Billygoatkid

So my 88 l98 is having idle problems, more so when it warms up.
It starts at 1000, settles to around 800 but after I drive it , goes up to 1200-1300 rpm
I did the iac reset and adjusted tps to .54
I can get it to idle at 550 with the reset procedure as per Lars notes. But after plugging in the iac it goes back to high rpm

I've cleaned the tb and timing is 6' , I did being the timing down as it was at 14 but it did do the same thing before. Regardless of timing. New to this car as I've had it only since October and want to drive it now the weather is warm

Thx for any suggestions

antfarmer2

Look for vacume leaks

JCrock

Yep, what antfarmer said. Mine does the same thing. A bit of checking found an intake manifold gasket leak. That will be job one this spring.

Billygoatkid

Thx for suggestions, but wouldn't it be doing it all the time if it's a vac leak? Say it idles at 1400 when warm...I can shut it off and start it right back up and it will idle at 750-800

playsdixie

tb butterfly could be sticking or one of the tb cables is sticking..disconnect the cruise cable and see if that helps...

Billygoatkid

Ok I have the cruise cable disconnected already. Could the butterfly stick even with the throttle stop touching?

JCrock

That is exactly how mine behaves. Besides, it's cheap and easy to check for vacuum leaks.

Billygoatkid

Ok , interesting. I've checked hoses but not the intake or runners. What do you think of propane test? Or how did you find the intake leak?

JCrock

I used a can of starting fluid. It all works the same. Spray it on the gasket areas and see if the idle increases.

VikingTrad3r

look up scotty kilmer cigar vacum leak test.

and also, you might be finding that as parts expand ever so little with heat, the vacumn hole gets a bit bigger. which explains why its worse after its heated up.

agillings

Mine was doing the same thing, I visually inspected and verified each vacuum line. I found many leaks, buy a roll of vacuum line and follow the diagram. There should be a vac dia under the hood. mine is in the front left corner next to the radiator

Billygoatkid

Thx guys,
I'm going to check tonight.
Drives me nutz as the car runs strong other than this annoyance
Was getting a lean code, so makes sense about a vac leak

Dt86

In checking your vacuum lines take a look at your vacuum check valve. They get brittle from the heat. I had one that developed several small holes at the neck where the vacuum line slid on. Also checking your runner and plenum bolts is a good idea.

Billygoatkid

Where is the check valve?
Thx

agillings

The Vac valve is right next to the dist on the passenger side one line rus to the inside of the car and the other to the plenum.

Does you ac/heat work? I mean a lot of air coming from the vents?

Billygoatkid

Not much air/heat at all

I think your on to something

Billygoatkid

My cruise doesn't work either. Does vac come from here to?
I was going to try to trace back from the cruise control.

Billygoatkid

Hey, so I found a hose by my blower fan off and now my vents are blowing air, which I didn't have before. I used a half can of carb/intake cleaner and could not find any leaks. My vac gauge reads 21 off the plenum. It was idling at around 1000 in the garage.
Think I'll take the TB off later once it cools down and take a look at the iac.
Any other ideas?

playsdixie

remove the Iac and clean it...especially where it seats in the tb...then reset it and do the min idle adjustment......

Billygoatkid

Ok thought I had it licked today. I bought a new iac, cleaned the tb up really good put it together, set it using procedure for idle and tps . Was working great. Then I get an error 33 code. I check it out as its a maf code, then realize I had not plugged it in. I plug it in and bang I'm back at idle of 13-14 again. With it unplugged I get 700. What's going on? No code plugged in yet idle is super high, unplugged it idles nice and low.