mrfish69

I have a 96 2000 model, and when in 1st gear i hit the accelerator the car starts off fine then starts to loose power then regain power and judder like mad really quite scarey very hard to explain but you feel like your about to get put out of the front window can anybody help or now a reason why it does this...

scoobyslut

Sounds very similar to "overboost" problems, as the engine is actually cutting power to the injectors momentarily.
I would check as to what boost you are running, plus fuel grade may cause a difference.

mrfish69

i have not got a clue what overboost is, the only things i have had modified on my car is a bailey dump valve fitted and a full magnex exhaust system i have taken off the cat down pipe and replaced the mid cat with a silencer could these changes cause the problem of overboost. antway thanks for replying.

mrfish69

and if it is overboost problems how do i fix them cheers

The_Judge

Decatting can often increase the boost pressure by a couple of psi, but if you haven't already increased boost by using a manual boost controller, I'd be surprised if you were hitting fuel cut, particularly in 1st gear. Is it a "surge", or a "BANG"? Is it only doing it in 1st gear? And is it only when you're flooring it?

If it is overboost, click here for info on how to clean your wastegate solenoid.

mrfish69

i took the car down to the garage and they put a boost gauge on and tested it for over boost and they did not think that over boost was the problem.
Now i had a k&n air filter fitted last year and got it removed because it caused the car to judder in 1st they seem to recon that this air filter has blown or damaged to air flow meter could this be the cause of the judder still. they also said that its more of a miss fire problem could this be it?

mrfish69

also can anybody tell me what the boost pessure should be on a 2000 model 96 cheers

The_Judge

If your problem isn't a "BANG" head hitting windscreen, then it isn't overboost fuel cut. It could well be your MAF, as that is often the cause of poor running. But I doubt it was damaged by the K&N air filter. Do you know if it was the original MAF? If so, at 8 years old, it was way past it's normal life expectancy.

Normal boost pressure's around 11psi I think, give or take.

mrfish69

is the maf the small black box just behind the air intake the one with a small wire hanging inside of it and if this is how do you know its broke. and i don't now if its the origonal one or how old it is thanks.

The_Judge

Not sure what the inside of your MY's MAF looks like to be honest! Got a feeling it's "hot film" whereas mine (MY00) is "hot wire" (not that that helps at all!). It's just to the right of the air box, at the back of the air intake tract, with a plug connected to it. Unfortunately, there's no actual way of knowing if it's knackered or not just by inspecting it. Unless it was something obvious like covered in air filter gunk. If you had an AFR gauge, and assuming your lambda sensor was OK, you could tell from those readings whether it was knackered/knackering. Or, if you had a knocklink, and it was indicating det, that's an expensive alternative of knowing whether it's knackered/knackering...