Rough Idle ???????????

[Pittman]

ALL vac lines checked and rechecked and checked agian
new plugs, new cap and rotor, checked the coil with a ohn meter and isnt great so will replace next. anyone have any other ideas. The idle is around 650rpm and will idle fine until it sits for a while at idle. then starts to bob down to 500 or less and then up to 650. Is it possible to adjust the idle speed????

 

[nick041881]

these things NEVER idle good. dont worry about it..

 

[kwick6]

Yeah you can adjust the screw in the throttle body to raise the idle.

Later,
Scott

 

[ParTyBoy]

Re: Rough Idle ???????????

ALL vac lines checked and rechecked and checked agian
new plugs, new cap and rotor, checked the coil with a ohn meter and isnt great so will replace next. anyone have any other ideas. The idle is around 650rpm and will idle fine until it sits for a while at idle. then starts to bob down to 500 or less and then up to 650. Is it possible to adjust the idle speed????

How many miles on your truck...??

 

[Pittman]

how many miles? 36,451 miles. OH I forgot to mention another symptom if at a steady idle and you turn the AC on 3 out of 4 times it will quit. I thought it was supposed to actualy bump the idle up a bit when you turn the ac on.

 

[Blake]

My Ty is doing this (just doesn't completely die/it recovers) and I believe it is related to my ignition being retarded too much. AC was the big tipoff. My compressor would run fine until I dorked with the timing. Now, when I'm at idle and the A/C is on, the compressor will turn on, idle will drop, and then the A/C will click back off really quick. Doesn't do this if you idle it up a little bit. There is a setting in promgrammer that disables A/C clutch at a certain rpm on the lower threshold.
Check your timing. I'll do a TDC check on mine this weekend because I believe my balancer has spun. You may be in the same boat.
George

 

[bigjohn]

you have a vacuum leak. spray some wd-40 or carb cleaner around the intake and hoses. see if the rpm comes up.

 

[manitoufs]

Do you have Datamaster or Diacom? Your idle air control (IAC POS) can be monitored via one of these programs. The proper IAC POS is between 14 and 45. It can be adjusted by turning the Torx screw located hidden under the aluminum plug near your throttle linkage. Do it when the truck is at normal run temp.

Check this first before you get too deep into other things.

 

[JoeLutz]

Your idle speed is set by the chip controled by the ecm through the IAC valve. How are your ignition wires? Timing?

 

[Pittman]

Vacuum lines are good I checked those and the entire intake, ignition wires: the number 1 showed higher ohms than the others, It will idle great for about 3 minutes and then starts to bob. It only does it in traffic and at long waits like the drive through.

 

[ParTyBoy]

Vacuum lines are good I checked those and the entire intake, ignition wires: the number 1 showed higher ohms than the others, It will idle great for about 3 minutes and then starts to bob. It only does it in traffic and at long waits like the drive through.

Ever replaced your PCV valves?

 

[JoeLutz]

You could try cleaning your IAC valve and throttle body. that ususaly helps idle some. Also, just because the lines are good doesn't mean that you don't have a vaccum leak. It can be leaking arround the throttle body, uper to lower intake, or intake to heads. I would remove and clean the IAC first oh and Like said above, replace PCV valves and check the hose for kinks or clogged. My PCV hose was kinked once and made it flood at idle when first cranked.