My son and I restored a non turbo 79 from the wheels up, everything was running fine until I replaced the gas tank sending unit. After driving for about 30 minutes it looses power and won't go above 3000rmp in every gear expect 1st and neutral, I've checked all the vacuum lines, replaced the fuel filter, added Heet just in case we had gotten bad fuel, checked all the injectors and the timing, what else should I check?

Thanks,
Grabo2u

 

Welcome to ZDriver. It kinda sounds like the classic AFM / TPS sensor problems... but if those things weren't touched, I'd suggest pulling the spark plugs & looking at the tips to see if it's running too rich or too lean. You may have a clogged injector.

 

I checked the plugs and it looks like I might be running a little rich, what do you think I should check next?

Thanks,
Grabo2u

 

does yer car have o2 sensors??? maf (afm)???? clogged lines/injectors,...?????????vacuum hoses.......i yam not the expert on those, but there are good guyz here---welcome--you said you and yer son-----how old is yer son and how old are you??????we have 'em all ages here--stick around and get to know the place.....not so bad here........lotsa helpers--some even know stuff.........

 

check the connector on the top of the throttle position sensor. Make sure its clean and DRY.

 

No O2 sensors, tried everything else expect the throttle position sensor, I'll check it today.

FYI my son is 17 and I'm 53

I love working on the Z, this is the first time I haven't been able to figure it out.

Thanks Grabo2u

 

From now on it should be stated that the FIRST thing to be checked when a ZX will not rev past 2,000-3,000rpm is the TPS connection and the FIRST question to be ask of the person with the problem should be "Has there been any liquid around the engine, sprayed or other wise?" Also, it should be suggested that anyone with a ZX should keep a can of compressed air around at all times to blow out the liquid from all under hood electrical connections. Peace and Chicken Grease!!!

Like Bleach says "Check the TPS connector.." Or like I say...push the gas pedal further.... J/K lol

 

I checked the TPS and it was fine, I started checking everything electrical, plugs were black and so was the tailpipe, running way too rich, I found out the air flow meter didn't match specs. Luckily I have a 82 parts car, so I tested it's AFM and it was fine, I put it in, cleaned the plugs adjusted the AFM and the timing, so far so good. I'll take it for a test drive tomorrow and let you know how itn goes.

Thanks for your help,
Grabo2u

 

Check to see if there is any moisture in the distributor cap. It can cause some erratic problems with revving. Also check the connection at the ecu. This is a common problem with 280zx's and sometimes reseating the ecu connection helps. I had to swap out my turbo's ecu plugs to 1st generation 300zx plugs. How is the idle? Check the EGR valve and make sure it's not getting stuck open.

 

OK, took it for a ride, same problem, too rich. Checked timing cleaned the plugs, checked the dist. cap and rotor, this car doesn't leave the garage if it's raining, only been in the rain 2 times since I've owned it.

I'll check the ECU plug,

Grabo2u

 

Were the ignition control unit or ignition coil changed on this car? Just like with my Turbo Z, the timing was correct, but thanks to the ignition module/coil, or combination of both it wasn't sending the right signal until I changed those and then re-adjusted the timing.

 

I test drove it last night and same damn thing! This morning I tested everything I could think of and then some, replaced the H2O sensor and the dist. module. The thing is it doesn't do it until the car is driven for about 30 minutes, something has to be getting warm and then affecting one of the thousand or so sensors Nissan put on the damn thing! My son really wanted to drive it to his Senior Prom this weekend, if I can't fix it I'll be renting a car for him! I have an appointment at the dealer (OUCH!!) Monday morning, if I find the problem before I'll post, if not I'll let let you know what they find.

Grabo2u

 

problems after the car warms up are some times the ignition module manfunctioning on the side of the distributor; although I have never heard of it getting rich or not revving above 3 grand.

 

Ha... the L28 efi is about as simple as fuel injection gets. It really sounds like the AFM now... I had that exact same prob when I bought my Z... it would run fine, then just crap out & have a hard time starting. After it cooled down, it would run fine again. New AFM fixed that. Do you have any way to swap AFM's? Maybe w/ one from a friend or junk yard?

The sensors that will wig the car out: AFM (and air temp sensor), TPS & CHTS. Have you checked the CHTS?

 

It could be the coil as well. They tend to fail when they heat up if they're starting to go bad. What is the number on your ignition module? I have an n/a 280zx distributor, and I'm pretty sure the module is still good. I hate having sidelined projects (like my very own POS haha), but I'm leaning more towards a coil going bad if you've replaced the distributor module already. Let me know if you still need the module too.

 

OOOOHHH OOOOHHH, see, I am not the only one who feels that way!! And I agree, it is a simple EFI system....for those who know EFI...some of us don't know so much about them and it gets frustrating...even with "simple EFI's"

 

i dont think it has to do with it being simple, i think it has to do with being old, and retarded...... and by retarded i refer to the AFM. lol.

 

I bought a new coil, adjusted the air gap, checked every electric connection again, timing, plug gap, did the AFM fix, checked every vaucum line, fuel preasure check, TPS adjusted, and did everything that was suggested here and it ran great in the garage! I took it out and it ran great for about 5 miles, then it surged and fell on it's face. I headed home and it kept getting worse, it wouldn't make it up the last hill, I could get RPM's to 3000 but as soon as I started to let out the clutch it died, after many attempts of getting half way up and then coasting back down the hill I started smelling burnt rubber and shut it down, called my son and he towed me home.

I give up, I've never had a car I couldn't figure out the problem, if anyone has a clue as to what it might be please LMK, it goes to Nissan Monday morning I think it will go there on the trailer just to be on the safe side.

Thanks,
Grabo

 

thats wierd that it only does it when the car is warmed up, you should check the sensors that have anything to do with temperature they might be going bad on you.

 

you have done a lot of checking from what I read, why not start cleaning I mean with abrasive like a wire brush and cleaner? if it only happens when the car warms up lets think about the basics. you have closed loop and open loop for example. start thinking about how the sensors work and how they work tegether, and when they work. your head temp sensor can be a colpret. check to see if not only you have a clean conection, but is it a good conection tight, are the pins making good contact clean those suckers with a wire brush or somthing for heven sacke man. what can be expected from these things if you have more resistance in your head temp sensor you are tipicly going to dump more fule than desired depending on how much extra. and what about the maf whel it is only so good up against a bad head temp sensor, and what about the air regulator? do the simple cleaning and then you can start crying after all that.

 

Did you check your belts? I kinda messed mine up while changing my alternator and somehow got my fan belt caught behind the pulley and it took it a while but it started to burn. Thats the only thing I can think of that would smell like rubber. Check all the pulleys and make sure they are all spinning freely....man that is just weird.

 

is your belt rubbing on the radiator hose???? or what thx said....

 

I checked and cleaned every sensor that the engine has in it, I replaced the distributor, cleaned and "re-built" the AFM, and it seems to be getting worse instead of better. I have it at the "best" import shop in the area, if he can't find the problem it might be time to just pull the engine and do a complete re-build, that way I'll know it's done right!

Let you know when I know,
Grabo2u

 

I've cleaned every part I can get to, even some internal parts, I don't mean to sound cocky, but this is the first time a car has gotten the better on me, the engine is the only thing I didn't personally re-build, it might be time to do that.

 

I am not going to doubt your skills or anything like that but I think these engines are really tough or strong if you will...having it rebuilt is cool and all but I will wager that the problem(s) are 90% electrical and not mechanical.