So i have been getting high idle. Thought it might be my iac so decided i was going to change it. Thought the upper intake would have to come off. Realized it didn't have to, so i rtved the upper intake back on due to not being able to get gaskets. All was good.

3rd ride out went to get on plane and at 2800rpm motor fell on its face. When i let back on the throttle it idles like normal and same thing again when i get back in it. So i watched what was going on and it would happen any temp. from 130-155ish. But it will happen 3-4 times then runs fine, till i let it sit. I never got around to changing the iac and now i have this problem. Any ideas where to look?

Its is a 98 502mpi. imco power flow exhaust. stock from what i know. I also notice all this has happened since i pulled the upper intake off. I replaced the rtv with the right gaskets and still same issue. Could i have screwed up a sensor while having the upper off? help me please

no one?

Have you put a scan tool on it yet? If not you will be chasing your tail. BTDT

Did you pull the upper plenum off all the way? Check the wires going to sensor on the back of the plenum. Also check the short vacuum line connected to the bottom-center of the plenum. You probably have to pull the plenum up to even see it. If it is/was unhooked that would cause your high idle problem.

i did pull the plenum off all the way. But the high idle issue was before i did that. everything is hooked up again i double checked myself. I do not have scan tool i will have to call around and see who has one.

not ideas on what else to check?

A scan tool would be ok, but might not show anything on this motor. There are several things to start checking, as it may not be directly cause by you changing the plenum gaskets, since it did run ok after you did that. Your water temp you stated was 130-155ish, it should go higher if it is stock. Check the fuel pressure on the fuel rail during the failure and see what it is and if it changes. Did you happen to knock any plug wires off on the cap or crack the distributer cap? Mine does wierd crap if I have a bad wire or plug, or bad plug wire connection. Start with the simple things and go from there. When's the last time fuel filters were changed?

so i did some more testing today..... same problem

fuel water separator was changed.

it will run fine ever bit of the way to 2700rpm and stay at that till i hit 28 then falls on it face.

also does this under no load (while in neutral)

I notice i am about a quart low on oil, is there an oil **** off sensor of some sort when low on oil?

I guess i am going to have to look for someone with a scan tool or change every sensor in the upper intake. tps, map, and air temp? I would assume its sensor related due to it happening under no load?

I would check the inside of the distributor cap for any cracks inside, loose wires, and pull the plugs. As far as I know, there is no sensor for oil, and 1 quart low wouldn't cause the problem. You really need to buy a fuel pressure gauge, connect to the fuel rail and see what is happening with that also.

when your on the water unplug the map sensor and see what it does,,,could have crap in the little hose that controls your fuel curve..

ok thanks guys i will look into getting a fuel pressure gauge
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also if i hit the throttle 5-6 time all of a sudden it works as it should with no problem? then i sit and it does it again.