ImprezaWRXsti

Hi everyone,
I own a 1998 Impreza GT555, its had an engine transplant with a jap spec red top STi engine around 2 years ago. Since I bought it in July I have had the follow porblem: When accelerating, the engine will start to shudder violently at 4400- 4500 rpm. This problem is consistent through all gears. Some days the engine will accelerate as normal. When this problem happens the engine check light comes on and stays on untill the problem decides to go away again. One thing I have noticed is that when the CEL comes on, if I press the clutch and let the revs drop down then the light wil USUALLY go out and the so the problem goes away for , sometimes seconds , sometimes days. We initially thought the problem was the speed sensor as the diagnostics were showing a fault there. The speed sensor was replaced and the problem is still there. The airflow meter was changed and the problem is still there. The problem may or may not be related to a faulty speedometer, which is also not a consistent problem, its all over the place sometimes and then fine other times, it seems to hapen independently from the engine problem but may still be related to it is some way.

If anyone has experienced this or could help me out with any advise on what I should be checking / replacing I would be very greatful

Many thanks,

Steve

GrantyBoy

I had a similar problem with my STI import, felt like lumpy acceleration. Turned out the engine had the wrong sparkplugs in it. I now use NGK 7s and have had no problem since. Do a few searchs on here for engine stutter/hesitant and see if you can find more info.
Hope that helps

ImprezaWRXsti

I'll try new plugs but I have a feeling its a bigger problem, gona try it anyway so thanks for the advise