1999 Mercury Tracer runs really bad

STEVEO

MEMBER
1999 MERCURY TRACER
4 CYL
FWD
MANUAL
170,000 MILES

Have owned car for 70,000 of it's 175,000 miles. It's been surprisingly trouble free. Changed plugs, wires, and oil two weeks ago and was running great (eliminates wire mix-up). Suddenly car is hard to start, rough running, and cannot get engine over 2500 RPM (even in neutral) without really working the throttle (softly). Low power. No codes (did get a P0500 after working on it but appears to be unrelated), No unusual smoke. Replaced: fuel filter, Air filter (very dirty), PCV valve. Checked spark, compression, PCV hose, Fuel pressure (35-40), MAF(cleaned), CAT covertor(dropped CAT off exhaust header). Still working on testing some of the other sensors one by one (TPS, knock.). After all this, it still runs really bad, pretty much undrivable. My question is this, I suspect the timing belt has slipped a tooth, is this possible and the compression to still be good? (All cylinders 180, unknown what reading was prior to engine trouble)

4 Replies

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Yes, the timing belt could cause the problem, and you could still have good compression. What happens is the ignition timing gets thrown off and will fire too late (after TDC) and cause an extreme power loss. Yes, the valves will open at the wrong time too, but one tooth on the belt can allow you to still have good compression.

Honestly, that is the 1st thing I would check at this point.

Let me know what you find.
Joe

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Sunday, January 2nd, 2011 AT 12:10 AM

STEVEO

MEMBER
3 POSTS

Thanks, that's the info I needed to coax me into tackling the timing belt. And yes, that was it. Not only did the belt skip a tooth (or more) but check out the picture. Count'em, that's 14 teeth in a row missing. I'm surprised the car ran at all.

Got a new belt on. Was surprised at how (relatively) easy it was to replace. No major items to remove, or motor mounts. Some of the bolts a little hard to reach but not too bad. I also replaced the timing tensioner/idler pulleys since the spring seemed a little weak. I never would have guessed that timing could be that far off and still have good compression. Hmmm, I wonder what the compression is now? Naw, I'm tired of messing with it. Runs like new!

Thanks Joe

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Sunday, January 2nd, 2011 AT 10:12 PM

STEVEO

MEMBER
3 POSTS

That should read pulley not pulleys. The timing belt only has one.

Thanks again

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Sunday, January 2nd, 2011 AT 10:25 PM

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Honestly, I can't see how it ran either. Regardless, I'm glad it's fixed. You take care and let us know if you have questions in the future.

Happy New Year,
Joe

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Sunday, January 2nd, 2011 AT 10:34 PM