Craigieloon

Just done an engine rebuild on my EJ20. Its a 1994 WRX. Had a problem with car running on 3 cylinders but sorted this with a new coilpack. Im getting mega backfires on idle and the car sounds like its out on the timing (popping thru the filter and exhaust) but ive checked and the timing is spot on.

I have zero codes on the ecu... could anyone shed some light???

Craigieloon

any idea's.... when cold it does struggle to start and hold revs... but once up and running it seems to bog down slightly then pick up, but i occasionally get a pop and a bang through the filter and exhaust. as said no codes.. Its got a new cam and crank sensor, also a new 3 wire universal lambda sensor. I thought it could be coolant temp sensor but fans aint coming on. ive not driven the car yet as she's still on axle stands after the rebuild. she's idling high and rather rough...

black smoke does come out which looks like she's running rich.
Mods are

FMIC
ESL Chip
Walbro pump
Gruppe S Headers and uppipe
TD05
blitz filter
bailey dump valve

Jolly Green Monster

iTrader: (4)

check the coilpack connections.. black go to the rear cylinders, also check the injector plugs.. again black or darker grey go to the back.

I suspect you have on or other wrong if you are SURE the timing belt is correct...

Simon

v8voodoo

I know this may seem a bit like teaching you to suck eggs by the sound of what you've done, but it happens a lot with engines with more cylinders and can be easily overlooked, but have you got the leads on in the right order..?

Double check all the casics, then start looking for trickier stuff.

Hope you figure it out.

Craigieloon

yeah ive tried the swapping, taking the rubber boots off, checked for cracks. It has to be summin simple... was hoping for the cavarly to come along with a quick fix...

Jolly Green Monster

iTrader: (4)

check cam wheels are correct..

Craigieloon

how do ypu mean mate... the cam wheels on the right side???

They have to be cos they need the pick up from the cam sensor.... Plus they have left and right, on them...

Jolly Green Monster

iTrader: (4)

the only one that has to be right because it is running of sorts is the one with the cam pick up on it..

seen exhaust and inlet cams wrong on one side before.. therefore the wheels were wrong.. this is terrible as v8 says, feel like I am teaching you how to suck eggs.

you have to have something wrong either injection or spark wrong.. either the coil pack wiring is plugged the wrong way, the injector plugs are the wrong way, the cam belt is not on correct, or the cam wheels / cams.. or you have no compression on one or more cylinders ( either because of cam timing or due to damaged valves).

Have you removed the injectors from the rails? or did you just unbolt the inlet manifold and refit it? could have an oring leaking on an injector.. you can tell that by removing the plugs and spinning it over with injector plugs off to see if you get fuel out the plug holes.. but keep the coil packs up out the way!!!

Simon

Craigieloon

not investigated the injector side yet. il do that tonight... Heads have to be 100% as they are fully rebuilt units and tested before i installed them. I just unbolted the inlet and bolted it back on with new gaskets...

As for plugging in, i have a white tag around the injectors. I was under the assumption they go to the front. but il check them tonight....

Jolly Green Monster

iTrader: (4)

you have to remove cams to bolt the heads on.. it is possible to then pick up the exhaust cam instead of the inlet cam.. and they fit..
not saying you have.. iirc even the wheels fit on the wrong cams.. so if it is that you won't be able to tell without pulling the rocker cover off.. but I would confirm everything else first. Also worth a compression test as it is possible to damage valves fitting the belt.

it is usually the light colour to the front.. I would be checking injector and coil pack plugs.

Also whilst it is running pull an injector plug off and back on until you find the one with the misfire.. if it is just one then swap a coilpack, plug etc and see if the problem moves.. if it is two cylinders then you know it is something relating to them both like timing or injector plugs or coil pack plugs swapped etc..

Simon

Craigieloon

Right just back and did loads of tests, and playing about...

Ive come up with 2 theories... I disconnected the MAF and she died, Started her back up and off she went... Zero misfires, ran perfect, revs sweet and sounds so much better. Idles at 2k constant... Plugged it back in, revs dropped, misfiring, popping and banging...RUBBISH!!!..

So i think i have a goosed MAF!!!

On the other hand... The orginal ECU that came with the car was sold as it had a fancy chip in it that i knew nothing about. I sold it and bought a 94 WRX ecu... With that i plugged in the ESL chip and away we went....

Could i have bought the wrong type of ECU!!!. I have no codes on it so i cannot tell... Thats just another theory but i do think its the MAF...

What do you guys think.... and what MAF can i use, There are a few for sale but do you have to match the part numbers...

Craigieloon

Still got this issue. Its a random backfire. Just a small pop out of the exhaust. When you rev it up she's fine. Sounds good!!

Its back at idle when you notice it. Ive changed the MAF.. No joy.

Could be summin simple like a faulty coilpack. Plugs are brand new.