I have a '93 960 (who lived through a timing belt brake) which has a problem for the past few months that a service shop can't find. When driving at around 45 MPH and the automatic transmission adjusts itself to around 1500 RPM, the engine starts hesitating, as if it wants to stall. Sometimes it is worse than other times. When I switch to a lower gear or gas it, the problem seems to subside/disappear. The tachometer does not fluctuate when this happens. This usually happens when the engine is warm, but most times a few miles after I first start out in the morning (temperature gage reads that the engine is warmed up at that time).

I brought the car a few times to the service shop and unfortunately it is an intermittant problem and the service shop can't figure out what to look for. They did the usual things such as look for trouble codes, check ignition system (they did say the plugs were worn and replaced them), fuel flow, etc.. They indicated that the engine has heavy carbon deposits and that should be cleaned out (e.g., fuel injection & air induction service).

Any ideas?

Alex

Regarding your stated symptoms, it is not an engine hesitation problem. It is an automatic transmission problem. It is likely due to an electronic glitch in your locking torque converter (locking solenoid) engaging or disengaging (or lack thereof) causing the tranny to hunt for gears. These symptoms appear only after the car has driven for a while, thereby indicating a possible involvement of ATF fluid temperature. I believe Lance Schumacher [sic] was having a similar trouble not too long ago and traced it to a faulty TCM computer module (very expensive though). Your case may be different, I would at least do the suggested procedures, including full ATF flush at cooler lines (not just a drain and refill), replace with synthetic ATF (requires at least 16~18 quarts after full flush), and keep a close eye on it.

-HB

I would start with a couple treatments of "Chevron Techron", usually availble at KMart, WalMart etc. Folow the directions on the bottle. It worked wonders on my wife's BMW in cleaning injectors and deposits on intake valves to get rid of some rough running spots. I'm guessing you have some minor injector "gunk". Another trick refered to around here is an "Abe Crombie" tune up. Put the transmission in a gear low enough so you can hold the engine above 4000 RPM for 5 minutes or so. (Somewhat similar to an "Italion Tune Up".)

I use Mobil gas, Mobil 1 synthetic oil and have a chance to do a wide open throttle run up to about 80 every morning when I get onto the interstate. This seems to be keeping my engine nice and clean.

I'm curious, why did the belt break? Had it gone past the recommended change interval? On that car I think it is every 30K.

Unsure at what mileage the timing belt broke since I bought it used from a dealer. Unfortunately it happened after the warranty was up. Since that time, I've read it is a cronic problem (i.e., design flaw) and 30k change over is the key. Overall, I like the power of the 960 but it's a high maintainence vehicle. Most annoying was the micro switch on the AT shift that went twice. On the other hand I also have a 86' 240 wagon (bought new and now has 210k) and 740 Turbo Wagon (bought used) that are running great.

Alex

There isn't any "design flaw" necessarily with the early B6304 timing belts...they just need to be changed at closer intervals. True, the later ones can go like 70K miles or something, but it's because the timing belt assembly was re-designed to allow for the longer intervals...not because there was anything inherently wrong with the older style. I've never heard of timing belts breaking on the inline sixes unless the owner exceeded the replacement interval (I'm sure there are exceptions, but in general, this seems to be the case). If someone exceeds the replacement interval and the thing breaks, it's not because there is a design flaw, it's because the owner was playing with fire...and lost. If the belt breaks within the replacement interval it's a different story, but again, this doesn't seem to be common. Volvo recommends 30K mile intervals for the early 960s and these should be followed.

I just wanted to nip this misnomer in the bud, lest the B6304 earn an undeserved reputation.

Lance

I would agree that a 30K change interval for a timing belt is a "design flaw"

See, I would consider the red blocks' timing belts to be a design flaw. Who on Earth designed it so the harmonic balancer had to come off? You add 30-40 minutes right there. And...if you want to get technical...timing belts in general can be considered flawed. The timing chain in my old B27 has NEVER been replaced in 300+K miles...whereas belts wear out. Chains last forever. It's all relative...

Design flaw or not...I'd much rather replace the TB on my 960 every 30K than have to do the 760's again...even at the longer interval.

Lance

I changed mine at 70K. It was a snap compared to the 740. On the B230, all those engine accessories had to be loosened to get the belts off, and there are lots of nuts and bolts to loosen. Then the crank pulley off, cover off, new belt on, on and on.

The 960, fan out, Serp. belt off, cover off, tensioner off, belt out, new belt, compressed tensioner in, pac man in, one revolution of the crank to make sure no valves and pistons collide, cover on, serp. belt on, fan reinstalled and you're ready to go.

See, a snap compared to the B230. Look at www.volvospeed.com/bay13 which shows the procedure for an 850 and is mostly the same for the 960.

When doing a timing belt change, it's a good idea to make sure the water pump is OK since it's driven by the timing belt, so why do it twice if you don't have to?

Smooth and powerful cars.

Yeh, the early 30K interval was an OOPs for sure. However the belt change is a cinch and is so easy you can easily do 2 for the price of one of the other cars. This was redesigned in '95 and the interval is now easily 70K. In defense of the other annoying things, these are features influenced by legislation that your older cars don't have. True they should have put the extra $.05 in and made it reliable.

The only design issue I've seen with my car is the weak intake manifold gasket. (And of course the AC problem that all cars have had since the change over to R134a.)

Good luck with your's!