Guru's! New 85 GM crate motor, runs rough, misfires when hot, shows up upon restart!
- Thread starter tpaul
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Okay, so here's the scoop. I installed the new Powermaster 140 amp alternator. Yeah, not quite bolt-on. Nothing big, the output lug is larger than the stock alternator, also, the mounting bolt is standard thread, not metric like stock. No big deal, a Dremel tool and a trip to Home Depot fixed those problems.
At idle Tlink shows 13.6 volts. That's a good thing. Took the car to the street. It ran rough at first, but within 5 seconds the problem cleared up. Pretty much the same situation as when I hooked up the battery charger. It's funny, I've been a GN owner for over 16 years and have never seen voltage cause these kind of problems. Then again, this is the most heavily modified I have ever had a GN.
Making short trips near the house all was well. I decided to make a longer trip, this is where the problem started. About 8 - 10 miles into my runs with the new alternator the Voltage idiot light comes on. I'm able to drive home without a problem. I've got the vacuum brake conversion, and my brakes seemed very soft after this happened. My I was hyper-sensetive at this point just hoping to make it home.
Anyhow, I get home, opened the hood, and what do I see? The alternator belt was gone (belt had less than 150 miles on it!) I heard no noise to indicate I had lost a belt! The AC belt was also twisted 90 degrees, I figure the Belts came in contact upon release. After installing a new belt it looks as if the Powermaster pulley wasn't quite right. They say it will work with belts up to 10mm, but the pulley seemed to wide for my taste.
I've swapped out the Powermaster pulley to a stock pulley and have yet to road test it. I have had a chance to run it in the garage though. When I run the car for only a minute or less the alternator belt is much hotter than the other two belts!
Alternator alignment seems correct. I guess I'll just have to take it out again and see what happens. The last belt didn't wipe anything out, I can only hope that if the same happens again, and I don't lose anything!
Now I have to figure this situation out. Also, my Manifold air temp is showing up at -58 degrees on Tlink. I have Casper's sensor and wiring kit, I'm sure the sensor is good, so I have to check my wiring at the ECM.
Thanks for your help guys! I never would have looked at voltage to solve this problem!
At idle Tlink shows 13.6 volts. That's a good thing. Took the car to the street. It ran rough at first, but within 5 seconds the problem cleared up. Pretty much the same situation as when I hooked up the battery charger. It's funny, I've been a GN owner for over 16 years and have never seen voltage cause these kind of problems. Then again, this is the most heavily modified I have ever had a GN.
Making short trips near the house all was well. I decided to make a longer trip, this is where the problem started. About 8 - 10 miles into my runs with the new alternator the Voltage idiot light comes on. I'm able to drive home without a problem. I've got the vacuum brake conversion, and my brakes seemed very soft after this happened. My I was hyper-sensetive at this point just hoping to make it home.
Anyhow, I get home, opened the hood, and what do I see? The alternator belt was gone (belt had less than 150 miles on it!) I heard no noise to indicate I had lost a belt! The AC belt was also twisted 90 degrees, I figure the Belts came in contact upon release. After installing a new belt it looks as if the Powermaster pulley wasn't quite right. They say it will work with belts up to 10mm, but the pulley seemed to wide for my taste.
I've swapped out the Powermaster pulley to a stock pulley and have yet to road test it. I have had a chance to run it in the garage though. When I run the car for only a minute or less the alternator belt is much hotter than the other two belts!
Alternator alignment seems correct. I guess I'll just have to take it out again and see what happens. The last belt didn't wipe anything out, I can only hope that if the same happens again, and I don't lose anything!
Now I have to figure this situation out. Also, my Manifold air temp is showing up at -58 degrees on Tlink. I have Casper's sensor and wiring kit, I'm sure the sensor is good, so I have to check my wiring at the ECM.
Thanks for your help guys! I never would have looked at voltage to solve this problem!
Jerryl
Tall Unvaccinated Chinese Guy
- Joined
- Dec 14, 2004
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Temp sensor reading that low will cause some fueling issues as well.
Usually, if you look at the high output alternators, they use 2 belts or a serpentine belt. Maybe the increased load heated and stetched the belt?(Should not though as others have succesfully completed this.
)Thanks again for the reply. As I was crusing around today I noticed on TLink that I was getting a spark retard of up to 20 at around 20 MPH. This was at the same time the MAT was @ -58. This reading would go back and forth from zero. Are these two related? I have not seen these kind of numbers before. With that being said, this is the first time the MAT has been wacky!
As for the alternator... I never paid attention to the stock setup temps. I have no idea what's wrong and what's right. Man, this thing get's cooking... my stock alternator was cooking as well! I attributed this to bad bearings, maybe these temps are normal.
As for the alternator... I never paid attention to the stock setup temps. I have no idea what's wrong and what's right. Man, this thing get's cooking... my stock alternator was cooking as well! I attributed this to bad bearings, maybe these temps are normal.
Jerryl
Tall Unvaccinated Chinese Guy
- Joined
- Dec 14, 2004
- Messages
- 9,644
In colder temps, the ECM will command more fuel to compensate for the denser air. Do you remember the MAF, O2 and boost during KR?
Typically, at such low speed and low loads, it is false.
(I am sure you are running fresh 93)
Your low voltage may have something to do wth this as well (weak spark).
I don't remember those numbers at this point. The car was running so well I didn't even record the numbers. I was just happy to drive a car that didn't feel like a steam train going up a hill! I will record the new numbers when I run the car on Monday.
As far as fresh 93... not so much, I filled the car at the beginning of this year when it came out of the shop. With this problem, the car has sat in the garage for months. My fuel guage is still screwed... acording to mileage I believe I'm at a half a tank. I know before the rebuild I could get 230 -240 miles on a tank before I had to worry about filling up. I'm about 140 miles into this tank.
Not to play stupid, but what does KR mean?
As far as fresh 93... not so much, I filled the car at the beginning of this year when it came out of the shop. With this problem, the car has sat in the garage for months. My fuel guage is still screwed... acording to mileage I believe I'm at a half a tank. I know before the rebuild I could get 230 -240 miles on a tank before I had to worry about filling up. I'm about 140 miles into this tank.
Not to play stupid, but what does KR mean?
Jerryl
Tall Unvaccinated Chinese Guy
- Joined
- Dec 14, 2004
- Messages
- 9,644
KR = "Knock Retard", same as "Spark retard".
I went out and put about 10 miles on the car today. The belt with the stock pulley seems to be working well. I didn't once smell the slight burning smell I had the other day.
The rough condition came back for a few minutes at one point after stopping in the driveway for a couple minutes. I think my new battery may be going bad. It's been on the charger quite a bit. I'll take it to the parts store and have it tested.
After I got back to the driveway I let it idle while I grabbed the laptop and low and behold, the problem went away. I went out for another spin without that acting up again... but, Tlink started showing 18-19 volts. I've got another thread in the test tools section for this problem. Bottom line, the multi-meter was reading normal from the alternator post to battery ground.
I'm still getting the occasional MAT failure. The pin is good at the ECM. I found the sensor that John sells so I will replace it on Thursday. $11 at the local parts store, it's worth a shot!
The rough condition came back for a few minutes at one point after stopping in the driveway for a couple minutes. I think my new battery may be going bad. It's been on the charger quite a bit. I'll take it to the parts store and have it tested.
After I got back to the driveway I let it idle while I grabbed the laptop and low and behold, the problem went away. I went out for another spin without that acting up again... but, Tlink started showing 18-19 volts. I've got another thread in the test tools section for this problem. Bottom line, the multi-meter was reading normal from the alternator post to battery ground.
I'm still getting the occasional MAT failure. The pin is good at the ECM. I found the sensor that John sells so I will replace it on Thursday. $11 at the local parts store, it's worth a shot!
Update
At first I thought the alternator solved my problems... I was wrong. Sooner or later I was driving the Jetson's car... putt, putt, putt! I pulled the plugs and found the problem was with the #2 cylinder. I changed plugs, wires, coil, and ignition module. Still no change, that's when I put the car on the trailer and sent it to KDK Performance in Orlando.
Kevin and Rob at KDK found the problem, a bad ECM. This pissed me off, the ECM in the car was a new 7148 Reman unit from GM!!! Sure enough, it was intermitant on #2!
I'm a big fan of buying GM parts when I can, however, now I have a part bought a couple years ago that is bad. I rebuilt this car over 4 years piece by piece. I fear the GM dealer will tell me "there's nothing we can do." I guess I'll bring up the fact that I bought 2 brand new cars from them on the same day. We'll see how bad they want me back!
Anyhow, all venting aside... a bad ECM will cause this problem. Many thanks to Kevin and Rob at KDK Performance in Orlando to finding my problem!
At first I thought the alternator solved my problems... I was wrong. Sooner or later I was driving the Jetson's car... putt, putt, putt! I pulled the plugs and found the problem was with the #2 cylinder. I changed plugs, wires, coil, and ignition module. Still no change, that's when I put the car on the trailer and sent it to KDK Performance in Orlando.
Kevin and Rob at KDK found the problem, a bad ECM. This pissed me off, the ECM in the car was a new 7148 Reman unit from GM!!! Sure enough, it was intermitant on #2!
I'm a big fan of buying GM parts when I can, however, now I have a part bought a couple years ago that is bad. I rebuilt this car over 4 years piece by piece. I fear the GM dealer will tell me "there's nothing we can do." I guess I'll bring up the fact that I bought 2 brand new cars from them on the same day. We'll see how bad they want me back!
Anyhow, all venting aside... a bad ECM will cause this problem. Many thanks to Kevin and Rob at KDK Performance in Orlando to finding my problem!
