This is my mom's car andhad not been drivien for several months. I tried to drive it at Christmasand it was running so rough i turned around and came back. The car was last tuned up in 1993 at around 25,000 miles and the dealer sold me new injectors at that time for $750. It was running similar to now if I recall correctly.Ireplacedthe plugs wires and dist cap and rotor and the car seems to stillbe runningon three cyclinders. At wide open throttle it surges slightly like the offending cyclinderis trying to kicking in. I'm thinking injectors again. I dumped in a can of seafoam and drove around for 20 minutes with no change. I know now that injectors can be cleaned. Can these be flushed on the car now or do I need to take them off and have them cleaned?Is that a good place to start?
thanks.
Dean

 

I doubt it's the injectors. Are you saying the car has TOTAL 45k? And the last tune up was at 25k in 1993? I'd start with a compression test to eliminate heavier problems such as valves, head gasket, etc.

 

Yep, 2 dr model purchased new by my mom and maintained by me. Oil changed with Mobil 1 every year and antifreez changed ever other year. Was running just fine in September.

 

If there is no Check Engine light on I'd suggest start with the basic 24,000 mile PM stuff you cando yourself, like the fuel filters, old gas could also gum up the pusher pump filter and while you have the pump out, you can inspectthe tank to see if moisture has gotten in there.

Electrically you can also try looking under the hood in the dark to see if thenew plug wires are grounding out somewhere. It needs to be pitch dark and the arc is usually very faint. Look around the bottom of the plugs and around the coil.

I've used seafoam in the tank proactively and was told it works best on long drives at hiway speeds. I'm not sure I like it, anything that will eat though varnish deposits I would think could alsoeat diaphragms, hoses, wires and pumps, plus it's expensive and smells awful, but that's just me.

 

I doubt it's the fuel injectors. The fuel filter needs replacement. If the fuel pump relay is more than 10 years old I would change that. Has the throttle body been cleaned?

 

Fuel pump relay and the outboard fuel pump were replaced about six years ago. It misseseven at idle. It revs out so I don't think it is fuel starvation. I was so sure the new ignition parts would cure it. It runs like it has a big vacume leak or the timingbelt is retarded.

 

Well, my 740 is running extremely rough. I believe it is 3 out of my 4 spark plug wires. I can't even get a resistance reading on 3 of the wires on a 20 Mohm scale and the one I did get a reading on showed 1.8 kohm. Next, I tried to see if a timing light would flash on the wires. Turns out, it only flashes on the 1.8 kohm wire. Still, the engine seems to be running on 3 cylinders-how, I don't know, since it seems it should only be running on 1 cylinder, if that's possible.

I am awaiting my new spark plug wires.

 

Well I bought two sets online and neither worked out, went to Autozone and ordered Bosh and they were almost identical to the 1993 vintage volvo wires.