1988 z31 rough idle
04-24-2014, 06:40 AM
#1
1988 z31 rough idle
its my first z and it has 176k on it, N/A, 5 speed.
it runs and drives but it idles really rough and has a missfire at idle.
there is a loud hissing sound coming from the engine, sounds like an air leak. i think it is one of the hoses on the passenger side of the intake manifold leaking.
the temperature gauge acts really goofy. it turns on MOST of the time but never gives me an actual reading and if left running long enough the temp gauge just turns off completely. the thermostat seems to be functioning because i can watch my coolant level go down when it opens.
once it gets warm a little bit of white smoke starts coming from somewhere between the intake and exhaust manifolds, possibly oil or something dripping on the exhaust?? its not very much usually but i cant tell whats causing it.
it has a slow oil leak coming from somewhere and the oil pressure seems low and drops to zero when i give it gas. but i dont know what psi it should be running at?
the fuel temperature sensor on the fuel pressure regulator is broken.
i changed the spark plugs and did an oil change but it didn't seem to help.
any insight would be greatly apreciated
it runs and drives but it idles really rough and has a missfire at idle.
there is a loud hissing sound coming from the engine, sounds like an air leak. i think it is one of the hoses on the passenger side of the intake manifold leaking.
the temperature gauge acts really goofy. it turns on MOST of the time but never gives me an actual reading and if left running long enough the temp gauge just turns off completely. the thermostat seems to be functioning because i can watch my coolant level go down when it opens.
once it gets warm a little bit of white smoke starts coming from somewhere between the intake and exhaust manifolds, possibly oil or something dripping on the exhaust?? its not very much usually but i cant tell whats causing it.
it has a slow oil leak coming from somewhere and the oil pressure seems low and drops to zero when i give it gas. but i dont know what psi it should be running at?
the fuel temperature sensor on the fuel pressure regulator is broken.
i changed the spark plugs and did an oil change but it didn't seem to help.
any insight would be greatly apreciated
Last edited by vindogg; 04-24-2014 at 06:45 AM.
04-24-2014, 10:08 AM
#2
Registered User
Join Date: Aug 2013
Posts: 1,103
Welcome to the ZDriver forums! 
Your new Z still has a lot of miles to go. Hard to know where to start but it looks like you have to catch up with all the regular maintenance that wasn't being done before you got her.
If you don't have a copy of your factory service manual, get a free one at XenonZ31 Reference. Get familiar with it and check out all the inspection and troubleshooting sections. They are step by step and easy to follow.
Check out the ECU diagnostic procedure around pages EF&EC 35... and run a diagnostic to get the codes your ECU is putting out. Those codes are a good indicator of your engine's health at this point and can tell you where to start.
Other guys here will have some ideas about what to tackle first and what are some of the specific problems you have right now. Welcome again.
Your new Z still has a lot of miles to go. Hard to know where to start but it looks like you have to catch up with all the regular maintenance that wasn't being done before you got her.If you don't have a copy of your factory service manual, get a free one at XenonZ31 Reference. Get familiar with it and check out all the inspection and troubleshooting sections. They are step by step and easy to follow.
Check out the ECU diagnostic procedure around pages EF&EC 35... and run a diagnostic to get the codes your ECU is putting out. Those codes are a good indicator of your engine's health at this point and can tell you where to start.
Other guys here will have some ideas about what to tackle first and what are some of the specific problems you have right now. Welcome again.
04-24-2014, 04:14 PM
#5
Grumpy & Helpful
Join Date: Sep 2006
Location: Mill Creek WA
Posts: 1,415
the fuel temp sender does absolutely nothing that I could discern after I spent the bucks for one on my 85T
Air leaks are the bane of the FI engine find and fix
temp gage you probably need a new sensor cheap. ground the wire the gage should pin out. ignition on of course. if gage no pin bad wire or bad gage.
the coolant level should NOT go down if the theremostat opens. you should see coolant flow to the expansion tank. be sure the hose at the bottom of the expansion tank is not kinked preventing free flow in/out of said tank
are you sure you have full coolant. when cold the expansion tank should be to the cold mark. open the what looks like a radiator cap but isn't on the radiator and check level. remove top of the heat control valve and see if coolant is to that.
your idle problem is probably related to all that idle garbage hanging off the left side of the intake. take it off throw it away and block off the hole with a metal plate and gasket. may have to up the idle speed.
you really need a passenger along to get the codes and write them down. HOWEVER all tho everyone says they do it I have never found them very useful (or perhaps my problems have been so bizarre the codes do nothing to help with a solution).
new dizzy cap and rotor. get a set of magnacore plug wires. check the ignition timing, fuel pressure and vacuum this will tell you a lot, or if it doesn't as you don't seem all that knowledgeable, at least you can add it to post and maybe give those of us who know an inkling of what is going on
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 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.
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. 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.
Air leaks are the bane of the FI engine find and fix
temp gage you probably need a new sensor cheap. ground the wire the gage should pin out. ignition on of course. if gage no pin bad wire or bad gage.
the coolant level should NOT go down if the theremostat opens. you should see coolant flow to the expansion tank. be sure the hose at the bottom of the expansion tank is not kinked preventing free flow in/out of said tank
are you sure you have full coolant. when cold the expansion tank should be to the cold mark. open the what looks like a radiator cap but isn't on the radiator and check level. remove top of the heat control valve and see if coolant is to that.
your idle problem is probably related to all that idle garbage hanging off the left side of the intake. take it off throw it away and block off the hole with a metal plate and gasket. may have to up the idle speed.
you really need a passenger along to get the codes and write them down. HOWEVER all tho everyone says they do it I have never found them very useful (or perhaps my problems have been so bizarre the codes do nothing to help with a solution).
new dizzy cap and rotor. get a set of magnacore plug wires. check the ignition timing, fuel pressure and vacuum this will tell you a lot, or if it doesn't as you don't seem all that knowledgeable, at least you can add it to post and maybe give those of us who know an inkling of what is going on
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 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.
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. 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.
Last edited by rogerz; 04-24-2014 at 04:22 PM.
05-02-2014, 10:46 AM
#6
where can i find replacements for all the electrical connectors? the connector to the air regulator and to the fuel pressure regulator along with various others are broken/gone. i tried Napa to no avail. the only place i can think of is at a junk yard from another vg from a pathfinder or something...
05-02-2014, 12:28 PM
#7
Fricfrac
Fricfrac 
has a really nice connector kit he has made up for us, they are on EBay, but he has been giving us ZDriver members a discount. I used on on my 280zx, most of the connectors are the same. Ill post a link to my project, a few pics of the connectors. PM him if you are interested, great upgrade.
has a really nice connector kit he has made up for us, they are on EBay, but he has been giving us ZDriver members a discount. I used on on my 280zx, most of the connectors are the same. Ill post a link to my project, a few pics of the connectors. PM him if you are interested, great upgrade.
05-02-2014, 08:22 PM
#8
Grumpy & Helpful
Join Date: Sep 2006
Location: Mill Creek WA
Posts: 1,415
Do you not read? I told you first line of my post forget the fuel temp sender it does nothing discernible to the way the engine runs. if the connection is broken off the air regulator you need another air regulator. if the wiring to it is bad see if you can file down a fuel injector connector to fit to the air regulator. or it just may fit I forget.
05-03-2014, 07:05 PM
#9
Registered User
Join Date: Aug 2013
Posts: 1,103
Another option is: There are '88 Z31s in recycler's yards still (even more '84-'89) - but they are at the crush-able age now because the parts market for them is shrinking. Go to car-part.com and do searches for common parts. Sort the search results by distance from your zip code and call the yards listed to see if they still have the listed car on the lot. If they do, you can drive there, convince them you are serious and check out the junker in person, then list/label/mark all the parts you want from it. Total price will be lower than anything you can find elsewhere - and you skip the headache of trying to find equivalent aftermarket stuff. Used-but-still-good OEM is better, in my opinion. You will find most of the original harness intact.
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