Engine codes
 

94 Turbo 850 Wagon. Engine light came on after a long drive,, Autozone pulled P0171, and P0422. It seems to run ok,,, a bit low on power and MPG is only about 17 per Computer. Any Ideas?? Thanks, Tim

P0422 Main catalyst below threshold.

This happened to us a few days ago with similar symptoms. My friend checked and cleared the code filled it with 91 octane and hasn't come on again. The previous owner just replaced the cat so I am curious to see what the cause of this could be.

It came on after a long drive and it was idiling for a while. Since it smokes a bit after it's warm and idles for a while I wonder if the Cat is getting some blockage. I guess I better drive it harder and clean it out!!! Tim

2-3-1: P0171, P0172: Long Term Fuel Trim Part Load
2-3-2: P0171, P0172: Long Term Fuel Trim Idling
4-3-3: P0422 TWC Efficiency

I would like to know the colour of the smoke out of the tail pipe. If dark gray/black, A/F mixture is too rich due to a fault in the fuel control/faulty O2 sensors. If the smoke has a hint of blue, oil is burning.


JPN

It's blue oil smoke. I also found a tear in one of the Intake/Intercooler hoses. That should help the sluggish problem. Tim

I have a 1995 Volvo GLT. I recently changed the spark plugs to (Autolite platinum), fuel filter ( an aftermarket brand) and air filter. Shortly after, I found the car ran smooth but the power seemed slightly less. I guess I expected a little more... Then I noticed my ability to accelerate was definitely not as good as before. I assumed the fuel injecters needed cleaning and added some GUMOUT fuel injector cleaner --- still no improvement.
Finally, I plugged in my diagnostic MEMOSCAN. It gave two codes: P0172 "Fuel mixture too rich" and P0422 "Cat..." My MEMOSCAN gives both the codes and verbal explanation.
My questions are:
1) Since the problems occured after changing the plugs, fuel filter and air filter did one of them cause the problem?
2) I had used fuel injector cleaner several times in the last sevral months. Is this contributing to the problem?
3) I am currently using 93 octane gas. If I drop it down to 89 octane will that help fix it?
Note: I am on the East Coast. We have 87-89-93 Octane ratings at our gas stations. I know that other States may use a different octane ratings for the same gas: 85-87-91

There's your problem(s)...

Code P0172 and P0422 -- Which spark plugs should I use ?
 

Thank you Gdog !
I kind of suspected it might be the spark plugs. I never used the Autolite platinum plugs before, but since they were 'platinum' I thought they would be better. Which spark plug brand and type do you recommend ? I will change the plugs first, and then the filter - if the problem persists.

Bosch Platinum or OEM; also make sure they're gapped properly...

https://volvoforums.com/forum/showth...ed+spark+plugs