I have an '87 GT with an auto tranny. Sometimes when I'm gently accelerating from low speed(1-5 mph) or a stop the engine seems to lose power (kinda hesitates) and I hear a popping noise from the back. If I let off the gas and try to go again everything is fine. Sometimes (again under gentle acceleration from a stop or when slow) the engine loses power without the popping, again if I let off the gas and try again all is well. What could be doing this?
Thanks in advance, Gareth

check your timing,do you get a check engine light?also could be a clogged cat or fuel filter.good luck,AL.

Ignition module, distributor, spark plug wires shorting, coil. Sounds like something in that area.

I had the same problem. I sprayed a can of carb cleaner in the throttle body and the car ran good from then on out. I think my timeing had somthing to do with it also. The only code I ever got was a bad MAP sensor. I replaced it and I havent driven the car since so I cant tell if it helped.

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Sean Heberly
Silver 86 GT 2.8
Killer Stereo System

I have replaced the spark plugs and wires, air, oil, transmission, and fuel filters. I don't get a check engine light except for when I'm starting the engine, but thats normal right? I had an error code for a bad MAP sensor, and replaced that, which got rid of the error code. How do I check for a clogged Catalytic Converter, and would that account for it only happening during acceleration? I will try Seanh's idea with the carb cleaner after work, and let you all know if that did it.
Thanks again, Gareth

a clogged cat can screw up everything my car wouldn't accerlate and would stall all the time till i had my exhaust system checked and replaced the cat... now it runs good as new.

oops, outta carb cleaner, guess I gotta go buy some... Anyway, if that doesnt make any difference I'm off to Midas and see what they say. One more thing I forgot to mention, I can hear a rapid clicking sound from the engine when its running, I think it the tappets, but I'm not sure, would worn tappets effect the timing? I will be working extensively on the engine at some point, but if this is going to become a serious continuing problem I may go ahead and replace the tappets, etc now.
Thanks again for the advice, Gareth

Gareth,

Sometimes you can tap the bottom of the kitty and exhaust behind it to determine if it is clogged. You should hear a difference in the resonance where/if the pipe is blocked somewhere.

William T. Thorn, III

I think our engines were assembled right next to each other. Mine clicks like crazy also, just like yours. When you hit the gas and your car loses power and pops, does it go away after the engine is warmed up? Mine does. I also notice the popping noise when I rev the engine at idle and let off real quick. Seems to start around 2500 rpms. Hows your gas milage? I am getting about 6-9 mpg before I started working on the car. I also had the bad map sensor code, and replaced it and havent driven the car yet. Is that clicking noise normal? The car has done this since I got it, figured it was normal. Thanks

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Sean's Fiero Page
Sean Heberly
Silver 86 GT 2.8 Auto
Going on to 3.4 in Jan.

Def. sounds like bad cat symptoms.
The "clicking" sound you hear is (more than likely) a leaky forward exhaust manifold (the one closest to the rear window). That is nothing short of a nightmare to replace to...believe me.
Now keep in mind you should hear a very subtle clicking noise..thats the injectors doing their job. But if its noticably loud, or at least loud enought that you can hear it clearly w/ the decklid closed..its the manifold....very common problem.
Seanh..I though my Formula got bad gas milage..but jeez, 6-9 is BBBAAAADDDD!!!

If the forward exhaust manifold was leaking, would I be able to smell it from inside the car with the windows/sunroof open? Also, when you say the Manifold is leaking, is that a hole in the manifold, or is it loose, or do I just need a new gasket?
Seanh, I am kinda a lead-foot, but I'm still gettin about 14 MPG(city) after replacing my oxygen sensor, was a little less before I did that. The popping/hesitation problem does seem to calm down after the engine warms up, but by that time I am in traffic, and usually only accelerating when I leave traffic lights. Accelerating in traffic was never a real problem, just from the slow starts or stops.
I can hear the clicking with the sunroof open, but not with it and the windows closed (especially when I have the radio up ) If my cat is clogged, I don't think it's as bad as btoth described, but I'm gonna check it when it cools down some (just got home from work). Would clogged/worn/dirty injectors cause a similar hesitation or popping?
Thanks for the help, Gareth

[This message has been edited by GarethWright (edited 11-02-2000).]

Leaky manifolds are notorious for making a clicking noise, you might not smell anything.
Fieros are notorious for leaky manifolds -it would be unusual if yours DIDN'T leak,

If you think your valve lifters are making noise you might want to check your oil -soon.

Stumble and hesitation? Never underestimate the crazy things that vacumm leaks can do. . .

I've been having similar problems, first it was hesitation from 65-70, then it started hesitating at real low speeds...I also sprayed carb cleaner everywhere and really cleaned up the the place...didnt notice much difference, infact it seemed worse the day after...havent done much driving since because my engine also hits my trunk and my cable bracket broke...the hesitation and over acceleration was probably a combination of low vacuum, clogged carb, and my throttle wires comming apart and getting stuck.

Hello everyone. Just a thought...but have you checked your TPS? Since the problem seems intermittent, and is directly related to throttle adjustments, I'd say the throttle position sensor is a good candidate for inspection.

How could I go about testing the sensor? Is there even a way to, or should I just buy a new one?

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Sean's Fiero Page
Sean Heberly
Silver 86 GT 2.8 Auto
Going on to 3.4 in Jan.