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I have a 94 Intrepid with a 3.5 ltr engine thats been acting very strange lately. For some reason whenever I place it in neutral, the engine sits idle at over 2000 RPM. Usually it stayed around 1000 RPM which should be normal. What would cause this sudden spike? I've also noticed that whenever I'm driving, the car will very slowly start to increase in speed all by itself. What would cause this and where should I start to look when troubleshooting? :confused:
 

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you have either a vacuum leak, or the notorious intake gasket problem that occurs on the 3.5. Or you may have something wrong with your IAC. and I think that this thread would probably be better suited for the First Gen, General Discussion...
 

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This is not a hardcore tech question and does not belong in the hardcore tech section. You are far more likely to get the best answer by posting in the best possible forum. Good day.
 

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garfield, get a can of carb and choke cleaner, with the car running, spray the cleaner around the plemun, and vacuum lines, when the pitch changes, you have found your leak. then its a matter of replacing parts/lines.

HTH
Bruce
 

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i had a 90 sunbird before this intrepid and it did the same thing. I screwed around with alot, IAC, EGR ,vacuum leaks but it ended up being the computer.
 

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hey dont knock the sunbird, that thing ran for 225,000 miles. I only paid $650(113,000 miles) for it and sold it for $500.
 

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When you install an Idle Air Control, the car will run at these high rpm's until the computer resets itself. It sounds like it is sticking open. So the computer cam be telling it to stay open or it may just be stuck. It's not a big deal to check. Look for the switch in a manual. It is to the bottom side of the injector. The opposite side of the throttle is the TPS or throttle positioning sensor. Just unplug it and remove the two bolts. Remove it and check to see if carbon has built up around it, or on the seat.You can use a carb cleaner to shoot the piston and the spring. Then reinstall. The car should go up to about 1800rpms right when you start it, then the computer would knock it down by closing the valve. If it doesnt, you need to drive the car over 40 mph to get the computer to reset the system. I changed 4 of the 16 sensors on the car because it runs rough when it gets hot. It seemed like it was running better right when I changed the part, but as soon as you drive over 40 and thr computer reset everything wrong it kept going back to the same problem.

Also, make sure the screw that opens the throttle is all the way closed. Alot of times, people will have trouble and just turn up what looks like the idle speed screw. This allows too much air to the engine and the computer will correct it as soon as you drive over 40 mph. When the computer resets all the sensors the car will run real rich and get terrible fuel mileage. If it was a mechanical seal like an intake gasket it would do it all the time, so since it is sparatic, it seems like an intermittent signal to the sensor. the only other easy check would be the MAP sensor, a plastic rectangle on the intake. Before you change it, just remove it and make sure that ther is not carbon built up in the port which would not let the MAP read the correct vacuum
 

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Response

To the folks concerned with high idle....you may want to make sure your throttle linkage isn't getting hung up....vacuum leak is possible but check the cruise control mechanism out as well...make sure it doesn't look as though it's actuating the throttle with out being summoned to do so. IAC is also possible culprit. Troubleshooting path should never blaze right through the big&obvious basics first. I.E. you went out to buy throttle body cleaner to clean IAC.....go through the trouble to do the job, only to find out the throttle was getting hung up with something, or there's a pile of acorns in the air box...peace.
 

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I have a 94 Intrepid with a 3.5 ltr engine thats been acting very strange lately. For some reason whenever I place it in neutral, the engine sits idle at over 2000 RPM. Usually it stayed around 1000 RPM which should be normal. What would cause this sudden spike? I've also noticed that whenever I'm driving, the car will very slowly start to increase in speed all by itself. What would cause this and where should I start to look when troubleshooting? :confused:
I am having same issue with my 1995 dodge intrepid 3.5 with it after starting its rpm is around 1500 then running up to around 2700 rpms and staying . Changed intake gasket, iac, map, cleaned all out still idling fast.















Response

To the folks concerned with high idle....you may want to make sure your throttle linkage isn't getting hung up....vacuum leak is possible but check the cruise control mechanism out as well...make sure it doesn't look as though it's actuating the throttle with out being summoned to do so. IAC is also possible culprit. Troubleshooting path should never blaze right through the big&obvious basics first. I.E. you went out to buy throttle body cleaner to clean IAC.....go through the trouble to do the job, only to find out the throttle was getting hung up with something, or there's a pile of acorns in the air box...peace.
 
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