Idle issues

344 Views | 4 Replies | Last: 15 yr ago by 80085
Dr. Doctor
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Long time since I have posted due to my summer job up in Arlington....

I have a buddy with a 1993 Chevy 2500 with the V8 350. The idle started getting rough so we first changed the IAC and then later the TPS. He changed the MAP sensor on the truck with a new one from O'Reilly's in their parking lot but it didn't do anything so they didn't charge him for it.

I have pulled the vacuum line going to the MAP and when you move it on and off, the fuel flow will change in accordance to the changing pressures. The EGR valve was removed, cleaned and it will open and close.

Now, of the vacuum lines, there are about 5 or so. One for the MAP, one for the PCV (which hasn't been changed, but should be shortly), one to a gas canister in the front of the engine and one to the other side of the valve covers (opposite of the PCV port).

I am convinced that there is a vacuum leak, but I am at a loss for where it is. The RPM is changing, going from high to low and then a big squirt of gas and then the surge to high RPM again.

There was a multi-pin connector on what looked like a round filter (said filter on the cap with a sponge underneath the cap) that was disconnected and the engine didn't change (RPM or fuel rate). Would that be a defective part (or what is that part)? The EGR and the canister both are not receiving andy vacuum pressure that I could tell.

The truck has 16k miles on it (yes, 16K), but the TBI has had a few cans of SeaFoam and cleaner run through it.

What say you TexAgs? I am stumped.

~egon
1agswitchin4lanes
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Intake manifold leaking ?
sts7049
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ahh, the infamous 350 rough idle
1agswitchin4lanes
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Egon, get a can of carb cleaner and spray little spurts along the intake manifold and see if the idle changes.

I bet the intake gasket(s) are leaking.
TexasRebel
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it isn't a rough idle...

it is eratic. ...and apparently it has me stumped, too.

It's a TBI, but I'm half tempted to suggest removing the TBI and installing a carb...

see if he'll bring it out tomorrow.
80085
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keep throwing parts at it, you'll knock the problem out eventually.



if that truck really only has done 16k over 17 years the next part you throw at it should be a throttle body rebuild kit
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