99 C70 - bucking around 3k when hard accellerate

HulkC70 · Post by **HulkC70** » 03 Oct 2014, 17:25

when i am going heavy on the gas pedal my car bucks hard like it lost all power then in a second catches it and puts you back in your seat. this will occur through 1 to 4 gear when only accellerating hard and only happen around 3 to 4 thousand RPM. would could be my problem? i can not seem to figure it out. I have the 2.3L T5HPT 5spd manual.

Post by **jblackburn** » 03 Oct 2014, 17:32

Wondering if it's overboosting and cutting power.

How are your vacuum lines at the turbo and turbo control valve on the airbox?

When's the last time you changed spark plugs? I saw blow-out at 5K on a set of old spark plugs - power delivery and upshifts were very rough.

HulkC70 · Post by **HulkC70** » 06 Oct 2014, 08:37

Vacuum is all good, turbo has some oil leakage, spark plugs only about 15k old double plat. If I disconnect the battery for some time it won't do it for at least a few hundred miles. I will check the spark plugs tonight though

Post by **jblackburn** » 06 Oct 2014, 08:57

spark plugs only about 15k old double plat.

Might be your problem.

These cars HATE platinum plugs aside from the Volvo OEM ones - I actually tried some double platinums and my car did what I said earlier at 5000 RPM after only 10,000 miles on the plugs. Stick to iridium or copper plugs in boosted cars.

HulkC70 · Post by **HulkC70** » 07 Oct 2014, 09:09

I will do that right away. Thank you. Any suggestions on the best plug brand to go with on this?

Post by **jblackburn** » 07 Oct 2014, 09:16

HulkC70 wrote:I will do that right away. Thank you. Any suggestions on the best plug brand to go with on this?

Bosch 7955 FR7DC or NGK BKR6E ("copper")/EIX (iridium). The copper versions will last ~30,000 miles or so.

Or you could always pick up a set of Volvo OEM plugs.