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Discussion Starter #1
I've got a '98 Mercury Tracer that I bought a little over a year ago from my dad that had its entire engine rebuilt 30,000 miles ago. When I bought it, it had a rough idle problem. Now the problem has escalated to wierd proportions. The Engine idles fast, rough, shakes the steering wheel when stopped in any gear ( park, drive,). The car also acts like it wants to stall on certain minor uphill or downhill grades, but if i mash the throttle, it drives fine.
It hunts for gears at around 60 mph and jerks the car back and forth, and occasionally gets "stuck" in a gear and I have to take my foot off the throttle or mash the gas and then there is a delay and the engine revs up really high then kicks into the next gear. soemtimes the engine revs slowly even if I have the pedal to the floor when i'm taking off from a standstill. It acts like it wants to die out when I brake to a stop, and acts better when I let go of the brake. I'm at a loss of what to try. Heres a list of things I've replaced :

Idle Air Control Valve
Oxygen Sensor (Before Catalytic converter)
Fuel Filter
Air Filter
Fuel Pressure gauge

I also cleaned the throttle body and adjusted the butterfly valve. If anybody has any clue to what this may be, please let me know. Any advice would be greatly appreciated, I can barely drive the car as is. Thank you.
 

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check the PCV tube, escpecially the end at the top. that little elbow seems to turn to mush and cause problems.

also replace the PCV valve.


is the check engine light on? what codes does it have?
 

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what pextor said..i had a problem similiar to that.

In fact pextor helped me with that ^-^


And a compression test would be a nice help too.
 

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pextor asks an important question... Has the check engine light ever come on?

Have you plugged in a code reader to see if the car's computer has any trouble codes stored in memory?

As a wild guess, I'm thinking it might be the throttle position sensor (TPS).. If the sensor is out of spec and faulty, the computer won't be able to tell how hard you're stepping on the gas.. That could cause the problems you are describing.
 

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Discussion Starter #6
No Check Engine Light, but its been hooked up to a computer, twice, with nothing. I would suspect the Tranny, except Ive taken it to the shop twice and they say its in good condition, oil is clean etc. I replaced the pcv valve, but i'll check the hose. I might want to do a compression check, just for the heck of it.

98_Jim, i think your on to something, that might be the cause. Is there also an idle speed control? Before I replaced the IAC, the speed of the engine would change every couple of seconds.....

Thanks for the help, any more suggestions, keep em comin...
 

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Sounds like an uneven vacuum leak, which could very well be caused by a deteriorated PCV tube or: Your EGR valve, power brake booster, bad intake gasket, or leaking EVAP system. Just some other things to play with.
 

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Discussion Starter #9
power brake booster you say? Could that explain the really bad engine shudders when I apply the brakes? the leak could be minro and get worse when the brakes are applied? come to thing of it would this leak affect stopping power, cause i have to put my foot down quite a bot to keep it from rolling in drive....
 

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Yes! Your power brakes use vacuum to boost stopping power. If the booster's diaphragm is leaking or torn, it creates a MASSIVE vacuum leak when you are on the brakes and also you lose significant stopping power. I would say replacing that wouldn't hurt.
 

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Discussion Starter #11
Ethangsmith, and everyone, thanks for the really good help. I'll fix what I can and let you know what success I have.
 

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As ethangsmith said and I agree it is most likely a vacuum leak either from the check valve to the booster or the booster itself.
 
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