280z, ruff idle, backward tach, rev cut

[Two80z4me]

Hi, I tried searching this and found a little on each all pointing to different things.

 

First of all, the car is idling ruff, and you can feel an unusual bubble in the gas pedal, and when your parked in place and rev it hard, the Tach needle goes down instead of up, and when your driving and try flooring it , it roughly makes its way to about 3 and a half k and then stops and wont go any higher, and when you accelerate hard the RPMS rise like normal but barely accelerates while still blippin the gas, the speed doesnt follow the RPMS like it used to.

 

It led me to think two things, the AFM was bad, so I replaced that and found that it had a 280zx AFM on it, and put the OEM 280z one on and now Im thinking its a hose issue between the throttle body and the AFM and possibly the ECU for the injection or something, I move later this week and dont have a trailer to haul on, please help me get this thing going again right.

[morbidsunroof]

I don't know about the tach but the symptoms match either a jumped timing chain (rare) or a plugged exhaust.

[morbidsunroof]

Severely retarded timing will do the same thing.

[Two80z4me]

Severely retarded timing will do the same thing.

 

the tach only started doing that when I put in the new Air Flow Meter, which went from being a 280zx AFM to a 280z AFM, the 280z afm was much lighter and had alot less things inside the cover, which kind of worried me.

[Challenger]

I don't know about the tach but the symptoms match either a jumped timing chain (rare) or a plugged exhaust.

 

You serious?

 

Have you check electrical connections yet? When did this start occuring? Also its hard to help someone when their post is a jumble of words. You say when you rev it hard the rpms go down... what does that mean? I thought you were reving it up. So in the future try to write with some cohesion.

[Two80z4me]

You serious?

 

Have you check electrical connections yet? When did this start occuring? Also its hard to help someone when their post is a jumble of words. You say when you rev it hard the rpms go down... what does that mean? I thought you were reving it up. So in the future try to write with some cohesion.

 

I checked the electricals, might be the fusible links. Sorry for the confusion here, When You Rev the motor, the tach needle goes down and the actual RPMS go up. It also has a small intake backfire which leads me to believe all of this is caused by Air Flow Meter Hose/PCV valve leak somewhere.

 

This all started occuring two weeks ago. It had happened before in the past but it had reset while I was driving it before, so I didn't think much of it this time till it didn't go away. I replaced the AFM with the proper one that belonged on my car and not a 280zx afm, It seems to have made a difference but it has created new problems.

[dan5138]

Find your FSM on this site, I know all or most of the S30 ones are in the download section stickies. Check your tach wiring, IIRC the tach signal comes off the ballast resistor for your coil.

 

It sounds like an ignition problem to me. Throw a timing light on it and make sure timing checks out, the FSM will show you how to do this. If you're in time ( or within a few degrees) try swaping out the dizzy, or possibly the ignition module.

 

Do you have an original dizzy or a reman unit? Cheapo reman units are usually rebuilt with crappy parts or slopped together original parts. I was recently having intermittent problems with my '76. Wouldn't idle, wouldn't rev past 3k etc. It would miss enough to foul the plugs and would start smoking as well. Put a dizzy in from a wrecking yard car in it and now it's fine.

 

Edit: Would'nt hurt to check the AFM boot like you mentioned, could cause the car to run poorly. I doubt its an issue with your PCV, that usually causes a rough idle, but has little to no effect once you hit about 1500 - 2k rpms.

[Two80z4me]

Find your FSM on this site, I know all or most of the S30 ones are in the download section stickies. Check your tach wiring, IIRC the tach signal comes off the ballast resistor for your coil.

 

It sounds like an ignition problem to me. Throw a timing light on it and make sure timing checks out, the FSM will show you how to do this. If you're in time ( or within a few degrees) try swaping out the dizzy, or possibly the ignition module.

 

Do you have an original dizzy or a reman unit? Cheapo reman units are usually rebuilt with crappy parts or slopped together original parts. I was recently having intermittent problems with my '76. Wouldn't idle, wouldn't rev past 3k etc. It would miss enough to foul the plugs and would start smoking as well. Put a dizzy in from a wrecking yard car in it and now it's fine.

 

Edit: Would'nt hurt to check the AFM boot like you mentioned, could cause the car to run poorly. I doubt its an issue with your PCV, that usually causes a rough idle, but has little to no effect once you hit about 1500 - 2k rpms.

 

ya, Im bringing out the timing light tommorow, checking the boot, and I have another dizzy for it, the one thats on it is from a 280zx, with new cap and rotors, any idea what the air gap should be retarded to? and shouldnt the timing be around the 8-10 area?

[suuz]

have you found a solution to your problem yet. mine seems to be doing the same thing. Interested in knowing

[FlatBlack]

I had the same thing happen on my 78 awhile ago with my stock ECCS rev it up, tach goes nutso. Like everyone else is saying check your wiring.

 

I think my issue was solved after the fusible link to fuse block swap, I can't remember though, it's been awhile. If you are in doubt, do it. Those are 30 year old boxes, and I'm pretty sure I remember you telling me they are uncovered, er... covered with snow

 

There is no way your timing jumped a chain, I don't know why that came up...

[Two80z4me]

Update to whom this may concern:

 

I got a new AFM courtesy of flatty up there, helped a little, had the same problem come up again and again.

 

Got new spark plugs, ran great below 3k, smooth good power, as soon as you hit 3k or kept going on up, the power was absolutely gone, so much that you can barely get it past 4k when driving it.

 

A week later, same problem comes back

 

sounds like this http://s181.photobucket.com/albums/x131/nwkled06/?action=view&current=MVI_1113.flv

 

I changed the timing and did all the idle adjusting, then it ran great again, with the same power drop, which could be due to the timing being off still, but then I go to drive it the next day and its back to sounding like it does in the video?

 

Help!!! This is my DD and I need to running reliably again.

 

my 2cents would be the fuel pump, but I need help with this.

[FlatBlack]

Hello there.

 

Go to your local auto parts store and get an inline fuel pressure gauge. Take off the fuel hose after your filter [i.e. in between in filter and fuel rail] and see what you are getting. That will tell you if your fuel pump is adequately fueling the injectors or not.

 

That sounds like when my stock fuel pump starting going out, so that's a good hypothesis, but if you have around 36 psi it should be good. If not go read the EFI Bible and figure out what it is.

 

As for the 'jumping' tach, my stock EFI did it as well, I can't remember if it was caused by my old fusible links, a backwards wired coil, or what - it has been a while.

[Two80z4me]

Hello there.

 

Go to your local auto parts store and get an inline fuel pressure gauge. Take off the fuel hose after your filter [i.e. in between in filter and fuel rail] and see what you are getting. That will tell you if your fuel pump is adequately fueling the injectors or not.

 

That sounds like when my stock fuel pump starting going out, so that's a good hypothesis, but if you have around 36 psi it should be good. If not go read the EFI Bible and figure out what it is.

 

As for the 'jumping' tach, my stock EFI did it as well, I can't remember if it was caused by my old fusible links, a backwards wired coil, or what - it has been a while.

 

well it stopped doing the tach problem, so thats out of the problem. its just the fuel pump, i'll do it tommorow, get on AIM around 5 your time tommorow or I'll call you.

 

the EFI fuel bile, well lets just say there is a link directly on my desktop lol

[FlatBlack]

Did you fix your tach issue or did it just go away?

 

I found my thread from when I was having issues with the stock EFI.

 

Those pesky fusible links...

 

http://forums.hybridz.org/showthread.php?t=141987

[Powerglide]

Sounds like a weak pick-up coil in the distributor or low fuel pressure?

[Two80z4me]

Sounds like a weak pick-up coil in the distributor or low fuel pressure?

 

I put a new filter in and it flows better, but still runs bad. now its down to the Dizzy and the Fuel Pump, I need to get a ZXT dizzy anyway for megasquirt so I'll pick one up and a walbro 255 fuel pump.

[Two80z4me]

Ok, update. I did the fusible link swap and put seafoam in, it ran great for a day and a half. but then I drove it to school the next morning, and it was stumbling but halfway to school it stuttered and went back to normal. I went to lunch and AGAIN!!! it started badly idled funny and drove odd, but on the way back from lunch, it ran just fine?! Now the hole way home it ran inbetween, it wasn't super bad and choppy ,but it was still stuttering on acceleration and idle, it never stutters on decelleration?

 

I tried using the EFI bible and testing connectors, everything is reading full.