C70: Engine goes flat and misfires under heavy acceleration

[bgwd]

Hi

I have a problem with my C70 T5 (auto) 1998,

When under hard acceleration from about 3000 rpm onwards the car goes 'flat' and loses power and feels as though the engine is misfiring, the car feels fine to drive under normal acceleration (that said i haven't driven it much since it started happening).

When checking the engine, when the engine is revved highly, the top pipe that is above the radiator actually sucks flat as though there is a vacum inside it (sorry don't know which pipe it is but it is part of the air system as I have been told by my mechanic, its the large one). Now i can assume that the starvation of air is what is possibly making it go flat under hard acceleration but need to find why this pipe is sucking flat, any idea's please

Justin

[alv70d1999]

mucky air filter..or blocked cold air intake........take it off and have a look

[bgwd]

Thanks, the air filter was replaced about a month ago, that said I will check it again and the cold air intake later, cheers.

J

[bgwd]

Just a quick note to add.... I have just spoken to my mechanic who has the car and he has said there is a slight misfire on tickover after the car has warmed up, not sure this is relevant but it might help, cheers

J

[FCPGroton]

Take a look at your spark plugs. I had the same issue on my 850 and I was running platinum plugs. Went back to the Volvo OEM plugs and the problem went away. The misfire was so bad that they CEL came on for the knock sensors.

[Chris_Rogers]

Sounds more like a blocked intercooler or something else in the induction line to me.

You could ask your mechanic to temporarily bypass the intercooler and maybe the turbo with a peice of large radiator hose or similar and see if this cures the problem.

[ocean238]

I agree with Chris, why else would the top pipe suck flat? you could try removing that pipe from the intercooler to see if there's an improvement. I am assuming that it's the same when the car is still just reving, which means you don't really have to drive it without it all connected to see what's wrong

might be worth disconnecting the TCV first tho, even tho in some cases this triggers the CEl light

Anyway just an opinion, of course, I might be wrong!

[bgwd]

Thanks for your reply's, the mechanic has said the turbo is on the way out as the main bearing has play and the fins are worn, that said it doesn't seem like the problem as I wouldn't of thought a turbo would cause this problem, probably just kill itself in a big cloud of smoke !! anyway, will try your suggestions and if we find whats wrong will post the answer after the weekend.

cheers guys

J

[alv70d1999]

id get a second opinion!

[Jod T5]

Originally Posted by alv70d1999

id get a second opinion!

Agreed, air leak or incorectly gapped plugs IMO...
Jod