Computer Says Random Missfire WTF

[l3igl3ang]

Yeah i bought a TSI and its missing like crazy and im stumped i have a 97 GST so i took out the plugs and wires that i know work and put them into the talon and still it misses. I did notice when playing witht he injectrs unpluging them 1 by 1 that the car idel down alot like crazy but on #3 it didnt it was like it was not working or braily working! i took it to a guy who races 1g dsms and he said it has a weak injecter and said its eather dirty or valve but the car has a new head so i scratched out the valve begin the problem so what else could cause the injecter not to work right besides begin dirty?

 

[Talontsi150]

Have you tried replacing the igniter, its the thin black box located between the fuel rail and intake manifold 95-99. If its a 90-94 its located on the side of the intak manifold down by the timing belt.

-Marc

 

[l3igl3ang]

no have not did that what dose it look like?

 

[Bubbs Malone]

Check the coil pack, I was getting CEL numbers for cylinder misfires and replacing it cleared it right up. It idles smooth and has normal power again.

 

[l3igl3ang]

but would a coil pack cause a weak injecter cause when i remove injecter 3 it dose not even effect the motor much as like 1,2,4

 

[Bubbs Malone]

but would a coil pack cause a weak injecter cause when i remove injecter 3 it dose not even effect the motor much as like 1,2,4

I'm not sure, but in my case the coil was intermittant. If I messed with the wires and ran the car a bit, let it sit for 10 or fifteen minutes, it would run fine. But the next morning it was back to running on two cylinders. You can test the coil with an ohm meter, this might help.

As an afterthought, if you have low spark, the injecter will probably not make much of a difference.

 

[cavillac]

l3igl3ang- What you are doing is referred to as a "Power Balance test". When you remove that injector plug or plug wire you expect to see a drop in rpms.. if it is not making a difference than you have found the problem, now you need to see if you have a bad injector or if it is an ignition problem... Pull out the plug wire and place it close to a metal object like the motor pull hook loop or anything that will ground out the spark.. start the car and see if it is sparking.. if it is than pull the plug and inspect.. if you dont know what you're looking for just replace if for sake of me having to teach you.. if that doesnt help than I'd do a compression test and if that comes back ok I'd go ahead and throw in an injector unless you have a DSO to look at the offending an injectors waveform.