Hi guys,

I tried posting this on the 700 board, but didn't get any responses. I'll try it here.

I'm new here and I've got a technical question I hope you can help me with. Let me know if I'm in the wrong section.

I checked the timing on my brick (88 740 2.3L non-turbo) and with the engine warm and idling, I get a timing reading of 0 degrees. I am concerned since it is supposed to be 12degrees BTDC. I did a search and found that the marks on the balancer can slip causing an erroneous timing reading. So, I took off the harmonic balancer and checked the alignment of the timing belt and everything is still aligned at 0 degrees.

So, my timing belt is ok, my balancer has not slipped, so this means my timing is being retarded BY something. Figuring a bad knock sensor, I unplug its connector and redo the timing check... doesn't change at all... still 0degrees. I install a new knock sensor... same thing, no change in timing.

I also read that a plugged cat can retard the timing (my cat is 1 year old), so I removed a port plug just in front of the cat to remove a little backpressure... no change in timing.

My next thought is that I have bad wiring from the knock sensor to the ignition computer... but I don't know where the ignition computer is located...

Am I on the right track here? Can anyone help me out?

BTW... all other Fuel injection components diagnose as OK... injectors, amm, the fuel pressure regulator is new and working, pumps, throttle position switch, etc.

I would really appreciate your thoughts on this.

THanks.

If you have an 88 740 adjust the timing by simply rotating the distributor after loosening the screws (2 if I remember correctly). Whoever thinks or says that you cannot do it is wrong. The 89 has a crank position and timing cannot be shifted, your 88 has a hall sensor in the dizzy, rotating dizzy changes timing.

Forgot O2 sensor, knock sensor etc, they will not cause your problem. The knock sensor is simply a microphone that detects knocking and retards if and only if knock it is detected, of course this will not happen when it is faulty.

Have you tried adjusting your timing? You do not mention if timing shifts when rpms are increased off idle.
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David Hunter

The ignition control unit is at the upper right of the steering column.Pull the underdash panel and look up.Connector wire #7 org should show continuity to ground with an ohm meter at idle and slight resistance with the accelorator pressed.This checks the throttle switch adjustment and wiring.#12 Blk and #13 green go to the knock sensor.Disconnect the knock sensor and check #12/#13 at ECU with meter and it should show open.If thats OK then jumper Knck sensor connector and check for continuity between 12/13 at ECU.Theese test should be with the ignition OFF.Other inputs are RPM sensor,Coolant sensor,FI ECU,EGR sensor(if it has one).Good luck

O2 sensor? Why not move the distributer 12 degrees and see what happens? And stop arguing with volunteers. It is very difficult to diagnose problems on a typewriter, don't make it impossible.

Klaus
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95 854T, 88 780, 88 245, 01 A4 Audi

stop arguing with the volunteers? I've spent half my time so far just trying to prove to the volunteers that the balancer isn't shifted!

written speech is so very cut and dried... people who want to be victims often become victims when they read something that doesn't agree with them.

I am not trying to piss anyone off here. I'm just trying to get intelligent advice about my car!

How does your car run? It sounds like it purrs but the bad timing reading is bothering you, as well it should. Just thinking off of the top of my head here, it sounds like you have a problem with the markings. 12degrees is way too far for the any computer to compensate for and your car shouldn't run well if at all, so it must be that your car is correctly timed but gives a bad timing reading.

With that in mind what are the possible culprits? 1) the harmonic balancer has slipped. But you took it off and put it back on again. Assuming, it wasn't in the wrong position and then you assumed that it was the correct position when you put it back on again, then that isn't the problem. 2) If you have a 230F engine in the car then you are measuring the timing by the little plastic shroud, make sure this has not slipped. I have heard of instances where the shroud had moved and people got readings like yours. 3) Are you measuring the timing with respect to cylander #1? Maybe you are measuring from the wrong wire.

The only reason I bring up the dummy checks is because I can't think of many reasons why you would get a wrong reading, there just isn't that much going on there. It seems like something simple must be overlooked.

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- Mike

Grif,

thanks for the reply.

Yes, the car runs like shit. It runs hot, it has no power, and it gets abominable fuel mileage...

the balancer clearly hasn't shifted... please see my latest post to 240snowmobile. I am pretty much convinced of that.

and yes, I am measuring with respect to #1 cylinder

What bothers me are my symptoms when I unplug the knock sensor and redo timing readings. If the balancer had shifted, then when I unplug the knock sensor, the timing should become even more retarded which it does not. I have replaced knock sensors and I get the same effect.

If you ignore everything else and consider that all the FI components are new and working, then I have classic symptoms of retarded timing.

the question is just why.

I think I figured out the problem. We all need to work on our diplomatic skills more than our cars.

In regards to your car, I don't think I have figured out the problem. But I do have a couple questions.

What happens when you try to adjust the timing? It seems like the first thing to assume, is that the distributer came loose and slipped.

What happens when you unplug the 02 sensor? If you are getting really poor mpg, then maybe the 02 sensor is picking up some poor readings and then trying to compensate by retarding the timing.

Also, what was the onset like? Was it slow and gradual or did one day the car just decide to do this?
--
- Mike

Mike,

thanks again for the reply. I'm not trying to piss anyone off here... just get advice on my car.

I thought I had mentioned this, but this is a 740 and I can't adjust the timing. I thought I'd post it here because I got zilch for replies on the 700 board. Seeing that the 240's and 740's share very similar engines and components, I thought I'd have a good chance of getting advice here.

The O2 sensor is working properly and is actually new, but I will try the trick you mentioned and see if it effects the timing.

Joe.

The O2 sensor is working properly and is actually new, but I will try the trick you mentioned and see if it effects the timing.

Don't bother. The O2 sensor has nothing to do with ignition.
And I share your pain in trying to explain the harmonic balancer marks. It made the thread so long that I'm reluctant to add to it, but in this case it seemed worthwhile.


--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

I stand corrected. The 02 sensor does not communicate with the ICU at all, like lucid indicates. Also, I had no idea that the 740 doesn't have adjustable timing. I guess I really don't know anything about 740s.

So, I checked the 700 series FAQ and it directly mentions that there have been reports on the knocksensor wiring getting interference from the alternator causing unexplained retardation.

I know you have played around with unplugging the sensor, swapping it out and all that but in order to diagnose this theory you will have to remove the knock sensor wire from it's current path. Even if you unplug the sensor the existing wire will still act like an antenna.

Here is a link to the FAQ that mentions it:

http://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm#RetardedTimingorKnockSensorCode



--
- Mike

It loks like Mike's tip on the FAQ entry above has real possibilities.

I also had an overnight thought that maybe the camshaft timing might have jumped a tooth. (I couldn't tell if your timing checks included the camshaft. Seemed like you were focussed on the balancer.)

By a rough count (using pictures), if the cam sprocket (1 rev = 720° of crank rotation) has something liker 44 teeth, then one tooth would = about 16° of crank rotation—maybe close to what you are off?

Just an early morning notion. Not all synapses snapping yet. If wrong, I sit corrected.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Yah agreed with other reply... maybe you harmonic balancer has slipped into two... The rubber between the two halves becomes brittle and eventually loses its adhesion to the metal. You really should just look at the crank position (on crank and align that with the timing rear cover mark... and when pistion#1 is at the top and the rotor is pointing to spark plug#1, the camshaft should point at the mark (I think 12 o'clock) as well.

Hope this helps... BTW the rotor is directly driven by the pulley between the crank and the cam.

Greg Mustang
Montreal - Ottawa
Canada

Greg, please read the full post.... I checked with the balancer OFF to verify that the timing marks on the block are still aligned....they were.

THEN, I put the balancer back on (WITHOUT MOVING ANYTHING) and the notch on the balancer is exactly at the 0 mark on the timing cover.

I think this verifies that the balancer hasn't slipped unless I am completely missing this...

"I took off the harmonic balancer and checked the alignment of the timing belt"

"So, my timing belt is ok, my balancer has not slipped,..."

The timing belt has NOTHING to do with the timing marks on the balancer's outer ring. TDC is referenced to the crankshaft, and nothing else.

The balancer has two major parts: an inner hub, aligned to the crank by a keyway. The second part is the outer inertia ring. Between those two parts is a heavy rubber ring, that allows the outer ring to move slightly in relation to the inner hub, thus dampening crankshaft vibrations.

It is that outer inertia ring that can slip and make the timing marks appear to be off. You will have to determine the true TDC (you can use a piston stop in cyl #1) and compare that to the marks on the balancer.

OK, you say the outer marks on the balancer don't have anything to do with the timing, but why does the notch on the balancer line up exactly with the 0 degree mark on the timing cover AND AT THE SAME TIME, with the balancer in that position, the crankshaft timing mark is aligned with the line on the block??? I could understand if I had the timing marks aligned and then the balancer notch was NOT at 0 that I'd have a problem.

When your car is at TDC, where does the notch on the balancer line up at? the 0degree line on the timing cover?


SHOULD the balancer be aligned at 0 when the engine is at TDC? Is this synonymous with having the timing marks aligned on the cam and crank sprokets?

I understand what you are saying, and you make some interesting points. But what if the belt timing was setup using a bad balancer? Everything would look "normal", but could you really say your balancer was "ok"? No, it just verifies that all the marks line up. (Okay, you could counter with "the engine would run like crap, etc...", but I think you get my drift here.)

If I really wanted to know if the marks were correct - without a doubt - I know how I'd do it; anything else would be inference at best.

240snowmobile,

thanks again for the response...

the balancer is irrelevant for setting up the timing.... you set the timing by aligning the keyhole on the crankshaft with the line engraved on the block...

THEN you put the balancer back on.... (it can only go on in one position)... by fitting it over the keyhole shaft on the crank. When I do all this, the balancer happens to also line up at the 0 degree mark on the timing cover... I don't think this is a coincidence... I'm quite sure Volvo designed it this way.

Now, if the balancer is truly off, then why the hell would it also line up with the 0 degree line on the timing cover... unless what Grif suggested that timing cover has somehow warped and the 0 degree line has shifted... But I doubt that.

REGARDLESS OF ALL THIS... when you look at my knock sensor symptoms, the timing should get even worse!!!

WHen I unplugged the knock sensor (the timing then reverts to full retard mode in this case), I get NO change in the timing measurement! It stays at 0 degrees... IF INDEED the balancer was shifted, then when I unplug the knock sensor, it should move even further PAST 0 degrees (which is does not)

I've only explained how to verify that the TDC marks on the cover and balancer are truly what they say they are. Whether you want to do that or not is totally up to you.

Good luck.

Dude, I'm not trying to get into a pissing contest with you on this. It sounds like I've upset you.

I think I've already verified myself that the timing marks are ok. If the camshaft mark and the crankshaft mark (EXCLUDING THE BALANCER) are lined up AND the engine is at TDC, then by definition, the timing is set.... balancer be damned!

...AND for the hell of it, if the balancer mark also happens to be perfectly aligned, then I'm not sure what all the fuss is about the balancer having slipped... it obviously hasn't!

Let's move on... what else could be retarding my car's timing??

FWIW, I think you have the timing defined correctly. The mark on the balancer is just a reference, one which aligns with the 0° mark on the t-belt cover when the crank and cam are at 0°.

As to your question why the dynamic timing reads 0°, I can't help, as I'm not (yet) familiar with the cam-driven dist. This IS a 700, right? If so, the 200 on the subject line muddies things up a bit.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

I don't know if this will work, but just replace two knock sensors on my car whick had retarded timing and everything whent well. I understand that you replaced yours also. First did you tourqe them properlly? 10 to 12 ft lbs. is all they require with some thread lock. Too tight and they are rendered useless. If so then I would look at the alternator sending a siginal thats causing a bad reading from the knock sensor. You may disconnect the belt from the alternator breifly crank her up and see if this is the cause. If it is two methods of fix 1,reroute the wire away from the alt.2, Sheild the wire on the knock sensor,May sound funny but I read somewhere that covering an object with a zinc coated, say for insenstance small grated wire fenceing will stop unwanted electro waves from contacting the part to be protected. Something smaller than regular chicken wire would do, couldn't hurt to try. Sound crazy
but what ever.
Good luck.