So I acquired this Z a while back. It apparently sat for a while, but drove fine the way home. Shifted normally, no limp mode. Some hesitation when on the pedal but thats about it. It randomly went into limp mode after about a week, I changed the spark plugs and it happened to be fine when I test drove it.

Then a couple days later back in limp mode. I ran the diagnosis and got code 12(MAF) so I replaced it with one from eBay. Still limp mode. The only code I get now is 41, so I assume the MAF I bought is good other wise the code would pop up. Also when warmed up, when you shift into drive or neutral(AUTOMATIC), it starts to idle really low and sounds like it wants to bog down(too rich?). If you stand behind my exhaust for more than a second , you can tell it is rich.

Now my question is, what could cause limp mode but not show any codes? Im under the impression that unless my ecu is bad, that something would send a code to the ecu, IF it was malfunctioning and causing it to go into limp mode.

Thanks in advance!

 

I wouldn't put much faith in the ecu codes. they have almost never helped me. test the maf per the instructiions in the fsm. you can download that from xenon's site. there is a whole bunch of junk that affects idle. i just removed it from mine. notice what is missing from mine. put a vac hose from the front of the plenum direct to the fpr. get rid of those four tubes running across the engine. reroute hoses to the carbon canister. Check your tps.

otherwise here is what i tell people to look for and do on a z31 before they get into anything exotic.

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.

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. all those things will make you think you are driving a diffent car. doing them piece meal is a waste you won't see a great improvement until you do the complete job. 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.

 

same thing happened on my 80' after I got the engine cleaned at dannys. The engine wouldnt rev past 2500. It turned out that the injector wires got wet or werent connected. Try unpluging everything and blowing it out and wiggling it around. Thats what I did and magically it worked

 

If it won't go over 2000 to 2500 rpm, it should be the MAF or MAF harness. It is in limp home mode.