'86 2.8L MPFI ignition problem...
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Junior Member
Joined: Jul 2001
Posts: 5
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'86 2.8L MPFI ignition problem...
I just recently bought an 1986 Berlinetta with fuel injected 2.8L. I've replaced the coil, distributor cap, plug wires, pickup coil, and the control module that is under the distributor cap. All this to fix a previous igintion problem. One day I was driving about 50 mph and the engine just dies with no warning. From what I could tell there was no spark. I let it sit for about 4 hours then tried to start it again, and it fired right up. I have no clue what it could be. If anyone has any ideas, please let me know.
One other problem is that I have a flash code "34" which is "Low voltage, high vaccum at MAS or MAP" that I can't track down. The Mass air flow sensor is good. If you have any suggestions please let me know! Thanx
------------------
-=Stone Rhino=-
Grey '86 Camaro Berlinetta. 2.8 MPFI
One other problem is that I have a flash code "34" which is "Low voltage, high vaccum at MAS or MAP" that I can't track down. The Mass air flow sensor is good. If you have any suggestions please let me know! Thanx
------------------
-=Stone Rhino=-
Grey '86 Camaro Berlinetta. 2.8 MPFI
Member
Joined: Jul 2000
Posts: 249
Likes: 0
From: Avondale, AZ
Try replacing the ignition control module. What's probably happening is your control module is running fine when it's cold but when it heats up it's failing. Some auto parts stores can test them but the tests are not very good.
Supreme Member
Joined: Mar 2000
Posts: 13,414
Likes: 6
From: Central NJ, USA
Car: 1986 Firebird
Engine: 2.8 V6
Transmission: 700R4
Yep; as far as the MAF code, the code for your '86 is technically "MAF low frequency (low air flow)". How do you know the MAF sensor is good?
------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!
------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!
Supreme Member
Joined: Mar 2000
Posts: 13,414
Likes: 6
From: Central NJ, USA
Car: 1986 Firebird
Engine: 2.8 V6
Transmission: 700R4
Well, if another one gives you the code, then there must be a wiring problem. It's easy to trace, and I'm about to tell you where -everything- is! All you need is a voltmeter and maybe a half hour. Ready... get set... go (and let US know the results)!!
-----------------------------------------------
DIAGNOSTIC CHART FOR CODE 34 (2.8L MPFI ENGINE)
---------------------------typed by Tom P------
First off, they want you to check out the air intake duct for being loose or
damaged.
Since you are getting the code 34, and no other error codes, we can kind of jump into
the middle of the chart:
1. Ignition off. Disconnect the MAF sensor wire. Connect a voltmeter between the
____harness pin "B" (center) and ground.
_______Less than 1 volt? Go down to "1A"
_______Over 4 volts? Go down to "2"
____1A: Disconnect ECM A-B connector. Check circuit 528 (brown/white, on connector
_________"B", terminal #6) for an open or short to ground. If it's not open/shorted,
_________it's faulty ECM connector terminal B6 or a bad ECM. By the way, this is the
_________MAF's "signal" wire.
2. Connect a test light between MAF harness pins "A" & "C".
_______Light on? Go down to "2A"
_______Light off? Go down to "3"
___2A: Faulty MAF sensor connection or sensor. So since you've tried two sensors,
________I'd imagine the connector's at fault. Try checking for corrosion on the
________connector's pins- I had that happen once. Also, try wiggling the connector,
________and seeing if you get a SES light. If I wiggle my current one, I can make
________a code 34 set, and the car almost stalls. I've gotta get another connector
________from a junkyard... Pep Boys sells new ones, but for an outrageous price.
---------update 10/2000: I replaced the connector (actually, the whole MAF harness!)
---------with one from a junkyard car. No more connector problems!
3. Connect a test light between MAF harness pin "A" and ground.
_______Light off? Go down to "4"
_______Light on? Go down to "3A"
___3A: The ground wire for your MAF, which is MAF harness pin "C", is open. Fix
________the problem with the black ground wire, either it's bad or burnt thru or
________it broke at the passenger-side-upper-frame-rail grounding point (a ring
________terminal on a screw).
4. Disconnect MAF relay, ignition "on" (not "start"). Connect a test light (at the
____relay connector) between CKT 840 (brown) and ground, and CKT 39 (black/pink) and
____ground.
____Okay, now, the MAF relay is located between your air filter box & radiator, on the
____radiator support, I believe. It should have one long black connector to the harness,
____NOT two connectors (one black and one gray)- that ones for your flip up headlights.
---------update 7/2001: For Camaros, you guys have a different location for your airbox.
---------But, the MAF relay's in the same spot, at the passenger side of the radiator, on
---------the radiator support. I believe it's the only relay you Camaro guys have down
---------there; just check the relay for the wire colors I mentioned for CKTs 840 & 39.
____The test on CKT 840 checks to see if voltage is getting from your MAF fuse to the
____MAF relay.
____As for CKT 39, that's controlled by your GAGE fuse. (So that's what it does! Cool.)
____It comes on with the car's ignition- that's why you need the ignition "on". When this
____black/pink wire gets power, it flips the MAF relay's magnet ON, which basically switches
____the MAF on- that's how power gets from CKT 840 to the MAF.
_______Only one light? "repair the open circuit".
__________No light on CKT 840? See "4A"
__________No light on CKT 39? See "4B"
_______Both circuits are fine? Go see "5"
___4A: If no light on CKT 840, find the MAF fuse- it's under your hood, screwed down
________to the upper-frame-rail on the passenger side of the car, closest to the
________headlights. You'll see two little black boxes, each with two wires coming out
________of them, screwed down to the upper frame rail by one screw each. One of them
________has a red wire and a BROWN wire coming out of it- that's your MAF fuse holder.
________Pop the top off to see the MAF fuse. (The holder with red & orange wires is for
________your computer and fuel pump.)
________If the fuse looks fine, try replacing it anyway... I've had that happen to me-
________the fuse looks fine but's really shot. Perform test #4 again. Still no light?
________Probe the MAF fuse holder's RED wire with a test light to ground. This checks
________the MAF fuse holder's connection to the positive-junction-block, located on the
________passenger side of your radiator support. If it's bad, follow the red wire to
________the junction block & fix it. Do test #4 again- still no light? Check
________for corrosion on the MAF fuse holder's contacts. You should get a light by now-
________unless your test light's shot!
___4B: If no light on CKT 39, check the GAGE fuse in the fusebox. As I said up in "3A",
________if the fuse looks fine, try replacing it anyway. Do test #4 again. If you've
________got no light, you get to trace CKT 39 thru the firewall, so hopefully you get
________a light on this one. This one would be a bitch to fix. All I could tell ya is
________that the black/pink wire goes to the GAGE fuse, and the GAGE fuse gets turned
________on when your ignition switch gets turned to "on".
5: Connect a test light between circuit 840 and CKT 450 (black ground wire from the
____relay connector).
_______Light off? See "5A"
_______Light on? See "6"
___5A: Fix the bad ground wire (open on CKT 450) from the relay to the chassis.
---------update 10/2000: This is buried! It follows the wiring harness along the
---------passenger side lower frame rail. You'll have to trace it the whole way. It
---------joins with 5 or 6 other ground wires at one point. Then, after that junction,
---------one wire goes to a ring terminal on the rear driver's side head.
6. Check out the condition of the orange/black wire that goes from pin "A" of the MAF
____connector to terminal "E" of the relay. If this wire is fine (not shorted or open),
____then your relay's bad... you could get a junkyard one but I think a new one is only
____$10 or so from GM.
If you've tried two MAF's, then the problems gotta be in the wiring... I actually had a flaky MAF connector on my car. The car would run great until I'd wiggle the MAF connector, then it'd stall & give me a code. I replaced the whole "end harness" for the MAF with that of a junkyard Camaro's for $5- Pep Boys wanted $15 for the connector alone. Good luck- and let us all know what you find!
------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!
[This message has been edited by TomP (edited July 23, 2001).]
[This message has been edited by TomP (edited July 23, 2001).]
-----------------------------------------------
DIAGNOSTIC CHART FOR CODE 34 (2.8L MPFI ENGINE)
---------------------------typed by Tom P------
First off, they want you to check out the air intake duct for being loose or
damaged.
Since you are getting the code 34, and no other error codes, we can kind of jump into
the middle of the chart:
1. Ignition off. Disconnect the MAF sensor wire. Connect a voltmeter between the
____harness pin "B" (center) and ground.
_______Less than 1 volt? Go down to "1A"
_______Over 4 volts? Go down to "2"
____1A: Disconnect ECM A-B connector. Check circuit 528 (brown/white, on connector
_________"B", terminal #6) for an open or short to ground. If it's not open/shorted,
_________it's faulty ECM connector terminal B6 or a bad ECM. By the way, this is the
_________MAF's "signal" wire.
2. Connect a test light between MAF harness pins "A" & "C".
_______Light on? Go down to "2A"
_______Light off? Go down to "3"
___2A: Faulty MAF sensor connection or sensor. So since you've tried two sensors,
________I'd imagine the connector's at fault. Try checking for corrosion on the
________connector's pins- I had that happen once. Also, try wiggling the connector,
________and seeing if you get a SES light. If I wiggle my current one, I can make
________a code 34 set, and the car almost stalls. I've gotta get another connector
________from a junkyard... Pep Boys sells new ones, but for an outrageous price.
---------update 10/2000: I replaced the connector (actually, the whole MAF harness!)
---------with one from a junkyard car. No more connector problems!
3. Connect a test light between MAF harness pin "A" and ground.
_______Light off? Go down to "4"
_______Light on? Go down to "3A"
___3A: The ground wire for your MAF, which is MAF harness pin "C", is open. Fix
________the problem with the black ground wire, either it's bad or burnt thru or
________it broke at the passenger-side-upper-frame-rail grounding point (a ring
________terminal on a screw).
4. Disconnect MAF relay, ignition "on" (not "start"). Connect a test light (at the
____relay connector) between CKT 840 (brown) and ground, and CKT 39 (black/pink) and
____ground.
____Okay, now, the MAF relay is located between your air filter box & radiator, on the
____radiator support, I believe. It should have one long black connector to the harness,
____NOT two connectors (one black and one gray)- that ones for your flip up headlights.
---------update 7/2001: For Camaros, you guys have a different location for your airbox.
---------But, the MAF relay's in the same spot, at the passenger side of the radiator, on
---------the radiator support. I believe it's the only relay you Camaro guys have down
---------there; just check the relay for the wire colors I mentioned for CKTs 840 & 39.
____The test on CKT 840 checks to see if voltage is getting from your MAF fuse to the
____MAF relay.
____As for CKT 39, that's controlled by your GAGE fuse. (So that's what it does! Cool.)
____It comes on with the car's ignition- that's why you need the ignition "on". When this
____black/pink wire gets power, it flips the MAF relay's magnet ON, which basically switches
____the MAF on- that's how power gets from CKT 840 to the MAF.
_______Only one light? "repair the open circuit".
__________No light on CKT 840? See "4A"
__________No light on CKT 39? See "4B"
_______Both circuits are fine? Go see "5"
___4A: If no light on CKT 840, find the MAF fuse- it's under your hood, screwed down
________to the upper-frame-rail on the passenger side of the car, closest to the
________headlights. You'll see two little black boxes, each with two wires coming out
________of them, screwed down to the upper frame rail by one screw each. One of them
________has a red wire and a BROWN wire coming out of it- that's your MAF fuse holder.
________Pop the top off to see the MAF fuse. (The holder with red & orange wires is for
________your computer and fuel pump.)
________If the fuse looks fine, try replacing it anyway... I've had that happen to me-
________the fuse looks fine but's really shot. Perform test #4 again. Still no light?
________Probe the MAF fuse holder's RED wire with a test light to ground. This checks
________the MAF fuse holder's connection to the positive-junction-block, located on the
________passenger side of your radiator support. If it's bad, follow the red wire to
________the junction block & fix it. Do test #4 again- still no light? Check
________for corrosion on the MAF fuse holder's contacts. You should get a light by now-
________unless your test light's shot!
___4B: If no light on CKT 39, check the GAGE fuse in the fusebox. As I said up in "3A",
________if the fuse looks fine, try replacing it anyway. Do test #4 again. If you've
________got no light, you get to trace CKT 39 thru the firewall, so hopefully you get
________a light on this one. This one would be a bitch to fix. All I could tell ya is
________that the black/pink wire goes to the GAGE fuse, and the GAGE fuse gets turned
________on when your ignition switch gets turned to "on".
5: Connect a test light between circuit 840 and CKT 450 (black ground wire from the
____relay connector).
_______Light off? See "5A"
_______Light on? See "6"
___5A: Fix the bad ground wire (open on CKT 450) from the relay to the chassis.
---------update 10/2000: This is buried! It follows the wiring harness along the
---------passenger side lower frame rail. You'll have to trace it the whole way. It
---------joins with 5 or 6 other ground wires at one point. Then, after that junction,
---------one wire goes to a ring terminal on the rear driver's side head.
6. Check out the condition of the orange/black wire that goes from pin "A" of the MAF
____connector to terminal "E" of the relay. If this wire is fine (not shorted or open),
____then your relay's bad... you could get a junkyard one but I think a new one is only
____$10 or so from GM.
If you've tried two MAF's, then the problems gotta be in the wiring... I actually had a flaky MAF connector on my car. The car would run great until I'd wiggle the MAF connector, then it'd stall & give me a code. I replaced the whole "end harness" for the MAF with that of a junkyard Camaro's for $5- Pep Boys wanted $15 for the connector alone. Good luck- and let us all know what you find!
------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!
[This message has been edited by TomP (edited July 23, 2001).]
[This message has been edited by TomP (edited July 23, 2001).]
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Thread Starter
Junior Member
Joined: Jul 2001
Posts: 5
Likes: 0
I fixed the code 34! about time! Got my 4 inch thick Helm manual in today and it pretty much told me what you wrote TomP. Thanx for your post! Anyways it ended up being the MAF relay. I thought I checked that a few times before. Oh well. no more codes.
The bad thing is that I still have an ignition problem that just waiting for the wrong moment to act up on me. I think the problem is temprature sensitive considering it did it while it was really hot and when it was really cold. I know that heat isn't exactly electronics friend so that prettly logical. But I have no clue why it wouldn't run when it was cold out side. If anyone has any ideas, let me know!
P.S. My ignition coil is new... so I know thats not it.
The bad thing is that I still have an ignition problem that just waiting for the wrong moment to act up on me. I think the problem is temprature sensitive considering it did it while it was really hot and when it was really cold. I know that heat isn't exactly electronics friend so that prettly logical. But I have no clue why it wouldn't run when it was cold out side. If anyone has any ideas, let me know!
P.S. My ignition coil is new... so I know thats not it.
Thread Starter
Junior Member
Joined: Jul 2001
Posts: 5
Likes: 0
OKay, I got the ignition problem fixed! guess what it was... the brand new Borg Warner control Module! The dang thing is bad! I only bought it a month or so ago! Thats the second bad Borg Warner part I've gotten for the ignition alone! But I put the old control module in and I haven't had any problems at all!
Thanx everyone for their help and input. It was very valuble!
------------------
-=Stone Rhino=-
Grey '86 Camaro Berlinetta. 2.8 MPFI
Thanx everyone for their help and input. It was very valuble!
------------------
-=Stone Rhino=-
Grey '86 Camaro Berlinetta. 2.8 MPFI
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