My car has been misbehaving the past couple of days. It has very little power coming off the line, lots of hesitation and some backfiring. Hunts for idle but does not cut off. When WOT, it will hesitate for a few seconds then just take off and have regular power somewhere between 3 and 4 thousand rpms.

compression test is as follows ( w/ sears guage)
front rotor: even bounces of 60 psi w/ shrader valve pushed in. builds to 100psi
rear rotor: even bounces of 60 psi w/ shrader in, builds to 110psi

I checked ignition w/ timing light and everything seems to be fine in that department.
Fuel pressure is normal. 38 at idle.
Cannot find any vacuum leaks.

I usually know right away what it is when something happens to the car, this time I'm a little worried. I possibly could have fried some electronics b/c my alternator might have been overcharging the other night, I was changing the wiring around, but it is charging right now.. mods in sig

thanks
Mike

 

forgot to mention, engine was warm, throttle was open, battery had pretty good charge

 

those compression numbers are fine.

 

TPS maybe?

 

I say its still a vaccumm leak. U try using a spray bottle full of water and spraying all the vaccum lines? If u are spraying and it runs good for a few seconds, then turns to crap again, u just sprayed the problem area. The water seals it for a few seconds temporarily.

 

i thought the numbers werent too bad for the guage i was using

I'll take it up to work this week. we got a machine that blows smoke into intake, its used for evap leaks mostly. if its not that I guess i'll hook it up to labscope.

 

Uhm.. what? What does the smoke do? Whats a "labscope". You mean oscilliscope? And if so whats that going to tell you?

 

umm.. yeah. it sends pressurized smoke through intake and if there is a vaccum leak then smoke comes out. much better than the old water bottle trick. its what garages use. yes, I mean o-scope. call it what you want.

 

Oh you said blow the smoke into the intake. Thats where i got confused. Ive never heard of that, but it sounds like a good idea. As long as the pressure isnt too great and blows any vaccumm caps off. I still dont understand what a scope is going to tell you though, other than that your getting ignition signals i guess.

 

smoke machine showed no intake leaks. the thing only pressurizes up to 2psi so it will find most vacuum leaks but maybe not all boost leaks.
that lead me to believe it was pressure sensor, afm or computer.
turns out it was a faulty pressure sensor. I was just messing around and unhooked the thing and the car ran great. the scope would graph any sensor on car. If i wanted to I would probably have found dead spots on the pressure sensors output with the scope, but I didnt go that far b/c I'm 100% confident thats what it is. I might do it tomorrow if I get bored.