still running it in at the moment, but when i first used it after rebuilding the engine, i used the old plugs with the intention of changing them when finished the run in.
however, was jerky as hell, and couldnt drive it properly. changed the plugs (to pfr 7b's instead of 6b's).
that solved most of the jerkyness, however, it is still there intermitently

it mainly happens when cold. today, i got onto the dual carriageway and accelerated swiftly to 70ish. when held at 70, it was jerky constantly, as if was running out of fuel etc.
also, the other day, pressed the throttle to accelerate, and it lurched quite badly.

any ideas? if i cant solve it soon, im getting rid, as it pisses me off.


cheers
ian

 

Does it get better when it warms up?
My wrx had the same problem and it didnt go away even when warm, turned out to be a fuc*ed up ecu as when the rebuild took place and rebuilt, the ecu could not understand the new settings the engine was at,hence not knowing at what rev to keep the engine at and so the "out of petrol affect".Problem was solved with a new ecu.....it was expensive!!!!

 

Check for air leaks. All pipes, clips etc everywhere. Are they all going where they are supposed to? eg MAP sensor. What about your wire cutting for the Apexi gear?? Everything definately correct? Are the fuel lines on the right way round ( feed/return, although I dont think it would run at all if wrong )All wiring intact?? Engine earths good?
What voltages are you seeing when the jerkynes occurs?

 

Ian

Might be worth checking the fuel pressure too, sounds like lean stumble, this would be worse when cold. As your last motor melted a piston, I'd be careful until you identify the cause

How does it run under power ? what's your lamda reading when it 'jerks' ?

Check that the plug is on your coolant temp transmitter, I had this plug split and it ran like a dog (under the intake plenum)

 

thanks for the replies

gangstor, your not meant to say things like 'new ecu'

steve/andy. yeah, i will have to make a proper check, unplug and reconnect everything again etc. when it jerks, ive not looked at the afr, but i did note that the boost (still low boost at moment) was perfectly smooth, no fluctuations.

i did bodge one bit, which ive just remebered with you mentioning the lean effect andy. when i fitted the new pump (walbro), and had to cut the wires to fit, well i couldnt find any connectors at the time, so i twisted the wires together and taped them up oops.

will rewire them tomorrow to be sure.

i am sure the apexi wires are all fine. one thing i noticed is that my boost guage backlight is not working. this happened when it was knocking the boost back to 1 bar. then one day, jumped in and it went back up to 1.8 and the light was back on the boost guage.....could a dodgy earth be the problem then
car electrics eh

ian

 

say if i eliminate the fuelling side of things, would a select monitor at the dealers pick up an error?

 

I dont have much faith in the dealers abilities to use their diagnostic computers. It will probably be something simple, that their computer wouldnt pick up anyway. Intermittent faults are a bollox though

 

intermittent as in 'they only happen when your not searching for them'

 

relocated that earth before, boost guage backlight now working again.

step no.1 complete anyway

 

new coilpacks?

 

im starting to think the same

however, i dont know for sure thats the problem, but starting to think it is.

they are expensive arent they?

cheers
ian

 

They are, but the ones from Oz arent. Including postage, they will only be about half the price of standard ones. Apparently they are better, but still havent fitted them yet. Should be around £25 each.

 

that dont sound too bad steve

i think i will see if anyone has any i can borrow to eliminate it first, as i dont want to buy some then still have the problem

a funny thing i noticed before though. jumped in the car at about 2.30pm, and both the clock on the dash and stereo were showing 11.08 !!
im thinking that the power supply from the battery must have gone iffy at some point, but its lost 3hrs!
so ive cleaned the connections etc, and will see if its any different later.

could the pfr 7B plugs be too cold for the engine, especially as im running it in?

ian

 

forgot to say, i looked at the afr meter before when it done its jerking bit again. i was on very light throttle. the voltage was still cycling up and down the range as it does when cruising.

 

7B's should be ok crusing around, i've had them in for a few thousand miles now.
I guess it is possible that your new piston rings are letting a bit more oil past until they are 'run-in' ?? What did you gap the plugs at ?
Coil packs failing usually cause missing at high boost, not cruise/light throttle.

I can send you a good set of NGK 6's with the other stuff. They have done less that 1k miles, I just changed to a different heat range. Worth a try.

 

andy, rings were gapped at:
top: 0.23"
2nd: 0.23"
oil: 0.25"

pistons are 3 thou clearance.

its a good point you mention actually, it has used a little oil while running in (only done 400miles so far).
the jerkyness mainly occurs when cold too.

you dont happen to have a set of spare coilpacks i could try do you? they are the two bolt fixing.

ian

 

oh yeah, you mention the coilpacks affecting at high boost rather than light cruise.
mines only running circa 0.5 bar max at the moment, no more than say 40/50%throttle, and 4000rpm max.

cars eh

 

me again

think i will do a compression test tomorrow after work, see if that shows up anything dodgy, or low readings.

 

David

 

update.
been trying it the last few days.

its practically only jerky when cold, and if you drive like a fanny, it doesnt do it much.

i suppose it could be due to the clearances etc that this car is gonna be a tw*t when cold.
seems to be fine when warm, hardly ever does it, if even at all.

suppose it may improve when run in properly and given a bl**dy good thrash