As per the title really, as soon as my car builds any boost, it hesitates/misfires really badly and I have to back off.

It's a 2000 Turbo 2000, VF35, STi 8 top mount, yellows, de-cat, full system, ECUtek remap, last rolling roaded at 324bhp by an owner a couple years back. The car is known on here by at least 2 owners.

I bought it and have just put a fresh bottom end in there, and fitted all modifications over onto this engine. Worried the previous owner has taken some vital parts off the car which could be causing this issue....

Apparently should boost to around 20-22 psi, but i've not seen more then 10 psi before it just quits on me.

Any ideas?

 

Check boost solenoid, plugs and coilpacks.

 

Plugs were changed today, awaiting new leads and coil pack. Going to look at the boost solenoid tomorrow as it looks to have an after market thing on there, but no boost controller to be seen....

 

Could be head gasket, as had this issue, changed sparks, coil pack etc. then had a sniffer test done, and head was on its way out. eventually did go. not good.

 

It better not be, as it's just all been done with Cometic MLS head gaskets on it!! lol

 

Just a thought mate, I had a new short block, head gasket only lasted a year. pants, but only throwing ideas bud.

 

Yeah no worries mate, i'll compression test it tomorrow to be on the safe side, cheers!

 

Sounds like a vacuum leak

 

Thanks, i'll check all the vacuum lines today also

I'd love to think that's all it is.

 

some good tips and highlights on misfire problems here:
http://www.mkivsupra.net/vbb/showthr...fire-diagnosis)

 

Thanks for that....

Changed a split vacuum pipe from boost solenoid to turbo, and also split Y pipe on the intercooler....went for a run...

No better. In fact, it seems to be getting worse.

I'm wondering if the previous owner has taken the mapped ECU out and replaced it with a standard one, as I done this today, and it made no difference whatsoever. Is there any way to tell if the ECU has been mapped? Has been ECUtek'd at some point, and has been mapped by Enginetuner in the past.

Also, joining the two plugs together under the steering column showed no fault codes, yet with them still plugged in, the car revved a lot better on the road, obviously not going anywhere quickly....

Starting to do my head in now and ready to put it on eBay lol!

 

So you have no idea whether the engine, as it is at present, matches the map?

Sounds like you have anwered your own question bud.

 

I had the same issue, I changed the coil pack, is it in the centre of the inlet manifold ?

I replaced the plugs and coil pack which sorted it for about a week then started again, my leads were breaking down causing the coil to loose power/spark, try and feed the power in slowly I found it didn't do it ?

I also tried regapping the plugs to 6.5 mm this helped also, try this if it gets better you know it's a spark issue

 

Hello mate,

Any joy on getting to the bottom of the problem?

 

Have you cleaned the boost solenoid or tried a known good one?

To clean a 2port, remove 2 pipes, connect the green connectors under the dash and blow carb cleaner thru it until it becomes clean, for a 3 port do the same but block off the top pipe i think.

https://www.scoobynet.com/showpost.p...92&postcount=2

http://www.scoobypedia.co.uk/index.p...ontrolSolenoid

Both better guides

 

I forgot to update this thread...


I replaced the plugs, but the issue was worse, so took them out and regapped them to what Autodata says the gap should be 0.7-0.8 IIRC, improved it slightly....

Slowly working through a multitude of issues mate. MAF was/is shot, tried it with a known good one, and the hesitation is gone. Still won't boost over 5-6psi though....glad it's just a weekend toy and not my daily drive!

Boost solenoid is next on the list, as it has an aftermarket thing on there at the minute, no idea what it is/off, but going to get a standard 3 port and switch it over to see if it makes any difference.

As above, the hesitation was due to a faulty MAF, but it still won't boost over 5-6 psi, when it should be boosting to 20-22psi....