xOrion9x

I drive a 2002 Z28 stock with the exception of an SLP fresh air kit). So for the past few months my car has been throwing codes left and right, torturing me with SES lights and frequent trips to the parts store for diagnosis. Always bank 2 running lean, or some variation thereof. It is especially bad in cold weather (my car is a straight up bitch in cold weather). I've cleaned the MAF, o2 sensors, throttle body, and air intake control. It solved my problem until now. I gave up and decided to replace the MAF (as this is the most likely culprit). I went and ordered an OEM replacement from the parts store, check it out... it looks different. Not just different but has moved a small black plastic covered sensor from my airlid to the MAF itself. This little sensor has its own wiring harness. So I am supposed to still use this sensor? Or is it now integrated into the MAF? Am I stupid to even be asking this? And as far as cleaning the MAF - should I be cleaning this black piece on the air lid? And what about the honeycomb? The SLP is NOT coming off of the housing, so the honeycomb and small black piece would have to be cleaned while still attached. Any help or advice would be appreciated (even if you just decide to tell me I'm a dumbass).

Burken01

iTrader: (88)

That little black plug in the slp air lid is the IAT sensor, it will have its own connector on it The maf sensor will have its own separate connector What code are you throwing?

You can buy maf sensor cleaner spray from autozone and spray it in through that screen and let it air dry for 5-10 min before you try starting the car

xOrion9x

I've used the cleaner (often) since this problem started but only on the sensor itself. Never the honeycomb or the IAT. Just cleaned them awhile ago and will put together later. On the Delphi maf at the store it has something looking identical to the IAT on the sensor that fits into the now plastic housing.
As far as codes go I don't have the numbers offhand but they are always bank 2 too lean. Except for today when I got bank 2 too lean AND too rich. They said replace your MAF and I was willing to until I saw how different it looked.

Burken01

iTrader: (88)

If it's p0430 (catalyst below threshold bank 2) then you have a catalytic converter going out or the 02 sensor is going out on it

Next time read the code so you can pinpoint it

xOrion9x

Thank you. I'll get the code and see what I come up with.

Fry_

If you want to replace your MAF with one like the original return the one you have and buy a remanufactured one. It looks like RockAuto and AutoZone both have them, and you wouldn't even need to remove your MAF ends from you SLP lid you could just remove the 4 allen bolts and swap just the sensor.

1 FMF

iTrader: (1)

happy new year dumbass

who was "they" that said to replace your MAF sensor, guys at autozone?
be careful of parts store mechanics, you get someone with a code reader and they think they know it all. you really need to understand the emissions and fuel system of the car in order to interpret DTC's properly. first and foremost you need to get the trouble codes, along with knowing under what conditions when they happened. a code such as P0101 maf air flow out of range does not mean MAF bad replace it, something else may be causing the problem, and same goes for just about any DTC.

MAF cleaner is rarely a fix. by nature the MAF cleans itself since it's a hot wire element, when it gets to the point that wire is fouled then it's done and cleaner is not necessarily going to help. and to know if the MAF is reporting wrong you use a handheld scanner to see if the values it's reporting for 'mass air flow' jives with current engine operation or you record data and look for anomalies. if you are not getting P0101 mass air flow out of range then you really shouldn't replace it unless you don't mind wasting $100.

if you are correct about it being bank lean, then given age of car it's most likely an electrical solenoid somewhere in the emissions system (air pump or evap) leaking air into exhaust or intake manifold that the PCM can't correct for or senses an out of range condition. you need to get the DTC's before anything but with age of car your money would be better used with new front (pre-catalytic) O2 sensors rather than a new MAF. with the codes being bank lean, it's caused by excess air either introduced into intake manifold or into exhaust system.... check the 2" long rubber hose that connects the pcv system to the throttle body, those crack and deteriorate.

RPM WS6

iTrader: (3)

Perhaps I missed something but I don't think the OP mentioned anything about a converter efficiency code? P0430/P0420 normally comes with no driveability issues at all, and very rarely would be triggered by a bad O2 sensor. And if it were a rear sensor, it wouldn't have any affect on driveability anyway.

I'm not directly familiar with the redesigned replacement MAFs, but personally I wouldn't buy a new one just yet based on what is known of the problem and with the only codes being for too rich/too lean. You mentioned that you've cleaned the MAF before with spray cleaner, but have you ever disassembled it and done a thorough cleaning of the wires? This might be necessary if you've ever had a K&N style air filter on the car, as they tend to cause oil build-up on the wires over time, leading to false readings and various driveability issues. So that would be my first step. As mentioned above, you can remove the ends while still attached to the SLP lid by simply removing the four torx bits. The center section will come out, and you can gently clean the sensor wires with a Q-tip and some rubbing alcohol (don't apply any pressure to the wires, just glide along the surface until they are bright silver again).

If the lean/rich codes are limited to only one bank, then I'd more likely suspect a vacuum leak or exhaust leak near the front O2 sensor for that bank, versus an issue with the MAF. I would also inspect the PCV system for any macro leaks that might affect both banks.

There also may be an issue with fuel pressure, if you're getting lean codes. So that's yet another thing to check (both at idle AND under load, as sometimes fuel pressure issues won't show up until the engine is under load).

Another test you can try is to unplug the MAF, thus forcing the PCM into SD mode, bypassing MAF inputs. If the engine runs better this way, then you have more likely narrowed the issue down to being MAF related.

So there are a few more things you can do before throwing parts at it.

1 FMF

iTrader: (1)

other thing with fresh air kit, i know from experience my 2006 truck came with a k&n kit that previous idiot owner routed into front wheel well which caught water/mud, and i would get P0101 about once a week that MAF cleaner did not help until i replaced the MAF. the old MAF had signs of dried water and dirt stains inside, clear evidence it got contaminated. so with you having a fresh air kit, if you find signs of water stains inside your maf sensor then in that case it might not be wasted money on a new MAF... the autozone ones are reasonable at $110 on the website and say lifetime warranty.
but again it depends on what your DTC codes actually are.

xOrion9x

Just reassembled maf after cleaning. Codes remain. Drove for awhile to give a chance to reset. Went to the parts store and codes read as follows: P0507, P0300, PO171, P0174. The random misfires are new. Haven't that code pop up since I did plugs and wires a little over a year ago.

RPM WS6

iTrader: (3)

I seem to remember P0507 to be a "high idle" code, usually the product of a vacuum leak or IAC motor issue. It would be helpful to have a comprehensive OBD scanner at this point to look at IAC counts as well as fuel trims and TPS readings.

P0300 can happen for a bunch of reasons, and again the comprehensive scanner would be nice, allowing you to look at individual cylinders for erratic behavior. But with lean codes on both banks (P0171/174), the unstable A/F might be the cause of the misfire and thus P0300.

Lean codes and high idle mean that unmetered air is entering somewhere. If it was the lean codes without the P0507, then I'd first look at fuel pressure and for an exhaust leak near or before the front O2 sensors. But with a P0507 as well, I think a vacuum leak is more likely. I'd start by inspecting the PCV system, since various parts of it tend to break down/crack/deteriorate as mileage and age pile on.

xOrion9x

How would I go about checking the vacuum line? I know that sounds stupid, but I desperately want to fix this myself. I enlist my husband for help with putting it on the ramps and then he leaves me to my repairs. He'll help when I can't reach or break something loose but otherwise this is my car and I want to do the work.

xOrion9x

Also just stopped in at our local Yearwood store. The gentleman at the counter looked at it with me and said he had previously encountered a similar problem and it turned out a ground wire was loose/corroded. I have an aftermarket car alarm that is tapped in to the ground wire on the driver side wheel well. He pointed that out as a likely culprit.

Fry_

I've had luck using a unlit propane torch to find vacuum leaks. With the motor idling slowly move the torch along all of the hoses and anywhere else there could be a leak, if there is one the idle will change when the propane is drawn into the leak.

RPM WS6

iTrader: (3)

This is a good method and won't leave such a mess like spraying carb cleaner around does (another common way that people check for a leak). The other methods include visual inspection (easy enough to see if the forward portions of the PCV system are rotted, usually this happens right at the PCV valve elbow near where it connects to the intake, but harder to see in the rear without an inspection mirror and some very skinny arms) or using a smoke machine (probably have to go to a shop for this, as few people can justify the cost of such a tool for home garage use).

Well loose/corroded wires can certainly cause weird problems, but it's just a shot in the dark really. Without a comprehensive scanner (which allows you to see more than just the code), you don't really know what's actually happening with LTFTs (long term fuel trims - you would notice these being extremely elevated, such as +25%, if the lean codes were correct), IAC counts (anywhere from around 10-50 at idle can be normal for a stock car, fully warmed up, with various electrical loads and outside temps), actual engine idle speed (should be 550rpm in gear/650rpm in park for an auto, or 800rpm for an M6 - and I think any sustained idle speed which is more than 150-200rpm above those numbers will trip the P0507), and TPS readings (sensor voltage as well as angle, to make sure that the throttle blade is fully closing and not tripping the P0507 - TPS voltage reading should be around ~0.4x-0.60 at idle with a percentage of 0% or sometimes slightly above, like 0.4%).

Point being, depending on what these various readings show, you can better determine if the codes make sense, or if it looks like erroneous junk due to wiring issues.

I would ask what sort of numbers your tach is actually showing for an idle speed, but after owning four of these cars I know better than to trust the stock tach. Only one of mine was dead accurate, the others all read about 100-150rpm too high.

xOrion9x

Took the car to a local mechanic. He could find nothing wrong with MAF/IAC/IAT. Did a smoke test and no vacuum leak. Put a fuel gauge on and got 58 at idle warm. Took it on the vhighway and gave it hell. Pressure dropped to 50. Said my pump is going bad. Quoted between $750-1000 (depending on the pump I choose) to drop the rear end, drop the tank, replace pump, & reassemble. Is this reasonable? Or does anyone have doubts?

Burken01

iTrader: (88)

cut a trap door behind the seats and do the fuel pump that way, then you don't have to drop the fuel tank.. Might as well upgrade the pump to a 255 walbro for $100 and do the labor yourself.. It's quite easy

Fry_

^^^+1 on the trap door and Walbro 255. Just make sure you get a Walbro Direct fit and not a universal one. Also you may want to find a better picture to use as a cutting guide, I've seen cleaner jobs with smaller holes.
http://www.ws6project.com/user_stor/...fit-fuel-pump/

A "hotwire kit" wouldn't hurt either Walbro's are more efficient when they have peak voltage.
http://www.summitracing.com/parts/cei-102150/overview/

xOrion9x

I'm all for doing this myself... But do you guys think this solves the issues? If it will fix the problem I'll order the parts but I really don't want to just throw parts and money at the car.

RPM WS6

iTrader: (3)

58psi at idle is fine, 50psi under load is a bit low but I wouldn't expect that to be enough to set a lean code on a stock engine. Again, I'm not confident on any solution without first seeing some scanner data and DTC freeze frame data (information stored at the moment the codes were set). If the lean codes are being set at idle, and/or the STFT/LTFTs are highly elevated at idle, then I don't see the fuel pump as the root of your problems, since pressure is normal at idle. And while pressure is a bit weak under load, this shouldn't cause a P0507 high idle code. P0507 is a result of the PCM losing control over idle speed (air flow is beyond the IAC's capacity to compensate for [vacuum leak or throttle blade not properly sealing within the range considered by the TPS to be 'closed'], or the IAC itself is not functioning properly). And just how high is the actual idle speed? Again, this would require a scanner to answer as the stock tach is not usually 100% accurate.

So you said it was tested with a smoke machine and no leak was found, but if the vacuum leak was the result of an "internal" air source (meaning that the EVAP purge solenoid was allowing more flow than commanded at idle), then the smoke would not indicate this externally. I've dealt with this exact problem before, and there is no code to indicate an EVAP purge solenoid that is opening further than the commanded duty cycle percentage. Unfortunately, it's a hit or miss thing that you can't really test without just replacing.

As for replacement fuel pumps, should you decided to do that (pressure under load is a bit weak), I'd personally go with a OE Delphi replacement for a stock car that's going to stay mostly stock. Most people recommend the aftermarket upgraded pump, but a stock engine doesn't really need that and if you go with an OE replacement you get an entirely new module rather than having to install a new pump on the old module. Of course the complete module is more expensive, so that might be a consideration for some as well.