I have been having this idle problem with my 92 B2600 4X4. When the engine gets warm and I turn off the engine. On restarts in neutral(5spd manual) truck idles fine at about 700rpm. When putting shifter into any gear 1st to reverse, the idle would drop low to 400rpmuntil I put it back into neutral. After running truck for awhile, then it would be ok.It is not a big concern but when you are going at a slow speed 10mph and you come to a stop in gear with the clutch pushed in, sometimes eng would stall. Any ideas?

 

sounds like your clutch is'nt disengageing all the way. there should be a place to adjust it. do you have a manual ? that will tell you how to do it. it should'nt make any difference in gear or in neutral, and no grinding when you put it in first or reverse. hope this helps.

 

I have the exact opposite happening. When i put it in any gear while idleing it revs up. I dont knwo what it revs up to but it does rev up, quite a significant noise change so i know its abit higher. Is this normal?

 

Check the clutch switch. Pushing the clutch in is considered a load on the engine and the PCM should kick the idle up. I have seen a few bad PCM's but more likely the clutch switch.

 

Similar problem with 99 B2500. Starts normal-runs normal. But when I come to a stop (usually first couple after start driving) it will stall like if you didnt push in the clutch, I think I notice that when I 'really" push hard on the clutch it wont happen as much. The idle speed seems ok. When it stalls I get the idiot red light for "battery" and "check guages."

 

I have had same problem for years. After reading about truck ECM's going bad I decided to check mine.Sure enough the resister leaked electrolite around it and there is obvious damage to the board. Now I just have to send it to AVPro in Florida to get it fixed. My feeling is that could be our problem.

 

I sent my ecm for refurbishing(it looks brand new) and still have the same problem with idle.(though it ran better) It's generally around 550-650 rpm's and drops lower when clutch is in in gear,which makes engine stall.I've spent hundreds of dollars at the mechanic trying to get this fixed.They usually just work on the timing,which doesn't help.I've done everything except for a fuel pump and rotor.Does the clutch sensor affect idle as mentioned? What else affects the idle?