I'm having problems with hard starts, rough idling, and hesitation on my '87 GTA 305 TPI when cold. If I jump the ALDL connector to put the ECM in diagnostic mode, the car starts and runs fine. I have just had the plenum, runners, and intake off to repair a leaking intake gasket, and the car was running OK before. I'm sure (and hoping) it's something stupid I've overlooked. Any ideas? I've double-checked, and as far as I can tell everything is hooked up properly. (No I didn't miss the MAT, EGT, or anything else I'm aware of.) It has to be something ECM related, since it runs OK in diagnostic mode. I've been reading through the posts and saw mention of a cold-start injector. I wasn't aware these cars had one. Where is it?

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'80 Firebird
'87 GTA

 

Boy, do I feel stupid...
I think I just realized what the cold start injector is. It's between the #3 & #5 runners, right? I wasn't sure what that was. Well, I hope someone has some ideas what I may have screwed up. Thanks in advance.

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'80 Firebird
'87 GTA

 

Bird,

Welcome aboard!

What you have found on the left side of the intake is indeed the cold start valve, or injector as some call it. The two intake runners are located above the #3 and #5 cylinders, but are actually for the #4 and #6 cylinders (remember, the runner tubes cross the engine, and the PORTS are adjacent to the cylinders. Just semantics, I guess. You have the right item.

This cold start valve is controlled by the cold start module, which is located in the front of the intake manifold at the coolant crossover passage.

The cold start will operate when the starter is engaged if the coolant temperature indicates less than 100°F and the intake air temperature is within 20°F of the coolant temperature. The maximum duration of the cold start valve operation is eight seconds. After the engine starts, the service injectors are operated in an enriched mode to allow the engine to run until warmup. In essence, once the engine has started the cold start valve is basically inoperative.

My guess is that the CTS is not reporting correctly, or your BLM tables are not correct for your engine. This makes sense if the engine has been running with an intake leak long enough for the ECM to learn bad data.

The easy thing to do is clear and reinitialize the ECM to eliminate that possibility. The new data tables should be written with better sensor data for your current engine conditions.

If that doesn't cure the problem, it should at least help.

Waiting for results...

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

Thanks Vader for your response. Yes, you are correct, it's actually the #4 & #6 runners. I'm about to go work on the car again now. I'm not sure where the cold start module is you're talking about. I'm gonna try to locate it, just to make sure everything is hooked up properly. You said in the event the BLM tables were hosed, to clear and reinitialize the ECM. I'm assuming by that you mean to disconnect the battery cable and clear the ECM memory. If so, I've done that to no avail. By the way, the leaking intake manifold gasket was leaking coolant, not vacuum. (At least not that I'm aware of.) But again, I'm about to go work on it now, and I will check the CTS. Thanks again for the response. I'll let you know what I find.

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'80 Firebird
355 c.i. Chevy (built)
8.39 E.T. (1/8 mile) Altitude Corrected - 8.27
'87 GTA (stock)

[This message has been edited by BirdRacer (edited November 30, 2000).]

 

the "cold start module" aka thermo time switch is in the front of the intake manifold, to the left of the coolant temperature sensor,, it has the same plug as the ones for the injectors. hope this helps.

 

Thanks Ron. Man, this thing's got me stumped. The CTS checks OK, but today all of a sudden, it threw a code 34. It wasn't storing any codes before. But after clearing the codes and running some more, the code never returned. The main thing that got me today was this: With the air inlet hose off (MAF still connected, however), the thing will crank and idle fine. As soon as I replaced the air inlet hose, the car was hard to start, and when it did start, it wouldn't idle. So I thought to myself, 'Self' this thing's not getting enough air @ idle. (Light bulb over head) IAC Solenoid. I took it off, cleaned it, replaced it, attempted to tighten it down as I guess Arnold Schwarzenegger would and broke the silly thing off in the throttle body! So, several hours and dollars later I put a new IAC solenoid in, and guess what? No difference. Also, back to some basic mechanics, I used some propane to check for vacuum leaks, and it acts like there may be a leak around the intake (that I just changed the gaskets on) on the drivers side, above the #5/7 cylinders. Either that or something in the area is sucking in the propane, because the idle raises every time I open the propane in that area. Sorry to write a book, but I hope we're near the final chapter. I'm going tomorrow to find a cliff to drive this thing off.

 

Silly me. When I got the code 34 today, I wasn't close to a computer. I called my wife, had her check on the internet for a trouble code listing and she said code 34 was EGR valve. I now find out it is for the MAF, which it probably set the code when I had the air inlet hose off. I still don't know what the h***'s wrong with the thing, though...