Intermitant Idle

OUMike · June 14, 2006

Hey guys,

So I've noticed sometimes when I start my truck either my idle will be very low or will bounce around a little bit. The truck does not run rough or get poor fuel mileage. When it jumps around its usually no more than 500 or so RPM. Obvious enough to tell, but not really seeming to be harmful.

Could this be fuel injectors? Throttle body?

Engine is a 1994 4.3L V6. 198,800 miles.

OUMike · June 15, 2006

Nobody?? Surely there are lots of high mileage pre-vortec motors on here.

Wingnut · June 15, 2006

I don't know...IAC maybe?

Argyll · June 15, 2006

...Could this be fuel injectors? Throttle body?

Engine is a 1994 4.3L V6. 198,800 miles.

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I used to have a '93 longbed with a 4.3L V6, and I had almost the exact same symptoms you describe after 130K miles or so. Engine ran great, but after getting up to full operating temperature, it would do what I called "idle hunting" just like what yours sounds like it's doing (although yours is at start-up). Mine only did it after I would take it out of gear (manual shift) and come to a stop from cruising speed. After about 30-45 seconds then the idle would smooth out again. Mine didn't ever do this though when starting it up, only after it was warm.

I narrowed it down to possibly the Idle Air Control valve (as Wingnut says), a possible vacuum leak somewhere around the TB or intake, wasn't really sure. It never stalled or anything, was just annoying. I don't think it's fuel injector related. Maybe the TB needs a good cleaning. I never did figure out what exactly was causing mine to do it. I know this isn't an answer to what's causing it, but I'd guess it's in the TB components.

OUMike · June 15, 2006

...Could this be fuel injectors? Throttle body?

Engine is a 1994 4.3L V6. 198,800 miles.

<{POST_SNAPBACK}>

I used to have a '93 longbed with a 4.3L V6, and I had almost the exact same symptoms you describe after 130K miles or so. Engine ran great, but after getting up to full operating temperature, it would do what I called "idle hunting" just like what yours sounds like it's doing (although yours is at start-up). Mine only did it after I would take it out of gear (manual shift) and come to a stop from cruising speed. After about 30-45 seconds then the idle would smooth out again. Mine didn't ever do this though when starting it up, only after it was warm.

I narrowed it down to possibly the Idle Air Control valve (as Wingnut says), a possible vacuum leak somewhere around the TB or intake, wasn't really sure. It never stalled or anything, was just annoying. I don't think it's fuel injector related. Maybe the TB needs a good cleaning. I never did figure out what exactly was causing mine to do it. I know this isn't an answer to what's causing it, but I'd guess it's in the TB components.

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Thats actually a lot of help fellas. I'm gonna check my hoses and what not and see that everythign is tight. I cleaned my TB a while back but I dunno how good of a job I did.

MustGoFaster · June 16, 2006

dirty IAC most likely. remove it, clean it, then clean out the TB bore really good. then do a top end clean. will maek a world of difference.

have a spare set of plugs on hand if you do the TEC though - there is some chance that it will foul one or more of them.

change the oil when youre though and you'll be amazed at how well it idles, and low end throttle response is. I was blown away when I did it on my jeep. seemed like it took 50,000 miles off the motor.