94 GMC Jimmy rough engine hesitation while idle and warming up

[Jacksta07]

I have a 94 GMC Jimmy. A little background on my knowledge... I am still learning things, but still knowledgeable enough to not get yanked around like an idiot. I help diagnoses our vehicles problems and my boyfriend does the actual fixing.

So our problem is tha our Jimmy has been running rough especially during warm up (until it is up to running temp all the way) and during idle. There is a hesitation like the power increases then drops. As well during this phase the engine shakes. Though upon reaching full warm up temp it diminishes to a minimum. Sometimes it is worse then other times on start up. I don't know if is a misfire, timing being off massively, a sensor (like the coolant temp sensor maybe), part of the fuel line (spider injectors). Please help. Trying to diagnose so we can fix it. Please and thank you!

[silverlite]

Try here: http://blazerforum.com/forum/

Also, if you can get access to a scanner that reads OBD1 codes then connect it and see what codes come up.

[Jeep_Comanche17]

is there any lights on the dash? being a jimmy i assume its a 4.3L V6, and that its TBI. i have a 94 S-10 with the same motor and it has a small miss sometimes but it never shudders, but u can feel the miss. i was going to replace the plugs, but the truck only has 65,000 miles! i have had it for a year, but before i bought it it had sat for 1-2 years in a sealed garage. over the 5,000 miles ive put on it it seems to have cleared significantly. but still misses on occasion. did this problem with your jimmy just randomly start or has it slowly started getting rougher and rougher?

[Ryan Wyatt]

By rough idle do you mean possibly surging? On startup rpm should be around 1200-1300 rpm. Is yours closer to 800-900 on startup? Does it sound like it's about to die and shudder bad when the AC is turned on and off?