My old Volvo is not running right, please help.?

Question

My 1990 Volvo 740GL that has 240000miles has been running rough lately. I took it to the shop a few weeks ago for a bushing on the transmission and they put a new pcv valve (not called that on the Volvo, I cannot remember what it is called.)

Anyway, now it runs rough, first I thought I got some bad gas, so my husband who is a mechanic, used some fuel injector cleaner on it. Then we thought it was the fuel filter. We have a new snorkel on order, the intake hose did have a leak, but we taped it with duct tape until the new hose comes in.

I was getting 27mpg, now that it is running so bad, I am down to 22.

When it runs real rough, especially uphill, or after stopping, if you put it in low gear it will take off just fine, its an automatic, but you have to shift like its a manual when it happens. Also if you try really hard, you can get the accelerator in the perfect spot, not too much gas, not too little and it will take off fine.

Is there anything else it could be. It is possible the snorkel is still leaking with the tape on it. I hope that is what it is.

Answer 1

old volvos sometimes run a heap better after you clean out the throttle body.  i'd grab a can of carby cleaner and try that first.

Answer 2

There is a possibility that its mixture could be too weak. When it is running or ticking over, feel the exhaust gases coming out of the rear. If they are cold it is weak. If it is hot it is a little rich. It should be somewhere in between. Good luck. h

Answer 3

It sounds like they may have knocked a vacuum hose loose or maybe broke one, check all the vacuum hoses for leaks, or take it back to the mechanic that "fixed" the pvc valve for you.