Ign Timing problem

None that I'm aware of. The points opening governs the timing. The rotor arm simply feeds the HT to the right segment in the cap. Or not if it needs replacing. Mike.

That's what I thought, but it was worth asking as I've run out of ideas on this engine :( Thanks anyway :)

Lee

Sounds more like a fault with the distributor advance/retard mechanism. Have you tried setting the timing using a strobe light/timing gun?

The message from Lee contains these words:

None - the rotor arm should be well within "distributing distance" at any time a spark is likely to come along even if it's quite worn.

What's the engine?

Toyota 3sgte :( Posted a question about it before and thought it was fixed, but it just will not run properly if set up to the correct timing. Of course, it ran fine before. Should point out that it's been to a main dealer, who can't find out the problem either...

Time to get out the chicken entrails I think... ;)

Lee

I think you might get more joy asking in one of the GT4 or MR2 forums. Presumably the base timing was set after shorting the appropriate terminals in the check connector box? Mike.

Very little. Sounds like the spark is correct when running fast- which indicates that the twenty degree static retard is being advanced to the correct setting at high engine speed. Check the auto advance weights and springs below the plate (if it has such archaic stuff) in the body of the distributor. Is there a vacuum tube from the manifold to the body of the distributor. If missing, perished, blocked, will cancel the auto advance mechanism. On the old Austin/Morris/BMC/BL/BP (bottomless pit- of taxpayers money) distributors, the drive shaft might become worn and sometimes bent. Lead to similar problems as you are experiencing. Swap it for one from a wreckers if you can find one. DaveK.

On my old Metro 1.0L with a contact breaker distributor, dwell angle was very important to good running, so it could be your whole distributor is worn. Or the contact breaker set needs replacing. Is it springy? ie, closes with a snap when pulled open by hand? No rust in there?

BTDT, even got a guy who specializes in tuning these to look at it and he can't seem to sus it out either :( It passes all the diagnostic tests - and the compressions are 165psi and even (hot). It is running a bit rich, but the O2 and MAF sensor check out, as do the temp sensors. On his recommendation, it's having the pump and injectors checked for leakage and spray pattern next week - but I somehow doubt it's that.

The basic fault seems to be, that at 10 btdc it sounds (and feels) like it's only running on 3 cylinders, with a constant misfire all the way up the rev range. (pulling leads is inconclusive). With the timing advanced to the point where the misfire disappears, it runs fine, but then it doesn't idle properly and cuts out at low revs. Pulls like a train, though but.

Suggestion on the forums was that the dizzy cap was u/s but that has been changed with no effect.

Lee

Ah, should have said that although it is a mechanical distributer, it is new enough not to have points ;) Though the sensor does pick up on the lobes, and the dwell angle is adjustable (a little), but it's setup right, according to the specs...

Lee

Has it, by any chance, got a coil pick up type thing inside it, and a small black box on the outside to detect the signal and trigger the spark?

If so, check the condition of both of these. Although I haven't cured my Metros engine's main problem, it's running much better overall since replacing the pick up and module, the rev counter does as it should, there's no high rev mis any more, and I do get the feeling the timing is now out, it might be it has been set since the ignition faults started.

If it's as easy a job as it was on mine, then it's worth trying to get a pickup and module at the breakers and giving them a go.

first check the cam timing, even if the marks are correct then actually check the cam timing by lift. if all correct then check the timing on each cylinder, then use a cylinder shorting method to establish which cylinder has less power. Such a dramatic problem as yours must have a major cause at a base level, not something subtle.

mrcheerful

Back to first principles I think. You need to determine TDC definitively i.e. with respect to a piston or flywheel mark rather than a front pulley mark. Front pulleys can be wrong. Golf engines for example are well known for the crank pulley moving relative to the crank nose because of wear in the locating slot in the pulley. Once you have verified TDC check the cam timing, if necessary with a degree wheel and dial gauge to be absolutely certain.

It sounds to me like the requirement for an extra 10 degrees of ignition timing is actually a symptom of something else like a cam timing error or an air leak somewhere.

-- Dave Baker - Puma Race Engines

I know the cams themselves are right, because both cams have timing marks that line up with marks on the respective front cam bearing caps. I did already have some suspicions about the front pulley, it's lined up on the marks it's supposed to be on, but I'm not convinced. I'll try to verify that it is actually correct. Can't find any air leaks, but I suppose it could still have one somewhere. Not doing anything till Monday now though ;)

Lee

No chance the valve timing is wrong?

The message from Lee contains these words:

Take a plug out - poke a pencil down and turn engine till the pencil sticks out maximally.

Such a dramatic problem as yours must have a major cause at

Crossed my mind too. In the old days we always whipped the head off any new (to us) old car and gave it a decoke whether it needed it or not. Made us feel better. Wonder if there's a burned out exhaust valve? You really need to do a compression test. Davek.

He has. He's even posted the figures.

-- Dave Baker - Puma Race Engines

Shouldn't have any effect on timing.

Sounds like the advance/retard mechanisms in the distributor (can you get another from a scrapyard?). What you'll need to do is run the engine with a strobe light connected and see if the timing mark on the pulley shifts as the engine speed changes. Try this first with the vacuum pipe disconnected, and then again with it connected (should be more movement on the timing mark).

I suspect that the rotating plate in the distributor which carries the points or pickup sensor has seized (you should be able to move this about

Darren