'93 GMC Jimmy Vin 'W' CPI Cold Start/Run issue

[mr_stimey]

Long time searcher and lurker, first post here. I have done a lot of my own repairs and maintenance to this vehicle (with alot of help from this forum), but this one has me stumped.

Vehicle: '93 GMC Jimmy Vin 'W' CPI

Issue: After sitting for extended periods of time outside (overnight, at work, etc) in temperatures below freezing (usually 25 degrees or lower) I get a nasty cold start where the engine will fire right up like normal, but as it begins to idle it will slowly start to miss and die. It does throw an SES code, which I need to jumper and read yet.
If you throttle the engine during this rough idle it will continue to run, but with a lot of “sputtering” or “backfire” type sounds. Once the engine temp begins to raise the code clears and the engine runs normally.
The same issue and SES will return however during highway driving when outside temps are ~25 degrees or colder.
The engine runs fine and operates normally if kept in a heated garage, and has previously run fine cold weather or not.
I will post back as soon as I read the code after work this evening. Any input in the meantime is greatly appreciated!

Cheers!

Tony

[MT-2500]

Welcome on your first post Tony.

You ned to pull the code and post back code no.

How is the tune up end?
Good Plugs and wires and filters?
Have you looked at dist cap and rotor and base time check?

[mr_stimey]

Thanks for the reply MT-2500, still at work, no code yet.

Plugs good, wires brand new

Fuel filter ~5-6k miles, getting close to the same on the oil, filter and fluid change

Im glad you mentioned the dist cap and rotor, I didnt even think to check. Ive had problems in the past with the distributor cap collecting moisture and corroding the contacts. The cup shape with the open bottom isnt the greastest design in the world. Replaced both cap and rotor this past April. Ill take a look the next chance I get.

[MT-2500]

You are welcome.
And check the code no and poat back no.

[mr_stimey]

Sorry for the delay on posting the codes, Im getting a 13- O2 sensor code and 34- MAP sensor code

[MT-2500]

Work on and repair the map sensor code.
Check wiring and vacuum to it.
Clear codes and recheck for what code comes back.
That may solve the 02 sensor code.
Good Luck and let us know how it goes.

[Chris Stewart]

I've had sticking Idle Air Control valve (IAC) trouble give me similiar symptoms. Removing it and wiping the plug & stem clean with a rag soaked with carburetor cleaner then spraying a little in the hole of the intake manifold where the IAC mounts helped me.

[mr_stimey]

Well I got some time to look at it this weekend and the wiring checks out, vacuum good at the sensor. I got it warmed up and to a point where it was starting normally and thought I would disconnect the MAP sensor and try starting it. Sure enough it started up fine and then began to repeat the exact issue I have been having.

I decided to replace the MAP sensor on this one and so far so good. Cleared the ECM codes and test drove it in the cold for about 30-45 minutes yesterday no codes thrown, let it sit out in the cold overnight, started fine this morning no issue no codes- whereas I would have experienced the problem numerous times by now. I guess time will tell.

Thanks for your help guys!

[MT-2500]

You are welcome and thanks for posting back how it went and the fix.
Good luck