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Brucey 95wrx

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My car is juddering and back firing at 4000 rpm just before the turbo kicks in after having head gaskets replaces 

so far I have changed 

fuel filter 

new plugs 

new coil packs 

green label maf 

turbo is brand new 

swapped injectors with spares 

still the fault persists but no check engine light 

It even stops at 4000 stationary and starts popping and banging 

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Is it definitely firing on all cylinders,  plugs all same colour ,none of the plugs flooded?

Sounds like a misfire , I wired the coilpacks back to front on 1 bank b4 🤐

Had the same symptoms, surprised it run on 2 cylinders at all tbh 🙄.

Try checking engine loom earths /breaks in the insulation on the loom and injector/coilpack plugs .failing that a compression test and check the timing Mark's 

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Deffo firing on all 4 

driving it around town up to 4000 rpm you would not suspect a fault at all sounds good ticks over ok plugs are all a great colour it’s almost as if it is hitting a limiter at 4000 and shutting down the ignition timing which is causing backfire 

compression was at 169 psi on all cylinders before the head gasket was replaced with the throttle closed 

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Your supposed to check compression with the throttle "jacked open " ,although those figures seem good have you checked compression since doing the headgaskets?

If the timing Mark's are out it could cause it to cut ignition at high rpm/load , due to crank n cam sensor readings. 

Are the plugs the right heat type (heat 6 for standard,heat 7 for mapped) are  gapped correctly ?

Have you done a self code check or just think theres no codes due to not having a eml ?

Maybe a code check and ECU reset might help ,along with checking vac lines from inlet ,turbo and fuel pressure regulator too 

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I have iridium heat 7 as running around 330 bhp on a chipped z4 ecu they are gapped at 0.6 

i have plugged the black connectors in and the engine light just stays on no flashes I have disconnected the Battery and left over night to reset ecu 

but still it persists 

is there anyway I can upload a video? 

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There's supposed to clearance for the hydraulic valves , compression readings would probably give you a idea if a valve has positive pressure at cam base circle . Causing a Valve to be jacked open with constant pressure from the cam .

If compression is down , it's very difficult to test valve clearance with the engine in stitu . So just checking that you can turn the lash caps with your fingers (when the cams at base circle) is a easy way to see if the cams are creating constant pressure on a lash cap (causing the valve to stay open)


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If engines still plumbed in , just do a compression check.  It should let you know if the valves are seating correctly.

2 main options for clearance adjustment. 

Measure the clearances with feelers gauge and buy lash caps that are the correct size (about £30 per lash cap)

I always get the engineer to "tip the valves" ,to take the same amount of material from the tip of the valve , as what he takes off the valve seat when machining the valve seat faces 

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17 minutes ago, Brucey 95wrx said:

Only 2 of the 8 on passenger head would twist but how do you adjust these? 

Was that with the cams at base circle ?

Cam lobe should be facing upwards and away from each lash cap so there should be no pressure on each lash cap (have to rotate the cam to check each one)

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Soz bud , people call em different things.

The hydraulic lifter cap that has a shim attached underneath , cam lashes onto it to push the valve .

The shims are non removable on most ej's ,so you have to buy a complete lash cap /lifter to get the correct size shim , to adjust valve clearances 

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I'd definitely start with a compression test (warm ideally) but as long as the figures are above 140 ish and all within 15% of each other , they're within factory spec afaik for a early classic. 


If it was limp mode or a timing issue I'd have thought you'd have a code but if its modded and "chipped " instead of mapped ?. I don't know if it would store a code or whether it's just a sensor reading something out of the maps parameters (then cutting ignition) .

If test comes back good ...

Does it rev freely in neutral or at cruise (part throttle) .

You've definitely plugged the coilpacks and injectors the right way round on both banks ? 

Fairly sure its light grey plugs to both side of each bank are for the rear cylinders for injectors and coilpacks .

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I'm not sure how to post a vid on here other than YouTube,  tbh I doubt it would help .

If it wasn't doing it before the headgasket change ?

Compression test ,to rule out valves being open and double check timing Marks.  As unless you've plugged coilpacks or injectors in wrong those would probably be the first things to check after rebuilding the top end 

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