My 1800ES is running rough. I pulled the head off put it back on with new gasket and started it up without adjusting the valves. It idled and revved up great. I didn't drive it at this point i was cleaning out the cooling system and oil. Then i pushed it into the garage and adjusted the valves to the correct settings in the manner the book told me (I've done this before and it worked fine). I do not know if the valve clearance adjustment has any relevance to the engine running rough but it did come in between. Anyway here is what is going on so far as I have tested. The roughness is coming from cylinder #2. When i pull the plug of this spark plug the engine speed does not change. The thing I think is strange though is that there is a spark going through this line i can clearly see it arcing to the plug. So then i think it must be the injector that is not squirting. I pull the plug on the injector and the engine slows down, what gives? Here is what I am thinking could be wrong with it now: improperly adjusted valves, bad trigger contact, partially blocked up injector. I can readjust the valves and I have extra injectors. Am I right in thinking that one of these could be the problem?

If you had the head off it is possible that the engine temp. sensor could have been damaged. Cooling system cleaners can also cause damage to these little sensors. A bad sensor can cause the problem you describe. I would check the resistance of both engine and air temp. sensors at known temps. and compare to specs. Also check for a vacume tight seal on your map sensor. These three sensors can cause all kinds of mystery problems. Sometime when you replace the temp sensors the small variation from one to another even though withen specs can cause a lean or rich condition if both new sensors are off a little in th same direction. The factory tuned the map sensor to perfectly match the other sensors in the car. If your map sensor has screws and not rivets and you are very good with repairs and you understand the workings of a variable vacume actuated induction coil you can repair and adjust it. I have done it succesfully.

Thad
Seattle

Compression test? Could be a bad valve...

Yes, could be a plugged or carboned-up injector. The Volvo manual describes how to evaluate the spray patterns and flow rates from each of the four injectors.

If you have extra injectors, try swapping in a spare. Or try swapping the suspect injector with a good one from a different cylinder.

The triggering contacts operate the injectors in pairs. So a bad contact set will affect two injectors, not one.
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Don Foster (near Cape Cod, MA)

Which injectors make a pair? I think #3 is also off.

The factory service manual shows injectors 1 and 3, 2 and 4 grouped.


--
Don Foster (near Cape Cod, MA)