Horrible bucking problem

I've been having a hesitation issue, i replaced the knock sensor yesterday. I know it didn't have anything to do with my hesitation but I saw the wires were no longer connected to the sensor. everything is back together and now the second I start moving and give it gas the car bucks so hard your head goes for the windshield and I can hear the motor bounce forward. When this happens my lights on the dash flash like the car died. Once I let off the gas it goes back to normal.

I have taken the top end back apart to see if I've missed anything and found nothing wrong. My friend has a known good ecu I installed that no change. I do have a bad battery I have to jump it for the time being... I don't know if that would cause any issue though.?

Things I have done since I bought the car, I added braided fuel lines with SX performance filter and FPR. I added PTE 550 injectors. I put in spark plugs I think they are bkr7e (I'll check for sure tomorrow).

I bought the car with 15g turbos, safc ii, blitz EBC, wideband.

Seems like everything I do makes it worse, now I can't even get it down the road.

Is your tps set right?

I haven't yet, im hoping to get it hooked up to a hhh soon.

Almost sounds like it could be a MAS issue.

Do you have a datalogger? If not, I would get Evoscan and the cable on order ASAP. I have a hunch that the logs will reveal all.....
Fuel pressure should be checked as well, if possible. You don't want starve those 15Gs for fuel with dropping FP on boost.

FYI, I was having similar problems bucking and hesitation. On the first datalog I found that one of my O2 sensors is reading 1.6-1.9 Volts( - should be 0 volts to .9 normally from what I read.)

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Originally Posted by stealthee

Almost sounds like it could be a MAS issue.

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This.

Unplug your MAS/MAF and see if anything changes. It will throw up a CEL but ignore it. If it makes no difference it's not the MAF. Unplug the battery for a few mins to clear the CEL. The other possibility is the fuel pump resistor. Mine was causing a stumble but nothing as series as what you're saying. When my MAF went though it was exactly as yours sounds.

Did you forgot to clamp down any intake lines?

Did you swap to an open atmosphere set up?

Sounds like a crazy lean buck. (large increase in un-metered air, could also be the result of a bad MAF as stated before)

-John