Bosch MAF Sensor -- What do the guts look like?
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 1,174
Likes: 125
From: Dunstable MA
St. Jude Donor '05
Bosch MAF Sensor -- What do the guts look like?
I've been chasing a nasty Code 33: 
MAF and Burn-off relays replaced. IAC and Throttle body cleaned. Scan showed O2 and Coolant Temp Sensors out of range, so they got replaced. Seafoamed the motor, including the intake.
The code does not always show. About half the time the car runs like a top. The other half of the time it stalls when I first start it; then I'm in for the SES, and a rough on/off throttle response for the entire ride.
The intermittent nature of this makes me think the wiring is funky; especially since morning cold starts seem to avoid the code. It is a good bet, though, that if I pull over and shut down the motor and restart it, that it will stall and the code will set. I have yet to probe the harness. It's not my favorite job, but it is on my to do list.
Meanwhile, I have been shopping for MAF's on the web, and one that I saw had wires running through it like a light bulb's innards. The Bosch unit in my car does not have any thin wires running across the insides. Can anyone tell me if it should?
Better yet, can anyone tell me WTF is going on??
MAF and Burn-off relays replaced. IAC and Throttle body cleaned. Scan showed O2 and Coolant Temp Sensors out of range, so they got replaced. Seafoamed the motor, including the intake.
The code does not always show. About half the time the car runs like a top. The other half of the time it stalls when I first start it; then I'm in for the SES, and a rough on/off throttle response for the entire ride.
The intermittent nature of this makes me think the wiring is funky; especially since morning cold starts seem to avoid the code. It is a good bet, though, that if I pull over and shut down the motor and restart it, that it will stall and the code will set. I have yet to probe the harness. It's not my favorite job, but it is on my to do list.
Meanwhile, I have been shopping for MAF's on the web, and one that I saw had wires running through it like a light bulb's innards. The Bosch unit in my car does not have any thin wires running across the insides. Can anyone tell me if it should?
Better yet, can anyone tell me WTF is going on??
Last edited by Rich Silvestris; Apr 30, 2006 at 09:32 PM.
Safety Car
Joined: Nov 2004
Posts: 4,991
Likes: 5
From: The Pines South Jersey
Are you saying you pryed the cover off of the electronics side of the MAF?
If you didnt, the seal on mine was missing over 50% of it, the cover came off easy when I removed the remaing sealant - inside was a bunch of what looked like condensate corrosion. The guts look like a circuit board with a bunch of solder
I shot contact cleaner in there hit it with a hair dryer and resealed it - then I cleaned up the connections to the weather pack connector.
Intermittent troubles suck, G/L
If you didnt, the seal on mine was missing over 50% of it, the cover came off easy when I removed the remaing sealant - inside was a bunch of what looked like condensate corrosion. The guts look like a circuit board with a bunch of solder
I shot contact cleaner in there hit it with a hair dryer and resealed it - then I cleaned up the connections to the weather pack connector.
Intermittent troubles suck, G/L
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 1,174
Likes: 125
From: Dunstable MA
St. Jude Donor '05
I haven't opened the electronics enclosure. I'm just talking about the view through the sensor into the throttle body. The sealant is mostly still on the electronics enclosure, but thanks for the heads-up.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Take a look at the wires in the MAF sometimes they get a foreign object in there and cause this type of problem. Just need spraying with contact cleaner if so. Need to troubleshoot the MAF since you replaced the power and burnoff sensors. Wiring might not be the problem. The troubleshooting diagram is in the FSM and if you don't have one.... pm Agent86, he's got a scan of one.
Team Owner
Joined: Sep 2001
Posts: 62,171
Likes: 1,735
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Probably the MAF itself. Expensive replacement.
Do not buy the aftermarket 'performance' sensors, stick with GM.
Do not buy the aftermarket 'performance' sensors, stick with GM.
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 1,174
Likes: 125
From: Dunstable MA
St. Jude Donor '05
RRT: I have the FSM, and I know I will be out there with the VOM soon.
Vader86: I just read your webpage instructions on the IAC. I didn't take mine apart, and I didn't push it in all the way before installing it either. I left it in the same position it was in when I removed it. Is that okay?
Vader86: I just read your webpage instructions on the IAC. I didn't take mine apart, and I didn't push it in all the way before installing it either. I left it in the same position it was in when I removed it. Is that okay?
Team Owner
Joined: Jun 2001
Posts: 26,196
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From: Orlando FL
St. Jude Donor '08-'09
Originally Posted by vader86
Probably the MAF itself. Expensive replacement.
Do not buy the aftermarket 'performance' sensors, stick with GM.
Do not buy the aftermarket 'performance' sensors, stick with GM.
Team Owner
Joined: Sep 2001
Posts: 62,171
Likes: 1,735
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Originally Posted by Rich Silvestris
Vader86: I just read your webpage instructions on the IAC. I didn't take mine apart, and I didn't push it in all the way before installing it either. I left it in the same position it was in when I removed it. Is that okay?
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Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
One thing you should do is reset the IAC. I think Vader may have a write up on his site. Pretty simple, but you may need to adjust your minimum airflow setting-then you may need to adjust the TPS voltage. If not, post, and either I or another member will walk you through it. I'm really dumb when it comes to posting pics. Gotta get my kid to help me when she comes back over again.
Well-looks like Vader says it should be fine.
I wouldn't be so quick to condem the MAF-it very well could be, but it's not cheap and there's quite a few things that should be thourghly checked first.
Well-looks like Vader says it should be fine.
I wouldn't be so quick to condem the MAF-it very well could be, but it's not cheap and there's quite a few things that should be thourghly checked first.
Last edited by rick lambert; May 1, 2006 at 10:18 AM.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
A bad IAC does not show a code. I consider this to be a mainanence item. You car stalling at start up this could be the IAC. You stated you cleaned the IAC and TB. Did you take the IAC out of the TB for cleaning and follow the proper steps? As for the intermittant code 33 You have a volt meter and FSM so just follow the steps. Once the code is fixed this will rule out the MAF and give a more narrow guide to fix any other problems. I'd fix the code first. IMO
