Had the same problem with my 240 recently. It was a broken valve spring. Had a complete valve job and all springs replaced. Volvo no longer makes the OEM springs and the replacement are stronger. Since you cannot match it would be best to go ahead and do a complete valve job.

Here is where I had mine done, they do good work. I think they have jobs sent to them from all over the U.S.

http://www.automotivemachine.com

--
1989 240, 1992 745

One question, when it backfires, do you hear it behind and infront of you "Exhaust", or only infront of you "intake". This may sound odd, but it could answer many questions. Most likely you have a sticky sticky valve, and if it is an exhaust valve, it will not last long.

In general, if I pull a head, I'll spend the few bucks to have the valves checked and ground, as I hate doing a job twice. I have skipped this step many moons ago due to cost, but the outcome was always the same... it didn't work and I had to do the job again plus the valve job... much more expensive than doing it right the first time.

jorrell
--
92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!

Spent one hour this afternoon determining that the valve clearances.

Exhaust #3 is .007.
Exhaust #1 is .010.
Exhaust #2 is .013.
All others where .014.

Since checking is .012 to .016, I most certainly have a problem with #3, #2 has crossed the line, and #2 is suspect but not worht adjsutable according to everything I have read. (Increments of .002).

I did find a vacuum leak!! At the cruise "motor" a vacuum line had a serious verticle crack to just above the nipple. Cut it back and now even cold will hold a rough idle.

This is where I need a bit of help/guidance.

Has anyone devised a method for removeing the valve shims that uses a "home made" or substitute compression device for the cam buckets??

I tried for about three hours before giving up on getting a bucket compressed enough to get a shim out. I was unable to determine how the "Volvo" tool actually worked.

(That might have been heat related.) Fried brain. Moved a friend yesterday in the heat and humodity and then treid to think in todays heat and humidity. Plus add to that a bit of frustration at the "shop" who does have the tool but did not check or adjust as I requested.

Thanks in advavnce.

Duane

Duane!
Sorry I didn't get to see you on the way back fm Omaha.
Is it possible you have a sticking valve? Did you actually take the
valves out while you had the head off? The fact that it actually does
come on strong sometimes (especially when hot) makes me think of a gummy
valve stem. The backfire sounds like a valve open when it shouldn't be
also.
--
George Downs Bartlesville, Heart of the USA!

squirt some heavy oil into the offending cylinder and use a compression gauge again.

if the compression rise noticeably it is likely a ring problem on that cylinder. if nothing changes look to the valves as a start.

Hi Duane,

Very possible. How are the valve clearances?

Oops, I see you've already asked yourself. That's what did a #4 in, on one of mine. The valve became too long for my smallest shim (took the stem to a grinder :-)