FastZ

So I am new to the z31 world, I have done plenty on the earlier z's(70-83). I just bought a 87 turbo and it would start and idle really rough, but would stumble and not accelerate. I had it running and was trying to keep it running hoping it was just because it sat for a while. Well then it stalled and now it will not start. It turns over well but just will not fire. There is good spark coming out of the coil, but I have not checked the individual plugs yet. I cracked the fuel line at the filter and seems to have decent pressure(I don't have a pressure gauge to see exactly what the pressure is). It has a Jim Wolf ECU and a Apexi Super AFC on it. Any pointers would be greatly appreciated.

86tcoupe

A cold compression test would be a good start ,unless you are saying it ran fine ,then just quit

FastZ

No it would idle but really rough....far from running fine.

rogerz

here is a start:
Get your battery load tested. Be sure you have clean, tight corrosion free terminals on both ends of your battery cables. Be sure the ground (negative) cable goes to a bolt into the frame before going to the starter. grounding through the starter is not a reliable connection. Z's don't like low voltage. causes the electronics to act funny. it is possible to have enough amps to crank but not enough voltage to run the electronics. If you have one size fit all cheapo clamp on terminals they are a problem waiting to happen. Usually on a rainy night around Oh Dark Thirty.

Clean the connectors for the maf or afm, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion. DON'T USE DIELECTRIC GREASE.

Replace outer tie rod ends, and ball joints. replace the bushings with poly (don't forget to lube them as directed unless you like squeaky things). New shocks. Get new boots for power steering. all those things will make you think you are driving a different car. doing them piece meal is a waste you won't see a great improvement until you do the complete job. You need to get the car realigned after messing with the front. Have your tires in good shape and rebalance. Rear bushings nice too but more work and you won't notice as great an improvement. Rear shocks also because if the fronts are gone so are the rears. if car squats when you jump on the gas the rears are gone. If you have the electro adjustable shocks they are DEFINITELY GONE.

If you are doing a turbo car shocks (electro adjust I think may be only on the turbos) then you need the adapter plates to fit modern shocks to the car in the rear. Easiest way is find an n/a at the junkyard and take the mounting plates. They may be available thru NAPA (listed) but I had the n/a plates.

You shouldn't try to swap experience on an L28 to the VG30ET they are quite different animals. that idle junk hanging off the right side of the plenum is often a problem with idle. Start with battery and cables they are the heart of the electrical system. Next up might be a new CHTS often the misery of the z31. VAc leaks on an FI engine are a bane be sure you have eveything after the turbo tight. look at the EGR for a blown diaphragm. Air control valve can also be a problem. go buy a cheap oil pressure gage at Oreilly or someplace like that. go to the hardware store and get some tubing and fittings to make up a pressure gage tee you can fit in the line between the filter and the fuel ring. pressure is critical not just "hey got some fuel running out here". Put a vacuum gage on it. should be pulling better than 20"Hg at idle. My guess you got an electrical problem for a start. download the fsm from xenonzcar. NOW READ IT.

rogerz

compression test won't tell you much unless you have a totally blown cylinder.

FastZ

Well I got the majority of it figured out. I pulled all of the plugs and they had carbon all over them, as well as being wet. I think the previous owner just would start it and let it idle and it never really had time to burn the plugs off at hotter temps. Anyways cleaned all the plugs for now ( will buy some new ones in a bit) gapped them and reinstalled and she fired up like a champ and I drove her down the road for the first time since I went to get her. Clutch and brakes both need to be bled, and then the fun can start!

86tcoupe

Oh brother rogers your no tech!
Why trouble shoot fuel electronics when you have a mechanical issue sounds like you do hot compression tests
A no no

rogerz

I've never seen a running problem solved with a compression check. Been doing spark and compression ignition engines. for about 59 years. sounds more like you know nothing about the engine electronics and think a compression check will help you make things run better. It won't tell you that you have low fuel pressure. won't tell you if your electrical; system is acting up. won't tell you if your turbo charger is blown. nor the myriad other things I have found making a z31 run poorly. In this case since he would have to pull the plugs to do the compression check it did get him to one of his problems.

86tcoupe

man I forgot about this thread

WWWhhhaaaTTT ? you really hate comp . tests Rogers
a compression test will tell you any thing ( almost ) going wrong with the mechanics of the engine
Compression = rings and valves leaking timing ( valve ) yes blown Head gasket swapping ,turning torque
A cold compression test that is
F I starts to flood the cylinders after about 7 seconds so pulling the spark plugs to check that is a good idea ,and why not check compression then
a fuel pump is $50 -100 but an engine $3500 +
it doesn't sound like he had this 30 plus yr old ride car long to really know it's condition and it is not running enough to tell it's condition so a comp.test is a good idea