Ok.. so I got my car running Oh so perfect and now this happens

I'm a little stumped and was looking to get some input before I start dropping the $$$ on parts.

Out of nowhere my car started choking when I was giving it gas and backfiring mildly. From there it just got worse and to the point where if I even hit the gas, the car would just stall..

The idle was decent, but it was definitely missing a little and my vacuum dropped from 20 to 14-15.

I changed the plugs and fuel filter today with no real change (did notice signs of rust coming out of the bottom of my fuel filter) and removed the ecu to check all my wiring. I started messing with my afm for a bit and noticed that if I loosened the spring dramaticly, the car would rev correctly but with there was a rough idle and the exhaust started getting grey/whitish and seemed to be running rich as all hell.

Any ideas? I was leaning towards the afm, but it was just replaced 4 months ago and looked clean as a whistle when I pulled it out. Last I knew there wasn't much that could really go wrong with those unless the carbon track was jacked..

 

vacuum leak

 

I say TPS... either disconnected, wet, or corroded.

If by chance it's not the TPS, it's probably the CHTS.

 

No vacuum leaks that I could find, the tps is still adjusted properly and I even tried unplugging it with the same result. I also just replaced the chts three months ago, so it (shouldn't) be that.

The one odd thing was that if I unplugged the afm, it would still run for 10 or so seconds, where before it fell on it's *** and died rather quickly.

It's getting hauled home this afternoon and I'll let you know what the magical problem is this time.

I'm seriously debating putting my engine/trans up for trade and get a carbed 302 or 350.

The motor runs great but the electronics on this car will be the death of me or my wallet someday.

 

Whelp.. no clue what is beyond the fact that it doesn't run correctly.

I'll probably end up just doing the 300z ecu/maf coversion since I have a spare chopper wheel sitting around.

blah.

 

Yeah... I have a similar problem right now. Usually it works itself out, but not this time.

The engine wants to idle around 200 rpm and lopes like its got a HUGE cam. Give it a little gas, and it wants to die. Now at higher RPMs, it runs great. If I'm doing 70 on the highway and floor it... that's trouble. Spits and sputters, belches out a puff of blackish-gray smoke.... just acts like the motor is getting to much fuel. Which it apparently is. I used to get around 400 miles to the tank. I'm down to about 250.

The air filter was nasty, so I replaced that. I have a new fuel filter I'm putting in tomorrow. Going to check the plugs for fouling along with the distributor cap and rotor. I'll double check the vac lines, but I doubt that's it.

Oh... Nice Z Midwest!

 

New plugs, new cap and rotor. It's... better, still not 100%. Feels like the computer is learning that there is spark now. If it doesn't even out in a week, I'll throw a new coil in there.

 

I ended up getting a afm online and hopefully it shows up this week...

It's so nice out and the z is just a treat to drive with the t-tops out in this weather.

If that doesn't work, I can only assume that something went wrong with my ecu. :P

 

not sure if you've already got her running yet, but if not... I had a similar problem on my celica. The terminals on the rotor cap were completely scraped down and when I replaced it, the spark was back to its normal strength and the backfiring stopped. Let us know if that was the case with yours.

 

I got the afm in today and it didn't fix my issue....

I'm going to assume that something went horribly wrong inside my ecu and it is messed up now.

Nothing else really comes to mind that could mess with the car that bad. The Z harness is pretty simple and everything else is in place and nearly new. Guess it's time to start scouring the forums for a 81-83 turbo ecu :P

 

Picked up a new chts under my last ones warranty and this didn't fix anything either :P

It has to be the freakin ecu.... This car is about to get "accidentally" torched lol.

 

How's your fuel pressure?

 

fuel pressure is good.

The car will start, but only if I use a spare afm and let the tension off the spring.

All my injectors are pulsing, the plugs are new, new dizzy, new wires.. well pretty much new everything.

This all happened slowly.. it's odd too. I slammed on my breaks to avoid hitting a deer and I noticed the car lost some of it's high end pep immediately afterwords. About a week later it started sputtering, backfiring and stalling when I gave it gas. It eventually got to the point where if I gave it gas during a it's rough idle, it'd die.

I've done resistance tests on my afm, chts, and checked voltage to my injectors and fuel pump. Everything looks A-ok.

 

Have you check the inlet screen on the fuel pump itself? Then checked the lines to see if the clogged? Maybe when you hit the brakes, you stirred up some residue or something in the tank and it picked it up and clogged something. You can still get good fuel pressure. BUT not enough fuel to run on.

 

I pull the float system and clean that on a monthly basis

Hopefully the ecu I ordered fixes all this....

 

I have almost thr same problem. Give it to much gas and it misfires. Havent had time to check every yet. Let me know if you figure it out

 

well here's another update...

changed the fuel pump to a walbro and cleaned my fuel lines... it made no difference.

I pulled the fuel injector clips off 1 at a time and noticed that injectors #3 & #5 don't impact the engine when I unplug them.. I took voltage readings, checked for the clicking noise in the injectors and checked fuel pressure again and it's all good....

Does this sound like clogged injectors maybe? The engine will start, but it chugs, sputters and will backfire through the afm if I try to give it gas...

I just don't understand what could cause this to happen all at once.

 

Did you check the EGR and its systems? Uh. Adjust the valves? Hmm... Test the compression as well? I made a little thing that with the injectors off the of engine but still hooked to the fuel rail I could test fire each injector with a 9v battery. Take them out and check for leaks/clogs. Maybe clean the fuel rail if you haven't

 

And if that's not it. Try checking your spark plugs. Even if they are brand new. Doesn't matter, because that was the cause of my slicktop running on 3 cylinders. I had 3 bad plugs from factory. But didn't figure it out. Until months later. After I already damaged the head gasket. From the car sitting so long. And only running it on 3 cylinders.

Try taking the plugs out of 3 and 5 cylinders. And switching them with ones that are firing. And see if it changes. If it does, then your plugs are bad. If not, do more testing on other things, until you find the culprit. Good luck

 

Think I figured it out.

I pulled the rail and when i removed the injectors, there was rust in the gas + some dark goop. Apparently my fuel filter wasn't doing it's job very well :P

So far I've changed the fuel filter, put a inline filter between my tank and fuel pump, cleaned the lines & fuel pump and am getting ready to blast out the rail/plugs with carb cleaner.

Hopefully this fixes my issues :P

 

You still need a compression test. i warped my head, and i loose compression on 4,5&6 when the engine is past it's norm op temp, say like a hot summer day in traffic. but if i never reach that temp, she runs like a hoss. and theres no fluid mixing.

 

Well the gunk might be half of the problem lol make sure to spray out the injectors too!

 

She purrs like a kitten again

I'm probably going to get a stock pump though... the walbro is freaking loud..

 

Awesome man, glad you got it all figured out. Enjoy the ride, I can't wait to enjoy my Z again.

 

Sweet! congrats!