Very rough idle - intermittent!
 

I purchased this 96 850 turbo wagen a week ago. Volvo service gave it a clean bill of health. But I'm having occasional very rough idle, engine struggles & sputters some but smooths out once up to speed. It was so severe twice it threw a check engine code twice. Both were "non-specific" codes. Fuel filter just replaced. I did put seafoam in the gas and washed under the hood, but the issue may have existed before. Car is 22 yesrs old, with 63000 miles. It just made a 1000 mile cross country trip. Not sure of plugs plug wire status. Any ideas where to stsrt? THANKS!

If you washed the engine then you probably got water down in the spark plug wells. The spark plug ends seal the tube pretty well and any water that turns to steam condenses again as the engine cools off.

I would warm the car up at idle, turn off the engine, then remove the spark plug leads and let it sit for a while to evaporate all of the water. I used to have to do this a lot when I cleaned the engine on those cars.

Thanks I will try that first! I'll be happy if it's that simple!

considering the car is new to you, I would consider installing new wires, rotor, cap and plugs - there's a date code on the wires - if older than 5 years, time to replace. OEM or copper core plugs work best - don't spend xtra on iridiums/platinums. Not sure which codes you consider "non-specific" - what sometimes happens is the code readers give you a generic mapping but there are manufacturer guides and posts on the board which can help you interpret the codes. Once you have dry or new wires, if you still get a rough idle, then you can look for vacuum leaks or consider cleaning the idle air valve or MAF.

Thanks
 

Plugs are dry. Service record shows new plugs 3000 miles ago. No record of plug wires, distributer cap or rotor in 63,000 and 22 years. That sounds like where to start. Any favorites? OEM, NGK, Bosh? I got an ICarSoft reader I hope it's not a waste but need to be able to deal with check engine light and trying to stall when on the road.

quality aftermarket brands should do fine - your cap/rotor will likely be Bosch which is probs the OEM. Wires can be Bosch or Bougicord and I'd bet NGK also makes them. FCP Euro and EEuro parts sell these brands at a fair price. I'd also suggest you check to see if your car has a cabin air filter - that was an add on kit (the cars didn't have them out of the factory for the earlier years) and check the intake air filter. Get the kit with the coil wire as well - I've seen them corrode from the inside under the insulator.

Personally I don't find error codes all that useful. Better to pull actual data and think. Torque app is very popular for that, if you have an android phone, but I don't. You could also use something like a scangauge which is not all that expensive. I use an old scan tool. Real scan tools have sort of gone out of style due to the above options.

Thanks! Downloaded torque and ordered bluetooth transmitter. Cabin filter new, air filter new k&n, ordering wires cap and roter.

After running great for a couple days when I started it mid day yesterday, very rough idle and check engine cam right on. Was barely drivable felt like it was missing badly. Had to pull over and got this report out of Tourque. Seems like a great tool THANKS! Wires in transit.
Fault log report generated by Torque for Android
=================================================

Vehicle VIN: Not present
Vehicle Manufacturer: Unknown
Vehicle Calibration ID: Not present

Current Fault Log
------------------
P0300: Random/Multiple Cylinder Misfire Detected
P0303: Cylinder 3 Misfire Detected
P0305: Cylinder 5 Misfire Detected
P1310: [Chrysler] Ignition Coil 3 Primary Feedback Circuit
[Toyota] Igniter Circuit Fault (Bank #3)
[Lexus] Igniter Circuit Malfunction (No. 3)
[Dodge] Ignition Coil 3 Primary Feedback Circuit
[Jeep] Ignition Coil 3 Primary Feedback Circuit


Pending Fault Log
------------------
ECU reports no pending faults

Historic Fault Log
------------------
ECU reports no historic faults
Other discovered fault codes
(possibly pending, current or manufacturer specific)
----------------------------------------------------
ECU reports no other fault codes logged

End of report.

The excess pressure from the PCV will cause misfires as it dilutes the AF mixture.

Is the IPD. PCV kit a good one? About to order and maybe give it a go.

You might want to read my recent post about these PCV systems.

https://volvoforums.com/forum/volvo-...service-96198/

I can see that additional work is probably necessary. I may need an honest volvo mechanic in Jacksonville, Fl! I found one video that claimed that an aftermarket cpv hose was cracked and bad after a year and suggested oem parts only?

That is an issue. URO parts don't have a very good reputation. There is a lot of plumbing on a Turbo, bit and little, and all of its downstream of the MAF.


There is no way that the PCV separator cleanout is going to help it run better, but fixing any vacuum leaks will. If it misses mainly at 65 mph, that is a bit of a strange diagnosis. Vacuum leaks mess it up more at idle and less under load.

Will need to monitor the miss rough idle for a bit the work done improved drivability. Plenty of smoke comes out of the oil filler cap and fill stickI understand indicates clogged pcv system.

Cap, roter & wires made huge improvement (after 23 years). Now looking at new topic pvc - no plastic PVC heater hose replacement!

MT6 you nailed it the cap roter and wires have it roaring along smoothly! Tourque was also a big help!

Replaced all vacuum hoses and the PCV system and it smoothed right out and is behaving nicely.