s3cret_stang

Well at the track last night during my last run something decided to go. There was no boom, or pop, smoke, or anything like that it just seems like it's misfiring now. Fuel pressure is good, when I hit the gas boost is good, it just idles kind offunny and the engine is shaking a lot. Also the exhaust is backfiring alot now. Just looking for any ideas of what it might be.

CobraStangGT16

Might have popped a vacuum line...that shows the characteristics of a vacuum leak.

Check all the vacuum hoses to the engine, and make sure they're all secure. Also listen for any hissing under the hood.

Hope that helps.

NaughtyGeek

I understand how that would indicte vacuum leak on carburated engines with vacuum advance on the distributor, but what component on our cars would be affected by a vacuum leak to cause the problems he's describing?

CobraStangGT16

Well I know that when that crossover hose from the intake to the driver side vave cover breather cap pops loose, my car runs like shyt. And sometimes when the car is not getting sufficient air at idle, such as an IAC block. It just seems to have to do with air, not fuel or spark. Maybe you're just misfiring, who knows...

Any noises from the engine that aren't normal?

NaughtyGeek

Did you notice the problem during the run or when you went back to idle after the run?

If during the run, what did you notice? A drop in power, did it backfire during the run under acceleration, etc....?

s3cret_stang

Yes, if I am accelerating slowly it will backfire and miss, and in idle it backfires a bit too. I checked all of the lines and it doesnt seem like it's leaking anywhere and on the boost guage its 20 in hg like it always is. I am going to check the spark plugs, hopefully one of them just died.

Zanador

Did you pull your plugs to check for irregularities yet?

AJ06GT

I'd check the plugs, wires, and coil packs. If you're not getting spark in one of the cylinders, then you obviously find your misfire, and it will dump the fuel into the exhaust which will cause AFTERFIRE, not backfire.

justingt

I'm almost positive you blew a plug. Same exact thing happened to me a few months after i did my own plug replacement. Sucked cuz i ejected a plug and stripped the threads and ended up needing a new head.

CobraStangGT16

justin, that sucks!

One of my plugs actually shot out of the head...and I just had Ford re-thread it for a whopping $600. ONE FRIKKEN SPARK PLUG THREAD!

Don't worry though...if that happened to you, you would DEFINATELY know something was wrong...you'd hear what sounds like open headers. [&:]

MAKE SURE YOU USEA SMALL HOSE ATTACHED TO THE SPARK PLUG PRONG TO THREAD IT BACK IN INSTEAD OF A WRENCH OR YOU RISK LOSING YOUR THREADS AND MAKE THE SAME MISTAKE ME AND JUSTIN DID!!! [:@][>:]