PT Cruiser Backfire

2003 PT Cruiser, Std Transmission, Basic Model.
This summer I replaced the plugs, Camshaft Angle Sensor, and both O2 Sensors. The car has stopped stalling and I have no codes. It has good power and runs smoothly. However, occasionally while in fifth gear, the car will backfire and come out of gear. It can put it right back into gear and the car seems to run fine. This only happens in fifth, does not happen consistently. It seems to happen between 2000 and 2,500 rpm, but I can’t be sure. Any thoughts?

As a WAG on this, it sounds (only to me, so far), like an injector is sticking or leaking and allowing excess fuel - enough to cause a backfire at the wrong time.

That would also require that there’s a spark of some sort to ignite it. Does this engine have dual coils? I’m not sure it’s there on that motor (I’m assuming you have the 2.4 SFI), which I’m unfamiliar with.

Hadn’t thought of an injector. Seems like it will be kinda hard to track down a specific one. Any thoughts?

I had a massive vacuum leak which had apparently been there for ever and the computer had “learned” to adjust for. After plugging it, I “reset” the computer by disconnecting the battery for about a half an hour. Now it no longer backfires, but I’m back to my original problem of stalling when coming out of gear and/or letting off the gas. This appears to happen randomly. I had already replaced the Cam Angle Sensor prior to this issue, to no apparent avail. Getting no codes.

HOw is your idle quality? Are you saying that your engine wants to dies between shifts? As thought it is unable to idle on its own? I would look into your air idle control valve…they get gummed up with carbon and other Schmutz…remove and clean it out and re-install…see if it improves.

I would also remove and clean your MAF sensor…this is a common issue and cleaning the MAF is quick and easy to do…usually returns great results. You can clean it with Starting fluid/Brake Cleaner/ OR MAF spray cleaner. The MAF has a thin filament inside it…this filament is heated…the vehicle measures the temp or resistence of this filament to determine how much air is passing by this filament…when the filament is dirty or oily…the engine cannot determine how much air is flowing past and subsequently how to fuel the engine… Pretty important stuff…

IN FACT My APOLOGIES…Clean the MAF FIRST !!!..see what you get then move on to the AIC valve… I bet its a dirty MAF… If your vehicle idles fine then it prob isnt your AIC valve being dirty… DO the MAF and let us know.

“Schmutz” a man after my own heart. I’ll look at the MAF and get back to you. Thanks for the tip!

Well, it ain’t the “MAF”. It had a small bit of what looked like soot which I cleaned. Still stalling. I’ll check the air idle control valve as soon as I can. Damn loss of daylight. Go to work in the dark and get home in the dark.