940 timing anomaly

Sounds like the timing belt slipped a tooth.

Pull the timing belt covers off and have a looksee.

- alex

'85 244 Turbo

Something is lying to you. If the ignition was advanced this much at idle then the engine wouldn't run at all, so the 30 degree BTDC reading must be wrong. It may also be unrelated to the idle problems you are having. Electronic timing seldom slips out of adjustment unless some relevant component has been dismantled and reassembled inaccurately.

Check that you understand the timing marks properly, and that you are not mistaking some other mark on the crank pulley for the timing notch. Also be aware that some timing lights have a calibration facility, which means that you can adjust where the light flashes relative to the spark.

Stewart Hargrave spluttered almost incoherently...:

There is just one deep cut on the inner rim of the bottom pulley. As I understand it, the graded plastic timing marker above the pulley is marked from -10 to 0 to +10, as in the picture. The idle should be around

billy_bunter spluttered almost incoherently...:

Excuse the "Spluttering" header - I gotta change that, but don't know how, my son put it in there !

You may be incorrect about this. Certainly on my 2.3 litre engine the scale is 0 - 20 degrees BTDC. The picture in the Haynes manual shows a scale of 0 - 30 degrees BTDC, but doesn't say what specific model this applies to. However, the numbers are embossed on the scale. If all else fails, remove the top half of the timing belt cover and find the alignment marks for the top pulley. These should coincide at TDC, and you can check where the marks are on the crank pulley.

I suppose you could have found an anomaly in the fabric of the space/time continuum. It's also possible that your timing light is up the creek.

It'll be under 'Options' or 'Preferences' or some such. But I thought it was quite amusing.

Our 940 once had mysterious idling problems. Don't know about timing, cause I did not check it.

The problems started after we had drained the battery and had to cable start. Apparently the engine control box got into a funny state from the low voltage and/or the electric transients caused by the cable start.

After a while I related the problem and the cable start, I removed fuse #1 (supplying battery voltage to engine control box when engine shut off) for a minute. Then reinstalled fuse, thereby resetting the engine electronics completely. The car has been idling fine now for the last 9 years.

I have told this story to a lot of people, some think I am crazy. It is however 100% true. So before trying more complex things, try the "total electronics reset", by disconnecting the fuse (or battery) for a minute. It may not solve your problem , but it can't hurt!

Gunnar Eikman said...:

If it worked for you, you are not crazy - I will go pull it out in the morning and see... Watch this space !

Stewart Hargrave said...:

Yes, I'm beginning to suspect the timing light myself.... I'm off to buy another in the morning, spacial distortion allowing.

There's not much I can think of that would cause a timing light to do that, they really don't have much inside them. Are you sure you have it on the #1 plug wire? This is the one closest to the front of the car.

James Sweet said...:

Yes, no.1 (and tested on no.4 to make sure...)

This is not entirely unbelievable. The later LH-Jetronic injection stuff did have adapative controls.

- alex

'85 244 Turbo

billy_bunter said...:

Ok, after disconnecting the fuse, nothings changed except the lambda light on the dash is now out - it had been lit for about 4 months since we had a new tail section put on the exhaust. The engine is still rough........

billy_bunter spluttered almost incoherently...:

Ok, I used another timing light, same results, the timing mark is still at about 3'o'clock, so about 30 degrees out ??

Not all that familiar with 900s and haven't read the whole thread but has anyone mentioned the infamous slipping 2 piece vibration damper/front pully?? 700s are well known for the 2 piece front pully slipping with the outer ring getting out of sinc with the inner giving all kinds of headaches to people trying to smog their perfectly running car which shows a whopping

Surely 3 o'clock would be over 90 degs out? This still doesn't make any sense.

I wonder if the crank pulley has been reassembled without it's key, depending entirely upon the bolt being done up tight enough to stop it slipping - which it has?

Stewart Hargrave said...:

Yes - 90 degrees, geometry never was my strongest subject... I now have another clue - apparently there are a couple of locating pins on the rear of the bottom pulley that can shear off, leaving the pulley to move independantly of the shaft sometimes.

I still fail to understand how it runs under these conditions, but I am forced into seeking professional help now - It's beyond me. I have a local man that thinks the bottom pulley is at fault, he is going to test the ignition electrics and look at the pins.... watch this space !

Why are these volvos so damned complicated?? Bring back the anglia !! (a 9/16th and a screwdriver was all you needed for a full strip down)

This sounds a likely bet. The pulley sounds to be a little different to mine, but if this is the problem then it simply means the timing notch has moved, not that the ignition timing itself is incorrect. However it could have contributed to an earlier setup being done wrongly, which may explain the poor running.

Yes, I remember that. I used a pair of mini-mole grips and an old butter knife for mine.

Ok, so now we know your problem is not the same easy one I once had.

You mention that the lambda lamp came on when replacing the exhaust system. That sounds a bit strange. Is it possible that the problem developed at that time? Could the wiring to the lambda sensor have been damaged while working on the exhaust pipes?

About the timing problem. You can easily check the notch on the belt pulley. Remove the spark plug for cylinder 1 (at front of engine). Stick a wire or similar into the hole, so you can touch the top of the piston. Turn the crankshaft by hand (22 mmm socket wrench) back and forth until the piston is in top position. You should be able to tell if the mark on the pulley is in its correct position or not. Piston at top = zero degrees on the scale.

The pulley (at least on some cars) has a rubber device in it to reduce crankshaft vibrations. According to old posts in this newsgroup that rubber can slip, causing the timing mark to be off. I have never seeen it happen myself, but those posts sounded convincing to me.