Potent68

Great weather here in Oregon so I was hoping for some great results. The car ran 13.1 @ 111 most of the day. It felt like it was hesitating in the upper RPM range in 3rd. This became more evident when I ran a newer Mustang GT. I had him by a few mph in the 1/8th and then he had me by a few mph in the 1/4.

A run or two later the check engine light came on yielding the famous P0171 and P0174 codes. When I bought the car somebody had put a Blackwing intake on it. I'm hoping that's the cause of the issue. I should definitely be trapping higher than the 111. (I did hit a best of 13.0 @ 112.) After clearing the codes they didn't come back for the mellow drive home.

I stuck a WTB up in the parts section to see if I can find a stock air box.

Oh, and my Bridgestone Potenza's coupled with my first time back at the track in over 10 years were yielding 2.2 60' times.

I am hoping that putting a stock air box back on the car will get my mph back up where it should be and then I can just worry about my launching technique.

bwill03z

Why would you want to change the Blackwing cai for a factory airbox?! I honestly don't think putting a stock airbox back on is going to make your car run any better. Right off hand I dont remember what those codes are, but did you check your air filter? May also want to maf cleaner on your maf wires. Also make sure your throttle body is clean as well.

Potent68

The codes are for a lean left bank and a lean right bank detected. The car barely has 10k miles on it at this point. I'll definitely check the MAF, the vacuum lines, the wires, etc. Unfortunately the P0171 and P0174 are well documented throughout this forum as being related to aftermarket air cleaners, regardless of manufacturer. It's so common that a vendor has created and sells a screen that goes in the inlet of the MAF to help with the way the air flow travels over the wires. When people are confronted with this problem most of the stories you read are about endless troubleshooting with no clear resolution. Well, okay, their resolution is usually to somehow have it tuned out of the computer (perhaps through recalibrating how the PCM sees the signals it's getting from the MAF? I really don't know how they "fix" that) or adding the metal grate into the air flow on the MAF. I will have the car tuned if I do more extensive mods down the road but I am certainly not paying to have it tuned because of an air cleaner that seems to be hurting performance, and the point of opening up the air flow (via a supposedly better air filter) is to help the engine breathe so putting that screen in the air flow path is working contrary to the original idea and seems redundant.

So for me the facts are...

- my car felt like it was hesitating at the top of 3rd gear
- my car has the P0171 and P0174 codes that are well known to pop up when an aftermarket air cleaner is installed
- my car has an aftermarket air cleaner installed
- my car never pinged audibly (it is possible to ping inaudibly, but I would need a data logger or computer hooked up to observe that and the subsequent retarding of the timing by the computer)
- my car has just passed 10k miles so it's really clean

I ordered a fuel filter when I first thought I felt this hesitation in the higher RPM's so I will be installing that as well as installing the stock Z06 air box assembly.

I've installed new blue valve springs, new GMPP red plug wires, and new valve guide seals.

Reading threads like this one have also helped me feel pretty comfortable about returning to the stock air box.

https://www.corvetteforum.com/forums...post-here.html

Hopefully my rambling explanation makes sense.

bikeriderga

You probably just need a street tune on the car. Could be some fuel issue but with the lean codes, obvious you are not getting enough fuel. You did not mention, but do you have aftermarket exhaust as well? The Z06s usually throw lean codes with an aftermarket exhaust and a CAI. Tuned somewhat lean from the factory due to EPA mileage ratings.

Go ahead and clean the Throttle body while you are at it.

Potent68

The car is all stock aside from the air filter. I can't justify tuning a car because of an air filter.

bwill03z

I would not waste my time tuning the car just for an air filter. Get the stock airbox back on, maybe run a bottle of Techron or Seafoam through the gas tank to make sure your injectors are clean. Change out your fuel filter... orr keep the Blackwing and start modding, then go get a tune

racebum

it should be trapping around 115 at PIR. possibly 116

if it has the OE fuel filter that could definitely be your problem. don't run it hard until you find this out. WOT and going lean can = broken ringlands.

you don't need to tune the car or any other BS, there is something up. need to find out what. the car can be ran without an air filter and not go lean. a blackwing isn't giving you codes and costing you 40hp

that fuel filter could

also clean the MAF. they make a special electronics spray cleaner called MAF cleaner. don't use anything else. don't scrub or touch it. just hose it down with that stuff and if you have specs of anything use a qtip very gently then rinse with the spray. you can use a hairdryer on low to speed dry if needed

MVR 155

I have to ask an obvious question..... How old is the fuel in the car??? With that low of miles it certainly isn't driven much, old fuel coupled with the air filter making the car run a bit leaner could have it pulling timing in 3rd which would make it feel like it's "hesitating". If the fuel is old, run it down until empty, top it off with fresh gas and then change the fuel filter.

MVR 155

Also.... If the fuel is old, don't drive it excessively hard until you run it low and refuel.

Potent68

I ran a bottle of Techron through it shortly after I brought the car home in January. I'll probably hang on to the Blackwing for down the road when I do some more mods for sure.

This was at Woodburn, not PIR but I agree it should definitely be putting up better number than it did. I'll be cleaning the MAF after I find a stock air box to put on. I have a lead on one from a friend but he told me to name a price and I have no idea what they're worth. I'll probably do the fuel filter this weekend.

Definitely a legit question. I bought the car with 8,6xx miles on it in January and rolled over 10,400 today so counting about 20 minutes ago I have put 6 tanks of Fred Meyer (Kroger) premium fuel through it.

Thank you everybody for your input so far! I am not opposed to modding the car once I get some more seat time, but first I really want to get it back to it's proper baseline. No sense in trying to throw mods at a car that's not running optimally.

I bought a set of NGK plugs but the stock iridiums looked good when I did the valve springs so I verified their gap and put them back in. I was feeling the same hesitation prior to touching the plugs too.

MVR 155

Ok.... So it certainly shouldn't be old fuel. Being as low mile as it is, it's likely that it has had stale fuel in the tank. It could have gummed up the filter or injectors at some point. Keep eliminating variables and hopefully you find the culprit. Even though you only have an intake, a tune will certainly give you a nice bump in HP. Personally I would invest in a set of Longtubes if I were you and then tune.

racebum

the only way a tune will bump hp on a stock car is increasing the timing or leaning out a bit both of which are dangerous to the health of the motor and all for maybe 10-15hp which is basically meaningless

running slightly rich like factory keeps cylinder temps down and that means when you run up to 150mph you don't pop the motor. more timing and a bit leaner run up cylinder temps. looks good on the dyno but not under hard use.

tom wong is one of the better tuners for the c5/c6/c7 in this area and he's in vancouver. bad gas, gummed fuel filter or injectors or an intake manifold leak are the main suspects as are any leaks AFTER the maf going to the intake manifold. if unregulated air is getting in that also can be trouble.

should be easy to troubleshoot this.

if you plan to mod think it all out ahead of time but imo modding a c5 is basically lighting money on fire. the stock ones have been the easiest to sell and mods get you about .20 cents on the dollar in resale. beings you have a nice low mile example, drive it, enjoy it, but why wreck the value and drivability modding it?

Potent68

I agree with your sentiments about tuning her in stock form. I've heard good things about Tom Wong and would likely take the car up there if I do start to mod it. For the time being, I bought the car because of how great they perform in stock form in all areas of racing. I'm going to take her to an auto-x in Salem at the end of the month. I'd like to do some road courses eventually too.

As for modding the car, I didn't buy it to preserve it for the next person. I really appreciate the previous owners who did that for me when they owned the car but I bought it for myself to enjoy. Having said that, I always had big ambitions for modding my '99 SS I owned but when I finally sold her the only performance mods were a lid, GMAF (only because the stock MAF died), and an American Thunder catback (no performance gains, just better sound). We're also working on our '68 Chevelle so getting that back on the road for my 16 year old son will be a priority over Z06 mods.

racebum

go visit tom when you get a chance. he's just across the bridge in the hazeldell area of vancouver.

corvette and corvette/porsche HPDE days happens a few times a year at PIR. cost is $100 to 200 for the day most the time

if you do mod just think out your plans before you buy. nothing worse that buying parts twice. the main areas the c5z benefits from if you're looking to go faster are

#1 tires
#2 shocks and weight corner balancing the car

stock brake pads work well with stock power. if that goes up, so must the rest of the car.

another perk of being stock is if you ever do autocross you can run the stock class. mods put you into the open category which means you run against exactly what it sounds like.

Potent68

That was actually part of my motivation behind getting the stock air cleaner assembly back in there. I realized I'd have to race in the modified category. I missed the first race but I'm going to go the next one in Salem at the end of this month.

Also, what you said about thinking ahead is a big consideration of mine. I don't want to make the car a drag strip focused car because that will detract from it's abilities in autocross and road courses. I'd much rather take my autocross/road course car to the dragstrip than take my drag car to go autocrossing!

racebum

do make sure you get an 02-04 air box. the 01 had a smaller air intake opening

sounds like you're on the right track with the car

01vetteZ!

I think everyone is forgetting the obvious! The blackwing on the car was rarely cleaned causing the MAF to get dirty. Hence the lean on both banks. these cars run 60psi of fuel pressure and i rarely see injector issues especially stock or close to. I deal with automotive driveability on a daily basis and when you get one lean code the hunt for vacuum leaks begin, when you get both banks the first steps is watching the grams at idle and WOT to make sure the meter is up to specs and LOTS of times especially with aftermarket filters people get lazy dont clean them enough and dirty meters result

racebum

i thought about this but the car goes open loop at WOT. dirty maf isn't likely but that vacuum leak sure as hell could be the issue. someone replaced the oil pressure sender. gaskets weren't clean. possible dry since it's a low mile car. settled. who knows but vacuum leaks can certainly do it

Potent68

The '02 Z06 air filter assembly will be on it's way here this week. I'll get that fuel filter changed out and the MAF cleaned with the MAF cleaner and then I'll report back on how it feels. If that doesn't cure it it will at least cross 3 possible culprits off of the list.

bwill03z

Sounds good. If this fixes your issue are you going back to the track? Just curious as to what differences in time/trap speed. Hope it fixes your issue!