2004 Vette convertable.

I bought this Vette in very good condition 5 years ago. A previous owner had installed a Vortex air cleaner. I started getting P0101 DTC's as soon as I started driving it hard. Had 2 reputable vette mechanics look at it and and they cleaned the MAF sensor, but the code kept popping up. Since it's a C5 I cleared the codes myself using the DIC. This year P0171 (oxy sensor) codes started coming up on medium acceleration like freeway entering. I get a small hiccup type miss as I'm accelerating. Took it to a Chevy dealer who charged me $260 for diagnostic time and realigning the fit and clamps on the Vortex snout. The codes came back on within 50 miles. Anybody have experience with this type of problem.

 

Have you just been clearing the MAF code for 5 years? Or it went away for 5 years and just recently came back?

I think there are two best options.

1. Find a reputable tuner in your area and have him check the tune. It's no surprise to get MAF codes with an aftermarket air intake if the car was not tuned after install.
2. Install a factory air intake.

 

Thanks for your reply.
Yes, I've been clearing the MAF codes from time to time. Sometimes, in cooler, humid air, they clear themselves (as does the oxy sensor code). How do I find a reputable tuner?

I've thought of reinstalling a factory air intake. Would I lose any performance doing that?

 

Hi !!
So you are no longer getting a P0101 just a P0171 ??...The P0171 is bank specific (bank 1 /drivers side) so let's say a leaky bellows after the MAF sensor where it connects to the TB would not set a P0174 "UNLESS" bank 2 fuel trim is below 23%...if it's 22 % no P0174 DTC...a leak would set off both DTC's !!...do you have a scan tool ??...I always suggest to C5 owners with almost a 20 year old car that it is very helpful to have one and teach yourself some basic engine diagnostics. I'm very fortunate to have both a higher end scan tool and 2 oscilloscopes so troubleshooting my '01 is fairly easy !!...You'd save yourself TONS of money and not change unneeded parts. Well, since that "dealer"... HA HA ...couldn't find it lets try to fix it here. Let me know about the P0101 and if it's still an issue I can help you check the wiring.,do you have a multimeter and would it have a "frequency" setting ??...if it's just the P0171 how does the car run at idle ??...if runs smooth at idle I'd shy away from a vacuum leak...a vacuum leak would cause the car to run better at higher RPM...you said you have issues on medium acceleration so I think it might be a fuel delivery problem like a bad injector, fuel pump, clogged fuel filter...it could be any number of things !!

 

Your car is running poorly with that intake right now, hence the codes. You might actually gain performance by switching to a factory system.

You could potentially gain a couple ponies with a proper tune on your current intake, nothing major. You can find a tuner here in the forum's regional section, or search for dyno shops in your area and call to ask about their experience tuning Corvettes.

 

If your car is otherwise stock, very little if any. If the intake is causing issues as said above; either replace it or get a tune (mail order ECS or TSP is what I'd do, depending where you live).

 

I ran the Breathless Vortex filter on my car for about 10 years. It never caused any codes.

 

[QUOTE=Rx7Rob;1597541568]I ran the Breathless Vortex filter on my car for about 10 years. It never caused any codes.[/QUOTE

I installed a SLR Blackwing CAI filter on my "01 about 4 years ago....no issues.... these new filters sometimes take a few drive cycles for the PCM to adjust the fuel trims !!

 

5+ years was probably long enough for the OP's fuel trims to adjust.

 

Couple of suggestions, first make sure the air intake at the radiator cover is sealed very good, then check along the intake system to make sure there are no air leaks. If you have any access to scan/log platform, have a good 20 minute run made using the GM enhancement model. That will tell you if you have fixed all the air leaks, what your LTFT's are (should be less than +/- 0) and other information. Personally I would change the O2 sensors to new ones as the originals are not as resistant to the effects of ethanol (change was made circa 2009). It is really hard to diagnose engine problems without a scan log so you will have to address them one at a time.

 

Thanks, Gordy.

What you describe is exactly what the Chev dealer did last week. After that work was done, the DTC for MAF reappeared after 50 miles and then the oxy sensor DTC reappeared after 500 miles. I'm observing the same behavior as before Chev did any work.

I'm gonna need to find a real expert with the right tools. I've had a series Vette Experts charge me a total of over $500 for their diagnostic expertise and the problem persists, although this year is the first year I've had an O2 sensor problem. Maybe I should just change them.

 

The car sounds wonderful at idle, a beautiful American V8 rumble with nary a hiccup.

I have a scan tool, so I'll try that; no frequency setting on my multi-meter.

O2 sensor problem is new this year, so maybe that's just failing under certain conditions.

Thanks for your suggestions

 

Yes !!... DEFINITELY a scan tool necessary to T/S this DTC...Lean conditions are usually the "cause" of this DTC...A O2 sensor DTC setting is the "effect" of the lean condition. An "O2 response test" would be a more definitive way to T/S the O2 sensor...the OP could use a multimeter set on the Mv scale and back probe the O2 sensor signal wire. Since the LTFT would be in 24 +% range disconnecting the brake booster hose would cause the fuel trim to decrease and thus Mv reading to decrease...if it doesn't it's probably a bad sensor...if it DOES respond and the Mv reading decreases the O2 sensor is telling the truth and you really do have a lean condition. If you want to check the circuit integrity of the O2 sensor disconnect the sensor pigtail. The multimeter will read 450Mv since the sensor circuit has a bias voltage...if it reads 450 Mv your wiring is OK !!

P.S. If the LTFT was say 22 or 23% on bank 2 and the bank 2 DTC did not set I'd be looking at Freeze Frame data...if the DTC set "under" load I'd look at a MAF Sensor or fuel delivery...fuel pump weak /faulty fuel injector/clogged fuel filter...if DTC set at idle I'd lean towards vaccum leak !!....This is a relatively easy DTC to troubleshoot...I CAN'T believe a dealership could not fix this !!

 

Yes, you really need to find a local, trustworthy shop that does custom tunes to fix this, assuming you want to keep the aftermarket intake. They will do a scan to see what the sensors are actually reading and use it to help determine why. It could be a vacuum leak somewhere, or the tune needing adjustment for your intake. A shop like this can fix either issue. Or they may determine a need to replace either one or both sensors.

A dealer is most often going to see the codes, maybe try cleaning the MAF and a quick check for vacuum leaks, and then recommend replacing the sensors. They do not troubleshoot as thoroughly in my experience, and would rather charge you for installing new sensors. Most dealers cannot handle aftermarket parts, and they cannot make tune adjustments for you.

 

So at the urging of several of you in the forum, I reacquainted myself with my OBD2 Scan tool and started looking at the data. Something wrong on bank 1 alright. So I did the leak checks suggested but found nothing. Idle was always smooth, so a leak was unlikely. I decided to take the entire air intake plumbing system apart. Whoops, what's that? I found a thin reducer (about 2" in and 3" out). It was loose and in the duct that connects to the engine air intake. It didn't fit anything on the input plumbing. I removed it and set it aside, put everything back together and set up my scanner to trigger on the DTC code. Took the car out and drove it gently, normally and really hard in 85 degree heat (usually this would trigger the DTC). Couldn't get it to trigger. No more hiccups on acceleration. I'll have to drive it another month before I'll believe it's fixed, but it looks promising.

I'd sure like to thank AutoNation Chev of Clearwater, FL for charging me $260 for not fixing the problem. They claim they fixed leaks in the air intake plumbing, and that solved the lean reading on bank 1. Cept it didn't. Vettes are really nice cars, but GM and their dealers have no idea how to service them.

Seriously, I want to thank everyone in the Corvette Forum who posted their suggestions, ideas and background data here. It was all useful to me in figuring out how to proceed.

 

 

There was no leak that I could find. There was a loose plastic part stuck in the airflow between the MAF and the engine air intake, very close to the engine intake like it got sucked into that position. Not sure why it was there because the diameter on both ends didn't match anything else on the intake path. It could have possibly restricted airflow to one side and increased it to the other. Very odd to find something like that in there. Not sure why the Chev guy didn't see it while he was re-positioning clamps and such.

I'm trying to get a refund from Chev. Suddenly my good friend Mike the service advisor is getting very hard to get ahold of. I live in Minneapolis and got the vehicle checked to make sure I'd make it back there when I was in Clearwater. I'll bring it up the chain of command all the way to the GM CEO if I have to.

 

More follow up on this. The plastic piece that was loose inside the duct near the air intake on the manifold was a Vararam VR velocity stack. It goes in the throttle body and supposedly eliminates the needed for a ported throttle body. Apparently the previous owner bought the whole Vararam B2 cold air intake plus the Vararam power duct plus the VR velocity stack. According to the Vararam website the C5 engine should now be producing over 400 HP. Who knows? My Vette has plenty of power and torque for 68 year old me. By the way, sorry I called the thing a Vortex air intake, that's what a mechanic once told me it was.

On the Autonation Chev front, a customer service guy named Jack Mathews called and offered to cut the repair bill in half. I thought that was fair, since they had done some repairs on the air intake and there was no chance for them to take another look at the car since I'm now in Minneapolis and they're in Clearwater, FL. Jack was very nice about it and I'm happy with the compromise.