hey guys I have a '99 GMC Jimmy SLT. I was wondering how rough an engine should idle in park. Mine seems to shake a tad bit, but nothing crazy. I fixed an engine misfire with AC Delco plugs, cap/rotor, ignition coil, etc. But it just seems that it will not cure the little vibrations. I've also heard that these engines were never really smooth idlers like others are.

Anyone here have one that idles smooth as silk?

 

Mine doesn't idle as smooth as silk. Every now and then there is a shake. Some days its worse than others.
When I was looking for a used Blazer, I noticed some I test drove would purr like a kitten and others would shake like mine.

 

Mine idles fairly good. could probably lay a egg on top of it and it wouldnt roll off.

Hmm..i should try it lol

biggest thing that will cause a little shivver is cap and rotor/iac dirty.

 

hmmm...i've had the same thing, test drove different years annd they all we different. like when i pop the hood and look at the motor, it doesnt shake at all. i just feel little shivers, wanted to know if thats normal or not. But, I will probably take a look at my iac, i'm pretty sure by now it HAS to be dirty. thanks for the replies gentlemen

 

It kinda pisses me off since I have rebuilt the top end (heads). I have the new MFPI, Ac Delco cap and rotor, plugs and NGK wires. My Throttle body and IAC are clean. My fuel trims are within spec. My distributor is new, my coil is new, cam retard is zero. Fuel pressure is 60 psi and holds. And yet periodically I get a hesitation around 2,000 rpm

 

Burned,swap the tps. Sounds like thats the issue.

 

Same boat, not sure what if anything is wrong. Slight vacuum leak at manifold?

 

ill have to also look into my TPS.

would a bad engine mount cause these? because pretty sure everything mechanical is in the A-Okay range.

 

Yeah I thought it had a dead spot long ago. I have swapped the TPS from my spare engine and felt no change.

 

Hey guys dealt with this for a few years.
Found that there are a couple hard plastic small vac lines around the motor. The heat and time makes them crack, I fixed mine double rubber electric sticky tape. Has purred like a kitten since.




PS the lines are hard plastic black molded and hard to find on diagrams.