John WRX

Thanks for the help mate. It is really difficult to explain it. If you were to drive it you would probably recognise it straight away. It kinda feels like the brakes have been put on, it will drive through the flat spot under slight acceleration no problem.

Its a Uk Spec WRX With hks dump valve, blitz filter and cobra rear box. Apart from that i dont know the mod history of the car. Its had the aircon removed, there is a spce on front of engine where it has been.Have only just started running it on super unleaded, could this have caused the problem?? im running it on super now so if it is would it sort itself out??. I just want to know what it is so i know what to do about it plus im a bit wary of driving it incase im making it worse but i go to ireland on monday for a week so i got to drive it. Any more clues?? Cheers for the info above

John WRX

Right cheers im going to ireland in the morning for a week so will see if it improves in the next week. Ill let you know what happens. Thanks for your help

WREXY

If there is no improvement take it easy with the car. You don't want to do any serious damage. Have a good trip.

Cheers,

Wrexy.

John WRX

Ok, thanks for having a look, here is whats up........

Basically, its driving like a bag of spanners, ive got a massive flat spot dead on 4000 revs and the power just dissapears there as the car seems to shudder. It is backing off all of the time and has no power under mid rev range acceleration. In 5th around 60-70 mph i can feel it shuddering. Havent got a clue what it is, just wondering if anyone else has had the same problem. Ive been into grasshopper with it and Latz is ringing round a few people as he doesnt have a clue. Please help.

Here is my power curve, notice the dip at 4000 revs.



[Edited by John WRX - 5/10/2003 11:37:17 PM]

WREXY

What model is the car?

When you hit 4000rpm does it feel like you've hit the brakes? Does the car dip as if the brakes have been applied? If so, your car is overboosting and the fuel cut is engaging. If you hit around 17.4psi (I think that's the figure) for 5 seconds or more, the ECU sees the overboost and engages the fuel cut for safety. Is the car modded? Do you have some form of boost control such as a Dawes or an electronic boost controller and perhaps the boost settings are too high?

The other possibility is detonation. Some causes of this are, faulty MAF sensor, (which would be giving a lean fuel mixture) bad fuel, Low octane fuel, or too much boost.

Then there are other possibilities which could be causing your problem such as fouled spark plugs, faulty coil packs, or a stuffed sensor, or even a faulty fuel pump. Also your solenoid may be contaminated with oil, mostly from everfilling the sump with oil. Check out the solenoid for contamination and clean it if needed.

Cheers,

Wrexy.

[Edited by WREXY - 5/10/2003 11:19:33 PM]

WREXY

You should always run on Super Unleaded. This could have been the problem. Your ECU may have been picking up some detonation and then knocking the timing back hence the flatspot.

Take the car out for a drive. Take it easy for say 8 miles so as the new fuel mixes in, then try it again.

At 4000 rpm are you hearing any engine noises which could be det? What you would be listening out for is a faint metalic type crackling sound.

Cheers,

Wrexy.




[Edited by WREXY - 5/11/2003 12:19:38 AM]