Advice needed. Seat leon mk2 lacking power ?

[Littlejim]

Hi all. Im just after some pointers or advice . I have a mk2 seat leon . BWA engine with a K04 conversion . it has been remapped by rtech and is at around 340 bhp . Problem im having is it feels like its set in a low power mode of sorts . I have double checked and its in the highest mode . Using vcds i can see everything is fine asin boost specified and actual aswell as fuel rail pressure.
However , the maf is only reading as high as 180 and the requested boost is only hitting highs of 1800. Comparing older logs i can see ive been hitting boost of over 2500 ? .any ideas on what else to log maybe or to check for. Thanks in advance.

 

[380bhpdaily]

Hi mate difficult one, if I had the maf reading like yours I’d be inclined to either clean or replace the maf and retest to see if the reading changed first? Also is all the wiring to the plug in tact? Not just to look at but continuity?

 

[Littlejim]

Thanks for the reply. The maf its self is giving me readings that seem right . Ill give it a clean and see if it alters anything. Is it the maf that dictates what boost is then specified? Any other suggestions on what i should log? Timing maybe ?

 

[380bhpdaily]

Ah ok sorry I misunderstood what you wrote I thought the maf was misreading. If the maf is misreading the fuel trims will be wrong worst case and mess up the AFRs Timing wise I know my bwj threw a code for being over advanced when I did the cam belt and chain. It’s a tuff one but were you working on the car before to this happening or it just happened out of the blue? When you used vcds did any under it over boost codes come up?

 

[Littlejim]

No worries. It may be that the maf is misreading. Problem i have is no codes at all but i can see via the logs and physically feel the car isnt pulling like 340 bhp used to . It was out of the blue . I have changed plugs and the front pcv to eliminate that. The only thing i do need to do is the thermostat as its stuck open and the car was seeing 80.degrees down to 63 at times but i doubt that will effect anything ?

 

[380bhpdaily]

That’s your problem there. I had this on my own Leon mk2 it would be down on power and judder badly when the car was anything below 90degs. The first thing you need to do is fit a new Thermostat mate. I’m glad I asked more questions now lol

 

[380bhpdaily]

You should put some card to block your rad so then whiling driving it forces the car to heat upto 90 and then it should be back to before. I know that sounds ghetto but I did the same thing on mine before changing the thermostat as I wasn’t really keen on doing that job as I had a bad back at the time and wasn’t able to use the ramp at work.

 

[Littlejim]

Honestly. So the ecu alters something as its seeing low temps. Right well i know what im doing tomorrow. Thanks very much for your help. I will sort it and report back

 

[380bhpdaily]

I think the ecu adds more fuel to warm up the engine until it sees 90deg. I could be wrong but for me as soon as I changed the thermostat and the car ran at 90deg it was a completely new car to drive. No more juddering at 2500rpm and nice and smooth all the way to 7k

 

[Littlejim]

Amazing. Makes sense tbf. Runs ok no fault codes just lacking which i guess is just the ecu telling the car its cold. Im guessing a pig of a job so ill sort it sunday along with the aircon pump. Puts my mind at rest really appreciate your time

 

[380bhpdaily]

Yea it was a pig without a ramp. Probably would of taken half the time of I’d just waited to do it at work on the weekend.