BumpaD82

Please help check my diagnosis ...

Car WILL NOT run with MAF plugged in. (or throw a code)

Code 33 once running (with unplugged of course)

Followed this flow chart to the end:

http://chevythunder.com/maf_code_33.htm

And it says MAF is faulty

The flow chart has me checking power / grounds at the MAF connector which to me means the MAF power relay is OK.

I swapped the MAF BURN and fuel pump relays (both old part# 14078907) and same story / symptoms.

I pulled the ignition module and it tests good, also checked the TPS voltage at 0.54.

Anything I'm missing or time to buy a MAF ???

Also which should I buy ? (thinking used BOSCH from Hawks) none of these seem avavilable:
https://www.thirdgen.org/forums/tech...-purchase.html

(especially the MicroTech / Wells Wells SU-145 unit)

THANKS !

~DaVe

Vader

Does the engine stall if the MAF is reconnected once the engine has been started?

If the inlet ducts are intact, there are no external vacuum leaks downstream of the MAF, the MAF is getting a 12V supply from the power relay, and the connections to the ECM are intact, there isn't much else to diagnose.

If the MAF has actually failed, the updated version is now available through AutoZone as P/N DL-6014, and probably other places. It's a clone of the Wells unit, and may be manufactured by them.

BumpaD82

Thank you for the reply !

I started the car with the MAF unplugged and then plugged it in (kinda difficult with spinning alternator on that side!) ... and it continued to run ! ... Then I got codes 33, and 36 ...

Traced code 36 with this:
http://chevythunder.com/maf_code_36.htm

And got to the box of :

"Faulty ECM or ECM connection, Code 36 can be set to any of the MAF connectors being faulty, high resistance, check all terminals for tightness and continuity before condemning ECM"

I have a hard time believing it's the ECM (as noted in flow chart), as the car starts and runs with the MAF disconnected ...

Tried switching the Fuel pump and Burn off relays again and same story.

Still thinking it's a bad MAF !

Thanks for the Autozone part # I can have them order it in locally (once I convince myself to spend the MAF $ )

~DaVe

Vader

If it will continue to run with the MAF connected after starting, you can perform a couple more diagnostic checks to determine the condition of the MAF.

First, back-probe the MAF connector at terminal "E" and read the voltage with the meter referenced at a good ground. There should be nothing - Zero volts. If there is voltage, the MAF will attempt to run a burn-off and report a high number to the ECM.

Then test terminal "C" to read what the MAF is reporting to the ECM. At an 800-850 RPM idle in neural/park the MAF should be reporting around 750-850 mV (0.75-0.80V) to the ECM. If this is correct, there may be nothing wrong with the MAF itself, and may be other system problems.




Also, verify that the MAF ground connections at both terminals "A" and "B" have Zero volts. Any voltage present there would indicate poor wiring and would skew the MAF reporting to the ECM.

One thing I know that will completely screw over the ECM regarding the MAF reading is having the burn-off terminal supplied with even a small voltage while running. This can happen if there is contamination or carbon build-up in the burn-off relay, across the relay electrical connector, or at the MAF connector. Another potential problem is having the auxiliary oil pressure switch and/or fuel pump power feed to the ECM intermittent. And of course, the MAF, ECM, and engine ALL grounds have to be clean and reliable.

BumpaD82

Awesome ! Thank you again ...

I'll get the DMM out tomorrow for more testing

~DaVe

BumpaD82

Todays results ... cleared codes and got the car running with the MAF plugged in (had to crack open the intake tube at the throttle body to keep it running / more air)

RED wire was full alternator voltage 14.4

GREEN maf signal wire .10/.11 volts

BLACK and BLACK/WHITE wires .07 volts each ?!

With the MAF burnoff relay unplugged all stayed the same other than the BLACK wire went to .00 ... BLACK/WHITE stayed at .07

~DaVe

Vader

This would allow unmetered air to enter the intake, causing the MAF output to be lower than it should be.

"RED wire was full alternator voltage 14.4" - That's normal.

"BLACK and BLACK/WHITE wires .07 volts each ?!" - 70mV may indicate a slightly resistive ground connection somewhere in the wire harness, and may SLIGHTLY skew the MAF output as a result, but probably not enough to set the codes.

"GREEN maf signal wire .10/.11 volts" - This is low, but not a surprise since the inlet air bellows was opened to allow unmetered air to flow in. To verify that the MAF is actually measuring intake air and adjusting its analog output accordingly, reconnect the DC voltmeter to the MAF output terminal with the engine running. If the inlet air bellows needs to be removed to admit more air, so be it, but as the engine is running and the MAF reading is being monitored, slowly close that opening in the inlet bellows to force the intake air to flow through the MAF. If the analog signal increases as air flow is increased through the MAF it is responding correctly. If not, the MAF may have a problem.

It is also questionable whether the burn-off function is actually cleaning the hot wire fully to allow the proper rate of heat dissipation to measure air mass correctly. It may be worthwhile to clean the MAF hot wire with a spray cleaner made for the purpose, like CRC 05110, and test it again. There should be no need to disassemble the MAF for cleaning.

I am also beginning to wonder what the ECM data stream shows for MAF flow compared to the voltage reading you are seeing. If the data stream shows an appropriate air flow the MAF is O.K. If not, the MAF and/or connections may be at fault.

BumpaD82

So thank you AGAIN !

I started the car again and did the testing on the green wire, with the intake tract almost completely closed up (99% clamped)

Voltage readings of .70 / .71 and 1.35 ... but never reached the .75 / .80 idle readings.

Threw code 34 of course, which had me unplug and and run again ... Code 33 ... Bad MAF

Car won't restart with the intake / maf system closed as it should be

I did clean the MAF (not with CRC, but w/ Jiffy Bath contact cleaner aerosol, had it available)

At this point I'm thinking replace both power and burn off relays , then if no change order the MAF ?

~DaVe

Vader

If you were reading 0.70-0.71 V (700-710mV) with the bellows not fully sealed off that sounds like the MAF is reporting correctly. The photo above is a fully seals off 305 TPI at 800-850RPM, which is pretty close to what you are reading with the intentional leak.

If the MAF is in fact reporting correctly, it may be time to go drop the ECM and back-probe the MAF input wires there to verify that the readings are the same. I suspect they may not be, or the connections/plugs at the ECM are not clean.

Test voltage from the analog ground in Pin A12 to the signal wire on Pin B11 (the diagrams on the linked troubleshooting chart are incorrect).

BumpaD82

Rain for the last couple days and a coolant leak repair in the G/F's '99 Formula, have kept me from getting to this, hopefully Thursday I can pay the ECM a visit

~DaVe

rusty vango

go and buy yourself a MAF from "rich - porter " they are NEW not re - man . its a once and done thing. i got mine from oreilleys . after going through 7 of those A1 cardone POS MAFs. that was around 3 years ago and so far no code 33 or 34 BS . and the car runs great

BumpaD82

Is this the one you mean ?

________________________________________________________________________________________________________________________________

So today's test have me pretty much back at square one ...

Testing the the connections at the ECM B12 (no green wire, or any wire in B11) and A12 (i checked to car ground first and then to this wire) ....

I get .73 -.75 volts at idle with the intake tract 99.5 % clamped, i get the same readings under the hood a few inches out from the MAF connection .73-.75 volts ... So it's telling me the MAF is reading and getting a signal to the ECM with the same readings ...

Throws code 12 (which I though indicated ECM is "OK") and also still code 34 when running poorly with the MAF plugged in & intake closed up ?

I'm sorta stuck

~DaVe

Vader

The MAF could be intermittent. The code will set if the signal drops below the threshold for as little as 600mS (6/10ths of a second) in order to detect a poor connection or cracked MAF hot wire. If you had a known good MAF to borrow that would resolve the question, but that's a big "if."

BumpaD82

I will try and find a MAF to borrow ...

"IF" not is purchasing one the next step in diagnosis ? ... I hope I don't end up buying a MAF, ECM, and relays !

Thanks again for all your help! ~DaVe

IROCgiraffe

iTrader: (3)

How do the power connectors to be MAF power and burn-off look? If they are/look melted, replace them and the relay if you haven't already.

BumpaD82

they don't look great, (the wires) but i have cleaned them all and checked continuity and they all some to test alright.

I haven't replaced either relay yet.

~DaVe

IROCgiraffe

iTrader: (3)

Replace them. Weakest link

rusty vango

yeah , thats the one MA157 . IMHO its the best one out there

BumpaD82

So starting with the cheapest option ... I ordered both the power and burn off relays, genuine GM, as I feel the autozone ones seem hit and miss .... Waiting for them to arrive.

Then onto the MAF if the relays don't solve the issues

~DaVe

DJP87Z28

Solve your problem and buy a Wells Maf SU-145 for about $100. Do a search on this site about this Maf, it uses a film and not a hot wire for air flow.

BumpaD82

I don't think the WELLS MAF SU-145 is available anywhere.

The Autozone P/N DL-6014, is suppose to be a clone of the Wells unit, and may be manufactured by them ?

Also there is the Richporter Technology MA157 MAF that is the newer design also, ... Autozone lists an alternate part # on the DL-6014 as DL-B157 ... May the Duralast brand is a Richporter Tech instead of the Wells ? (the 157's matchup)

~DaVe

DJP87Z28

Bought a Wells SU-145 in July this year from Rock Auto for $108.00. They are still out there.

BumpaD82

So I tired both new relays (actual GM part #'s .. I have a magician for a parts man ) and same results ... runs with MAF UNPLUGGED only, fires and dies with it plugged in ...

Ordered a Wells SU-145 tonight ... to have it for the weekend !

~DaVe

BumpaD82

New MAF did the trick ! "fire breathing" once again

The Rock Auto Airtex / Wells unit is possibly more Airtex than it is a Wells SU-145 ... no SU-145 label / sticker on it as pictured on Rock Auto site. But it is the circuit board type and has a patent #, so who knows who makes it. It works

So two new GM relays (read somewhere it's not a bad idea to replace them with the MAF anyhow), MAF sensor, and new air filter for good measure.

THANK YOU everyone for the help (Vader), I really appreciate it !

__________________________________________________________________________________________________
EDIT : Upon cold start after work at 5am, intermittent code 33 .. thinking it's the relay harnesses (as they look like ****) ... this car has me pretty frustrated !

~DaVe

BumpaD82

Well I sent the AirTex MAF back to rock auto today for a refund ...

also still waiting on the relay harnesses from http://tpiparts.net/ ... rewire / install them, then try the factory BOSCH MAF, then maybe an AutoZone unit ...

~DaVe

rusty vango

man . i feel your pain . air tex , A1 cardone . all belong in the trash . as long as youre fooling with re man MAFs you aint ever gonna be happy . "rich porter " MA157. its a NEW MAF sensor. i bought mine a couple years ago and since then , not one code 33 34 or anything else . it just plain works. and i can drive my car when ever i want . you can too

BumpaD82

The AirTex I tried (that was suppose to be a WELLS SU-145) was a NEW unit, just didn't work

Do you know anywhere to buy the RICH PORTER, which now seems to be a http://www.spectrapremium.com/home.html 2014 Acquisition of Richporter Technologies ... (auto parts store(s)) that have a warranty on it ???

Amazon has a good return policy, but with one bad review and no warranty, I'm still leery to order from them.

EDIT: Summit has it (Spectra anyhow) $291.97 !!! http://www.summitracing.com/parts/sgt-ma157
-OR- rock auto seems too SPECTRA PREMIUM / COOLING DEPOT MA157 $168.79

~DaVe

rusty vango

oreilleys is where i got mine . and i truly HOPE "spectra" hasnt bought them. have you seen the lack of quality ?? its as if A1 cardone and spectra are having a contest to see who can make the biggest POS available

BumpaD82

Looks like it as of 2014 ...

http://www.spectrapremium.com/overview.html

~Dave

Cardone Ind.

Hello Rusty,

We are disappointed to hear about your bad experience with our car parts. We would love to talk to you about this matter. If you could call our Technical Service Team at 1-888-280-8324 that would be greatly appreciated. We look forward to hearing from you.

Phil Curry - AV Tech
Cardone Industries

rusty vango

well , if you would quit re building them in china .where , apparently they use wasp nests and mud ***** to do it , thatd be great. and its not just MAF sensors .the whole cardone line seems to be the cheapest it can be. think of your customer base ,instead of some "share holder ". profit margin . that would be great too . otherwise . in a few years . you wont be able to sell snow cones in hades.

Bob88GTA

iTrader: (2)

Yep...true

2014
Acquisition of Richporter Technologies, which extends Spectra Premium product line coverage into engine management parts.

Cardone Ind.

Hey Rusty,

Totally understand where you’re coming from. We have made a concerted effort in the past year to be more connected with customers. It’s called our tech council. Quality is number one and customers are willing to pay more for a part that they know is high quality. The manufacturing process contains many quality check points and we are continuously improving not only our processes but our raw material vendors as well. We would certainly be interested in having a further conversation with you. Please contact our Technical Director at 215 912 3245. Look forward to hearing from you, and certainly appreciate your feedback.

Phil Curry
Customer Experience

IROCgiraffe

iTrader: (3)

Forget that noise... Go with the AC Delco reman.... mine works just fine. RockAuto + AC Delco = FTW

BumpaD82

UPDATES :

Last I posted I was waiting on the relay harnesses from TPI parts ... got them, un taped all the wires and found THIS ! on the burn off relay harness, the wire was completely broken through and only the insulation was holding it together (sometimes making connection I suppose)



So I installed both new color coded harnesses (nice products from TPI parts), and then decided to install the stock MAF for results ... same code 33's and the car ran pretty strange ....

Got the refund from the Airtex MAF, and purchased a used BOSCH , "good when removed" MAF from a TPI corvette setup (same part # as my L98 stock MAF) ...

It arrived (and had been descreened (would have prefered not), it is installed and so far initial startup / warm up (don't think I got to closed loop) and NO CHECK ENGINE LIGHT / CAR TAKES RPM normally !

Test driving today (in the rain / sleet storm ?!)

~DaVe

DJP87Z28

[QUOTE=BumpaD82;5976789]UPDATES :

Last I posted I was waiting on the relay harnesses from TPI parts ... got them, un taped all the wires and found THIS ! on the burn off relay harness, the wire was completely broken through and only the insulation was holding it together (sometimes making connection I suppose)

So I installed both new color coded harnesses (nice products from TPI parts), and then decided to install the stock MAF for results ... same code 33's and the car ran pretty strange ....

Got the refund from the Airtex MAF, and purchased a used BOSCH , "good when removed" MAF from a TPI corvette setup (same part # as my L98 stock MAF) ...


My guess it was not the Airtex Wells SU-145 Maf. And it would have worked fine, if you did not have that screwed up wiring.

BumpaD82

So far so good 3 separate drives (short) but it did warm up to closed loop easily, and no Check Engine light / code 33 yet

And I agree it's too bad the shipping times didn't coordinate that I had both the harnesses and the new MAF at the same time(s) ...

I was disappointed in the fact the the AirTex unit DID NOT have the SU-145 # / Sticker on it as pictured though

~DaVe

FireballXL5

He should check to see if the power and burn off relays are the same, that could be his problem as they are not constructed the same.