I am trying to learn what's been going on.

My car has been missing a cylinder for a few months, finally I wound up sending the fuel injectors out to PTE. They tested all the fuel injectors out, all but one was normal. It's the abnormal one that I want to learn about.

They said that the injector flowed fine at first, but after it ran for a while the injector flow rate dropped off like 30% after a minute or two. And guessing from the way my car's been driving, it probably would have continued to drop (my O2 sensor showed VERY lean on the right bank, where this injector came from). He backflushed the injector and said after that it ran fine, but I don't know if I should trust it.

Why would an injector flow rate drop off after it runs like that? Can I trust this injector? I don't want to go lean in one cylinder and lose a head gasket or worse...

Thanks!

-Bob Cunningham

Two reasons I can think of why flow rate would drop off. 1. If the injector is getting plugged up, a backflush would solve the problem. 2. Resistance in the winding may increase due to heat or vibration. Unplug the injector and look at the pins to be sure they are clean. You may want to run an ohmmeter across the pins when the injector is hot to see if there is any excess resistance. If the car continues to miss, I would go ahead and replace the injector.

Well the reason I sent them the injectors in the first place is that the engine seemed to be missing a cylinder. Usually a dirty injector has a consistenly low flow rate, this seemed to have a variable flow rate (I also guess heat related). The injector ohm'ed at 16 before I sent it in, so that was fine, unfortunately I couldn't do that test after the engine was running for a while.

Anyhow, I am not gonna take any chances, I am going to replace the injector.

Thanks!

-Bob