NEED Expert help, '89 v6 backfiring

Hi Guys, and thanks in advance for your help!

Just bought an '89 "88" w/v6 for my son, previous owner obviously had problems, had changed-out MAP sensor with one from a junkyard, but seems it didn't help.

It starts great, seems to run great (except for some "chattering" noise seems to be coming from the auto tranny.....???) but at some point, usually after warm-up it wants to die, surges, and "pow" backfires through the intake, sometimes dieing, usually just fighting to keep running, then "pow" again. It then usually dies and is hard to re-start until later. Sometimes yes, sometimes no.

The "service engine soon" light seems to work when the key is first turned on, but does not stay on when it runs. I GUESS this would be the 'trouble code' light????

THanks again, looking forward to your advice, Steve Weible, rural Missouri

PS. Could this be an ignition module??? If so, where is it located?

Hi Guys, and thanks in advance for your help!

Just bought an '89 "88" w/v6 for my son, previous owner obviously had problems, had changed-out MAP sensor with one from a junkyard, but seems it didn't help.

It starts great, seems to run great (except for some "chattering" noise seems to be coming from the auto tranny.....???) but at some point, usually after warm-up it wants to die, surges, and "pow" backfires through the intake, sometimes dieing, usually just fighting to keep running, then "pow" again. It then usually dies and is hard to re-start until later. Sometimes yes, sometimes no.

The "service engine soon" light seems to work when the key is first turned on, but does not stay on when it runs. I GUESS this would be the 'trouble code' light????

THanks again, looking forward to your advice, Steve Weible, rural Missouri

PS. Could this be an ignition module??? If so, where is it located?
Lots of possibilities here, you need to check fuel pressure to confirm proper fuel delivery, when it dies and won't start do you have spark and injector pulse, basic first step diagnostics. Try tapping on the maf sensor, see if the engine responds, another possibility.

Also check for harmonic balancer separation, and timing chain slop in addition to what Max suggested.

Thanks, I checked with an induction tester, and it seems most difinate the ignition is causing the problem. The coil seems to start stuttering on it's firing, then quits.
And it always re-starts, but won't stay running. Even if i rev it up, it runs/doesn't fire at all in 1/2 to 2 second intervals then completely quits, but as I said will restart and maybe sound fine for a few seconds or minutes, seems to be heat related.
Thanks, Steve W.

OK, found on the i-net how to do trouble codes, and got code 34, Mass Air Flow Sensor (GM/Sec Low) whatever that means, and wherever it is.....

Could this be my problem? and if so where is this sensor????

Thanks Again, Steve W.

Your MAF is actually the MAP that you identified as being from the junker... If I remember right, these engines don't have anything labeled as an MAP sensor, but I believe the MAF and MAP serve the same function. Electronics from a junkyard are generally a waste of money unless they are obviously new so you may be well off to buy a new one...or perhaps risk another one from the junkyard.

Other possibilites include a bad/stretched timing chain, requiring replacement (not an easy job). Other possibilites could be that your coils are failing at operating temperatures, causing misfires and eventually the engine stops. Also, you could have fouled plugs and worn-out wires...or perhaps a vacuum leak.

This is the order that I suggest you go in:

1. Replace MAF sensor.
2. Check/replace any vacuum hoses (if they are cracked or dried out they could be leaking)
3. Replace plugs and wires (DELCO plugs only! and don't skimp on the wires either)
4. Test Coils (turn on car, remove one plug wire at a time with INSULATED pliers from each terminal.) If no spark or an erratic spark, then replace.
5. Test ignition module (ICM). Remove (3 11mm bolts, 1 7mm bolt on connector) and have Autozone or similar test. Be sure they test it several times to heat it up a bit to simulate operating temperatures.
6. If problem persists, then take it to a mechanic to have the timing gear, chain, damper, and cam interruptor magnet (GLUE IN to avoid a code 41!) replaced all at once unless the mechanic knows otherwise. This is especially true if the timing chain hasn't been replaced in about 100k-130k miles.

This is kinda what the MAF looks like:

http://www.leoberkhout.nl/massairflowsensor/MassAirFlow-Sensor_02_big.html

http://www.carcareandrepair.com/carcare-parts-massairflowsensor.htm

It is located between the tubing from your air cleaner and the throttle body...should be an electrical connector and 4 screws.

(forgot this in the last post)

Thanks!
I'm pretty sure it's not the coil(s) as all cylinders seem to quit at the same time, and the backfire thru the intake as well as the readings I get from the induction tester show it's definately electrical.
After disconnecting the battery to reset the computer, I no longer show an eror code for the MAF sensor, although I've started the engine and let it "malfunction several times.
Where is the ignition control module you recommended I have tested located on the engine?
Thanks again, Steve W.

The module is the part the coil packs mount to. IF it checks out ok, I bet you have a bad crank position sensor. When it dies, does the tachometer (if equipped) drop to zero just prior to it stalling?

Hrm...Backfiring through the intake is usually either a lean condition or your timing is off. I'm sure it's possible but generally a bad crank sensor will only make it quit running, not really mis-time the firing. Could be though, I've seen stranger things.

I would start by listening to the ECM about the MAF sensor. The code is telling you that it's reading an unusually low amount of air going into it. If your intake is fine it means the failing MAF is going to make the engine run lean, backfire through the intake, and shut down. It's really a common problem.

Since the ECM is telling you that's the problem, and the problem would fit your symptoms, I would either use a scantool to test it or just replace it.

Good luck.

Hrm...Backfiring through the intake is usually either a lean condition or your timing is off. I'm sure it's possible but generally a bad crank sensor will only make it quit running, not really mis-time the firing. Could be though, I've seen stranger things.

I would start by listening to the ECM about the MAF sensor. The code is telling you that it's reading an unusually low amount of air going into it. If your intake is fine it means the failing MAF is going to make the engine run lean, backfire through the intake, and shut down. It's really a common problem.

Since the ECM is telling you that's the problem, and the problem would fit your symptoms, I would either use a scantool to test it or just replace it.


I agree. Although I wouldn't totally rule out the crank, it is unlikely. If I were you, I would replace the MAF with a new one and then see what happens. If the problem persists, then the next likely culprit is your ICM or coils.

The ICM...well...here is a link to a neat tutorial on how to upgrade coils. It has pics of everythign you should need to know where it is :

http://www.thejmfc.com/autos/delcoignition.html

Wow, what a problem.
I took the ignition module and had it tested like 15 times and came-out good.
So I let it run and un-plugged the maf sensor several times, seemed to make little to no difference in the way it started and died, except the computer of course started giving me a trouble code for it.
So I disconnected the battery to reset the trouble codes, and did a start/let it die about 7 times, now I'm getting trouble code 41, "cam sensor circuit".
I have NO idea what the cam or crank sensors are or where they are. Thanks again for any help guys. I'm lookin' at just selling this thing as junk, taking the loss, and looking for something else for my son to drive.
Thanks Again, Steve Weible

Poor car :(

Anyway, a code 41 means that either your camshaft sensor went south (easy to replace) or your camshaft magenet broke/flew and is no longer telling the computer the position of your cam (not an easy fix). If you want details, just do a forum search...code 41 comes up quite a bit

Thanks, I did a search for code 41, and got lots of pages with no advice whatever.
What I need to know is Where is the cam sensor located? You said it was an "easy fix" if that's the problem. I'm a "newbie" here. Can it be tested at the shop?
Thanks again, Steve W.

The cam sensor is located in the timing cover just above and behind the harmonic balancer. It's located at about 10-11 o'clock in reference to the balancer. It is retained by one bolt. The magnet is in the cam gear and is what the cam sensor picks up it's signal from. Either could cause a code 41.

The cam sensor itself isn't too hard to replace, as richtazz explained. However, if the cam sensor interruptor magnet is gone then it is a whole different story. This magnet is held in by a plastic clip that can be broken by a sudden jar of the engine (wreck, pothole, slam on brakes, etc.) and the magnet is then thrown into the oil pan.

Without the magnet, the cam sensor doesn't recieve a code as to where the magnet is located (it spins past the cam sensor), resulting in a code 41.

There are two ways to replace it. One involves getting a new magnet, shaving off the clips on the plastic around the magnet and then jb-welding it in the camshaft sprocket by shoving it into its recess from the front of the engine (rigged way). The second way (the right way) involves removing the harmonic balancer and front cover of the engine and installing it into the back of the cam sprocket. If you go this route, you might as well replace the timing chain, gear, damper, and GLUE in the magnet (to avoid it being thrown out at a later time).