let missfire

[belly257]

just took my let nova out to see what was what as ive just finished sorting the whole car out, anyways it seems to have a missfire or like hesitation when the boost is coming in and its very bad,it has a intank pump off a mpi astra (which ran a red top fine) and it has blue injectors and has what looks like an ecotec fuel rail on it for some reason the previous owner showed me it running in a vectra and it ran fine and drove fine, it seems to do it only when its driving, ive got a few things to check tomorrow it could be the timing out a tooth or c.t.s or may be the fuel pressure, o the lambda sensor, but anyways thought id ask youse guys on here first before i have a play tomorrow, any ideas?

[R1CH]

Blue injectors ? weren't they just fitted to the later XE's ? what fuel pressure you running ? Never came across an LET running Blues, could be the prob ??
Is it just on std management or phase 2 / 3 ect ... ?
Obviously check plugs (plug gaps), leads, rotor arm, cap ... what boost are you running ?
If the boost is set to high (actuator wound up) then that could cause the ECU to cut the boost - makes it seems like it has a bad missfire when on boost.
Could be any number of things tbh, LETs are a pain in the **** when they aren't running right.

[belly257]

its running pj evo 5 chip, and the boost is set at 20 psi (so ive been told) leads rotar arm dizzy cap and plugs are all brand new its runnig standard fuel pressure as far as i know it revs up fine when not driving, maybe get a proper gsi/gte fuel tank and a adjustedable fuel pressure regulater?

[Philsutton]

could be the VXR blue injectors? if they are the xe ones then you need to change them, especially if you are using evo 5 chips.

Fuel pressure needs to be about 4.5 bar with yellows (?) and 3.8 on saab reds. As far as I can remember.

Also check the spark plug gap, the amount of times Ive had people with miss fires on turbo cars only to find they are running about a 2mm gap.

[craig green]

Plug gap is what I was going to say, new plugs are useless if the gaps are too big.

Make sure the engine block is well earthed also. When it comes on boost, the ign & electrical systems will begin to draw the most current.

[ck]

if it is on xe blues then your asking for trouble and cearly just waiting/wanting it to blow up very soon.

yellows aprox 4.5bar
vxr grey injectors aprox 3bar

it should have the let fuel rail still no matter what tbh. you get any pics of the injectors for us to confirm?

management light on at all?

[meritlover]

sounds like a lean missfire if its happening under load/boost. possibly due to the small injectors. this needs to be sorted out soon-soon. and you need to know exactly what fueling and boost conditions your chips mapped to as this will be sure to end in tears (not meritlovers tears, your tears)

also check all vacuum/ boost pipes and jubilee clips for leaks and holes. and get a boost gauge on there so you can see whats happening.

a wide band O2 sensor would help too.

[belly257]

its go them injectors and fuel rail on it by the looks of it:
http://cgi.ebay.co.uk/VAUXHALL-OPEL-VXR-FUEL-INJECTORS-Z20LET-Z20LEH-C20LET_W0QQitemZ350118176218QQcmdZViewItem?hash=it em350118176218&_trksid=p3286.c0.m14&_trkparms=72%3A1432%7C66%3A2%7C65%3A12%7C39%3A1%7C 240%3A1318

i didn't want to change anything on the engine as i heard it running fine in the previous car, but i may have upset something or different fuel pump could be used, can get pics of anything if anyone wants pics to help me out:thumb:

thanks guys

[belly257]

think it could be the crank sensor now as ive just had a play with it and its stopped sparking, went over everything except crank sensor:confused: