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Discussion Starter #1 (Edited)
I picked up an '88 Z31 N/A that was said to need a front main seal and a MAF sensor. The car has trouble starting and will not stay running unless you give it gas. The engine is very low on power and won't rev past 2500 while driving and 3000 out of gear (manual trans). If you try to force it past 2500 while out of gear, it just dumps tons of fuel out the tail pipe and slowly struggles to 3000. In gear, it bounces off of some kind of limiter and tries to stall unless you change gears. The car overheated after about three miles.There is no CEL. The plug wire to the #4 cylinder needs replaced (arcs off to vacuum lines). The fuel gauge and speedo don't work, if it matters. I am worried that the head gasket may be blown, but haven't had a chance to do a compression test. The oil and coolant don't look contaminated, but the front seal is leaking pretty badly.

Does any of this sound like a MAF sensor problem? I did try unhooking it, which did not change anything. I then took it out and cleaned it, which also did nothing.
 

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You already know it's got a mis-fire from a bad wire. Replace what you know is bad, get that compression test done, and go from there. I doubt you could tell if a sensor is bad if you've got a dead cylinder.
 

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Discussion Starter #3
Fixed the misfire (the wire got pulled off the plug by the throttle cable return spring). The car starts easier and runs slightly less roughly, but still spews fuel after about 3k. I think the overheating was caused by a lack of oil pressure. Is the oil pump in the front of the engine? The oil leak is coming from behind the crank pulley. I really hope I didn't cook the engine, but it still sounds alright (no knocking or ticking). I'm going to pull the plugs and do the compression check in the next day or so. I'll also try pulling any trouble codes from the ECU.
 

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Discussion Starter #4
Pulled trouble codes 12,14,22,23 (MAF, VSS, Fuel pump, Idle switch). The fuel pump connectors are very corroded, but I don't have time to check the harness today. The idle switch looks like it has been unhooked at some point (the locking tab for the connector is missing). More testing to come tomorrow.....

Does anyone know if the fuel pump code would be from the fuel gauge that isn't working? The FSM doesn't say anything about testing the sending unit, just the pump.
 

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Discussion Starter #6
Changed TPS and adjusted, swapped out MAF for a junkyard part (looks very clean). Slightly smoother idle, no change to revving symptoms. Engine will now hit about 3000 with the pedal floored. If you hold it down, it will slowly bog and drop off to 2000 before recovering. I pulled the distributor and it looks to be quite out of time.

Can I just move the distributor like a normal car, or do I have to go through a process to tell the computer that I'm doing something to the timing like in my Sentra?
 

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I would suspect the wiring between the AFM and ECU is bad if you have tested the new AFM and found it to be good.
 

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Discussion Starter #8
Do you mean the MAF? I checked the wiring before I replaced the sensor. Is there a way to test the MAF itself? The FSM didn't have a procedure.

At this point I have the front of the engine torn apart, since it was backfiring out the intake. Both cams were off a tooth or two, so hopefully that was causing at least some of the problem. I need to change the oil pump (or at least the front seal) since its leaking. While I'm in there I'll change the CHTS, since I've been told it can cause strange problems and a new one is only 8 bucks.
 

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Definitely sounds like an electrical problem between your ecu and sensors.
 
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