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Discussion Starter #1
I have a 1989 5.0 GT Convertible Automatic and it started occasionally idling rough. It starts up instantly and theres no problem with it starting, but when it idles you can feel the car shaking and it makes a sound like a really lopey cam. When I drive you can hear that it almost sounds like it's missing. It has a complete lack of power until around 1750 rpm. The voltage drops a ton when i turn on any accessories (ie. headlights, heater, a/c...). The voltage also rises and drops at random times. I don't know if these 2 problems are related, but the way the car is running right now upsets me. I figured I'd see if anyone else had these problems before getting my hands dirty. I plan on replacing the fuel filter and running sea foam in my gas and replacing ignition components. The only other thing I can think of if that doesn't work is the battery, alternator or voltage regulator.

Any help is appreciated, as I'd love to get her running like a champ.
 

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Try testing your tps. My battery voltage acts strange at times too but don't trust the dummy guages. Bust out the voltmeter and test things. Your alternator could be on its way out or the belt could be slipping or not tensioned properly. Could be so many things. If your idle is surging though, test the tps. Mine surged like crazy because of a faulty tps.
 

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Well I was driving around 20 minutes after i started this thread and hit a good ol Michigan pot hole and the trans decided to not shift into 3rd or od so i took a look and turns out the TV has been the trans problem. I think it either came out of adjustment and/or the cable stretched. But when i hit the pothole the whole TB end popped off so I'm going to put that back on then probably replace the entire cable and get it adjusted professionally unless anyone has any tips on how to do it myself.

Btw thanks for the responses.
Also, by tps you mean throttle posi sensor right. Bare with me i'm 17.
 

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The usual causes of a rough idle are 02 sensors, MAF if you have one, TPS, IAC, and the number 1 culprit, a vacuum leak. Replace 02 sensors if it's been more than a year since you last have, clean out the maf iac and throttle body with carburetor cleaner and cotton swabs, and i heard in some cases cleaning out the distributor cap helps as well. As for the vacuum leak, check out youtube there are loads of remedies
 

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Yeah, throttle position sensor. Pull the codes man and try to pinpoint the problem that way so you don't replace parts you don't need. If you get the codes or get no codes, then post back and we can give you help from there. Most sensor failures, if not all, will throw a code.
 
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