Ping or rattle?
 

On my 94 80 Series Landcruiser I have a noise. I thought it was pinging. Switched to hi-test fuel. No difference. Could be a rattle. Thought maybe a heat shield. Can't find a loose one. Makes the noise under load. Not evident with slow acceleration on the flat. Omnipresent under heavy acceleration or uphill. Any good ideas on how to chase it down? My check engine light comes on frequently but everytime I've checked it, it's the EGR code which is a frequent occurrence on the 94's.

Answer: Timing was over advanced by about 14 degrees. Retarded it. Pinging went away.

did you check the muffler bearings?

Kerry,

Good work in finding the problem. Just so you know, the EGR system can indeed effect pinging if it is right on the edge. To oversimplify, EGR leans it out, which if the conditions or on the edge of pinging, the pinging could then develop.

Now that you have the timing set, the EGR code could be considered a nuisance code, but it would be best to run it down and fix it. Fixing it might allow you to add a little timing which would help performance and fuel economy.

Hope this is useful.

The EGR system is specifically made to lower combustion temps. It will have a significant effect on pinging. That said, 14 degrees of over advance is more of a problem. Do you know how it got that way? Are you sure it was really that advance, as opposed to the being a specific procedure that must be followed to set/adjust timing? 14 degrees is quite a bit. How does it run now?

MV

Not sure how it got that way. Had the headgasket replaced some time ago. Maybe they did not time it correctly. Had someone help me do some power steering hose/pump repairs not that long ago. He was working in the vicinity of the distributor. Maybe he grabbed and turned it.
I don't have a specific timing procedure outlined in the Chilton's manual I have so I just hooked up the light and checked it. It was about 17 degrees advanced. 3 degrees advanced is the spec. It runs fine now with no pinging. In fact it seems to run much better with a lot more power. I should have checked the timing sooner but stupidly, I thought the ECU was controlling it since it has a knock sensor on the engine. But that must only function correctly once the timing is manually set correctly.
My wife drives it regularly and I only drive it occasionally.

With that as the results, it sounds as if you followed the correct procedure. I'm glad you got it all worked out.

Actually, there is a procedure. It looks something like this:

WARM UP ENGINE
With transmission in neutral and A/C off.
Allow the engine to warm up to normal operating temperature.
CONNECT TOYOTA HAND-HELD TESTER OR OBD II SCAN TOOL.
Remove the fuse cover on the instrument panel.
Connect the TOYOTA hand-held tester or OBD II scan tool to the DLC3.
CONNECT TIMING LIGHT TO ENGINE.
CHECK IDLE SPEED.
Race the engine speed at 2,500 rpm for approx. 90 seconds.
Check the idle speed.
Idle speed: 650 ±50 rpm
INSPECT AND ADJUST IGNITION TIMING.
Using SST 09843-18020 or equivalent, connect terminals TE1 and E1 of the DLC1.

http://img.photobucket.com/albums/v2...X/56537588.gif


Using a timing light, check the ignition timing.
Ignition timing: 3°BTDC @ idle
Loosen the hold-down bolt, and adjust by turning the distributor.
Tighten the hold-down bolt, and recheck the ignition timing.
Torque:13 ft lb
Remove the SST from the DLC1.
FURTHER CHECK IGNITION TIMING.
Ignition timing: 2 - 13°BTDC @ idle
HINT: The timing mark moves in a range between 2°and 13°.
DISCONNECT TIMING LIGHT AND TOYOTA HAND-HELD TESTER OR OBD II SCAN TOOL.

And yes, the knock sensor system does require that the base engine timing be set correctly to function correctly. The above procedure is for the '94 4.5 liter Landcruiser. Give it a shot and see if anything changes.

MV

Mine doesn't have OBDII. Later 94's did I think but earlier 94's didn't. Apart from the scan tester and jumping the pins on the DLCI, that's the procedure I followed. The 17 degrees advance was the low end of the range. When the engine was first started and the rpm's were high before they settled down, the timing mark was way off the scale. So I was doing the procedure under 'further check ignition timing'. Do you know what is the purpose of jumping the pins in the DLCI?

Mine doesn't have OBDII. According to this link:
Ignition timing for the 4500cc petrol motor

Jumping those pins puts the engine (ECU?) in service mode. Do you know what 'service mode' means? When I tested the timing initially it was ranging from 17 degrees advanced to way off the scale as the rpm's move from the initial high rpm's when it was started and once it settled down.

Ok, sounds like you're on the right track. I thought it was a bit early for an OBDII connector, but there were some early adopters out there... Service mode basically just ensures that the engine computer won't be adjusting the timing at all. Making sure that the timing you set, is actually the base timing (if, for instance, the computer was holding the timing 2 degrees advanced when you set the timing, your base timing would actually be off [2 degrees retarded]), thus ensuring any future adjestments the computer makes would be from the correct "starting point".

Sounds like you've got it. I'd still look into the EGR problem, as it can certainly cause driveablity concerns, but you've made quite a bit of progress in the right direction.

MV

Yes, the EGR issues on this engine are notorious. I replaced one vacuum modulator in the EGR system but it didn't make a difference. One of these days I'll have to spend a lot of time chasing down the exact problem. The check engine light will go off, stay off for a while but then typically at around 68mph it will come back on and stay on until it cycles off again.