signs of a bad injector?

shaodome · Post by **shaodome** » Thu Jun 22, 2006 7:08 pm

Ok, so i redid my turbo setup and put everything together. Go for a drive and as soon as I hit about 5psi it all goes to hell. Starts to misfire rapily like it was blowing out spark or something.

Its runnign wasted spark in wheel decoder mode. Brand new coilpack and a nice white hot spark. New wires and new plugs (gapped a .030). The MS is fine because this same behavior is exhibited among 3 different Squirts. All are running 29q2 Extra on a v3 MS1 processor.

The fuel is good and timing is dead on. Attached is a datalog. The o2 is supplied by an AEM Linear wideband. I can't seem to find anything wrong electronically on the MS side.

A friend suggested it was a bad injector(s). Everything is fine n/a even at WOT. The problem develops at about 135kPa. All the plugs looik good an no signs of deonation and the tips look clean.

The car drives fine and idles like a rock.

shaodome · Post by **shaodome** » Sun Jun 25, 2006 8:56 pm

nobody?

fscott · Post by **fscott** » Mon Jun 26, 2006 7:50 am

I had this happen to me when I melted down one of my sparkplugs. It still ignited fine until boost came up, then it couldn't jump the gap anymore.

shaodome · Post by **shaodome** » Tue Jun 27, 2006 6:26 am

All the plugs are peachy

I even replaced them. Same problem.

jharvey · Post by **jharvey** » Tue Jun 27, 2006 9:30 am

I tried to view the xls, but was unable to get a nice graph out of it. How did you get the log? I tried opening it with mslvv.exe and MSTweak3000.exe.

shaodome · Post by **shaodome** » Tue Jun 27, 2006 11:13 am

The log is from Megatune 3.0. You might have to delete the top line in order to view it in a log viewer. You aren't going to see anything out of the normal in it though

PSIG · Post by **PSIG** » Tue Jun 27, 2006 12:51 pm

Check your running fuel pressure. The FPR should track the manifold reference and confirm the fuel inlet and outlet are correct or the pressure will not be what you expect.

Don't ask how I know that little tidbit...

David

PS: I only glanced at your log, but noticed a leaning of the O2 when MAP went higher such as at 93.1 seconds. The O2 kind-of rolls-off at the higher MAPs? This could be a sympton of misconfigured FPR. I'd have to study it more.

shaodome · Post by **shaodome** » Tue Jun 27, 2006 1:12 pm

The FPR is currently holding a static 44psi confirmed both by the in car digi gauge and a liquid filled gauge in the engine bay. The trail off in o2 is probaly from the misfiring in boost. The oxygen isn't burning so it shows up at lean.

keithmac · Post by **keithmac** » Tue Jun 27, 2006 2:20 pm

I had a similar problem and it was down to sparkplugs (at 170kp), 1 set were Denso Iridim IK20 (didn`t work) and the set I replaced them with IK24 (2 grades colder) worked a treat. What have you changed suince having the car running fine on boost? Could it be a dwell problem with the coils not having enough power to fire the spark across the plugs?

Boost is the highest load the ignition system will come under so will show up faults first.

shaodome · Post by **shaodome** » Tue Jun 27, 2006 2:41 pm

I have a thread going in the extra forum related to the coilpacks....

The only things that changed were:

Plug wires
new turbo pipes
new turbo
plugs for injectors (as opposed to hardwired)

It is my understanding that if each injector is firing at idle the "signal" that triggers them is fine, so I don't think the wiring is an issue.

jharvey · Post by **jharvey** » Wed Jul 05, 2006 9:43 am

Hmmm you said miss fire not back fire. Do you have an idea what your compression is when your at the 5 PSI? I'm assuming this was a turbo engine to begin with. If not then perhaps you are igniting early from extra compression.

Hmm compression ration of 8:1 would mean 14psi becomes 112PSI but a naturally aspirated engine would be lower so lets guess the losses drop you to 10 PSI or 80PSI when compressed. Now if you start at 19PSI you get 152PSI. Nearly twice the normal engine compression.