Vs l67 into VH running rough and crossfiring when cold only

[vscom88]

My ecotec (l67 top swapped) runs like a bag of **** and fouled up 4 of 6 iridium plugs only when cold. It's currently in a for a tune but we can't get the damn thing going properly despite mucking around with AFRs and map/maf tunes.

It would idle lean (as per the wideband gauge) and once at operating temperature it would be fine. It has since, leaving my house, decided to cross fire and back fire in the left exhaust bank in the extractor at the collector. I have 9mm eagle leads, iridium plugs which we swapped out for brand new std ngk ones, coilpacks from mace engineering (not msd) and a Bosch dfi off eBay (both done in 014 when it was running like poo when cold). I have injectors that have been serviced by myself but not flow tested (will be replacing them with flow tested ones I bought).

I had it going OK then we put an old map tune in with a map sensor and adjusted it to suit for the further mods and now even reverting back to a stock maf tune it just sounds like it's cross firing.

The car doesn't want to run right when cold but when it heats up it runs ok. Initially it was just running rough with the occasional pop in the exhaust and idling at about 16.5 there abouts.

I fitted a 4" intake pipe on and stuck the maf on the very end which caused it to start back firing from just running rough.


A quick run down on the mods are;

Fresh block and heads with just 6000ks on it.
Oversized valves, forged pistons @ 40 thou over size. Block been decked to 0 and heads modified to suit extensive lift. (1:98.1 mace rockers and .307" on the cam) it has LS1 throttle body and wide band o2 sensor in the passenger side exhaust bank. 10:5.1 cr, 87mm pulley and l67 injectors with new o rings and baskets. I have 1000cc injectors for when it goes to e85 which aren't being used yet. It also has a new fuel filter with a new 450lph wallbro e85 rated fuel pump.

I've missed lots of stuff so if there's anything else you need to know I'll answer it.

This is driving me crazy and I just want to sort it out.

 

[car_driver]

Doesn't the block on the supercharged V6 have a lower compression and different internals?
It would need a touch up tune to run properly I'd say?

 

[vscom88]

You must've misread the first paragraph.

We've mucked around with afrs and going from maf to map tunes. None of which seem to be working out very well.

 

[The1]

if it's idling at 16.5:1 it will be popping as you'd expect, it's just to lean, 14:1 will be loads better.

But without datalogs etc it's hard to know if there's anything else at fault, if your 1000cc injectors are genuine bosch use them now.

 

[_R_J_K_]

Have you tried running stock gear for the intake side of things? I'd throw the stock throttle body and intake as a start for trouble shooting.

Is that left bank issue with both sets of plugs?

Which MAF are you using? Take it you're also not running a Delco ECU?

 

[vscom88]

if it's idling at 16.5:1 it will be popping as you'd expect, it's just to lean, 14:1 will be loads better.

But without datalogs etc it's hard to know if there's anything else at fault, if your 1000cc injectors are genuine bosch use them now.

Thanks for the reply mate, I'm worried that if I put the 1000cc Bosch injectors in now I'll flood my motor?

The afr has gone all the way to 21.4 and started popping at that ratio only. Previously it just ran rough at the slightly less leaner ratios.

 

[vscom88]

Have you tried running stock gear for the intake side of things? I'd throw the stock throttle body and intake as a start for trouble shooting.

Is that left bank issue with both sets of plugs?

Which MAF are you using? Take it you're also not running a Delco ECU?

Hey mate 4 of 6 plugs fouled up. I'm not sure which 4 yet.

Thing is I had it running better than what stage it is in now with all the same gear and it was only just rough on cold running. And I'm using a Delco ecu for both the map and maf tune.

 

[EYY]

Guessing you assembled it yourself? It could be as simple as a vacuum leak or exhaust leak.

If it only happens when cold it's probably when it's running in open loop. In that case it's probably just an issue with the tune. Does it lean out under load?

Anything above 15 would have me very worried under load. You can do serious damage very quickly running so lean.

 

[vscom88]

Guessing you assembled it yourself? It could be as simple as a vacuum leak or exhaust leak.

If it only happens when cold it's probably when it's running in open loop. In that case it's probably just an issue with the tune. Does it lean out under load?

Anything above 15 would have me very worried under load. You can do serious damage very quickly running so lean.

Yes I did assemble it all myself. All the vac leaks have been sealed up which brought the idle better but the way it idles now is a crossfire. There's no way that a vac leak could possibly do this.

I haven't pushed the car yet to see what it does under load but cruising conditions was around 15/16

 

[Immortality]

So it's cammed up with a **** load of comp for a boosted engine?

Sounds like the tune needs a lot of work.

What plug gaps you running? Standard gap on 10.5:1 CR probably ins't going to work either (especially when it's lean as ).