1982 Turbo ZX 2+2. 5 speed.
So after reading a crap pile of posts and going over the car a bunch of times, I think my distributor is not advancing properly, mostly because I had a car doing that some time ago. However this distributor doesn't have a vacuum advance, so I assume it is electronically advanced (at least I couldn't find a vacuum line to the dizzy).
Is there a way to test the advance? Just with a timing gun?

The symptoms are:
1. Only acts bad when warm.
2. Intermittently lacks power, won't rev smoothly, stumbles, hesitates.
3. If I get on the clutch, and just rev the engine, it revs fine, then usually the power comes back on (for a bit).

Is there anything sticky that needs cleaning? Can the dizzy be serviced, or just replaced?

 

have you used a timing gun/light to see what the timing reads?

 

Yes the timing is controlled by the ecu. The turbo ECCS uses a CAS (crank angle sensor) inside the distributor. If you are wondering if the ECU is advancing the timing, just fire the timing gun at idle, rev engine, and watch the timing mark change.

I would start with checking the CHTS and AFM specs, along with the condition of their connectors. Also check for timing chain stretch (often overlooked), check for vacuum leaks, check condition of cap & rotor, and read spark plugs. Also make sure you are ONLY using NGK plugs.

 

Thanks guys. I have read a lot on this website while getting the old girl on the road. You folks have helped me find a lot of issues like vac leaks and replacing spark plugs with NGK's.
I did check the connectors on the CHTS and the AFM (I got a bit confused finding the cylinder head temp sensor, I assume it is the one at the front of the engine buried under the skinny coolant line). I guess next is to test them, but I don't know how to test those parts. But I bet someone is about to tell me to check the service manual I already downloaded (first thing I did on this site!).
And yes, when I woke up this morning, the first thing I thought was "Oh, I should get out my timing gun!" which I haven't used in a long time of owning coil pack cars...

 

CHTS = Cylinder Head Temp Sensor ... located on the CYLINDER HEAD between spark plug 5 and 6. FSM has the ohm specs.

 

So now I am even more confused. I dug out the old timing light, found the mark on the pulley, marked it bright yellow, and then fired it up.
So the timing mark first of all is a PAIN to see with all the accessories in the way. I don't know what engineering genius thought of that setup, but once I held my mouth just right I could see it.
When the engine was cold:
1. The timing mark appeared about 10 notches down on that serrated plate I can only suppose is there for timing: I assume one tooth equals 1 degree of timing? So I think I was 10 degrees BTC.
2. Funny enough when cold, when I revved the engine, the timing mark moved UP the saw-tooth, so I think it was retarding the timing as I revved it.
3. When the engine warmed up, then the timing mark moved down the saw tooth, but not consistently. When I revved the engine (by hand on the throttle plate) it would sometimes move a lot or a little, and sometimes not at all.
I was looking in the service manual but I cannot find how far the timing should move...

 

Now I have found the CHTS (thank you) and tested it on the car:
At about 40 degrees it was 1 kOhm, and at close to 80 degrees (car hot) it was 0.3 kOhm, so it looks like it is in spec. Also, when you unplug it while idling, the idle gets noticeably rougher, and when you plug it back in, it evens out nicely.

I guess I should check the AFM next...

 

So I have determined there is something intermittently wrong with my spark advance. The timing light would sometimes show the timing advanced when revved, and sometimes it would go the wrong way (retard) or sometimes it would not even show up on the guide.
On the road the issue is similar, sometimes it is fine, sometimes low power, and sometimes it is back-firing (when I say back firing, I mean REAL backfiring, the kind that goes backwards up through the intake, so it is firing while the intake valve is still open).
So what controls the spark, is it only the dizzy, or is it the computer telling it when to spark??? Anyone seen this before?

Can a thorough cleaning of the dizzy slotted rotor help? Is there a vac/boost line somewhere that goes to some sort of sensor?

 

Have you done this yet? If not I suggest doing so now. Also remove cap and check rotor position at TDC cylinder 1. It should be just down from pointing straight forward (about 8 o'clock looking at it from the drivers side).

I've worked almost exclusively on the turbo model for the last 10 years and found that the majority of the turbo problems come from: improperly set mechanical timing (timing chain, distributor shaft, crossed plug wires), dead, disconnected, or corroded CHTS / AFM, ecu connection or ground problems, vaccum leak(s), dead injector(s), or improper fuel pressure. Any of these will make the ecu go crazy trying to compensate.

Also check out: https://www.zdriver.com/forums/240z-...p-guide-40951/

 

I have a feeling to check for timing chain stretch, I would have to take the cam cover off, which looks like a crap-ton of work with all the injector stuff on top. Does anyone have a super easy way to check for that before I start pulling wrenches?

 

Unless you have x-ray vision.

We have a https://www.zdriver.com/forums/240z-...e-l28et-30099/ thread stuck just for you.

And another good link: http://atlanticz.ca/zclub/techtips/timing/mechtime.html

It only takes a few minutes to get the valve cover off: Remove 3 10mm bolts to top plastic injector fan (the Y) and remove, disconnect plug wires from spark plugs and lay on intake manifold, disconnect vacuum lines and breather hose, remove valve cover 10mm bolts, remove valve cover.

Set engine to TDC cylinder 1, check distributor rotor position, then check timing chain / cam sprocket alignment marks.

 

So something didn't feel right with the things I checked over, so I thought about how it was running, and felt that because if I pumped the gas, I could get the hesitation to go away, I thought that it could be the fuel injectors boiling from too much heat, or the check valve to the vacuum control intermittently leaking.
I hooked up the battery to the "hair dryer fan thingy" and it fired up with a purr, although it really doesn't move much air, so I assumed that was alright, so I turned my attention to the check valve.
I yanked off both vacuum lines around it, and blew through both ways, and sucked both ways (that doesn't sound right). I found it was making some bubbles in water when it shouldn't be. I tried to pry the lines off of the check valve to see if I might be able to get a look at the diaphragm, but then one of the nipples broke off in the vacuum line!
Grrr, so I tried to fix it by drilling it out, and glueing in a new nipple from another vacuum fitting, but I didn't trust that, so I went and found a check valve on a Volvo. But then the vacuum fittings were too big, so I just tried the old, glue repaired check valve, after blasting through a bit of compressed air to clean out any dust or debris, and now it runs awesome when hot!
I will never know if that is exactly what fixed it, but it is good for now!

 

Well crap, same old problem. I put the timing gun on it again, and the ignition timing is retarding when the throttle is opened. What could possibly cause the timing to retard? Most things should advance the timing? Is the dizzy toast or the computer? Any way to tell?
Grrrrr.

 

So I disconnected my boost sensor from my dizzy and my throttle position sensor (TPS) at the same time, and went for a drive. It was a little down on power, but didn't retard the timing. So I hooked up the TPS, and kept driving, and the bucking came back! Disconnected the TPS and hooked the boost wire back to the dizzy, ran a bit different, but still ran fine!
Brought it home, looked at the TPS again. I had tested it and cleaned up the contacts. Tested it again and it was reading as per specs. I ripped off some of the rubber wire boot (it was ripped already anyways) and I could see massive piles of corrosion at the back of the wires! Ugh and grrr. At any rate, stripped the wires, crimped them onto some new, shiny connectors I had laying around, and reconnected them.
I hate chasing electrical gremlins. I just hope this fiasco helps those in the future: providing people still own these cars!

 

Good finds so far.

 

So hopefully the last thing I find wrong (this summer) will be the coil: I found a tiny bit of very light oil in the top after removing the spark plug wire to it. At first I thought it might be residue from some old dielectric grease that a former owner might have put there, but about 5 minutes of searching and I realized my coil is leaking! Apparently that is bad!??!
Fortunately the local NAPA has a coil for it (shockingly enough) and I will see how she runs with a new coil!
As a side note, I finally went through a whole tank of gas (or at least most of one) and I couldn't believe I got almost 300 km out of 40 litres of gas! And that while running like a bag of hammers trying to shake out all the issues. I was pretty sure the fuel mileage would put a spike in the coffin for this car, but maybe it can be a daily driver with fuel economy like that...
Well, maybe not... Kelowna BC gas prices are only next to Vancouver in craziness...