Calling all Z24i TBI owners - Need some assistance

[Saudade]

My 86.5 Z24i has a driveability problem cutting out at around 2500 rpms. Some of you have read my other threads on this subject. I've burned a lot of cash swapping out parts and I'm now reaching the end of my patience (and bottom of my wallet).

I suspect the MAF at this point but a new MAF is outrageously priced. I did manage to find a JY TB complete with MAF, TPS, and FIs. First I swapped only the MAF with no joy. Then swapped the entire TB, still no joy. Possibly, the MAF on the JY TB is bad too.

So I measured the resistance between different pin pairs on the MAF (4 pin). I did get readings on Pins A-B, and C-D, with open readings on every other combo. However, my original MAF reads exactly the same as the JY one.

If someone, while having the aircleaner removed could take the readings on your own MAF and post them in reply, I can determine if it's really the MAF or not. I certainly don't mind dropping $200 on a ebay refurb but would like to be reasonably certain it's going to work.

I did locate some online stores that have a refurb MAF for $60 but they are *ALL* on backorder (for like the past month). I've been scouring the local JYs for another but can't find the 4 pin.

TIAS

[Saudade]

One more thing, converting to a carb (I've read the Weber conversions) is not really an options due to the ridiculous emission testing here in Cali.

Thanks Again.S

[arootbeer]

Have you swapped or unplugged the O2 sensor? I was having all sorts of power delivery issues with my '89, and as soon as I swapped the O2 sensor it smoothed out. I read somewhere (either this forum or nissanforums) that the computer can run without the O2 sensor plugged in, but since it was only $20 at AutoZone, replacing it was a no-brainer.

[Saudade]

Yep, one of the first things to go when this started.

Thanks,S

[Saudade]

Bump for the new Board software...

[seang]

Since you can't swap out the TBI for a carb, I don't know what to tell you. I wish someone would post the MAF resistance for you, if they knew.

[nismoka24e91]

If you think its the maf you might want to look into swapping a maf from a different nissan. i know a popular maf swap is a rb20det onto a sr20det, but i dont know if any other mafs will work on a z24i engine. also i know if you have to go through emissions a good way to pass easily is to retard your timing a lot. i know oregons emission laws are far different from calis but my truck wouldnt pass. it had like 200 or 300 hydrocarbons. i retarded my timing probably 7 deg. enough to cause a big power loss but my hydrocarbons decreased to 24 at idle. so you might be able to do that if you convert to carb. just a thought. wish i could be of more help.

[seang]

I just remembered, I think you can have your MAF tested somewhere. Maybe you can call around, OP.

[Saudade]

When I went scavenging a few pick-n-pulls I looked in every Nissan I came across. Those that still had one in it was different in mounting or were 3 wire.

One thing I'm still unsure about is if it's the ign or fuel that cuts out. This weekend I'll get some starter fluid, run it until it cuts and spray the fluid down the TB. If it continues to run, then I know something is shutting off the fuel (still could be MAF). If it still cuts out, then most likely ign related. I've already swapped out most of the ign components but we'll see.

Thanks for the help.

[seang]

The MAF sensor, when unplugged (or suspected failure in your case), will cut the fuel and not the ignition.

[nismoka24e91]

yeah with the maf unplugged it should cut out between 2500 to 3200rpm. also i know its a different engine but my friend has a rb20det in is 240 and the maf from jdm was bad. idle it ran almost perfect but if you tried to drive it, it would sputter, die, and backfire. with the maf unplugged it didn't hold a idle but it drove as long as you kept the rpms under 3k. just something i though id share. i know some cars wont even run without a maf but some can. i also know that the z24 have two ignition coils. i heard that sometimes people will wire the exhaust coil to the intake and the intake coil to the exhaust. the intake coil is more powerful and fries the exhaust side and the exhaust coil isn't enough for a normal ignition.

how many wires are on your current maf?

[nismoka24e91]

also you mentioned that you found some mafs that were in different locations. did thoes have the same amount of wires as your z24? because if they do then you can make a makeshift 'cold air intake' and use that. just be sure if you mess with wiring to do only one wire at a time. because i fried a maf from doing all the wires at once before.

[Saudade]

Problem with a CAI is my stock aircleaner is the "old school" round style with a small attached manifold that connects a number of vacuum lines. Certainly not hard to replace but smog testing here in CA is nuts. An inspector might consider that an alteration and cause for failure so I'd rather not mess with it.

One almost failed my Jeep XJ because the hose connecting the shroud around my exh manifold and the air intake (warm air bypass) came off one end. He couldn't "fix" it because he was a "Test Only" center. Of course, I merely had to place the hose back on and we were good to go.

[nismoka24e91]

wow. way worse sense i left there. i lived there 6 years ago. im kinda glad i dont now lol. ive also heard that first time offense street racing they crush your car

but yeah its probably in your best interest to leave everything stock. when your testing do you know if they test for hydrocarbons?

[seang]

Saudade, did you try that starting fluid thing? Pouring a little gas down the TB would probably do the trick, too, even use an old ketchup bottle so you don't flood it.

If you do end up looking for a MAF, one of our members "Lino" has in his signature a link challenging owners to beat these prices on Datsun/Nissan parts. Just a idea.

[Saudade]

Thanks Sean. No I haven't yet. That's on my list for tomorrow. Just got my DMV renewal for it too. Gonna have to get it smog tested this year.

[nismoka24e91]

retard the timing.... like alot..... it will help alot with your hydrocarbons. i had to floor it to get to the test station but it defiantly helps bring down the hydrocarbons.

[Saudade]

I'm more concerned that the cutting out will prevent the guy from completing the smog check rather than have the emission levels fail. Smog testing has never been a problem with this truck. Despite owning it since new, I know very little about it since it's never really needed any major work (beyond brakes, a clutch and usual tuneup stuff). On the other hand, I'm quite an expert on my 88 Cherokee.

[Saudade]

Well, a quick update. I tried the spray down the TB and it did pick up some RPMs while spraying so it seems to be a fuel issue. I scoured the "universe" trying to find the right MAF and none seem to exist. Everyone is out of stock/backordered/Etc. I've tried several JY's over the past few months and can't find the right one. Funny thing happened while doing this. I drove around for a while to heat everything up to temp. While idling, I removed the aircleaner cover, the RPMs dropped. Put the cover back on, blipped the throttle and the idle recovered. Remove the cover and the RPMs dropped again. It's a new air filter so I can't see why that would matter except that without any inlet restrictions, there's more air coming in and the MAF is not compensating. Just a wild guess.

Good News: During my searches, I found the place that remanufactures them and they're only 20 minutes away.
Bad News: They don't deal directly with the public so I have to go through a dealer.
Good News: They referred me to one.
Bad News: They don't have any in stock either.
Good News: I can send them mine for a rebuild.
Bad News: Shipping to dealer, then to the "remanufacturer", then back to the dealer then back to me could take a couple of weeks.
Good News: I was able to arrange paying the dealer, who emailed me the paperwork so I could drop it off personally. Took it there this morning.
More Good News: It will be ready tomorrow.

So it'll be done tomorrow. I'll either break out the Champagne or the torch.

[nismoka24e91]

dont for get the cigar.

[Saudade]

dont for get the cigar.

I'll have one regardless of the outcome.

[Saudade]

It's the torch. I lit a nice Romeo y Julieta Anniversary torpedo (for you fellow lovers of the leaf out there).

[Saudade]

Well, hold the torch. I've been on another forum with someone else having the same problem. Looks like my inboard injector (closest to the VC) isn't working. I can look down the TB while running and see fuel sprayed on the throttle plate on the outboard side, but not much on the inboard. I've already swapped out the TB with injectors so I don't believe the injector's bad. I found a wiring diagram on Autozone's site that shows the inj schematic. I've been told there's a junction inside the harness that splits power to each injector. The other injector leads go to the ECU. Occasionally this junction corrodes, weakens and may even break. I've long suspected a wiring issue due to the intermittent nature of the problem earlier on. Hopefully have some time this weekend to check it out.

I'll have another cigar regardless.

[Saudade]

Well I couldn't wait since this is a 5 minute test. Key on, engine off with harness disconnected, I measured full battery voltage of 12.3v at only one of the FI feeds. The other measured almost a full volt less. The one that measured less is the one that appears not to be spraying any fuel. Later, when I do have time, I'll backprobe it while running and see what happens. Maybe I'll even jump from one to the other to get full V to the inboard injector.

[Saudade]

SUCESS!!!! This was right on!! Turns out there are 2 splices in teh main harness between the firewall and the injectors. Two wires splice down to one, then run about 8 inches, then splices back to 2. This is one of the dumbest a$$ things I've seen. The one closest to the inj was completely corrode and and came apart with the slightest tug. Clipped, stripped and crimped, I can run it to the redzone now! Woohoo!!!

I'll post pics later in a new thread once I get done taping everything back together. Thanks to all for hangin' in there.

[seang]

Our humble trucks forum just doesn't get as many replies as, say, the 240sx forum. Still, good looking out on the updates, that is what keeps the info alive. There is much to see in the archives, and this is a great addition to that.