not over a couple psi the pump is shut off. As soon as your start to crank the engine and the plugs start to fire the pump is started right back up, there is very little delay.
And yes all new FI engines work this way. Some of the older ones has a lockout relay tripped but impact that had to be reset before you could ever get the engine running again. Was alway fun looking for the reset switch. or button.

Reason being, if your in a accident and pinned in the car you don't want the fuel pump dumping gas on the ground under your car or over the engine. Once the engine stops the pump turns off.

If you wire it to the power on with key there is no way to stop it other than turning the key off which you might not be able to do.

[This message has been edited by Dodgerunner (edited 10-07-2006).]

Thanks for the replies. It is getting interesting. Safety features sure causes some problems but are better to be safe than sorry. I guess I will have to build a pressurized 1/2 gallon tank and have a pressure regulator to control the pressure. Then the fuel pump would shut off as normal but I would still have pressure on the fuel line. Back to the drawing board. I am having fun and learning also. Thanks everyone
Don