Bypass 1987 MAF sensor
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Bypass 1987 MAF sensor
I'm tired of dealing with malfunctioning mass air flow sensors in my 1987 vette. They seem to work for awhile then eventually go bad. I've read that swapping the prom in my ECM to a prom for a later C4 model that doesn't use a MAF sensor will work well. If that is true, what is involved in the swap, and where can I buy one of those proms?
Team Owner
Joined: Jul 2004
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From: Hartford WI
I'm tired of dealing with malfunctioning mass air flow sensors in my 1987 vette. They seem to work for awhile then eventually go bad. I've read that swapping the prom in my ECM to a prom for a later C4 model that doesn't use a MAF sensor will work well. If that is true, what is involved in the swap, and where can I buy one of those proms?
You are correct. You can swap out the EPROM to get rid of the MAF sensor. However, that still leaves a question. How does the ECM know how much air you have? AFAIK, on my 91, it is Speed Density. To convert your car to SD, you need to have a MAP sensor. That needs to be hooked into the manifold and that is the EASY part. Now you need to wire it to the ECM and possibly repin it to get the right location. Not looking at the diagrams, you may have to even get a new EMC, IDK. My suggestion is to see what the real problem is. If it is really the MAF that is constantly going bad, either you are getting junk parts or there is nothing wrong with them and the problem lies somewhere else.
For instance, in my 99 S320 Mercedes, we had a code that led us to the upstream O2 sensor. Chased a bunch of stuff and as a Hail Mary, changed the downstream one. That was the fix.
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I don't have MAF so I'm not totally sure which are the good ones. On my other cars I use OE or Bosch and not something from a parts house store brand.
You are correct. You can swap out the EPROM to get rid of the MAF sensor. However, that still leaves a question. How does the ECM know how much air you have? AFAIK, on my 91, it is Speed Density. To convert your car to SD, you need to have a MAP sensor. That needs to be hooked into the manifold and that is the EASY part. Now you need to wire it to the ECM and possibly repin it to get the right location. Not looking at the diagrams, you may have to even get a new EMC, IDK. My suggestion is to see what the real problem is. If it is really the MAF that is constantly going bad, either you are getting junk parts or there is nothing wrong with them and the problem lies somewhere else.
For instance, in my 99 S320 Mercedes, we had a code that led us to the upstream O2 sensor. Chased a bunch of stuff and as a Hail Mary, changed the downstream one. That was the fix.
You are correct. You can swap out the EPROM to get rid of the MAF sensor. However, that still leaves a question. How does the ECM know how much air you have? AFAIK, on my 91, it is Speed Density. To convert your car to SD, you need to have a MAP sensor. That needs to be hooked into the manifold and that is the EASY part. Now you need to wire it to the ECM and possibly repin it to get the right location. Not looking at the diagrams, you may have to even get a new EMC, IDK. My suggestion is to see what the real problem is. If it is really the MAF that is constantly going bad, either you are getting junk parts or there is nothing wrong with them and the problem lies somewhere else.
For instance, in my 99 S320 Mercedes, we had a code that led us to the upstream O2 sensor. Chased a bunch of stuff and as a Hail Mary, changed the downstream one. That was the fix.
Team Owner
Joined: Jul 2004
Posts: 28,413
Likes: 3,270
From: Hartford WI
Thanks for your reply. I didn't realize there was more involved in the swap. Your info makes sense. I'm using lifetime warranty parts from a well known parts house, and that may be my problem. Recently I was getting a repeat of GM code 33 errors when driving in a cold, high fog environment. I'm wondering if that might be normal considering the sensitivity of the MAF sensor in those conditions.
MAF means that the values are high. http://members.shaw.ca/corvette86/Code%2033.pdf
Drifting
Joined: Aug 2010
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when you switch to MAP or speed density system,there are lot of stuff involved.
part needed:
90-91 map sensor
730-(727) ECM
v8 memcal for 730 ecm
knock sensor 730 dedicated
lots of repinning of your original 165 maf ecm wiring harnes.
i will consider to buy a complete 90' speed density wiring harnes,and all the stuff mentioned above.The knock sensor circuit is built into the memcal for the 90'.You need to program the eprom with your Anth or Aujp .bin file.
Take a look at this third gen guy...this is the bible of ecms swap from 85 870 to 86-89 165,and from 86-89 165 to 90-91 730...
https://www.eecis.udel.edu/~davis/z28/ecm_swap_730/
part needed:
90-91 map sensor
730-(727) ECM
v8 memcal for 730 ecm
knock sensor 730 dedicated
lots of repinning of your original 165 maf ecm wiring harnes.
i will consider to buy a complete 90' speed density wiring harnes,and all the stuff mentioned above.The knock sensor circuit is built into the memcal for the 90'.You need to program the eprom with your Anth or Aujp .bin file.
Take a look at this third gen guy...this is the bible of ecms swap from 85 870 to 86-89 165,and from 86-89 165 to 90-91 730...
https://www.eecis.udel.edu/~davis/z28/ecm_swap_730/
Melting Slicks
Joined: Nov 2010
Posts: 2,216
Likes: 113
From: Michigan
As said, there are guides on the SD swap. I did an ecm upgrade on a 85 TA and it wasn't that hard.
Still I'd swap to a better more friendly tune-able aftermarket setup if your looking to upgrade a lot of other stuff, like maybe the ebl flash or Holley HP if you don't mind spending a lot.
Or just swap to the 400hp Fitech setup with a carb intake and a two wire cd style(msd, summit, allstar) locked out dist if you want something kinda simple, user friendly and about the same cost or less than the Holley HP setup.
LOL I've looked into a few options vs my 86 maf setup.
Still I'd swap to a better more friendly tune-able aftermarket setup if your looking to upgrade a lot of other stuff, like maybe the ebl flash or Holley HP if you don't mind spending a lot.
Or just swap to the 400hp Fitech setup with a carb intake and a two wire cd style(msd, summit, allstar) locked out dist if you want something kinda simple, user friendly and about the same cost or less than the Holley HP setup.
LOL I've looked into a few options vs my 86 maf setup.
Team Owner
Joined: Jul 2004
Posts: 28,413
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From: Hartford WI
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Melting Slicks
Joined: Jun 1999
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From: Ashland Alabama
If he is running a k&n filter that could be his cause.
MAF sensors do not go bad over and over normally. In fact on the few Ive had fail they all had over 250k miles on them.
One had 370k miles on it. So if it was me in place of hunting for a speed density solution I'd figure out why the sensors kept failing or erroring. They may just need cleaning or it could be wiring problem.
MAF sensors do not go bad over and over normally. In fact on the few Ive had fail they all had over 250k miles on them.
One had 370k miles on it. So if it was me in place of hunting for a speed density solution I'd figure out why the sensors kept failing or erroring. They may just need cleaning or it could be wiring problem.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
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From: Ashland Alabama
Oh and if its not a k&n filter shorting them out from coating and pooling then I would of course check the relays but as old as the cars are now Im seeing more bad harnesses and plugs than relays these days.
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
You will get an error code 33 if you lose the connection between the MAF and the ECM. That can happen with a broken wire or a bad connection. I suggest pulling apart the MAF connector and spraying the pins with contact cleaner.
Melting Slicks
Joined: Nov 2010
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From: Michigan
Just remembered I had some code 33's that were cause by the hose clamp on the air intake being in the right place to not let the connector go in just right. All it took to fix it was reclocking the clamp end slightly.
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Interesting reading here about Codes 33, 34, 36.....
Have you tried cleaning the MAF? CRC makes a MAF Sensor Cleaner that may help.
Most of the reman MAF's from Cardone and Standard don't seem to last. The AC Delco OEM part will work but they are a ton of money; $750+
Have you tried cleaning the MAF? CRC makes a MAF Sensor Cleaner that may help.
Most of the reman MAF's from Cardone and Standard don't seem to last. The AC Delco OEM part will work but they are a ton of money; $750+
Team Owner
Joined: Jul 2004
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From: Hartford WI
Interesting reading here about Codes 33, 34, 36.....
Have you tried cleaning the MAF? CRC makes a MAF Sensor Cleaner that may help.
Most of the reman MAF's from Cardone and Standard don't seem to last. The AC Delco OEM part will work but they are a ton of money; $750+
Have you tried cleaning the MAF? CRC makes a MAF Sensor Cleaner that may help.
Most of the reman MAF's from Cardone and Standard don't seem to last. The AC Delco OEM part will work but they are a ton of money; $750+
Team Owner
Joined: Sep 2001
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From: Athens AL
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I've never had one fail in 15 years, but I've always used Bosch/OE part. I also run a K&N Filter for all of those 15 years.
I suspect your problem is actually wiring. A connector or a frayed wire. Go through the procedure in the manual to find the problem. Do not throw more money at it by just swapping in a new MAF.
I suspect your problem is actually wiring. A connector or a frayed wire. Go through the procedure in the manual to find the problem. Do not throw more money at it by just swapping in a new MAF.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
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From: Ashland Alabama
I've never had one fail in 15 years, but I've always used Bosch/OE part. I also run a K&N Filter for all of those 15 years.
I suspect your problem is actually wiring. A connector or a frayed wire. Go through the procedure in the manual to find the problem. Do not throw more money at it by just swapping in a new MAF.
I suspect your problem is actually wiring. A connector or a frayed wire. Go through the procedure in the manual to find the problem. Do not throw more money at it by just swapping in a new MAF.
But at the same time like I mentioned above most of what I see these days are bad connectors and wiring.
Team Owner
Joined: Jul 2004
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From: Hartford WI
In my case, WGAS, I have speed density.