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Discussion Starter #1
**** car (82 280zx turbo) won't idle good, my dad says it sounds like a stuck valve, so I decide to do a compression test:

Cyl 1: 115
Cyl 2: 100
Cyl 3: 100
Cyl 4: 90
Cyl 5: 90
Cyl 6: 90

Engine was moderetly warm (first line on gauge).
But after reading Blue's tech tips, I need to do it again with all plugs removed and the TB open.

What do you guys think? It ran perfect after my cylinder head temp sensor problem, sat for 2 days because of pulling the stereo, then started sounding really bad at idle.. I didn't drive it, and that was two days ago.

Idles around 600rpms, 500 with the car in gear.
Plugs look black. Its the rings, isn't it....

Mario
 

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Does it blow blue smoke out the exhaust? My 82 was run out of oil by the PO and the rings are shot. Blue smoke out the exhaust is a sure sign of rings or valve seals. Black plugs (not oily) is fouling from too much fuel. Did you replace the plugs after the CHT deal? Carbon on the plugs can cause arcing, screwing up the ignition.

Bad idle can be from incorrect vacuum at idle. Pinch off the vac lines down the side of the intake.(the ones going to the EGR, etc. Or get a vacuum gauge and check it. I had to replace all the vac lines on the 82 to finally get it to idle properly, then i blocked off the EGR with a Mountain Dew can, and solved the rest of them.
 

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Discussion Starter #3
Thats the thing, it doesn't blow ANY smoke. Maybe, just maybe, when it is warmed up and restarted, a puff comes out, but I haven't seen that in a while.

BUT the rear bumper over the exhaust has soot deposits, you can't really tell its there unless you wipe it.

I've replaced all vacuum lines, this car ran great until now.
Plugs were wet fouled after CHT thing, just let dry and the car ran for two days flawlessly. After two days of sitting is when this started.

Thanks for the fast response,
Mario
 

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I'd definetly do the comp test again with the plugs out, and and the throttle open. it should make a big difference.

also, after you test it again, put some oil in the cylinders and try it again. see how much the numbers rise. if its a lot, then the rings are bad.

soot on the bumper I'd say is normal, especially for an older car.
 

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You could have done some damage to the cylinder walls driving it with it running super rich. Some miles could straighten it out or it may still be real rich and causing this. Fuel soaked cylinder walls can keep the rings from sealing right.

I also doubt this is why it's idleing bad. Black plugs is fuel not rings.
 

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Discussion Starter #7
Yeah, steves280, I thinking the same thing about the fuel. I never drove it when it was super rich, but I did try fixing it/setting the timing, etc. Never fully warmed up when I had the bad CHT connection. Maybe thats what screwed up my compression test, as the plugs were wet fowled.

Checked all boots when I replaced hoses. The only one with cracks was at the clamps before the AFM, but thoses are now sealed. If I have to, I'll check it again.

I just hate how this car seems to have moods swings :p
Oh well, the test will have to wait till tommorrow (too late and too cold to do anything).

On a side note, is there a way to clean plugs without sandblasting?

Mario
 

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Those "mood swings" are why I hate the ZXT electronics. My boss had a 280ZXT that would do this crap. Run great one day, the next crank up would run crappy, 2 days later would start running fine again and this was 10 years ago when the car was still pretty new. (Can't blame old electronics...) Replaced the ECU and it fixed it but that was $700 back then. I have found some respond to having the ECU unplugged and then plugged back in. I used to think it was corosion but have seen cars this would fix for a while and everything was clean. Again replace the ECU and this problem would go away as well. If you want to really enjoy this car, save your money up for a different fuel management system.

On the plugs, just go buy some new ones.
 

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Here is another tip, you have to do full 4-5 cycles on each cylinder

so your reading should be of this format

110 - 150 - 160 - 160 (or something like that)

then go on unto the next cylinder
 

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be sure you check your air filter and be sure its not clogged. Listen to the intake and exuast for a popping or a whoosh sound, if you have a valve stuck open you should hear it. You may need to pull the pipe at the TB to hear anything. And do as stated above and check and clean the ecu plug......
 

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Don't overlook............

..........partially plugged exhaust system.............

Got a cat in there?
 
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