oddscrounger

Hey guys I have a 1987 IROC Z 305 TPI G92 package with edelbrock shorty headers and a 3 inch exhaust. Has new plugs, wires, cap, rotor, rebuilt trans (t-5) and a new performance Ram clutch. Just over 81,000 original miles on body and engine.... Car runs GREAT... except when it's cold. Had no problems but now that the temps are dropping here in Chicago (50 degrees overnight) the car runs like absolute crap until it's warm. I am already replacing the alternator and belt because it loses power if I have too many electronics running; I get the same loss of power/runs like crap when it's cold. Are these issues related or do I just have to let my baby warm up in the morning a little longer?

grumpyvette

Id suggest pulling trouble codes and looking for a vacuum leak, that symptom is commonly the result of an overly LEAN fuel/air ratio while the engines cold, thats one reason cars with carburetors used chokes too get started, a richer mix tends to burn and and better when the engines cold, once it warms to operational temps fuel vapor forms far faster, fuel atomized better.
Id also check your injectors electrical resistance with a multi meter, and replace the fuel filter, verify the TPS and IAC are set correctly, and verify your getting a consistent 38 psi or higher at the fuel rail,and throw in a can of injector cleaner in a tank of fresh high test fuel

oddscrounger

The fuel filter is new. I am not an expert when it comes to cars. What is TPS and IAC and how do I set it? I understand the 38 psi at fuel rail, I'm sure I can figure that out. And you're saying get some sea foam or gum out in my next fresh tank?

grumpyvette

Id suggest pulling trouble codes and look for a vacuum leak, that symptom is commonly the result of an overly LEAN fuel/air ratio while the engines cold, thats one reason cars with carburetors used chokes too get started, a richer mix tends to burn and and better when the engines cold, once it warms to operational temps fuel vapor forms far faster, fuel atomized better.
approach the problem in a logical step by step, verify and check every component before assuming its functioning correctly approach.
Id also check your injectors electrical resistance with a multi meter, verify the TPS and IAC are set correctly, and verify your getting a consistent 38 psi or higher at the fuel rail,and throw in a can of injector cleaner in a tank of fresh high test fuel

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oddscrounger

Thanks... wow looks like I have some reading/work to do. I have some gearhead buddies who may help me with this stuff. Sounds like it would be the problem with the TPS

albertgeorge1

I have the same issue i replaced the iac and 02 nothin but my car also does after sitting for about 30 min i will be. Checking fuel pressure today

oddscrounger

I ran trouble codes and I got 33 and 42 so that narrows it down to a vacuum hose problem, faulty connections at the ECM, faulty Mass Air Flow sensor, or improper HEI module....

What's an HEI module? Where is the ECM? And I will check vacuum hoses either with or friend or just bring it to the shop. What do I need?

grumpyvette

check these lines first and verify the brake boosters not leaking air as thats semi common

YOU NEED A FACTORY SHOP MANUAL, the TYPICAL AUTO STORE MANUALS ONLY PARTLY USEFUL
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oddscrounger

mr. Grumpyvette thanks for all the input. do you think it'd be worth it just to replace all the hoses instead of looking for leaks?

grumpyvette

obviously the condition of your current hoses and budget will effect that call, but Id be looking for leaks and correcting problems before spending cash that might be spent more effectively elseware

grygost

HEI module is inside the distributor. In order to get to it you have to take the wires off the distributor cap and take the cap and rotor off. The unit will be a small black thing in the back with 2 wires connected to it. See if the bolts on it are rusted bad. That could be an indication it has never been replaced.
If that is bad it will give the wrong signals to your ecm causing bad spark, little spark, or even no spark.

oddscrounger

ok tonight I checked for vacuum leaks tonight... No obvious whistling, humming sounds and I used the diagram to spray carb cleaner all around the connections and the length of all hoses and no changes in idle and/or engine stalling out. Also, my idle is very steady; on start-up it hangs around 1000 RPMs and after that it idles down to about 600-700 and stays very even. So I don't believe it is a vacuum leak and/or anything to do with the IAC. However, I am going to remove and clean/reset the IAC this week.

The other thing I did tonight was remove the MAF and clean it with MAF cleaner. I cleaned the throttle body with throttle body cleaner. Sprayed the throttle body cable and made sure to open the butterfly valve all the way to clean inside there very well. Disconnected the battery to clear the ECM and when I restarted the car, the idle still sounds great. but the Check Engine light came right on and this time after a drive the only trouble code to come up was 42, so I'm leaning more towards an ignition module and/or ECM problem.

The problem is, my car will not just get up and go; it idles great but as I ease off the clutch to get the car moving in first gear, it just stumbles and won't go unless I floor it. When I floor it, the RPMs will finally shoot up and the car will spin the tires. It's like all or nothing.

So I am thinking I need to get a voltometer and check all the connections to and from the ECM, IAC, TPS.... check the voltage at the TPS at idle and at WOT and make sure that's not the problem. Perhaps replace the MAF is a code 33 resurfaces. I am kinda lost right now... I really don't want to take it to the shop and just tell them to fix it. I am trying to avoid labor costs and to learn how to work on cars....

oddscrounger

OK problem solved for now but i'll repost tomorrow or later in the week if the problem comes back. I took out the ECM and checked connections (All of this with the battery disconnected). I removed the ADS superchip that I found inside, checked all the pins and they were straight. Put the chip back in and reconnected the battery.

Then checked voltage on the TPS and found it to be very low, adjusted the TPS until voltage was within spec. Voltage increase was smooth as I slowly moved the throttle up to WOT. Then readjusted the IAC so my idle was closer to 600. Reset the IAC by inserting the key to the on position and waiting a minute and then turning the key off.

Fired her up and she idled higher in warm up mode but then idled back down to a nice rumble between 600-700. During the test drive had no loss of performance issues and the stumbling/popping at takeoff was gone. Code 42 still shows so next I am going to try replacing the ignition module. Sound like a good plan?

I will also put some fuel injector cleaner in my tank. Also should I have the timing done again? I know my ECM is going to be "re-learning" how I drive and the engine operates. Grumpyvette what you think?

grumpyvette

as long as the results of adjusting the sensors are helping your most likely improving things
most problems are the result of bad electrical connections or vacuum leaks, but bad sensors or failure to properly adjust components is also possible.
Im glad things are improving, reading the links and sub links posted will help in most cases.
Id strongly suggest getting a factory shop manual, a timing light,a trouble code scanner, multi meter and fuel pressure and vacuum gauge as those tools help.
Ive tuned dozens of these cars and most have the IAC, TPS out of adjustment, the timing off or vacuum leaks and/or defective fuel pressure regulators , but learn to read spark plugs as a huge amount of info is available

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oddscrounger

still having the problem but only when I have a lot of power drawing, my battery gauge shows a very low reading when my lights and cooling fans are on, along with radio and/or wipers or if i'm using the power windows. I am putting a new alternator and belt in (the belt is frayed)... does that sound like it could have been the problem too? Also, I agree I am going to start accumulating those tools to do routine checks.

FireDemonSiC

I'd say there is an 80% chance your MAF is shot.

My car did this from the time I bought it and during my "Young jedi" days, it took me around 2 years to solve the problem. The issue was I had trouble with a combination of codes 24 (Vehicle speed sensor) and 44 (O2 lean). When you started the engine cold even on a warm day, you'd have to let it idle for around 5 minutes or so before driving it. It if was a cold start in the winter, you were really in for it.

Why? Because trying to drive it when cold would result in bogging/stumbling, hesitation, sometimes backfiring through the intake (The popping noise you are describing) and an almost guaranteed CES light (Code 44) and the ECM entering limp home mode (Very rough idle + stallout sounded like I had a big duration cam in the car).

I tried everything O2 related. I must have replaced the sensor about 3 different times. Replaced the harness, did data scans and it looked like the problem was going to get the best of me. I was replacing ignition modules, spark controllers, calibrating sensors, adjusting idle, swapping ECMs and even did a full tune-up trying to correct the problem.

Then, one morning after an immediate stall on crank, a code 33 (MAF voltage high IIRC) popped up, which was the first time that had ever happened. A few months later I finally threw in the towel and came up with the money to replace the MAF. My car has had none of the aforementioned problems since. My code 44 and 24 (I still can't figure out why the VSS was showing an error because of this) waived bon-voyage and other than a missing 2* of timing at the dizzy the idiot who dropped the motor in forgot to add I had no more driveability problems when cold.

Give it a shot and if it doesn't fix your problem, return the new MAF and tell you NEVER USED IT

oddscrounger

that's interesting....

after cleaning the MAF and throttle body and finding no vacuum leaks.... I cleared the computer and no more code 33.... so I feel the MAF is fine. Especially now that the car runs awesome after tweaking the TPS and IAC/minimum idle speed. New alternator going in this weekend to fix the rough performance at night when i have my lights/wipers etc. all going and my battery volt gauge reads way low; halfway between 9 and 13...

new alternator and belts should fix that and I think my problems are solved, for now....

oddscrounger

the only code I keep getting is 42, which a mechanic told me months ago he thinks it's an aftermarket ignition module that is setting the code off... but IDK if it's actually bad or the ECM just doesn't recognize it.

oddscrounger

so replacing whatever ICM I had with the OEM ignition module cleared the code 42 and no more popping/stumbling/hesitation... who woulda thought