My 94' 855 has had a code for inefficient cat for a while now. After putting on a hi flow cat today, when under boost(maybe 9-10 psi) I feel a little hesitation in acceleration and any more throttle/boost(11-14 just before fuel cut) and the engine "really begins to misfire". I'm thinking my old cat was somewhat clogged and now there is more air then fuel. Forgot to mention I upgraded to a 16T turbo. So shouldn't the ECU compensate for the higher air flow and dump more fuel?
Any input would be highly appreciated.... CJ
Should mention the code is gone and there are no new ones.

 

Is the cap,rotor,wires and plugs new?
If not I would start there.

 

Whats up Tech!
Yes, I did a stage 0 and then some since getting the car last Nov.
Just got back from driving around about 30 miles. Seems to be doing a little better but still busting up under high boost.

 

What plugs did you put in?

Not to much here same ol stuff!!! LOL

 

ah, forgot the number but they are the same autolites used in the turbo mustangs. Actually seen them used in a few different boosted cars.
Put them in months ago though. Car ran great until it came off the rack at the muffler shop today. At first I was thinking something got shorted by the welding but it probably would not even start if that was the case.

 

It might be the plugs. The Autolites usually don't do all that well in the Volvo's.
I am running Bosch Platinums but people have had problems with them as well.

Does the check engine light flash when it acts up?

I have a problem with mine kind of like that as well but only sometimes.

 

I've had problems with bosch myself. They're no lights or codes(first time ever..lol) so I'll check my plugs tomorrow.

 

Keep me updated.

 

today I regapped the plugs and problem got worst. But with factory boost setting the autolite 3924/3923 worked pretty good. Will try ngk's next I guess.

 

Fixed!
Put in some NGK's today along with my new inmotion tuned ECU. Car runs great. I think the .044 gap of the autolites was too large for high boost levels. NGK's are at .028.
Thanks Tech.......

 

Drop the gap to .025 and you will be good for a while.

 

Damn! .025? Okay. You the volvo tech, Tech....

 

LOL I had a problem at .028 then regapped to .025 and all was fine.

 

the tips on the NGK iridiums are so tiny, I'm afraid to touch the plug. Running real good right now and these type plugs are suppose to hold a gap for a long time. We'll see next time i pull them for inspection.

 

Sounds like a plan.