03 A4 Vert loss of power at WOT

[03WhiteConv]

Struggling with this problem for a while now.

The car has 30k miles and is all stock, I am the second owner.

Car is throwing two codes P1415 and P0600, I have already replaced the drivers side AIR Check valve but the code still shows up every morning

The P0600 misifre code only happen at WOT. I can feel the power dropping off and the engine starting to run rough as it approaches 4500RPM, If I push it any farther I can hear a rattle and then the P0600 posts. Otherwise, the car pulls strong although I can't break loose the tires even with the AH/TC turned off.

I have replaced plugs (bosch plat +2), plug wires (OEM replacements), disassembled, cleaned, greased and reassembled all of the chassis ground connections. Havent got to the one behind the drivers head yet (not sure how to get to it).

Have not replaced the fuel filter or checked the HO2 sensors yet. Hoping this is not a valve spring problem or a broken rocker.

Anyone have some thoughts on this one? C4C5Specailist??

[BruceF]

I'd switch back to the stock plugs and reset the codes and see if they come back. These cars don't like the Bosh plugs in my experience.

[03WhiteConv]

The problem started prior to the plug change and is identical since. What kind of specific problems have you seen with the bosch plugs? I've been running them in my cars for the last 12-15 years, but never in a Corvette. I am interested to hear your opinion. I really don't mind buying a new set of plugs, but I don't want to just throw money at the problem unless I am sure. The original OEM plugs I pulled from the car really didn't look too bad so I don't think they were contributing to the problem. I just changed them to be sure.

[c4c5specialist]

HI there,
The latest is 41-110 ACDelco iridiums.
Bosch does NOT LAST as long and will not assist in your condition.
And there is no DTC code P0600, so please relist your codes.
Allthebest, c4c5

[03WhiteConv]

Sorry for the confusion there, I meant P0300 Random/Multiple Misfire. I put an actron reader on it once and got the P0300 consistently 4 or 5 times with the exception of one P0305.

[c4c5specialist]

HI there,
I would be looking to first change the spark plugs to the 41-110, then check to see how it runs.
From there, an AFIT fuel injector test would be my next course of action with a fuel pressure test.
Allthebest, c4c5

[03WhiteConv]

Is it possible to do the fuel injector and fuel pressure test myself or is this better done in the shop. I don't mind taking it to the dealer for specific tests, I just don't want to hand over my wallet.

Are these tests that a good non-dealer mechanic could perform? Will the procedure include a high RPM test, I'm a little worried of what damage might be done if there is a mechanical failure in the valve train that just hasn't gotten out of hand yet.

Would you recommend a new fuel filter before I go too crazy? I didn't mention that I also did a Sea Foam treatment quarter can through the PCV, quarter through the brake vaccuum and the rest in the tank. Is it possible that the tank let some crud loose and the filter is gunked up?

[03WhiteConv]

Bump..

[03WhiteConv]

OK so I found out that my local autoshop on the USAF base has a Genisys diagnostic setup and I was able to use it for $5/hour.

I changed out the plugs and there was no change.

I switched the HO2 sensor side-to-side and it seems to have resolved the P1415 code.

I ran a fuel pressure test and got about 53 pounds key on engine off and 60 pounds with the engine running at idle and up to about 4000 rpm. Fuel seems ok

I also looked at a bunch of sensors, here are the results:

All at idle:
HO2S Bank1/sensor1 39-929 mV
HO2S Bank1/sensor2 69-733 mV
HO2S Bank2/sensor1 65-916 mV
HO2S Bank2/sensor2 807-851 mV

Ignition Signal 13.0V

Reduced Engine Power Inactive

STFT Bank 1 Avg did not exceed +2.3%
STFT Bank 2 Avg did not exceed +1.6%

LTFT Bank 1 Avg did not exceed -4.7%
LTFT Bank 2 Avg did not exceed -0.8%

Loop Status Closed

MAF 5.41 g/s
MAP 9.45 inHg

All injector PWM @2.55

It is misfiring on virtually all cylinders at idle and heavier on 3 during accelleration. The engine load never went above 35% when I got on the throttle.

The bank 2/sensor 2 doesn't look like the others, Does that indicate a bad sensor? Could a rear O2 sensor cause all of these problems. I'm ready to put it on a trailer and drag it to Corvettes of Dallas!!

Is there any thing else I ought to look into?

[03WhiteConv]

I drove the car to work this morning and it set the P0300 within 5 minutes of normal driving (under 55 mph). I filled the tank with premium (91 octane is the best we get here) and parked it. THe engine light was on solid and it had a P0172 and P0175 in addition to the P0300. I also noticed this morning when I started the car that the exhaust smelled rich (before I filled the tank).

Could this be caused by that rear HO2S running so high all of the time?