A little while back I posted this problem-
'86 745T went from running well to iffy idle, slight misfire, poor mpg, lower performance.

This happened while on the highway, heavy right foot, nothing I hadn't done before.

After some basic troubleshooting, I found the ignition advanced to about 35 degrees BTDC. I rotated the distributor as far as possible to the driver's side, and could only bring it back to about 25 degrees BTDC. Idle improved somewhat, performance and mpg still lacking.

On other's advice, I've checked the following:

Coolant Temperature Sensor- I've checked the wiring, resistance values, and voltage at the ECU, all both hot and cold. Everything checked out within spec.

I read up on this and the temperature switch that controls the a/c cooling fan that when closed sends 12 volts to an input on the Ignition ECU. This switch is mounted on the radiator. The Haynes shows that this voltage powers the fan and tells the ECU to advance the ignition 15 degrees or so at idle (throttle switch closed).

I disconnected this harness to ensure that the input wasn't being triggered. I measured voltage at the firewall from the A/C controls in the dash. It was hot, even with the a/c turned off. I tested the fan- it works properly. I figure this fan/switch and ecu input work properly, and will double check after replacing the fuel pressure regulator this afternoon. I will also check the a/c relay operation.

I've also checked the integrity of the crank pulley and the timing belt. When the crank timing mark is lined up on zero, the lobes point straight up on cylinder #1, and after removing the spark plug I can see that the piston is at TDC. I'm reading from this that the mechanical timing is where is should be, and the crank pulley does not exhibit any "spinning" effects when under the timing light.

I know of no other way to adjust or affect the timing than these devices. I was told by the past owner that they had the timing "advanced" as they were running 15 lbs or so of boost. I removed the Dawes device involved after the onset of symptoms (kicking myself for not doing it earlier).

Any input on this diagnosis, or more clues, would be great.

-Dylan

Thanks to everyone for the terrific responses-

I feel like there's some money riding on this.

Finally pulled back the timing cover and peeked at the cam gear markings. With the mark lined up TDC, and the piston head checked through the plug hole, the crank timing mark was about 15 advanced. I think that's my hint. Called my parts guy and ordered a new crank pulley- I already have the belt. Did one of these a long time ago on a B23F, but didn't pull the crank pulley. I see the removal instructions on the FAQ, I'll let you know what happens next.

So betting opportunity #2. If my timing read about 35 degrees advanced when I first read it, post performance problem, and the crank pulley mark slipped 15 degrees, that would put my initial advance to about 20 degrees. When I played with it, I got it to read 25 degrees, so that put me at about 12-10 degrees advance. And the car was a little better- better idle, mostly. And then I removed the bolts, read 12 degrees, was probably 0, and the car had NO power.

What this all adds up to, however, is that my igition timing has been fine, and something else is really the culprit for this power issue.

Who wants to bet it's a slipped crank pulley AND a slipped belt?

218K miles on the car, and I think 60K on this belt. Yeah I know that's why I bought the belt already.

I'm hoping to have this done by Sunday.

Thanks again-
-Dylan

The one thing I didn't see mentioned was the timing belt. Perhaps it slipped a tooth? How old is it?

In fact, if you're asbsolutely sure that your crank pulley/harmonic balancer is okay... bite the bullet, spend the $7 or so and install a new t-belt. Of course if you didn't want to do that, you could check that when the crank pulley is at TDC, the cam is at the appropriate mark as well.

- alex

'85 244 Turbo
'84 245 Turbo

Thanks to all the high rollers placing their bets....

New belt and crank pulley are now on and tested.

Those who placed their chips on "slipped belt" win by a tooth.

I had to turn the crank 1 tooth clockwise to get the index lined up. I did this by wrapping the old belt around just the crank sprocket and pulling on the left. It moved quite nicely into TDC.

Don Foster's Rope Trick did a great job torquing the crank pulley bolt.

The car performs much better than before. Ignition timing was set at around 8 TDC, I reset to an honest 12 BTDC and the motor seems to be running very nicely.

Thanks to all for the help-
Dylan

Yeah, the joke is I already bought the belt. After a quick check today I'm ready to replace the crank pulley too. The cam gear was indicating TDC and the crank mark was 15 advanced. So I'm figuring that's my hint.

Thanks for the input-
-Dylan

what state is this car in? some smog laws made it not posible to manually adjust the tmeing via the distributor.

I would take a look at your knock sensor, if it died it will throw your timeing out of wack.

Also note a harmonic balancer will cause the problem your having, if it slipped when you floored the car youll never get the timeing set correctly unless you replace it, remove all the belt and see if you can get it to move, if it cracked in the center ( the rubber porition ) then thats your problem right there.

This car's been around. It was a brought over from Sweden via "diplomat delivery" program when new. It's a little odd, some of the things I've found on this car aren't on most of the 740s I see here. It lived in Boston MA most of it's life, and the second owner lived in Ft Lauderdale. I bought it late last summer and drove it back to Connecticut.

I put marks on both the inner metal pully (where the timing mark is) and the outer pulley, and didn't see them run at different speeds under the light. I understand the failure involved, but still want to assume that if the pulley halves slipped then the timing mark wouldn't line up with 0 on the scale when the #1 piston and cam lobes indicate visually they are also at TDC.

If people still think it could be the pulley, I'm game to replace it. I'm replacing the fpr now, and will double check the timing after resetting base idle and checking O2 sensor operation. I'm going to measure the resistance as noted in the 700/900 FAQ, thanks for the hint.

As far as timing adjustment, it does seem to be affected by distributor position relative to the head, as outlined in the Haynes.

Thanks
Dylan

On my '87 745T w/ EZ117K, a thermal switch on the radiator closes above a certain temperature and does two things; It turns on the electric fan in front of the A/C condensor and it sends a signal to the EZ117K computer which, in turn, advances the timing. If you can't find anything else, you might check for a shorted switch. Also check the integrity of the wiring harness.

HTH
--
bagle 87 745t

I mentioned that part of the harness in my first post- everything checks out, and about all that's left to do as far as testing this area would be to energize that trigger at the ignition ECU and verify that the ignition *does* advance. If not, I'd suspect a bad ECU.

Here's where it gets fun-

I replaced the FPR, O2 sensor seems to register slightly lower voltages, still a little high. I suppose if the burn isn't right with the timing so far advanced then I would expect to see a "rich" exhaust stream.

Out of frustration I pulled the two bolts securing the distributor and limiting its adjustment- I was able to bring the timing to 12 degrees BTDC and decided to take it for a short trip. Turned out to be very short- the car had no power off boost. This was a more magnified version of what I had before, not much power off boost.

So I drove the car home and yanked the knock sensor- for some reason I had two more sitting around, same Volvo PN. They all test the same- 300K ohm, and one looks like it has never been used. I checked the harness- ground is good, and the 'hot' side of the sensor coax shows totally open to harness and chassis ground.

I put the new one in just to double check.

I'm begining to consider replacing the crank pulley & timing belt, but will test for separation as per VolvoSteel's advice. After that, I suppose I'll throw an O2 sensor at it.

Two strange thoughts-

- Could a bad O2/rich mixture/something-like-that cause the Fuel ECU to tell the Ignition ECU to advance the timing? I've read that the Coolant Temperature Sensor, connected to the Fuel ECU, will tell the ignition to advance based on cold coolant temperatures. Is the O2 system that smart too?

- The past owner mentioned they had the mechanic "advance" the timing. Could the mechanic have reversed the distributor in the head intentionally? I've read that when replacing the distributor you can install it 180 degrees out of whack and then have no luck getting the timing right. Any way to verify this distributor is in right by pulling the distributor?

Thanks for all the help-
-Dylan

Slippage of the pulley will not change the cam and ignition timing in any way. It will only change what you read on the timing light because only the outer part of the pulley that has the timing mark on it will have moved. Even though the outer pulley slips the small cogged pulley behind it which drives the timing belt stays as it was.

I would not pursue O2 sensor or mixture at this time as that will not change the timing. Likewise coolant temp sensor and knock sensor as they will only initiate slight timing changes in the order a few degrees. Something is causing that apparent or real timing error of 23 degrees. Solve that first.

I would recheck the timing of the camshaft more carefully by removing the front timing belt cover (actually you do not even have to remove it just loosen and pull back at the top and you can line up the mark), line engine up to TDC according to timing mark on the crank pulley then check that cam is timed according to it's mark. I think that taking a visual on the cam lobes may not be accurate enough. Remember that a 23 degree error at the crank will only be a 12.5 degree error at the cam and thats not much to see when you are eyeballing those egg shaped cams.

Is it possible that mechanic did something weird such as slip the chopper disk that the hall sensor reads to get the timing he wanted? I am not sure how this could be done because I should think the engine would then ping like crazy.
--
David Hunter

David,
Your statement, "I think that taking a visual on the cam lobes may not be accurate enough. Remember that a 23 degree error at the crank will only be a 12.5 degree error at the cam and thats not much to see when you are eyeballing those egg shaped cams"
Is perfectly valid, but a much more easily visible check is to ensure that, with no.1 cylinder on TDC. compression, No.4 cylinder valves are rocking, ie.
inlet and exhaust valves just opening and closing respectively, as the engine passes though TDC.
Before I get shot down in flames over this, I do appreciate that this does not work with engines with asymmetric valve timing, or those with large valve opening over-lap but, for most normal, ie. not high performance/race tuned engines it is much more accurate than judging the position of two cam lobes pointing skywards!
Colin.

Well I guess that may another way to look at the cam timing. I was assuming that he was peeking in through the oil filler at the # 1 cam lobes. Kind of hard to see all the way down to #4 though.
--
David Hunter

Thanks for telling me I'm not crazy about the pulley. I figure if I can turn the motor over by hand by turning the crank pulley, it's probably okay. Maybe I'm wrong. The timing mark, however, always shows up right where I expect it under the strobe.

As far as the sensors causing timing changes- they can be big. The thermal switch associated with A/C causes 15 degrees advance at idle, throttle switch closed. The CTS can call for 12 degrees, I think. But anyhow, they all check out. The CTS, Knock sensor, and thermal switch all test out fine.

I'd be glad to look under the timing belt cover- I agree that eyeballing at this point just won't do. What am I looking for? Lining up the marks on the belt, or something else?

I know people are always quick to blame the ECU, but I'm wondering if I should swap in a known good one just to get that out of the way.

Thank for the help-
Dylan

Forget the marks on the belt, they are only for initial installation of the belt, once the engine spins those marks are no longer relevent.

Turn the engine to line up the cam pulley so that the notch on the rear of the pulley lines up with a mark on the rear part of the belt cover. This is very easy to see by peeking in with the front cover loosened and pulled forward. At this point the timing mark on the outer part of crank pulley should read 0 degrees (TDC). It may be prudent to double check for TDC by removing #1 plug and insert something down to the top of the piston, move the engine back and forth slightly and observe that the piston is truly at the top of its travel. This will confirm to you that the outer crank pulley has not slipped on its rubber bonding.

Timing of the intermediate shaft is not a concern as it only drives the oil pump on this model engine.

Good Luck and I am anxious to hear what the final resolution will be.
--
David Hunter

Thanks to all the high rollers placing their bets....

New belt and crank pulley are now on and tested.

Those who placed their chips on "slipped belt" win by a tooth.

I had to turn the crank 1 tooth clockwise to get the index lined up. I did this by wrapping the old belt around just the crank sprocket and pulling on the left. It moved quite nicely into TDC.

Don Foster's Rope Trick did a great job torquing the crank pulley bolt.

The car performs much better than before. Ignition timing was set at around 8 TDC, I reset to an honest 12 BTDC and the motor seems to be running very nicely.

Thanks to all for the help-
Dylan

Someday I'll learn how to read! Since the temp switch checks out, how about the throttle switch?

To help answer your questions...

1. "Could a bad O2/rich mixture/something-like-that cause the Fuel ECU to tell the Ignition ECU to advance the timing? I've read that the Coolant Temperature Sensor, connected to the Fuel ECU, will tell the ignition to advance based on cold coolant temperatures. Is the O2 system that smart too? "

I was not aware that the LH 2.2 coolant temp sensor had anything to do with the ignition pulses from the EZ117K, but we both know the rad. switch does. The EZ117K does get a "load" signal from the LH 2.2 pin 24 into pin 8 on the EZK, but I think this comes from the AMM. The EZK will also tell the LH when a knock has been detected, so the LH can increase injector pulse width, but timing retard for knock comes from the EZK. O2 is part of the Lambda = 1 system and is strictly fuel.

2. "- The past owner mentioned they had the mechanic "advance" the timing. Could the mechanic have reversed the distributor in the head intentionally? I've read that when replacing the distributor you can install it 180 degrees out of whack and then have no luck getting the timing right. Any way to verify this distributor is in right by pulling the distributor? "


The distibutor shaft has two drive dogs offset from center on either side of the shaft that engage two offset slots in the cam. I think you would have to do some serious cut/grind/smoke wrench work to reverse it, or repostion the hall switch, or reposition the rotating vane on its shaft. To verify, you could pull the distributor and look for any evidence like this.

I think the throttle switch is worth checking at this point. With no throttle closed signal the EZK (and LH) will set up the timing ( and injector pulse width) according to whatever is on the data map for the remaining valid parameters.

Finally, to see if your harmonic balancer is slipping, turn on the A/C.

Good luck

--
bagle 87 745t

"I think the throttle switch is worth checking at this point. With no throttle closed signal the EZK (and LH) will set up the timing ( and injector pulse width) according to whatever is on the data map for the remaining valid parameters."

You are right. Can't overlook anything right now.


"Finally, to see if your harmonic balancer is slipping, turn on the A/C."

You mean with timing light attached? That does make sense.
Thanks-
-Dylan

It is possible to install it 180 Degreees off, most of the time though the car will not even start, and even if it does it wont run very good period, its possible though everything on your car is working to fac specs and this could cause your problem, it pretty easy to pull the dist and flip it, just undo the same bolts you did to adjust pull it back rotate the spindle 180 and put back in, make sure that the flange lines up and clicks into the cam shaft ( inside ).
i would think with a 180 dist out you would get a wavy time on it but i could be wrong there as with my california car even 180 the ECU will adjust and correctly set the timeing , at least thats the way its supposed to be.

I did test that theroy too, installed it ran it pulled it turned 180, didnt have any problems.

Does the timeing mark move while you look at it or is it dead set at 12tdc or what its currently set at?

"Does the timeing mark move while you look at it or is it dead set at 12tdc or what its currently set at?"

The timing mark is very steady. Every time I re-check the timing, the mark is where I left it. When I increase the engine speed the timing advances. Pretty much like every other Volvo I've had.

I probably won't pull the distributor, as this is the stumper-

Whatever the PO did to the car, it really doesn't matter. The story is-

Car ran great. Drove car one day, and after a little hard driving, car doesn't run that great anymore.

So it seems like the $64K question is:

timing- is this the chicken or the egg? Could something I've yet to ID cause a great change in the timing? OR is timing the egg- can some other part of the car fail (ie fuel delivery) and cause the EZK to advance the timing to correct for it?

Thanks to everyone for all the help.

Dylan

Have you verified that your cam timing is proper?

With the crank mark lined up, the cam sprocket should have a little notch or dot that'll line up with a notch in the valve cover (B21/23) or rear timing belt cover (B230)

A slipped timing belt...

- alex

'85 244 Turbo
'84 245 Turbo

On the LH 2.2 system with EZ117K ignition system it is impossible to insert the distribtor 180 degrees out of alignment. The dogs that engage it are offset to specifically prevent this. Even if it could engage the ECU cannot posssibly self adjust the timing. It can only advance or retard from the nominal setting of 12 degrees BTDC and then according to programmed parameters, overtemp signal from rad and the knock sensor.

What year, model and engine of a California car do you have that allowed you to do that?

--
David Hunter

David i managed to do it on an 86 740T, i havent tried that on m 89 yet, the 89 is more advanced with the california crap unfortunally.

On your 89T I doubt that engine would run even if you were able to engage the distributor backwards. In addition to the ECU not getting timing pulses in synchronization with engine position the rotor would point at the wrong plug wire. Maybe best to not even try.

--
David Hunter