1988 Fiero GT, starts and stalls when cold outside..help! (Page 1/2)
phils88GT OCT 21, 11:27 PM
So the temps outside have finally started to drop so in the morning, we are getting around the 40’s in the mornings for the past week or so.

So I noticed it when the engine is started cold after sitting all night. If it is “warm” outside, I don’t really have any issues.

So what it will do it start up instantly (it’s a 5-speed btw). Sometimes it will just shut off almost instantly.. if I keep trying it over and over, I will get it to start up and idle, which can be kinda rough-ish, but eventually smooths out after a few minutes. At this point, I can drive it. If I try to before this, while acting up, the engine will quit, not matter how much gas you give it.

I read another post from a fellow Fiero owner on this forum who had pretty much the identical problem, replaced a ton of parts that still didn’t fix the problem, and the post left off with a potential fuel pressure issue, but the post never was fully explained and no fix was listed.

Can anyone help me with this? Thanks!
Patrick OCT 21, 11:50 PM
Get a scanner (or WinALDL) on there and see what temperatures the CTS and MAT sensors are sending to the ECU. If either one or both are reporting temperatures too high, it's possible the engine is running too lean while cold.

And as mentioned, it could be low fuel pressure as well... which is so easy to check on the 2.8 V6.

[This message has been edited by Patrick (edited 10-22-2024).]

phils88GT OCT 25, 03:03 PM
So I have an update. It seems that outside temperature is not asa much a factor as I thought. It seems that time is what matters the most. It gets worse with the passage of more time not running. For example, morning starts after sitting overnight are the worst. But, this morning I took my handy can of starting fluid, and after the first crank, start and stall (immediately), I sprayed some into the intake on the quarter panel (how convenient is that! :-) and it started back up and idled high until the spray I shot in there was used up, then started to bog down and almost stall until I sprayed more into it. On the third start and a quick shot of the spray, it worked ok, until I started to back out (5-speed) and she quit again. That could have been my fault, not sure, but I cranked it back up and all was good!

I guess I should check the fuel pressure and see what it is both off and running and after it sits for a while after running. I should also mention that the Check Engine light comes on when it does this, then goes out after it calms down. I will have to check the codes and see what it is. I don't have a scanner or the ALDL cable for Windows, so I cannot actively view what the computer is doing. Which cable will I need?

I have read this could be a cold start injector issue. How would you test that? Being a 1988, EFI programming and tuning was probably pretty basic, well, just not nearly as sophisticated as it is now, or even as the years progressed after 1988.

thanks,
Dennis LaGrua OCT 25, 03:32 PM

quote
Originally posted by phils88GT:

So I have an update. It seems that outside temperature is not asa much a factor as I thought. It seems that time is what matters the most. It gets worse with the passage of more time not running. For example, morning starts after sitting overnight are the worst. But, this morning I took my handy can of starting fluid, and after the first crank, start and stall (immediately), I sprayed some into the intake on the quarter panel (how convenient is that! :-) and it started back up and idled high until the spray I shot in there was used up, then started to bog down and almost stall until I sprayed more into it. On the third start and a quick shot of the spray, it worked ok, until I started to back out (5-speed) and she quit again. That could have been my fault, not sure, but I cranked it back up and all was good!

I guess I should check the fuel pressure and see what it is both off and running and after it sits for a while after running. I should also mention that the Check Engine light comes on when it does this, then goes out after it calms down. I will have to check the codes and see what it is. I don't have a scanner or the ALDL cable for Windows, so I cannot actively view what the computer is doing. Which cable will I need?

I have read this could be a cold start injector issue. How would you test that? Being a 1988, EFI programming and tuning was probably pretty basic, well, just not nearly as sophisticated as it is now, or even as the years progressed after 1988.

thanks,



It could be the cold start injector but it could also be the cold start switch. Jump the cold start switch terminals for a couple of minutes and see if the engine keeps going. If so its the switch.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

phils88GT OCT 25, 03:54 PM
Where is this cold start switch located at?
Patrick OCT 25, 07:28 PM

The cold start injector is only active during the initial crank. If the engine is stalling after it's been started, this has nothing to do with the cold start switch and/or injector.

As I've already mentioned, the fuel pressure is so easy to check on the 2.8 engine... and it sounds to me that low fuel pressure could very well be your problem.
Vintage-Nut OCT 25, 08:52 PM

quote
Where is this cold start switch located at?




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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

phils88GT OCT 26, 06:05 PM
I bought a fuel injection pressure tester today and checked the fuel pressure. The car had sat for about 5 hours and had not been started at all. I attached the gauge and turned the key on, and the gauge showed around 44 psi. I did a code check while this was going on and got a 12 (normal), 32 and 34. I have read the 32 is EGR, and the 34 is MAP sensor.

So I started it up and she fired right up. I let it warm up and checked the pressure again. This time was 35 psi at idle. This was a fully warmed engine. If I blipped the throttle at the throttle body, it would shoot up to 40ish and then back down to 35 idle.

Does the pressure and behavior sound normal? I am guessing the PSI went up because of the lack of vacuum at the regulator?

What of this MAP sensor error? Where is the MAP sensor? Could this have been triggered by the startup issue, or be causing the issue altogether?

Thanks everyone!
Vintage-Nut OCT 26, 06:49 PM

quote
Where is the MAP sensor {located}?
phils88GT OCT 27, 08:03 AM
Ok, so I think I found the problem. The clip on the connector for the MAP sensor is broken and since the connector is vertical, it was loose and not making a good connection at all.

I noticed this while fishing around the vacuum lines in that area, checking for leaks. I bumbed the connection while it was running and it cut out. I continued to wiggle the connecter, as it was, and was able to repeat the problem.

I managed to secure the connection and this morning, I came out and started her up and she started up perfectly!

Now I need to find a pigtail to replace the connector on the harness before this happens again.

Thanks everyone for your help! I hope helps others down the road.

Have a great weekend all!