Hi all,

I have a knock issue with my B230E (high compression ratio). It wasn't knocking in its early life - only for the past few years. It had its head skimmed so maybe the CR is higher than spec but it didn't knock immediately after the head job. Changing the knock sensor, new plugs (changed ol Bosch to NGK) and retarding the timing to 5*BTDC have not been able to get rid of the knock. I'm using the highest octane rated fuel available which hasn't helped.

My mechanic think it's due to carbon deposit in the combustion chamber and wants to open up the engine and give everything a good clean. I was hoping to give a go at chemical cleaning first though. I did a search on the brickboard and I've tried FP60 (one post said this is the best). Results - better engine idling and better mileage but knock still there. Maybe this product cleans injector better than the combustion chamber?

I also came across a post saying that the red blocks don't accumulate carbon that much, how true is this I'm not sure. Besides removing the head, is there another way one can verify the combustion chamber is truly caked with deposits?

And if so what's the best way to clean it? My options are Techron or BG44K. How good are they I was hoping the brickboard can advise me. One fellow brickster tried BG44K and wasn't so impressed when he had the head removed later on. The FAQ also describes the water cleaning method but a couple of posts in the archive discourages that and I think one fellow actually had engine damage after doing that.

Appreciate any help. Thanks

"It had its head skimmed so maybe the CR is higher than spec but it didn't knock immediately after the head job."

This makes sense to me; when the head was machined the combustion chambers were cleaned but over time deposits built up raising the CR and detonation starts.

Does this engine use EGR? Malfunction here has been known to create detonation.

How much was was the head milled? Had it been milled previously? .020" shims are available for many applications, we don't offer one for Volvos but some research might turn up such an item.

Go out and buy a can of berrymans b-12,Remove an vac line and then rev up your engine put the line in the can.DONT get any on the car paint,will eat it of!1 Can only about 3 bucks.

Of the modest number of OHC red blocks I've pulled heads off of, exactly none of them had what I would consider major carbon deposits. I've never seen major buildup on the intake valve stems either (that seems to occur mostly on BMWs, some models of Toyota, and some GM cars) Note that all of these were US spec "F" models with lower compression than your "E". However, if anything, I would think the higher compression would tend to stay clean better.

The way to find out for sure if you have carbon buildup is to find someone with a bore scope who can take a look inside the cylinders for you. The bore scope is normally used to examine the interior of gun barrels, but will go right in through a spark plug hole just as easily. Unfortuantely, this is not an inexpensive (or common) piece of equipment, so you will want to try to find one you can borrow, or rent, or pay someone a few bucks to take a look for you. Much cheaper and easier than pulling the head if you don't have to.

I suspect your problem is more likely to be somewhere in the ignition system--bad sensor readings causing the timing to advance too far, or something along those lines.

Can't recall if it was your old posts I dig up in the archives but that was what I read which is carbon deposit does seem to be a major issue with the redblocks.

I've thought of directly using some form of scope to visually look inside but as you said these sort of equipment are not your everyday tools you can find round the corner. I too suspect the problem may be in the ignition system but I can't pinpoint it.

Get a really good compression test, then post the results here.

You are looking for small difference between cylinders. What the "normal" compression test should be - on your B230E I do not know.

Another approach - does the knocking occur only on acceleration? If yes, check the spark advance system.

Good Luck,

Bob

:>)

I think I can get a compression test done though what's the normal CR for the B230E is something I have to search first.

Yes the knock occurs only on acceleration or more precisely at high rpms (above 3000). At around 2000 rpm (in idle) my timing advance is way too much. Problem is I'm not sure how to troubleshoot this.

Could you elaborate more on the spark advance system and how can one check it?

Thanks

Have you done a compression check to see if it's too high? Using higher octane gas should have helped unless there's some carbon buildup in the cylinder head. Have you tried a different brand of gas or octane booster? Water cleaning will help temporarily but you have to be VERY CAREFUL to use a hard plastic hose with a very small ID. Not more than 1 mm maybe less. If the engine sucks in too much water the spark will fail and the cylinder will fill with water jamming the engine and very possibly bending the connecting rod. This is a tricky procedure but there are water injector systems on the market. I had to use one in my Nissan 510 (not the old early 70's version). It had a small vacuum actuated pump that dripped water into the carberator air cleaner. Worked really well but keeping the pump going was a chore.

Thanks for the advise on the hose ID. I have tried an octane booster which didn't help. Different gas also didn't work

Thanks for the advise on the hose ID.

I have no experience with Volvo engines in this area but in teh 'old days' we used to drip water in the carburetor to clean Carbon off the Cylinders.

I'm sure you can find a Vacuum line going into the Intake manifold and use that.

Let others chime in.
--
'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.no.net/ebrox/Tony's%20cars.htm

There is a long discussion on this topic in the FAQ "Engine Performance" section.

Thank for the reminder! I went through that section and found something else I may need to look into ...my air box thermostat