Outer Limits 4x4 Board

I have a 1993 3.5 ltr auto disco. The disco is pinging under load especially with the camper trailer in tow. I have replaced plugs,leads,rotor,dist cap,air cleaner and cleaned the air flow sensor. The timing is nearly at tdc.Any hints on what to do next would be appreciated thanks

Timing should be 3 degrees BTDC but you can go advanced to about 9 degrees without issue. TDC is too retarded.

garrycol wrote:Timing should be 3 degrees BTDC but you can go advanced to about 9 degrees without issue. TDC is too retarded.

Funny that it is pinging underload, I would have expectable a stumble due to lose of torque with retarded timing.

If it is indeed a stumble, and you are certain the timing marks are correct. I would suggest adjusting the timing to 6°BTDC and report back the results.

what fuel are you running it on? my old car used to ping with the cheap 91 octane fuel in, i put the 98 in and it ran great no pinging

[quote="Ye Olde Rangie"]what fuel are you running it on? my old car used to ping with the cheap 91 octane fuel in, i put the 98 in and it ran great no pinging[/quote]

That is treating the symptom not the issue. The V8s have not issue on 91 Ron.

I have a 1993 3.5 ltr auto disco. The disco is pinging under load especially with the camper trailer in tow. I have replaced plugs,leads,rotor,dist cap,air cleaner and cleaned the air flow sensor. The timing is nearly at tdc.Any hints on what to do next would be appreciated thanks

I also suggest that you try a tank of 98, if only to be sure it is actually pinging you are hearing, as it is very unlikley that it will ping on 98. if you still hear the noise, I would be looking at exhaust manifold leaks.
A hard worked engine should not have excess carbon build up, but maybe an exhaust valve is carboned/sticking.
My 3.9 does not ping, althoughI am a bit deaf, with 8 degrees advance and an extra 3 on a Unichip. And 3.5s can take a few degrees more total advance.
BTW how do you load it at low revs with an auto. It is unlikley to ping over 4K as the advance curve is very conservative.
Regards Philip A

garrycol wrote:That is treating the symptom not the issue. The V8s have not issue on 91 Ron.

Is this the same for the 3.9's which have a slightly higher comp ratio?
There was a recent discussion on the yahoo group, many said they needed 95.

garrycol wrote:

Ye Olde Rangie wrote:what fuel are you running it on? my old car used to ping with the cheap 91 octane fuel in, i put the 98 in and it ran great no pinging

That is treating the symptom not the issue. The V8s have not issue on 91 Ron.

Well, depends how you look at it, I'd prefer to think of it as optimal timing for the fuel used, the joys of using high octane petrol is being able to advance the ignition timing, but it will ping when anything lesser is used

Timing it to 91 is a waste

Oh and fuck the timing marks, just advance it till it rattles (pings) then retard it a little, that's optimum timing....without getting into advance curves of course

Thanks everyone , i been told to set the timing back to standard , put a heat range colder spark plug in and run an octane booster through it and see how it go then. Whats the best workshop manual to get.

glowe wrote:Thanks everyone , i been told to set the timing back to standard , put a heat range colder spark plug in and run an octane booster through it and see how it go then. Whats the best workshop manual to get.

save the hassle of buying octane booster and just put in premium. it will probably be cheaper too