MAF Sensor signal High
Thread Starter
Heel & Toe
Joined: Sep 2005
Posts: 17
Likes: 0
From: Fayetteville NC
MAF Sensor signal High
Check engine soon light prompted use of scanner to read codes which indicated that I had a problem with the MAF Sensor. I took a drive and checked the operational data which shows a slightly high MAF signal under normal acceleration. Have been unable to determine the cause of this condition. Does anyone have any experience with this issue?1988 Coupe
5.7
automatic
code 33
Condition is triggered when driving not during start-up or idle
Last edited by bmwrollin; Mar 12, 2006 at 08:57 PM. Reason: Additional Information
Team Owner
Joined: Jan 2003
Posts: 20,304
Likes: 240
From: Summerland B.C. Canada
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Tough to crack when it's not a component. Make sure the Burnoff Relay isn't powered up. There might be a short to voltage on the signal wire or it's soaking up voltage from somewhere else. The only place that might come from would be the plug wires. Check them closely on the right side, particularly from the distributor to where they snake under the EGR tube. That's near the ECM harness and if one was leaking - worn insulation, the signal wire might pick it up and report a high voltage to the ECM.
Melting Slicks
Joined: Aug 2003
Posts: 3,395
Likes: 393
From: Lakeville MI
In the chip there is a threshold of flow vs. rpm for setting this code, if you're modded enough you can exceed the threshold.
This can be edited or disabled easily in the chip. I think heads/cam/intake would put you close to the threshold. I didn't check to see your mods, if any.
MAF high diagnostic threshold looks like this (data from my 88):
rpm maf gm/sec
0 23
400 23
800 30
1200 48
1600 68
2000 89
2400 111
2800 141
3200 170
3600 200
4000 220
4400 236
4800 245
5200 247
5600 247
6000 247
6400 255
This can be edited or disabled easily in the chip. I think heads/cam/intake would put you close to the threshold. I didn't check to see your mods, if any.
MAF high diagnostic threshold looks like this (data from my 88):
rpm maf gm/sec
0 23
400 23
800 30
1200 48
1600 68
2000 89
2400 111
2800 141
3200 170
3600 200
4000 220
4400 236
4800 245
5200 247
5600 247
6000 247
6400 255
Thread Starter
Heel & Toe
Joined: Sep 2005
Posts: 17
Likes: 0
From: Fayetteville NC
Relays
All tests indicated that the relays are functioning correctly and so I didn't replace them however my patience is about gone and ready to change anything and everything that may cause the problem. NOT!
The only mods are a performance chip and ACCEL fuel injectors(24lbs/hr). No other mods have been made so I doubt I have reached the threshold for air flow but I will compare with the numbers I recieved. The plug wires are not new but not very old either. I will inspect and make sure the clearence between them and any other wires. Thanks for the input guys.
The only mods are a performance chip and ACCEL fuel injectors(24lbs/hr). No other mods have been made so I doubt I have reached the threshold for air flow but I will compare with the numbers I recieved. The plug wires are not new but not very old either. I will inspect and make sure the clearence between them and any other wires. Thanks for the input guys.
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Burning Brakes
Joined: Jun 2002
Posts: 1,001
Likes: 1
From: sd
This is just a thought but after my fiasco and code 33 on my 85 I'd check the wires to the harness for your MAF sensor. Mine appeared perfectly fine however contact was not being made with the pins from the MAF sensor itself. Take a small screwdriver and push all of the pins closer together in the harness and try that. You have nothing to lose if you try it but maybe this will help. The others have good advise for you as well but this is something little to try and I wish I would have done it 2 weeks earlier as it would have saved me a boatload of frustration. Good luck!
Drifting
Joined: Mar 2005
Posts: 1,923
Likes: 0
From: GA
Start by checking the wiring to the fuel pump relay, look for bare wires near the socket. then move on to replacing the relays. I had a code 33 that would come and go, even while driving it would disappear and turn off the ck eng light. Checked the power relay and it functioned as advertised, but aparently the constant current going through it after being on for a while made it satrt to screw up.
Drifting
Joined: Apr 1999
Posts: 1,261
Likes: 6
From: Middletown New Jersey
I went through this when I tried one of the thin film MAF's (Wells SU-145). It would periodically throw a code. granted I'm highly modified but when I put my Bosch gutted sensor back on the problem went away.
