Wow, and it's been running like that for a couple years? Luckily mine keeps throwing cylinder 3 misfire so maybe it'll be easier to find a solution for mine....maybe. Thanks man, good luck!

 

If yours is throwing the #3 misfire, that is probably the source of the rough idle. That #3 plug is a challenge to get to and if the plug wire is not routed correctly the steering shaft can wear a break in the insulation causing the energy to go elsewhere instead of the plug.

In my case I have no codes, no problems at all...except for the rough idle when stopped with trans in Drive. Does require the engine to be running for a few minutes before I notice the rough idle, so may be something to do with going into closed loop..IDK....I have given-up trying to figure it out, has not gotten any worse in the two years...so until it does, I just live with it.

Good luck with yours.

 

New spark plugs and wires are on their way. That's the first thing I could come up with. To be honest, the spark plug wires are original....at almost 140k, oops. I've been getting better with maintenance since I've been searching and learning things the past 6 months.


It's just funny that the problem only occurs in drive and reverse only. Figured if it was spark plugs or wires, it would occur all the time but I'll see once I change them out! Thanks man!

 

Right side is no problem; left side not bad except for #3 plug and that is because the steering shaft is just flat in the way. Easy solution is to move it. There is a plastic shroud around the steering shaft joint. This is a bit tricky to get apart, just take some time here so as to not destroy it. Once out of the way, there is a single (11mm??) pinch bolt that holds the steering shaft to the joint...it is green....remove this bolt and then pull the steering shaft towards the steering wheel to compress it enough to move it out of the way of #3 plug.

Replace plug and wire and then put the steering shaft back and the plastic joint shroud.

Also when replacing the plug wires, be sure to notice that the odd side is not in sequence like the even side is.

Have fun.

 

Hello Lanny,

Did you ever come to a conclusion with this?
I have a 97 with similar symptoms.

Thanks - Mark K

 

Nope...never have and have just learned to live with it. Although I have thought about replacing the IAC just to see....but have not.

Perhaps I did something to the injectors when I did the upper intake gaskets couple of years ago....IDK.

Good luck with your search.

 

Hello Lanny,

Guess What. I just changed my IAC out and it solved all my issues.
I had been chasing this for about a month. It was a defective
new part only 10-11 months old. Well respected part too.(DELPHI CV10011).

I put in my 20 year old one with 225,000 back in and all is back to normal.

Thanks - Mark K

 

Maybe I need to invest in a new IAC and give it a try....although a bit expensive for "give it a try".....

 

UPDATE: hooked-up a TECH 2 and everything was good except misfires on #1, sometimes #2, but alot on #1.

Cam Retard was at 2°, so I will attempt to adjust that back to zero.

At least I now have someplace to start with....#1.

 

I'm experiencing the exact same issue after recently getting mine back from an electrical system tune up. New plugs, wires, and distributer cap cleaned. I don't know what type of plugs they used. It's an '89 s10 blazer 4.3L. Since I didn't notice this until I had the work done, I can only assume it's related to the plugs they used or the installation itself, or maybe the cap needed to be replaced also?

Were you able to find a solution?