90 iroc tpi 5.0 convertible
Symptom- runs great from cold start to operating temp. turn off for 20 mins, (hopefully in the garage) then restarts, but runs rough and stalls. Wait for an hour, and it runs like new. If I keep it running, then it runs great the whole trip, as long as I don't turn it off.

New additions:
1. New fuel filter
2. New O2
3. Clean IAC pintle
4. Fresh Gas
5. New ICM with a gob of white paste
6. N


Check:

 

Symptom- runs great from cold start to operating temp. turn off for 20 mins, (hopefully in the garage) then restarts, but runs rough and stalls. Wait for an hour, and it runs like new. If I keep it running, then it runs great the whole trip, as long as I don't turn it off.

New additions:
1. New fuel filter
2. New O2
3. Clean IAC pintle
4. Fresh Gas
5. New ICM with a gob of white paste
6. New Distributor = 2 new modules
7. New Temp control sensor
8. New cap
9. New rotor

Since it runs great for miles and miles at operating temp, I figure the fuel pressure and other systems are fine.

What is next?

 

You might want to check the EGR Valve system, a badly sticking valve could cause rough idling and stalling.

 

thanks, but wouldn't I get a code? I will do a vacuum test on the EGR solenoid tomorrow. I bought a $50. fuel pressure gauge tonight, and fuel pressure is 42 to 38 and holds it when warm. I found a disconnected vacuum line on my EFE cannister and reconnected it, my Idle slowed 50-100 rpm. but I don't think this is my problem. Now, when turning on accessories, AC and lights now make the Idle adjust. (alternator is shiny new). I just started it again warm, it surges, then the idle flattens out, but stepping on the GAS KILLS IT. Let off the gas, and it goes back to idle.. step on the gas and it chokes. If I start it from cold it runs normal until I turn it off and restart.

 

I know on a 85-89 TPI your problem ends up being the CTS 90% of the time. People usually assume its the MAF sensor.

 

Thanks- New Coolant Temp sensor last week and my '90 is speed density.

Tonight EGR vacuum test Haynes manual has 'a process of elimination' test based on the EGR solenoid. Since it is 18 yrs old, I should probably buy a new diaphragm anyway.
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I left the fuel pressure gauge on all night.

42 at turn off
38 for 15 minutes
28 after 2 hours
0 this morning.

Is this a prob?

 

and yes, it went right back to 40 when I turned on the ign.

 

Tested egr vacuum, it holds vacuum. Took the Distr. out, cleaned, and regooped the module, retimed it at 10 degrees. WOW did it fire up and spin rubber all the down the street!! went 2 exits, turned around and almost made it back. The car doesn't die, there is just no power after it reaches operating temp. I'll go back in couple of hours to retrieve it-- once it cools off.

These terms come to mind, obstinate, pissed off and frustrated. I have poured through all the posts- it seems like no one has an answer.
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and, add another cap and rotor to the list-- I overtightened the freaking stainless tie down screw and snapped it.

 

Sounds like your running too rich in closed loop with reduced airflow. I wonder if your temperature sensor is operating normal which signals the ECM after operating temperature is reached. It's time to put a code reader on it and find out what the OB diagnostic is telling you. Mine was shutting off when hot intermitently and it was a carbon tracked rotor causing the fault.

 

The coolant temperature sensor was replaced last week. The plastic on the old one flaked and cracked when I took it off. After installation, I let it get to operating temp in the garage, and the fans kicked in, proving the new sensor works and send signals out.

The IROC use to have a problem with normal temp starting, for over 6 years. Previous symptom was sit and idle, like waiting in line at the DVM Sniffer, tech would turn it off, then no start. I always thought the CTS was telling the ecm the car was too hot, the ECM went into failsafe. This was a real possibility as the temperature gauge was reaching 200-220 waiting in line in the summer. I changed out the water pump and it has never reached that temperature range again.

ECM is the next item on the menu.

 

I ALDL'd the A and B while it was running bad and got the fast blink, meaning it's in closed loop. still no codes with engine running.

I need the OB diagnostic run before I change out the ECM.

 

just ohm'd my injectors

looks like five of them are 8 or worse.

looks like a new set of injectors are on my horizon.

 

ordered from JEGS, got the VENOM 19's. I have everything taken off the top of the motor and going thru it. Any suggestions on what I should be doing while waiting for my injectors?

 

Jegs was proper in delivery. I was a little thrown with the plastic tips, they almost looked like protective packaging. The INJECTORs were the problem. Changing out the TPS was also needed, and lastly, the 180 degree thermostat, which allows the motor to get warm enough for everything to cycle. Fired up strong after installation, and ran great after it warmed up.

 

not tps- I meant the CTS COOLANT TEMP SENSOR!! Thanks for everyone's help.. and a word of wisdom-

OHM sensors before laying down cash for new ones!!!!