aekerley

I am trying to clear up the famous code 36 on a 1988 LB9 Formula 5-spd. Last year I was able to clear the fault with two new relays for the MAF power and MAF sensor burn off. The code came back. I checked all sensors and connections and then replaced the MAF sensor with a new Delphi AF10320. The car would start and run fine until it went closed loop. Then it has a surging idle and will stall. Looking in the Delphi sensor the internals are different than the OEM Bosch. I ordered a Reman Bosch from NAPA XTP44712. It looks identical to the one on the car. I installed this one and had the same result, surging idle, hard start, stall....However, neither of the new MAF sensors sent a code 36 and the check engine light stayed off. What has me beating my head against the wall is when I put the old sensor back in the car runs fine, except for the code 36.

I need some advice from a TPI guru to help get this thing straightened out. The car will not pass the annual inspection with a check engine light. And I want it to be right anyway.

Any input on where to go next would be appreciated.

aekerley

I'm not sure if this is relevant but I checked the resistance between all the post on both new sensors and they were very different readings. Also when the car is running with the old sensor and the new reman the flow readings look fine on the scan tool.

aekerley

Update: I called Bosch tech line. They confirmed the reman sensor was the correct one for the application and these sensors are discontinued. However, there was a newer version of the sensor P/N 0986280105. He said it sounded like a defective sensor. So I took it back to NAPA and they reordered another one for me to try. It will be three days before it comes in.

Anyone out there?

Tuned Performance

iTrader: (92)

Different readings when running like gps were different?
How much was the Napa maf ? The tend to be good quality .
https://www.ebay.com/itm/Chevrolet-1...0AAOSwcQxetDwl

aekerley

That's the same reman I had and it's the same sensor part number in the car. I paid $134 At NAPA.

Tuned Performance

iTrader: (92)

Thought the eBay one might be a good deal apparently not. Hope the new maf fixes the issue.

aekerley

It is a good deal. I already bought the NAPA one and returned it for replacement. I'm afraid it will have the result. Still dont understand why the current one works and a new one doesn't. It's my understanding that if a MAF goes into default it will not run in closed loop. I'm getting a signal and it goes into closed loop when warmed up. So hopefully someone can weigh in and give some possible reasons why. What circumstances would let this happen?

Tuned Performance

iTrader: (92)

Have you monitored gps to see if the are normal with the new maf. Any other errors with the new maf 33 or 34 ?
default you mean limp home mode ?

aekerley

New MAF was reading around 5,000 GPS at idle where the old one is a little higher. I attribute this to low and "hunting" idle. The new sensor; hard start, surging idle, and will stall if throttle is opened. This is when engine is at operating temp. When cold in open loop it will run fine. No codes with new sensor. Old sensor runs fine all conditions, but sends a code 36 sel.

Tuned Performance

iTrader: (92)

Don’t see how you can get 5,000 gps
idle should be around 8-9. Max gps is 255. Should have set a code 33.

aekerley

Default meaning with the MAF unpluged and ecm default parameters. Again, just what I've read in some other post. Can't find ref to that in the manual.

aekerley

Might be talking about different readings. I was referring to the input signal from the MAF. Old and new seemed to track similarly.

Tuned Performance

iTrader: (92)

Alpha n ?

Tuned Performance

iTrader: (92)

http://support.moates.net/theory-alpha-n/

aekerley

I will have to get connected in the morning and make sure I know the units and numbers. What would cause New to run bad Old to run good, New no codes Old burn wire fault?

Tuned Performance

iTrader: (92)

The burn wire is just there to burn off contamination after engine run.
does not effect running. The only thing I can think of is fluctuations with gps reporting to the ecm. Should be pretty stable at idle no way it can read 5k gps not sure what scanner or software your using.

aekerley

Attached are the scanner views of the car running in both open start up and closed loop with the existing sensor.

Tuned Performance

iTrader: (92)

Gps isn’t a correct reading. Try win aldl or better yet tunerpro $32b mask.

aekerley

Update: I received the replacement reman. MAF from Napa. Plugged it in and it works. No codes, runs fine. Some mystery around why the Delphi didn't work, but looks like the first Napa sensor was a defect. If it acts up again my only thought is the connector. That's the only thing I touched during the last swap out.

Thank you for everyone's help

Annihilate

iTrader: (1)

What reading are you getting with your scan tool now? I'm having a similar issue.

aekerley

The units do not match what they should be if they are measuring gr/s. I called Actron and they did not have an answer. All I know at this point is that the MAF reading at idle is 1536 @ 750 rpm and 3328 @ 1,300 rpm (cold). The car runs fine, no codes.

aekerley

11-12-20 MAF Update. I have been driving the car without issue until this week. Running down the highway 70 MPH cruse control on and engine dies. No warning, no faults just off. Pulled over and checked everything out. After 20 minutes of checking connections, spark, fuel pump, all obvious things I pulled the connector on the MAF. Engine fired up and I drove another hour and a half to my destination, with the check engine light. I called NAPA and they will stand behind the reman MAF I bought four months ago. I told them I would rather not get stuck on the side of the road with another reman, so I ordered a new Delphi. This is aggravating, anyone have good luck with the new Delphi's? not many options out there.

aekerley

Finally got the new Delphi from Napa. Plugged it in the started the car. Warmed up and once at temp. died. So far will not restart, even after unplugging the battery and disconnecting the new MAF. So now what??????? ECM?

Vader

Three replacement MAF sensors would tend to indicate that the problem is elsewhere. Investigate the connectors at the MAF itself, as well as BOTH relays (including the relay contacts themselves), and connections to the ECM.

Annihilate

iTrader: (1)

I recently had some issues after I had thought I solved the issue with a Delphi MAF.

I was sitting in a drive through and things started taking a turn.

Went through a similar line of thinking as you, however I dont believe the issue is the MAF for me.

Im still doing some trouble shooting, I've found my fuel rail pressure to be a bit low.

Perhaps your issue lies in the fuel circuit.

Im getting my rear end rebuilt so ill be pulling it out, and will be replacing the fuel pump and filter as well.

Also during winter I'll be doing spark plugs and maybe injectors.

Id be insterested to hear how you solve your issue.

Tremo

I'm running a Delphi MAF I bought from Rockauto. Runs fine. No codes.

A month or so back I got a simultaneous code 33 and 36. I replaced both relays and those codes went away.

The Cardone MAFs that Rockauto sells are reman Bosch.

I'm now fighting erratic idle. Sometimes it idles fine, other times it just stalls and dies, but if I can blip the throttle before it dies it will come back up and idle fine. WTF?

Tremo

Won't start at all? Even with the MAF unplugged? Unplugged it should run in open loop mode. It should start. i don't think it is the MAF.

BTW, I see those Delphi MAFs sell on the Napa site at, what, $280 each? Rockauto sells the same MAF for $160. They sell the Reman Bosch MAFs for about $120.

Annihilate

iTrader: (1)

I've got the Delphi myself, haven't had any MAF issues since that install. However it might be worth checking o2 sensor, as that was giving me a bunch of issues.

My EGR is up on the block next for diagnosis.