Missfire Problem
 

Hi I'm pretty new to this forum been reading through it and have found loads of useful information. I was wondering if you could help me.

I bought my first Subaru 97 JDM WRX which had a known head gasket failure. Got it really cheap. It was running fine just a little warm. I had to wait 2 months to save up the extra to get the work done. It was in my garage for the two months where I was cleaning it giving it the once over. The battery went flat a couple of times so I charged it up.

The morning I drove it to the garage it was running really rough. I think it was missfiring. It feels like it is running out of petrol very stuttery just like a missfire.

They fixed the head gasket and every other little thing they could find wrong £1600 later I got it back. They road tested it they said it was fine!

I drove it half way home it started doing it again!

It idles fine.

The day I picked it up I ran it on 99 Tesco when it was fine. Since then on 98 Shell so it may have something to do with this? The bloke I bought it off said he ran it on 98 Shell.

Or could it be something simple like plugs and leads?

Any ideas appreciated.

cheers Jamie

Definately best to start simple.

Is the misfire on Boost only ? Part throttle only ? Or all the time ?


Were the plugs replaced with the headgaskets ?
If not , How old are they ? & are they gapped correctly ?
Well worth replacing if they have not been replaced.

Does that cure your probelm ? Well we don't know yet :D

Unplug a HT lead in turn & see if it makes a difference to the engines tickover/ running, If one makes no difference it would point at a faulty Ht lead.

O2 Sensor / Lambda Fooked. Turn car off, Unplug lambda start car & drive

Has this cured the issue ??

Maf Sensor Fooked.

Warm car up, Unplug maf whilst running, If it still runs Ok, Drive the car OFF BOOST.

Has that cured the issue ??

If the car Dies , SPlutters & runs like a bag if Sh!te whilst the Maf is unplugged then it is probably not the Maf

Best of Luck

Dean

Missifre
 

Thanks for the speedy response Dean.
I'll start at the top and work my way through them.

What brand is the best for Spark Plugs and Leads.
Oh and where can I find info on the correct gap setting for the Spark Plugs for my car?


Thanks Jamie

I think yours should be NGK PFR6B or PFR7B if your running high Boost.
Gap them to 0.65mm accurately. Others will say 0.7mm
You could go for a quality lead like Magnecor Or just stick with the standard
Subaru Impreza Turbo Parts, Tuning, Spares & Accessories - Ignition - Plug Lead Sets -

Best of Luck
Dean

Plugs and leads
 

I usually put a set of Magnecor Leads on my cars as they are very good quality.

What about Denso Iridium plugs are they not meant to be the best?
SVK20R-Z8 ???

They will be fine as long as they are an equivelant, Everybody uses the Ngk & you never here of many if any troubles, There was a test done with the Denso Iridiums in Jap Performance on Project Scoob, It lost something like 15 Bhp as they just did not suit the motor due to the electrode design, They switched back to Ngk's & all was well.#No two things work the same on all cars :D

Dean

Plugs
 

Just fitted some NGK plugs today but I'm still awaiting my new leads to be delivered this week. Just wondering what torque the plugs should be set to as they were not very tight, they came undone very easily.

I think my problem is the leads as one of them fell apart when I removed it from the coil pack.

Fingers crossed it will be all back together next week and I'll be able to start driving it!