QUOTE(Vitor @ Feb 28 2005, 03:37 PM)Your problems may be a bit too complicated now.
You are correct in assuming that there were no valve problems when you took the car to the dealer. An engine with low compression in so many cylinders may not even start.
You will need to verify the compression in each cylinder to make sure of the values.
If you in fact have low compression in 5 cylinders, then the head will need to be removed to find out why the damage took place.
Now, here's something else.
I have a 99 S80 T6, one of four Volvos I have. I am the one who rebuilds the ABS/STC control units.
One of the problems you described is your problem with the ABS/STC unit.
When I repair an ABS unit, I install it on my S80 and put it through its paces to make sure all functions work. Sometimes I remove the unit I'm testing and don't install a unit on the car because, I tell myself, I will do it later.
When I jump on the car and drive away, at least 4 warning lights will turn ON and if I ignore them long enough, I get the engine to start misfiring and in one instance I lost the use of the throttle.
When I re-install the ABS/STC unit all problems will go away and the car is back to normal.
Check my website for more ABS/STC information.
Vitor's Volvo ABS website
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You are correct in that it is very complicated. First, I am going to concentrate on the engine. I have a friend that can check the compression (I can do it, but I don't have the extra time) and go from there. I have been told that the timing belt has broke but this isn't the case. The car will start and run but it's rough. I brought the car used last year with 84,000 miles. Before that we had an 850 with +175 K miles so I know these cars will go the distance. It now has 117K now. I called the dealership I bought it from and they told me that the belt needs to be replaced @ 105K. Right now my wife is in college 5 days a week so she hasn't have a chance to replace it yet. Enough on the history of the car. I asked the dealer if the timing belt was able to ride over (jump a notch or two) to get off time in order to warp a few valves. He said no that most of the time it just breaks. This hasn't happened. It still runs. I also asked if the tensioner broke or lose tension and caused this. Again, this was unlikely as the belt would snap. I plan to check the compression. If it is low then I will have to go into the motor. If not, is it possible that these abs/stc and other modules are trying to shut the car down? I going to try this first and go from there. I check my receipt and it doesn't have any codes on it. Thanks!