1988 vette engine trouble
Thread Starter
Intermediate
Joined: Jul 2007
Posts: 34
Likes: 0
1988 vette engine trouble
The saga goes on. I have owned the car for three years. I have never seen it run like it should.
1. changed plugs cap rotor
2. new fuel injectors
3. new fuel filter
When you first start it up it runs like a champ once it hits closed loop (i assume) it stumbles like it is running on 7 cyl.
It finally coded today 34+36
Things I have modified
4+3 Tranny. I ran a toggle switch to lock out the OD. I think its the 36 code.
I have a plug in code reader.
I have impulse from o2
The fuel seems ok it flashes for a second on a sec off except when I get off the throttle. It will rich out for a second. all looks good there.
I can reset the codes and it will run for a day before coding again. I have a friend who has a computer to hitch up to but I have not got there yet.
Does this sound like a maf ??? I am sick of throwing money in it please help.
1. changed plugs cap rotor
2. new fuel injectors
3. new fuel filter
When you first start it up it runs like a champ once it hits closed loop (i assume) it stumbles like it is running on 7 cyl.
It finally coded today 34+36
Things I have modified
4+3 Tranny. I ran a toggle switch to lock out the OD. I think its the 36 code.
I have a plug in code reader.
I have impulse from o2
The fuel seems ok it flashes for a second on a sec off except when I get off the throttle. It will rich out for a second. all looks good there.
I can reset the codes and it will run for a day before coding again. I have a friend who has a computer to hitch up to but I have not got there yet.
Does this sound like a maf ??? I am sick of throwing money in it please help.
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Joined: Oct 2007
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From: So. Cal.
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maf
Unplug maf and see if it runs better. Dont have my FSM close by so I cant remember codes. Maybe check o2 sensor, since it runs of it when in closed loop. Good luck.
Corvette Enthusiast
Joined: Oct 2007
Posts: 6,797
Likes: 2,721
From: So. Cal.
2025 C7 of the Year Finalist- Unmodified
2024 C7 of the Year Finalist - Unmodified
2023 C7 of the Year Finalist - Unmodified
Maf
Unplugging the maf is an easy way to see if you have maf issues. I have did this before. I think it makes your car go back to open loop. There are lots of people here in this forum with more knowlage than I that will probably chime in.
Thread Starter
Intermediate
Joined: Jul 2007
Posts: 34
Likes: 0
Changed plugs looked a little lean. Took for ride and about 5-10 min into ride it started running like it was on 7 cyl. I unplugged the MAF sensor it coded 33 but ran better. It was alittle jumpy up threw the throttle but ran better. Before I spend 150 bucks does anyone think this has been the root cause of all my trouble.
Intermediate
Joined: Oct 2006
Posts: 39
Likes: 0
From: Mesa AZ
Deerkill10
Codes 33, 34 and 36 are all MAF codes (at least from my 87 FSM). Code 33 is MAF sensor circuit. Code 34 is MAF sensor. Code 36 is MAF burnoff. Testing procedure for code 34:
1. Check for loose or damaged air duct between MAF sensor and throttle body.
2. Step 2 deals with rough idle on startup (which it sounds like you dont have)
3. clear codes (remove battery voltage for greater than 30 secs)
4. Start and run engine above 2300rpm for 1 minute or until code 34 sets
does code set? no: Code 34 intermittent (use different procedure)
yes:
1. ignition off
2. disconnect MAF sensor
3.repeat test
4. code 33 should set does it
yes: faulty MAF sensor
no: circuit 998 shorted to ground or faulty ECM
This procedure is from an 87 but I cannot see why it shouldnt work for your car. 85 through 89 used Bosch MAF. Good luck.
John
Codes 33, 34 and 36 are all MAF codes (at least from my 87 FSM). Code 33 is MAF sensor circuit. Code 34 is MAF sensor. Code 36 is MAF burnoff. Testing procedure for code 34:
1. Check for loose or damaged air duct between MAF sensor and throttle body.
2. Step 2 deals with rough idle on startup (which it sounds like you dont have)
3. clear codes (remove battery voltage for greater than 30 secs)
4. Start and run engine above 2300rpm for 1 minute or until code 34 sets
does code set? no: Code 34 intermittent (use different procedure)
yes:
1. ignition off
2. disconnect MAF sensor
3.repeat test
4. code 33 should set does it
yes: faulty MAF sensor
no: circuit 998 shorted to ground or faulty ECM
This procedure is from an 87 but I cannot see why it shouldnt work for your car. 85 through 89 used Bosch MAF. Good luck.
John
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
If you are going to keep the car why not get a cheap scan tool. The OBDI stuff is dirt cheap and allows you to read the actual sensor values to see if they make sense in the first place. I paid 75 bucks for a used auto xray and while probably not the best it allows you to see all the sensor values on a '91 that would cause a drivability problem.. Way better than reading codes as you can see if something changes wildly between running good and running bad.
Dave
Dave
Race Director
Joined: Sep 2005
Posts: 10,878
Likes: 1
St. Jude Donor '07
I had your problem. I solved it!
http://www.digitalcorvettes.com/foru...d.php?t=120118
Search eBay for the connector. $10. Good Guy.
http://www.digitalcorvettes.com/foru...d.php?t=120118
Search eBay for the connector. $10. Good Guy.
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Intermediate
Joined: Oct 2006
Posts: 39
Likes: 0
From: Mesa AZ
deerkill10
The MAF burnoff relay is located on the firewall behind the battery (2 relays there, the MAF burnoff relay is on the inside/engine side and the MAf sensor power relay is on the outside/door side. Did it reset code 36?
John
The MAF burnoff relay is located on the firewall behind the battery (2 relays there, the MAF burnoff relay is on the inside/engine side and the MAf sensor power relay is on the outside/door side. Did it reset code 36?
John
Intermediate
Joined: Oct 2006
Posts: 39
Likes: 0
From: Mesa AZ
deerkill10
It sounds like it could be. I am looking at my FSM and it states:
"a faulty MAF sensor should not be considered as the cause if code 36 is set. Go to this site http://members.shaw.ca/corvette86/
It is from another corvette forum member named agent86. The procedures for the different codes are covered. I am a computer idiot and am not very good at attaching links. Hope this helps.
John
It sounds like it could be. I am looking at my FSM and it states:
"a faulty MAF sensor should not be considered as the cause if code 36 is set. Go to this site http://members.shaw.ca/corvette86/
It is from another corvette forum member named agent86. The procedures for the different codes are covered. I am a computer idiot and am not very good at attaching links. Hope this helps.
John
