Hi all,
I'm trying to breathe life back into my '86 n/a which had been sitting for two years until a month ago.

It was running fine when I put it away 2yrs ago, except that it had a fuel leak. First thing I did when I took it out of my garage was charge the battery and turn the key to the on position so that the fuel pump would kick on and allow me to try and locate the fuel leak. Bingo, pressure regulator and injectors 1 and 2.

Took things apart and replaced: all injectors, fuel filter, pressure regulator, all plugs. I also drained the gas, put in ten gallons of 91 octane, changed the oil/filter, sprayed a tad of auto trans fluid into the cylinders, and replaced the coolant.

Put it all back together and the car seems to be running on only a few cylinders, it revs real "non-smoothly" and idling shakes the whole car badly. Distributor and wires I believe are 2yrs old and look fine. I resistance-tested the wires and they seem to be good.

Since it runs and idles without stalling, is it safe to assume that air and gas aren't an issue? I am just struggling to figure out why some cylinders run and others don't considering I installed 6 new injectors (and that the car ran fine when it was put away 2yrs ago).

Any advice from you gurus would be much much appreciated, I'd love to get this thing on the road before the weather turns.

 

new plug wires, dizzy cap and rotor. would kinda eliminate the ignition system as a problem. time it with a timing light. Check for vac leaks. bane of the FI engine. lots of gizmos on the z31 engine can affect idling. Get a noid light and be sure all injectors are receiving a fire signal. download the fsm from xenon and read it. probably want to put a fuel pressure gage in there to see what is actually happening to the fuel pressure even tho you have put in new stuff. the fact that it seems to be running on less than 6 cylinders would indicate something is awry. Mouse nest in the air intake system? did you make sure the plug wire connectors are firmly on the plugs. often need a pair of long nose pliers to seat them. did you blow out the holes where the plugs reside to be sure there was no loose crap down there that would fall into the cylinder or keep the plug from seating properly.

here is a list of things that often make the z31 unreliable
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.

Clean the connectors for the maf, 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.

 

^^Thanks for your thoughts man, I was expecting to get flamed but just wanted someone familiar w/Z31's to give general guidance which is just what you did. I'll check the few easy possibilities before buying test gear but I should just pony up, and learn a little more about the car as I go. I hope to report back to this thread and state that: this noob ended up not wasting server space!

 

download the FREE fsm from xenon website - read it. Take the time to study the information on the system you are dealing with before throwing money at new parts.

A battery sitting without charge for 2 years is problematical get it tested. if you buy new get an Interstate they are well worth the few extra bucks more than a WalMart.

 

Update! (FSM carefully read and followed and a new battery before I even started tinkering.)

Replaced distributor cap rotor and plug wires. Verified with a noid light that all 6 injectors are getting power. Verified that all 6 plugs are sparking. Ran compression test and found compression to be low (~150+or-) but consistent for each cylinder. Determined that cylinders 5 and 6 are the only ones not firing.

One thing i'm suspecting is I didn't replace the intake cover gasket upon reassembly, can this be causing a vac leak resulting in just those cylinders not firing right? I'm surprised the engine still runs so "shaky" when 1-4cyl are in operation. Can I be wrong to rule out fuel since the car runs & idles on the 4cyl? I'm running out of things to eliminate. Any help appreciated and thanks in advance for bearing with my noobness.

 

You might want to pull the spark plugs for the cylinders that you know aren't firing after you've idled it for a while, to check if they are wet with, or smell strongly of gas. if they don't, take a closer look at your injectors. plugged, possibly?

 

duh!! old thread. a waste of my meager typing abliity.