85 L98: Bipolar performance
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I've seen that too. I was troubleshooting a problem and got home from work and started working on the car and noticed the MAF connector was disconnected (I did that the previous day). I couldn't tell by the way the car drove.
Last edited by Cliff Harris; Jun 14, 2013 at 03:28 AM. Reason: Fixed missing quote bracket
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
Good to hear. Hopefully I find something tomorrow because I have the day off, but still curious to hear about the results if other factors can cause this.
As for "Limp" mode, my 85 only went into it when the MAF was plugged in and it threw a code. The typical symptoms of limp mode are terrible acceleration (next to none) and about a 25mph top speed. A lot of people assume that as soon as the "check" light is on, the car is in limp, but this is not correct.
As for my situation, in which I've unplugged the MAF and tied off the plug, it literally drives normally to the point that if I removed the "Check" bulb from behind the console and gave someone the keys, they wouldn't know something is wrong. Obviously, I'm not commuting with this setup, but it works well enough when I'm testing things, or when the car would go into limp mode and I needed to get farther than 50 feet, faster than 20mph.
As for "Limp" mode, my 85 only went into it when the MAF was plugged in and it threw a code. The typical symptoms of limp mode are terrible acceleration (next to none) and about a 25mph top speed. A lot of people assume that as soon as the "check" light is on, the car is in limp, but this is not correct.
As for my situation, in which I've unplugged the MAF and tied off the plug, it literally drives normally to the point that if I removed the "Check" bulb from behind the console and gave someone the keys, they wouldn't know something is wrong. Obviously, I'm not commuting with this setup, but it works well enough when I'm testing things, or when the car would go into limp mode and I needed to get farther than 50 feet, faster than 20mph.
You replaced the MAF and got a new Code 33 (signal voltage too high). While this may be frustrating, it is not entirely unexpected. With the faulty MAF, the ECM was not getting a reference signal. Therefore it would not trigger a Code 33 (high signal voltage).
If you continue with the Code 33 troubleshooting tree, there are a few outcomes. 1) Faulty ground. There are 2 grounds to check. 2) Faulty 12v source to MAF. You've already checked this but it would be a good idea to re-verify. 3) Faulty reference signal from ECM. Faulty reference signal can be caused by wiring or ECM. 4) Faulty MAF sensor. It is entirely possible you got a bad one.
Thread Starter
Racer
Joined: Aug 2012
Posts: 279
Likes: 2
From: Las Vegas Nevada
O yeah, of course it's throwing a 34 with the MAF unplugged.
I know what you mean on the C5 part... there's one in the garage next to the C4. I just wish the C4 ran just as well!!!
I've already layed out a basic plan for an LS swap(for obvious reasons), but I need to wait until emissions is due again so I can have time to swap and work out the bugs without needing to go into non-op. I'm trying to fix this bugger so I can at least have it running until then, and be able to smog it.
I know what you mean on the C5 part... there's one in the garage next to the C4. I just wish the C4 ran just as well!!!
I've already layed out a basic plan for an LS swap(for obvious reasons), but I need to wait until emissions is due again so I can have time to swap and work out the bugs without needing to go into non-op. I'm trying to fix this bugger so I can at least have it running until then, and be able to smog it.
Cruising
Joined: Feb 2013
Posts: 11
Likes: 0
O yeah, of course it's throwing a 34 with the MAF unplugged.
I know what you mean on the C5 part... there's one in the garage next to the C4. I just wish the C4 ran just as well!!!
I've already layed out a basic plan for an LS swap(for obvious reasons), but I need to wait until emissions is due again so I can have time to swap and work out the bugs without needing to go into non-op. I'm trying to fix this bugger so I can at least have it running until then, and be able to smog it.
I know what you mean on the C5 part... there's one in the garage next to the C4. I just wish the C4 ran just as well!!!
I've already layed out a basic plan for an LS swap(for obvious reasons), but I need to wait until emissions is due again so I can have time to swap and work out the bugs without needing to go into non-op. I'm trying to fix this bugger so I can at least have it running until then, and be able to smog it.
Thread Starter
Racer
Joined: Aug 2012
Posts: 279
Likes: 2
From: Las Vegas Nevada
Trust me, it can't be as bad as my headache is. I haven't been this frustrated with anything for years.
Yes, I remember what we did. I only went slightly backwards to get the car going if a test or short drive went wrong. I know the MAF is good because it drove perfectly without a code for a solid week, then this 33 came back after I had the car lifted by a friend at his shop to inspect something under the car. I almost want to strangle myself for doing it because the car was running fine and I shouldn't have started to get curious.
I'm picking through the wires around the MAF and I'm about to remove the wiper motor and battery to check those areas that Lee mentioned.
Yes, I remember what we did. I only went slightly backwards to get the car going if a test or short drive went wrong. I know the MAF is good because it drove perfectly without a code for a solid week, then this 33 came back after I had the car lifted by a friend at his shop to inspect something under the car. I almost want to strangle myself for doing it because the car was running fine and I shouldn't have started to get curious.
I'm picking through the wires around the MAF and I'm about to remove the wiper motor and battery to check those areas that Lee mentioned.
Thread Starter
Racer
Joined: Aug 2012
Posts: 279
Likes: 2
From: Las Vegas Nevada
Thread Starter
Racer
Joined: Aug 2012
Posts: 279
Likes: 2
From: Las Vegas Nevada
Good news. I think I solved my issue and got rid of the code 33.
I spent a few hours cleaning some grounds and plugs/connectors and got the car started without throwing a single code!
I started by focusing on the ECM. Unplugged it, along with all the other cables under the right dash and sprayed all electrical connections with...... electrical cleaner. Hooked all of that back up then started hunting for hidden grounds around the engine. The worst/most dirty ones I found were under the battery. Absolutely sludged from debris because that part of the frame collects mud and grime. I unscrewed the two grounds there, brushed them thoroughly with wire, and also the spot where they screwed down. After those, I started it up a few times, and it still didn't throw a code for a good 30 seconds. I had to adjust the throttle cables because the car went straight to half throttle on start up, but got it regulated and now it idles and revs normally. I'll update with any issues after a drive tomorrow.
I spent a few hours cleaning some grounds and plugs/connectors and got the car started without throwing a single code!
I started by focusing on the ECM. Unplugged it, along with all the other cables under the right dash and sprayed all electrical connections with...... electrical cleaner. Hooked all of that back up then started hunting for hidden grounds around the engine. The worst/most dirty ones I found were under the battery. Absolutely sludged from debris because that part of the frame collects mud and grime. I unscrewed the two grounds there, brushed them thoroughly with wire, and also the spot where they screwed down. After those, I started it up a few times, and it still didn't throw a code for a good 30 seconds. I had to adjust the throttle cables because the car went straight to half throttle on start up, but got it regulated and now it idles and revs normally. I'll update with any issues after a drive tomorrow.
Last edited by Ziggy91; May 18, 2013 at 03:48 AM.
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Thread Starter
Racer
Joined: Aug 2012
Posts: 279
Likes: 2
From: Las Vegas Nevada
Just thought I'd update everyone.
My mechanic replaced some hoses to the PCV valve because there was a small vacuum leak at the plug near connected to the intake manifold. This didn't change anything, but fortunately it was free.
I also got rid of the code 32 by replacing the EGR with a new unit. After readjusting timing down to 6* I took it for a ride and it really felt good... like never before! This is definitely on the list of replacement parts if anyone is still running their original unit.
Unfortunately, there's still a code 33... but the car's driving very well with the new EGR so I have no idea what's the problem now. I suspected the bad EGR was causing most of my performance problems, but now I still have this 33 lingering.
Good god... 7 pages of madness.
My mechanic replaced some hoses to the PCV valve because there was a small vacuum leak at the plug near connected to the intake manifold. This didn't change anything, but fortunately it was free.
I also got rid of the code 32 by replacing the EGR with a new unit. After readjusting timing down to 6* I took it for a ride and it really felt good... like never before! This is definitely on the list of replacement parts if anyone is still running their original unit.
Unfortunately, there's still a code 33... but the car's driving very well with the new EGR so I have no idea what's the problem now. I suspected the bad EGR was causing most of my performance problems, but now I still have this 33 lingering.
Good god... 7 pages of madness.
Instructor
Joined: Nov 2012
Posts: 120
Likes: 6
From: Phoenix AZ
Zig and I have our own focus group now.
Ken Carallo at the Vette Shop ran the entire trouble tree and it passed although some values were near the bottom of the range. He discovered that my ECU is bad(tap on it, and throws one code after another), but he suspects that my eprom is shot too. He had a spare ECU, but no chip, so I ordered a Motorvation chip from Summit yesterday. Chip should be here in a day or so, and then we'll know if that is the source of old 33.
Ken Carallo at the Vette Shop ran the entire trouble tree and it passed although some values were near the bottom of the range. He discovered that my ECU is bad(tap on it, and throws one code after another), but he suspects that my eprom is shot too. He had a spare ECU, but no chip, so I ordered a Motorvation chip from Summit yesterday. Chip should be here in a day or so, and then we'll know if that is the source of old 33.
Instructor
Joined: Nov 2012
Posts: 120
Likes: 6
From: Phoenix AZ
Ken calls me today and says its all done. New ECU, PROM, and new black/white wire on the burnoff relay. I get there, and he starts it up.....SES light.
Scan closed loop....now its a 36. He thinks it must be another bad wire. I am loosing my mind with this car.
Scan closed loop....now its a 36. He thinks it must be another bad wire. I am loosing my mind with this car.
Instructor
Joined: Nov 2012
Posts: 120
Likes: 6
From: Phoenix AZ
Well, my update is that Ken replaced the ECU again, drove the car for two days....no light so I swung by and picked it up yesterday. Today on my second trip of the day, 36!
Ken said if if came back, drive it for a couple of weeks and see if it eventually goes away on its own (this has happened to a few on the forum). I have the first week if July off and I'm probably going to run a new CKT 900 ground from the ECU to the Burnoff relay. I'm convinced that the 36 is resistence related either in the rebuilt MAF, or ground circuit. That appears to be another trouble spot for code 36.
The good news is that the car runs FANTASTIC even in 100+ degree heat. Mad props to the Summit Motorvation emprom adapter. Even with my 18 year old son in the car tonight, the car pulls like some of my old LS cars.
At least I traded a debilitating code 33 for a burn-off 36 that is more anoying than hurtful.
I'll post another update after the CKT 900 replace.
Ken said if if came back, drive it for a couple of weeks and see if it eventually goes away on its own (this has happened to a few on the forum). I have the first week if July off and I'm probably going to run a new CKT 900 ground from the ECU to the Burnoff relay. I'm convinced that the 36 is resistence related either in the rebuilt MAF, or ground circuit. That appears to be another trouble spot for code 36.
The good news is that the car runs FANTASTIC even in 100+ degree heat. Mad props to the Summit Motorvation emprom adapter. Even with my 18 year old son in the car tonight, the car pulls like some of my old LS cars.
At least I traded a debilitating code 33 for a burn-off 36 that is more anoying than hurtful. I'll post another update after the CKT 900 replace.