1991 360 Pinging Questions

[nograin]

Thank you, that's very helpful.

I've tested the vacuum advance with a hand vacuum pump and have some numbers.
It starts moving around 7" of vacuum, and stops advancing somewhere between 15-20 (sorry that's a bit vague).
...
Do those vacuum numbers sound about right?

Service manuals for '79 and for '84-86 show that it should start moving around 3 to 4" Hg and be fully advanced by 12" Hg.
Of course its possible a major change was done after '86.

I looked at reconnecting my EGR, but it wouldn't hold vacuum so looks like it needs replacing first.

Again not sure about '91 but your EGR probably won't hold vacuum without exhaust pressure. Makes it hard to test off the engine.
The pressure from the exhaust on diaphragm 1 closes the vent at 3.
EGR-Working

[Brynjminjones]

Thank you for that. I've been distracted with other Waggy issues lately so haven't had a chance to look further into this, but will update on here once I've had a play.

[Brynjminjones]

Hi guys, I've been having some more problems with this so wanted to come back to it.

I've still not had time to play with my timing gun and see what total advance is - I'm waiting for my girlfriend to come and hold the rpms for me whilst I point the gun. I think I'd get my head stuck in the fan if I tried doing both myself!

I did have a play with the vacuum advance though. I hooked up my hand vacuum pump and tested it. Originally it was beginning to advance at around 3" vacuum, all in my about 17".
I've dialed it back now so that it starts at about 7", all in by ~20" or so.

Yesterday I took it for a drive and it was pinging really badly. Cruising along it was fine, but on the flat if I dug my foot deeper into the throttle without downshifting, it started to ping noticeably. It did it once so badly that it lost power momentarily, just before it did then downshift.

I had been thinking all along that the problem must be the total advance, but it doesn't seem to ping at WOT. Surely I would be having WOT problems if it was because of the mechanical? I'm still struggling with this as I've never dealt with this problem before. Nothing else on the engine has changed since before the rebuild either. Any thoughts would be much appreciated!

[nograin]

Hi guys, I've been having some more problems with this so wanted to come back to it.

I've still not had time to play with my timing gun and see what total advance is - I'm waiting for my girlfriend to come and hold the rpms for me whilst I point the gun. I think I'd get my head stuck in the fan if I tried doing both myself!

I did have a play with the vacuum advance though. I hooked up my hand vacuum pump and tested it. Originally it was beginning to advance at around 3" vacuum, all in my about 17".
I've dialed it back now so that it starts at about 7", all in by ~20" or so.

Yesterday I took it for a drive and it was pinging really badly. Cruising along it was fine, but on the flat if I dug my foot deeper into the throttle without downshifting, it started to ping noticeably. It did it once so badly that it lost power momentarily, just before it did then downshift.

I had been thinking all along that the problem must be the total advance, but it doesn't seem to ping at WOT. Surely I would be having WOT problems if it was because of the mechanical? I'm still struggling with this as I've never dealt with this problem before. Nothing else on the engine has changed since before the rebuild either. Any thoughts would be much appreciated!

Yes better to have a helper. Although you can use the idle speed screw for the first few hundred rpm above idle.
What's the timing at 600 or 650 rpm?
I assume you have a tachometer??

[PlasticBoob]

Mr. Jones,

Just go ahead and retard the timing already as Babywag suggested.

You can mark the distributor shaft to the timing cover with a thin line of paint, a marker, etc., and then retard the timing a hair (in steps of 1 millimeter or so clockwise).

Retard, drive, repeat. Retard, drive, repeat.

If that makes no difference, you can then easily rotate it back to exactly the way it was before by lining up the marks again, obviously.

Having the distributor marked will also tell you if it is wandering. I have seen that happen before on a friend's FSJ with the Motorcraft distributor.

I advance/retard my timing in this way all the time, depending on the season. After spending enough time around your engine, you begin to tell by ear whether it needs to be dialed back or advanced a bit. I haven't used a timing light in years.

[Brynjminjones]

Thanks everyone - I have to come on here sometimes to air my thoughts otherwise nothing seems to make sense!

nograin - I've set the idle in gear to exactly 600 with a tach.

PlasticBoob - Yes, you're right. It's currently with the engine builder for other reasons so he's going to help. We're going to set the all-in mechanical advance to the right ballpark to see if that stops the problem, then see what the initial advance is.
If it's too low, I will do as Babywag said and change slots in the distributor.

Thanks all for the help - I'll report back.

[Brynjminjones]

I think I have some news on this. We investigated the timing and found that it was actually set to about 8 at idle, and was at 26 or so at 3500rpm.

Based on this, I think I can safely say that total timing probably isn't the issue.

After discovering that, I played with the vacuum advance some more. I wound it right off until it needed about 10" vacuum to start coming in. I found that I could only delay the vacuum advance to a certain point. If I wound it further off after that it started to reduce the maximum travel.

Anyway, I've driven it pretty extensively after that and I think the pinging seems to be totally gone. It feels much better to drive and has some more power too.
I can now do what I want with the throttle on hills and it hasn't pinged once so far.
Time will tell, but it looks like it might well be solved.

[Brynjminjones]

Damn, it looks like this isn't solved.
It has been pinging a bit again so I've had a play around.

I've stripped down the distributor and swapped it over to a different limiter slot. It was previously in the 21 (!) slot but now I've moved it to 16. There is also a bumper on the limiter peg so it will be less than that. Also, the heavier spring is tight enough that I doubt it would ever get that high in normal driving.

I then set the base timing to 10 degrees.

One thing I noticed is that there is a bit of rotational play between the distributor and the camshaft gear. I figured however that this play would nearly always be taken up whilst the engine is running.

The vacuum advance is now set to start around 10", all in by about 22", connected to ported vacuum.

Now for the weird part: I've driven it quite a bit today. Once it was 100% warmed up, I didn't manage to get it to ping at all. However, when it had only been driving for 5 minutes or so, I could fairly easily get it to ping under load.
That seems like the opposite of the norm.

Has anybody else experienced increased pinging when cold before?

[babywag]

are you sure no vacuum leaks and not running too lean?

also need to know how much advance is the vacuum adding?
it could be adding too much some folks have modified the arm to adjust/limit amount of vacuum advance.
@ idle plug it into manifold vacuum and with a good timing light see how much advance is present.

[Brynjminjones]

I'm pretty confident there are no vacuum leaks. I ruled out fuel issues early on, as this engine is dual-fuel (propane and gas) and it seems to do the same on both fuels.

I've not yet managed to check how much advance the vacuum is adding - I'll do that soon.
Do you know how I could go about limiting the amount of vacuum advance? This stock canister only allows me to delay it, rather than changing the amount it brings in.

[babywag]

I recall seeing some that the "arm" was made adjustable.
I'll see if I can find the thread...

I would use a dialback timing light to see/check it out first though.
Seen several that add too much.
Setting it up with a gauge doesn't tell you how much it's adding.

[wiley-moeracing]

Do you have the correct spark plugs in it? Running to hot? Exhaust plugged?

[Ristow]

yeah,see if the heat riser on the end of passenger exhaust manifold is stuck shut.

[Brynjminjones]

Thank you again for all of the replies guys. I've been on vacation this past week in the Wagoneer and have put ~850 miles on it.

At the beginning of the week it was still pinging a little under certain conditions, but since then I haven't heard it ping once. I've not been driving it gently, and sometimes we've had four adults in the car on steep hills but it made no difference.
I've also noticed that sometimes it feels very, very slow and other times it feels a good bit more torquey.


Now, to reply to the points made:

It doesn't run too hot (except continued idling, but that's a separate issue). Spark plugs are one stage cooler as recommended for running on Propane. I use Autolite 63s.

I think the point about the heat riser might well be a very good one! The heat riser is pretty free to move by hand, but it doesn't feel very springy to me. When it's cold it will just stay in whatever position I put it in.
The spring is still attached, but may be weak?
I just went out and looked at the position it's in right now. It hasn't been driven overnight and the heat riser was at about 45 degrees to the exhaust.

Stupid question, but which position is open and which is closed?

[Brynjminjones]

Right, this problem is getting even weirder/more irritating.

I played with the heat riser yesterday to see if it made a difference. I set it open when cold and it felt like it would stay there.

I went for a drive to see if it made a difference and about 2 minutes in I had to pull onto a hill.
It chugged up the hill just fine, so I decided to try poking the throttle harder as that is usually exactly what it takes to make it "ping".
As I reached about full throttle (but before kick-down) it made this awful grinding metal noise - kind of how I'd imagine it would sound if the starter were to engage with the engine running.

After that happened, I drove it gently until it was warm. Once it was warm I couldn't get it to make any strange noises at all.

Today I disconnected the vacuum advance and took it for another drive, and it did the exact same thing.

Previously I thought this sounded like pinging/detonation, but this new noise really sounds like something different.

Any ideas where to start?