Timing won't stay set, can you figure this one out?

[datsunan]

Ever since I did my turbo swap I have had this problem with my timing changing for no reason. I set it to 20deg with the TPS closed, and the engine up to temp, then for some reason the car will start running poorly and when I check the timing it may be 25 or as low as 13. This has been going on for over a year and I can't figure it out. What would cause it to change? I know the ecu changes it for different engine temps and during load, but why would it change the Idle setting. Can the ecu adjust the idle timing? It is a JWT ecu. I'm thinking about pulling the ecu and going with MSNS but I don't need to if I can get this problem fixed, the car runs great when the timing is right. Any Ideas? Thanks Paul.

[Guest Loose_Screws]

What MSD ignition are you running? You could have two different things altering the timing, the MSD box (???) and the ECU. Which ECU setup/year are you running?

[datsunan]

The MSD 6A was added 6 months ago and I had the problem befor I put it on. One thing that was wierd when I put the MSD on was that I lost the tack signal to my APEX digital boost controler that was the same wire that went to my ecu. I had to hook the APEX boost signal wire to the MSD to get my signal back but if I tried to hook the ecu to that wire it would kill the car. Well the car runs with the ecu still hooked to the original tack wire so I guess its getting what it needs. Any who, the ecu is out of an 88 na z31 and is reprogramed by JWT.

[Thumper]

It might sound stupid but make sure the bolts are tigtned down on the distributor. At higher rpm they can come loose and walk around. Also check to make sure you rotor is good. If its bad it can also move around and effect timing.

[datsunan]

Yeh at first I was only tightening one bolt on the dist because I had to change it so often but now I tighten both of them good.

[johnc]

Is the mechanical advance mechanism still in your distributor?

[datsunan]

No mech advance its an 83 dizzy so it has the disc in it.

[Guest bastaad525]

I had similiar problems myself... one thing I did was when adjusting the timing, I will disconnect the TPS entirely. I coulda swore this was how the Haynes manual said you're supposed to do it. Yes the ECU can and will adjust the setting at idle. I actually watched my timing once when i started the car cold... when I first started the car the timing was quite a bit retarded, then after the car warmed up, it suddenly 'switched over' to warm running mode (you could hear the idle suddenly change), and then the timing was up to 20ish degrees.

 

Another thing... and man this is gonna sound stupid... but are you sure that the little screw that holds the rotor onto the distributor is in place? I had a friend with an '83 once that also had this problem... timing jumping all over the place... and turns out he had forgot to screw that screw back in when he replaced the rotor.

[datsunan]

took the dizzy apart today and found the rotor could move if I twisted it kinda hard. The little screw was in it and tight so I pulled it apart farther and found the screw that holds the the base that the rotor screws to was not tight enough and allowed some movement if enough stress was applied. Well that only took me 1 1/2 years to figure out but then I did'nt really try to hard to fix it seeing as how this is the first time I have taken it apart.

[Guest bastaad525]

sweet so I sorta had it at least got you in the right direction. I was baffled with my friends setup too but then, I never even knew that on the '82-83 turbo there is a screw holding the rotor down. As far as I know no other L6 Z distributor has this. I thought his ECU was going nuts just moving timing all over the place and almost had him convinced to start replacing major/expensive EFI components.

 

So you just tightened that screw and all is well now?

[datsunan]

Well yes and no, it was not the screw holding the rotor on to the shaft from the side it was the screw holding the shaft or colar thing that screw to the top of the dist shaft. If you take the rotor off there is a gold colar or cylinder that sandwiches the crank angle disc to the dist shaft, and it is what the rotor mounts to, the screw holding it down was not tight enough. Time will tell but I'm 99 % sure that was it. Now if I could just get rid of my detonation. Thanks for the help.

[Guest bastaad525]

yeah I think I know what you're talking about, that's the screw you need to remove if you want to pull out the CAS chopper wheel right? on the '82 dizzy I just bought that screw is in there EXTREMELY tight and I haven't been able to get it out gonna suck when the time comes that I go to install the 300zx ECU/MAF I have *DOH*.