6 replies to this topic

[JLH96]

( I posted this in general discussion but thought it would be better off here)

Hey suby fam, hopefully you're all well, just after some advice or any personal experience of the same thing. As of lately my B4 hasn't been cooperating with me. Most times when idling it's quite rough, like makes the car rock quite a lot, then when I go to take off it stutters for a couple hundred rpm then seems to be fine but normally comes back when coming to a stop. Second problem is under moderate or heavy load it won't rev past 4500rpm. The rough idle started after I put about a litre of 91 in it but I wouldn't think that would do too much seeing as it was only a litre. So I'm now stumped. Would love some help thanks guys!



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[duncanm]

could be two things.

 

rough idle sounds like a spark issue -- fouled plugs or failing coilpack?  Either that, or idle speed too low - usually a gummed up IACV. Take off your intercooler and give it a blast of UEC. Wouldn't suggest removing it unless you have new gaskets handy.

 

Is the 4500rpm problem also a result of misfire?

[TSG]

It wont rev past 3500/4500 if it detects excess load or knock. Until the ecu picks up everything is ok again and it perks up. That condition has happened to me with a clogged air filter on the highway one time, no check engine light either. It might need an ecu reset? But if its idling rough, it might be a prick to get it out of limp mode. Its just the ecu protecting the engine from another underlying issue.

[JLH96]

could be two things.
 
rough idle sounds like a spark issue -- fouled plugs or failing coilpack?  Either that, or idle speed too low - usually a gummed up IACV. Take off your intercooler and give it a blast of UEC. Wouldn't suggest removing it unless you have new gaskets handy.
 
Is the 4500rpm problem also a result of misfire?

Okay thanks matte I'll give that a try I'm hoping it's just sparks for rough idle.

No the 4500rpm started after I got my catback put on


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It wont rev past 3500/4500 if it detects excess load or knock. Until the ecu picks up everything is ok again and it perks up. That condition has happened to me with a clogged air filter on the highway one time, no check engine light either. It might need an ecu reset? But if its idling rough, it might be a prick to get it out of limp mode. Its just the ecu protecting the engine from another underlying issue.

I've just replaced air filter with K&N high flow so not too sure about that mate. Does a ecu reset just involve disconnecting the battery?


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[TSG]

If its an oiled K&N (I think they all are), you've dun-goofed. It needs to be the dry unwashable type. Genuine is the best and flows just fine, or STi, it takes the same size as WRX I believe. I've used a Cosworth before too. You'll have to clean the MAF with CRC Mass Air Flow Sensor Cleaner if you've used an oiled filter - do not touch the MAF element, just follow the instructions on the can.

 

Catback (after the cat) shouldn't require a re-tune. But if the cat was changed for a higher flowing one, it would need a re-tune.

 

Yes resetting the ECU just involves disconnecting the battery for 10-15min. If your car has the Brant alarm still, this can be problematic as the code may reset - but it should be fine. 

[JLH96]

If its an oiled K&N (I think they all are), you've dun-goofed. It needs to be the dry unwashable type. Genuine is the best and flows just fine, or STi, it takes the same size as WRX I believe. I've used a Cosworth before too. You'll have to clean the MAF with CRC Mass Air Flow Sensor Cleaner if you've used an oiled filter - do not touch the MAF element, just follow the instructions on the can.
 
Catback (after the cat) shouldn't require a re-tune. But if the cat was changed for a higher flowing one, it would need a re-tune.
 
Yes resetting the ECU just involves disconnecting the battery for 10-15min. If your car has the Brant alarm still, this can be problematic as the code may reset - but it should be fine. 

Unfortunately it is an oiled one

Thanks for the advice mate


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[Robbks]

-K&N In the bin
-CLean AFM
-Reset ECU
-Check entire intake for Air Leaks (incl BOV, under manifold intake pipe, Recirc pipes on Secondary turbo, under the TMIC, inside the BBoD, inatke manifold, etc)
-check exhaust for leaks

test-drive.