91 Volvo 940 SE Turbo - Rough Idle

I have a 1991 Volvo 940 SE Turbo, Fuel Injected, gas, 4 cyc. I cannot get my car to idle smooth. I run super unleaded, and have put a bottle of injector cleaner in it.

I found two fault codes for the O2 sensor so I replaced it with a universal one (three wires, two white and one black) does it matter which way the white wires are hooked up))?
Now that I replaced the o2 sensor I still have one of the O2 faults along with a new one for my injectors. I listened to then and it sounds like all the solenoids are working on the injectors.

I recently changed the plug wires, re-gapped the plugs to .028, and replaced the rotor & cap. I have replaced various vacuum hoses and check valves. Today I installed two new hoses on the Evaporative Canister for the intake manifold. When I went for a test drive I heard a pop and the car started running rough. After looking around I found the vacuum line from the fuel tank to the evaporative canister had a split in the side. I replaced it and the engine is running smoother but the idle is still not smooth, plus now there is a strange smell coming from the engine area (almost like a gas/exhaust mixture smell). The canister is not broken. I removed the gas cap, which did not make a difference. I don’t have a hand vacuum pump to ck the valve on the evaporated canister.

The idle is around 750 with about 100 rpm variance, the timing is at about 12 degrees BTDC.

more info............

I checked the mass air flow and the ground is 18 ohms, not good! I have not found the short yet. It looked pretty clean though.

I found out that the spark plugs keep fouling, black!!!

No fuel on the vacuum side of the fuel pressure regulator.

I replaced the fule filter today, some junk in it.

I also found oil in the intake tube, traced it over to the turbo i believe. It appears that the turbo is leaking oil into the intake ducts. I havent figured out the cause or solution yet but its probally part of the problem!

The car wont start without holding the gas pedal, then it runs rough all the time.

[Suterman]

try cleaning out the oil breather box and pipes, if its blocked up with oil and gunge then oil could be getting into the intake tract that way and choking the engine. If the main vapur retun pipe has lots of oil in it you've found the problem.

you can take the box out by undoing the harness bracket bolts and the two bolt holding the box on. remove all the pipes and wiggle the box out. give it a load of brake cleaner or petrol r somthing like that and shake it all up then rinse it and refit.

[Richardkimber]

Richard.

Sounds like you have a shed load of trouble.
Since 50,000 miles my turbo has been passing a small amount of oil, enough to wet the inside of the delivery pipe to intercooler, but not enough collect in the intercooler base.
The rough idle could be due by a sticking Idle Air control valve. Look in the 700/900 FAQ and click on the highlighted fuel system text an excellent set of IAC notes.
I am planning on cleaning mine this week end, as the idle speed varies 600-900.

Good luck.

Richard

[James_N]

Im glad this has come up because sometimes my idle is a bit rough and sometimes when i stop, i can smell exhaust fumes. The car flew through the MOT in June with almost zero emmisions!

I know I can try and clean a few things out, but im not sure what lol. Im useless.

/edit - from reading this: http://www.volvoforums.org.uk/showth...280#post156280 its the throttle body that i think could do with a clean too. How do i do this?

[Suterman]

a faulty or broken IAV wont cause uneven idle.

It will cause the engine to idle a little under normal and stalling on going from running the car in gear to neutral (eg. coming up to a T junction) this is because their natural position is closed, they are meant to open when the throttle plate is closed to allow a little air to get through so the car doesnt richen out and stall.

still worth taking it off and cleaning it and checking its operation with a 12v supply as somtimes they dont work quite fully.

cleaning the throttle body is easy too. you dont have to take it off really but its best if you do, you can clean it on the car by removing the air intake pipe and spraying it with carb cleaner and getting in there with a tooth brush. to clean it properly means taking it off and dismantling the whole thing and cleaning each part, especially the throttle body and plate. EDIT : you can re-use the gsaket as long as you dont tear it.

[James_N]

i dont even know which is the throttle body! got a picture?

[Suterman]

[James_N]

Thanks so just take that pipe off and spray carb cleaner down it?

[Jod T5]

Originally Posted by James_N

Thanks so just take that pipe off and spray carb cleaner down it?

no james i think you will have to be a bit more thorough than that..., carb or brake cleaner will only disperse the minimum of crud.., for a proper clean you will have to remove the throttle body, complete, to ensure you get to all the nooks and crannies around the butterfly....with a lint free cloth or toothbrush (not your own tho lol)
cheers
jod