Rough idle when using air and accessories

**aberlin** · 05-04-2009, 02:17 PM

Hey guys,

I have a 1990 Suburban 2500 5.7 V8 4x4.

Just got a tune up including new wires, spark plugs, cap rotor etc.
multiple vacuum leaks fixed.

I have to let the car warm up for about 5 minutes or else it sputters under the load of the trans being engaged. Also when in park, or drive, if the air conditioning is on it starts to sputter wanting to stall. I also noticed when headlights are on, it wants to stall when idling. Runs perfect when on the gas pedal.

Any suggestions? Is there an Idle up valve? is there idle speed adjustment? what should i be looking at.

Thanks,
Alex

**L0sts0ul** · 05-04-2009, 11:27 PM

dirty injectors? fuel filter? Air filter? PCV valve? fuel pump, and or pressure?

lots to look at for this problem.

you have TBI setup right? or are you carb?

**silveradotrailblazer** · 05-05-2009, 11:08 AM

I would take off the throttle body and clean with a good throttle body cleaner (CRC works well) and take out the idle control valve and clean, they get carboned up and wont move in and out. Also check out your altenator.

**opusd2** · 05-07-2009, 02:34 PM

Check your ecm in the distributor to see if the timing is off. It the problem usually happens under load, chances are it's a timing issue

**wolfie** · 05-07-2009, 03:16 PM

I have had a similar issue in a chevy car. the fix for me was new alternator and cleaning the wires on the battery for better current flow. if the alternator isn't bad you could try checking out its nearest components in the electrical system. other than that I'm just not sure. wish i could be of more help.

**aberlin** · 05-07-2009, 04:20 PM

I have new wires, new fuel filter, new fuel pump, new plugs, new cap and rotor, it is not carborated. I think I'll start with the throttle body cleaning and the idle valve. hopefully that does something.

**daddytech** · 05-07-2009, 04:35 PM

need to start with the fuel filter and work your way up from there , could also be the fuel pump not delivering enough fuel to the carb. Might also try running some Seafoam through the brake booster vacuum line , run the whole can through it , the truck will smoke a while but when it's done you should notice a big difference.

**RWK** · 05-08-2009, 02:29 AM

The idle problem on my car was fixed with a new Idle Air Control Valve. The old valve would extend out and not retract. When you turn on the A/C, the IAC Valve should bump up the idle a little.