Z06Vette.com - Corvette Z06 Forum

Z06Machine · 09-19-2008, 05:23 PM

04 Z06 6,500 miles

Blackwing / Ice Box - Connections fine
SVO 30lb injectors
Dynatech Long Tubes

Car is not driven a lot mostly to track events.

Drove is about a month ago to get an axle seal replaced at the dealer, ran fine.

Last weekend I fire it up and it runs like crud, rough idle, congested, missing. I put it around for awhile, let it warm up and cleared her throat a bit and it was fine. Acted like old car cars that had not been driven awhile. Put some fresh gas in and parked it running fine.

This weekend I fire it up and the same thing, but does not go away, far worse. Seems to be running on 6 cylinders. Rough idle, Revs in neutral you can feel it missing. If you give it too much gas the codes light up on the dash.

Po171 - Lean Bank 1
P0174 - Lean Bank 2
Po175- Rich Bank 2
Po300- Misfire

Po420 - TWC low eff bank 1 - Dynatech's have throw these since day 1
Po430 - TWC low eff bank 2 after long freeway runs and then down to idle.

I have searched most of the code info here, but most do not associate any actual issues other than the code. They do not describe that the car runs like crud.

My first thought was sticky injectors. But that seems remote with both banks calling out codes.

Ideas?

**jub jub** · 09-19-2008, 05:48 PM

If it ran fine before and not now, maybe you developed an air leak around the vararam thus setting the codes. Now your engine is running lean and the injectors add fuel to compensate for the lean condition. Too much fuel is injected causing the engine to run rough which in turn sets the misfire codes.

You say you have SVO 30# injectors. Have they been scaled to you engine via a tune? They need to be because stock injectors are 27.8# @ 58 PSI. The SVO 30# are rated at 43 PSI so at 58 PSI they are more like 36#.

Z06Machine · 09-19-2008, 06:25 PM

Jub,

They have been scaled via tune.

It's actually a Blackwing not a Vararam.

I have had the codes when I had a VR like others, but it never ran bad.
This is not a mild missfire, it is like you pulled two or more plug wires.

It fires up fine and will idle. Give it any gas at idle or load and it feels like I am missing cylinders. No hot rodding or anything. It just seems so odd that from one week to the next it acts so funny fo no good reason.

I keep thinking back to a couple weeks ago when it acted like that but cleared itself up. Kinda like blowing ou tthe carbon in our old cars.

Kinda temped to stick the oem injectors back in to see, but was hoping someone here had a similar issue.

Z06Machine · 09-19-2008, 10:02 PM

Well some more new data for those that understand this better than I .

Long term fuel trims on one bank are about 9% higher than the other from my scan. Short term trims did not register at all. So I ran an o2 test to see if it was going into closed loop.

All else appears fine there.

It is going into closed loop, but the O2 scan is making me think one rear is no switching. It stays lean till about 200 coolant temp then goes rich.

Any dyantech header owners have plugged cats?...starting to think that may be the issue. I can't find too much else in the charts that looks goofy to me.

**jub jub** · 09-19-2008, 10:31 PM

I think my next plan of attack would be to switch O2 sensors from left to right. If the lazy one is still on the same bank then try switching out to your stock fuel injectors. Also, look for burnt O2 wires that might have got burnt on the headers. I've seen that happen before causing what you describe.