1991 K1500 StiLL CoLD STarTinG - H E L P ! ! !

Anybody have any clue what this may be??? MODIFIED and REPOSTED

My truck (1991 K1500 Chevy 4WD Auto 5.7 EFI) runs very strong with no intake or exhaust leaks, no "ticks" or "pings" from the motor, and it'll sit you back in the seat when you gun it... but when it's been sitting cold overnight or even during my 8 hour shift at work it has the hardest time getting started. By saying that I don't mean it cranks and cranks and gets no where. It will fire right up within 4-5 crank revolutions... everytime. But when it's cold it stutters, shakes, spits, and let's out lil backfires and dies. It'll then fire right back up the same way and when the initial burst of fuel has ignited and it starts doing it again. I'll give it a little gas to raise the rpms a bit and it'll do better, but it's still not solid. It gets a little better as the motor gets warmer (better enough that I don't have to nurse it along) and then it runs perfectly. You can't tell it was even stuttering after about 30 seconds of babying it. It will do this exact same thing every time I start it cold.

I have replaced the following parts due to other issues and I invite you to view the other posts I left to see the other issues.... distributor (+ cap & rotor, etc.), iac, and thermostat. I have been told it may be the TPS -or- Coolant Temp. Sensor?
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Just replaced the ECT (next to the thermostat housing) because it was throwing a 15 code. Which in a book on the shelf at the store said ECT. Didn't help at all. Wiring into the ECT tests at 4.9v.

Tried what another guy said before on here about it possibly being the brake booster having a vacuum leak. He said to hit the brakes a few times while it was stuttering in the morning and see if it made a difference. It didn't. It did help me find a rusted rear brake line that exploded midrail and emptied my reservoir.

Had the headlight switch recently go up in smoke. Autozone... instock...$15.

The brake light on the dash is still flashing a seven code (6 short and one long - beep, beep, beep, beep, beep, beep, beeeeep).

The service engine light comes on after about 20 minutes of normal driving and it throws an EGR code. I put a vacuum pump on the old one and it held nothing. So I blocked off the vac line and I guess it'll light up until I get the new one. Could this have something to do with my cold starting?

Had an issue with the oil pressure dropping almost to the point of stalling when I turned corners or idled down at lights, so I put a new oil pressure switch in last week and now its been fine.

I AM DESPERATE TO GET THIS TRUCK FIXED! I have the basic know-how and a lot of tools so please just shoot a suggestion at me. I'll try it. Does anyong know what the voltage coming out of the ECT should be when it's hot and cold? Is there a way to test the unit by testing voltage without having a scanner? The yellow wire has the 4.9 volts when running... what should the black have coming out of it?

Could my pick-up coil going bad in my distributor have caused any underlying issues in my ECM/Computer that my be affecting the system now?

Thanks alot for your help either way. I check this daily and will be checking again soon.

P.S... If you get this one right... you have proven yourself to be the BEST one in here. Thanks again to all who have attempted.

Jeff

I had a similar problem with my 92 K2500 until I changed the Coolant Temperature Sensor. That would be the one in the intake near the thermostat housing. I bought a Delco, which by the way was cheaper than the aftermarket sensor. You can check your sensor with an ohm meter. I think there may be charts online to determine the reading. I wasn't getting a check engine light problem so my sensor was only out of skew. It was reading 90 deg F when it was 5 deg F out.

[quote=...Coolant Temperature Sensor. That would be the one in the intake near the thermostat housing...[/quote]

I did that and it did nothing for me. I guess I could have bought a bad one, but whats the odds of that? I've been told that the ECT plug is notorius for going bad. I have no idea where to start testing it.

Any other suggestions?

To check the ECT sensor, remove the plug and measure the resistance across the sensor.

For 40 Degrees F, the resistance should be 7500 ohms.
For 0 Degrees F, the resistance should be 25,000 ohms.

To check the ECT plug, you need to use a scan tool or back probe the connectors at the ECM.

Other possibilities for you cold start problem:
- EGR Valve, EGR Solenoid
- Fuel Pump Relay
- Fuel Pump, Fuel Pump Ground
- Intake Manifold leak
- Bad ground strap or ECM grounds at the intake manifold.

//2000CAYukon

FIXED!!! - - - Remanufactured Cardone distributor was J U N K! Pick up coil would not spin out until the metal was warm enough, therefore not letting it make full contact and making it run rough until it was warm. I have since been told that alot of people in the auto industry are already aware that when Cardone remans a distributor, they don't spend alot of time fixing or testing on that area of the unit. I'll never buy another cardone distributor again after how much time and effort I spent trying to get the problem resolved. Thanks for everyones help.