1983 280zxt AT - bogging on light acceleration, rough idle
07-15-2021, 11:22 AM
#1
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Join Date: Jul 2021
Posts: 6
1983 280zxt AT - bogging on light acceleration, rough idle
Hey everyone,
Long time lurker, first time poster. I have an 83 ZXT 2+2 AT (94k miles) that I've recently resurrected after a 12yr driveway slumber. I've gotten the car to a really good place, but just hit a stumbling idle/ acceleration issue that suddenly appeared. I've searched this topic to death on all the Z forums so wanted to post this to show what I've done so far and what the solution ends up being (as long as I find it!).
The car has been running pretty good now and passed CA smog with flying colors. Compression in cylinders is 140psi except cylinder 6 is at 120psi. The car had been having zero problems idling and only had a slight stumble on acceleration. WOT had no stumble and the car pulled hard. NOW a week or so later and the car has developed a stumbling idle and will sometimes sputter out and die. It seemed like a fuel thing, but I went through the whole system and also installed an inline gauge that reads 28psi at idle and 40psi at WOT which seems correct. It also holds pressure when off. I next suspected a vacuum leak. My engine will die when I remove the oil cap and I've carefully checked for leaks and can't find any. What's weird is that when the idle is struggling, if I disconnect ANY vacuum line into the intake manifold, the idle vastly improves. So it LIKES an intake vacuum leak for a smooth idle (which makes me suspect ECU). This was not the case a few weeks ago and I haven't changed anything. I suspect the ECU connector problem that seems so common with these cars. My car also had a lot of moisture corrosion in the dash from sitting so long under a tarp and that was the one connector I did not mess with during all my dash work.
Things I've done
- New plugs
- New fuel lines/filter/tank checked (clean)
- New vacuum lines in engine bay (most replaced)
- New fluids
- New PCV (made a HUGE difference and solved my oil smoke problem)
- New (ebay) digital dash cluster - works now
- Disconnected and cleaned most electrical connectors (under dash)
Thing I have not done
- Clean ECU connectors (I HIGHLY suspect this could be the cause based on previous posts)
- Disassemble and clean throttle body
- Test TPS
- Test CHTS
- Replace distributor cap and rotor
- Replace injectors
- Replace MAF
In general everything I take apart on this car is pristine (except the interior and dash) and factory original. The car was dealer serviced up until its long nap and is 100pct stock. I'll be going for the free stuff first of course
I just wanted to post because I found a TON of similar posts that don't ever make it to the solution. The ones that were solved tended to be because of the ECU connectors. I'm at the stage where that's being tried next and so thought this could be helpful to others and maybe saves someone from buying a bunch of sensors they don't need. I appreciate you all immensely and I have learned so much about these cars because of the wonderful community that loves them so thank you! I'll post my ECU cleaning results tmrw.
Long time lurker, first time poster. I have an 83 ZXT 2+2 AT (94k miles) that I've recently resurrected after a 12yr driveway slumber. I've gotten the car to a really good place, but just hit a stumbling idle/ acceleration issue that suddenly appeared. I've searched this topic to death on all the Z forums so wanted to post this to show what I've done so far and what the solution ends up being (as long as I find it!).
The car has been running pretty good now and passed CA smog with flying colors. Compression in cylinders is 140psi except cylinder 6 is at 120psi. The car had been having zero problems idling and only had a slight stumble on acceleration. WOT had no stumble and the car pulled hard. NOW a week or so later and the car has developed a stumbling idle and will sometimes sputter out and die. It seemed like a fuel thing, but I went through the whole system and also installed an inline gauge that reads 28psi at idle and 40psi at WOT which seems correct. It also holds pressure when off. I next suspected a vacuum leak. My engine will die when I remove the oil cap and I've carefully checked for leaks and can't find any. What's weird is that when the idle is struggling, if I disconnect ANY vacuum line into the intake manifold, the idle vastly improves. So it LIKES an intake vacuum leak for a smooth idle (which makes me suspect ECU). This was not the case a few weeks ago and I haven't changed anything. I suspect the ECU connector problem that seems so common with these cars. My car also had a lot of moisture corrosion in the dash from sitting so long under a tarp and that was the one connector I did not mess with during all my dash work.
Things I've done
- New plugs
- New fuel lines/filter/tank checked (clean)
- New vacuum lines in engine bay (most replaced)
- New fluids
- New PCV (made a HUGE difference and solved my oil smoke problem)
- New (ebay) digital dash cluster - works now
- Disconnected and cleaned most electrical connectors (under dash)
Thing I have not done
- Clean ECU connectors (I HIGHLY suspect this could be the cause based on previous posts)
- Disassemble and clean throttle body
- Test TPS
- Test CHTS
- Replace distributor cap and rotor
- Replace injectors
- Replace MAF
In general everything I take apart on this car is pristine (except the interior and dash) and factory original. The car was dealer serviced up until its long nap and is 100pct stock. I'll be going for the free stuff first of course
I just wanted to post because I found a TON of similar posts that don't ever make it to the solution. The ones that were solved tended to be because of the ECU connectors. I'm at the stage where that's being tried next and so thought this could be helpful to others and maybe saves someone from buying a bunch of sensors they don't need. I appreciate you all immensely and I have learned so much about these cars because of the wonderful community that loves them so thank you! I'll post my ECU cleaning results tmrw.
07-17-2021, 10:39 AM
#2
Registered User
Thread Starter
Join Date: Jul 2021
Posts: 6
SOLVED - So I did the ECU connector re-seat and the plugs didn't have any corrosion on them. It didn't seem to do anything; however, while poking around the throttle body I bumped the connector to what I think is the TPS sensor (3 pin on the side of the TB). I thought it was the cold start but its a 3 pin not a 2 pin connector. Anyways as soon as I touched it, the idle suddenly changed. I unplugged it and it was super corroded with green wizard dust. I cleaned and re-connected and the car runs and idles fantastic now. The low rpm bog seems to be gone or 90pct gone. I think the next thing I need to do is just disassemble the TB and clean everything but now I'm afraid to do any more fixes if its running so good.
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