What did we do wrong? (89 Mustang 2.3L Problem)

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It's been quite some time since I last posted, and I thank all of you who gave my son and I guideance on repairing his 2.3L 89 Mustang with the hole in the intake manifold that caused it to act like the head gasket was blown.

Well, we finally got the timing problem figured out and got the car to start... but that's where our problem begins. We think we put everything back together as it was when we took it apart, but when we start it, the engine races to 4,000 rpm so we have to shut it down.

We didn't do anything to the throttle-body, just removed it as a unit and put it back on as a unit. We had a minor timing problem when we first replaced the timing belt, so we took if off and reinstalled it correctly, and were able to get it to start by making a minor adjustment in the timing at the distributor.

Anybody have any thoughts on what we did wrong that caused this over-reving at start-up?

What do we need to do to fix this?

Is this something that we'd be better-off taking the car to a repair shop to figure-out and fix?

Thanks for any suggestions you all may have!


posted by  cargoman

Well Lee, I wouldn't be too concerned...it sounds like you may have an intake leak somewhere...whether it be at the manifold gasket or the throttle body gasket. First off, I'd recommend checking to make sure that the throttle body is fully closed, sometimes the throttle cables can get hung up. If that's all good, then I'd recommend checking for vacuum leaks at all the hoses that go to the intake/throttle body. If that's all fine, then try spraying starting fluid around the intake(where it bolts to the head), if the idle speed changes, then you know your problem is there. If that's fine, try the same method where the throttle body bolts to the intake. I understand you don't like the car racing to 4 grand upon start up but these tests will have to be performed with the engine running.

If you perform all the tests I've gone over and you're still having problems, it may then be time to take it to a shop. Good luck!

posted by  Sick88Tbird

Thanks Sick88Tbird,
We'll try your suggestions and see what we find.

Is it possible that a code in the Electronic Engine Control could have been re-set to WOT (Wide Open Throttle)? I wouldn't think so, since all the work we did was with the battery cables removed, but it's a thought since that seems to be what's happening.

Thanks for your help!


posted by  cargoman

Nah. But what you said made me think of a suggestion. Check TPS voltage with a digital multimeter.

posted by  DodgeRida67

Thanks, DodgeRida67, we'll check that too.

For others that may read this, the important sentence from my original question may not have come across clearly. I said: "..., but when we start it, the engine races to 4,000 rpm so we have to shut it down."

We should have added a clarification to this; the engine never does slow-down from this start-up point. We shut the engine down while the rpm's are still climbing, which is why I thought a code in the EEC may have been changed, somehow, to WOT.

We're still having a problem with this, so any and all comments/suggestions are very welcome.


posted by  cargoman

There's one fly in the ointment of the people wanting to look at the WOT switch and the TPS that is so obvious only Tbird see's it. While there may be a problem with one of those input devices (sensor), the only thing they're going to do is add or subtract fuel. To have an engine that won't run below 4k rpm you would have to have one hell of a vacuum leak or more likely a throttle plate hung open plus the additional fuel required to run that fast. Honestly for the engine to "idle" that fast you're going to find multiple problems. Go back to the basics and start there and don't overlook anything. Even if you've already checked it three times... Check it a forth.

posted by  vwhobo

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