Misfiring Gti6/mi16 Hybrid

[markw 1]

Gents,

 

I ahve a misfire with my GTI6/Mi16 alloy block engine, its at both idle and throughout the rev range, the engine a new build with only 200 miles on from new,

it is fitted with omega pistons, catcams 4903271`s as below, double valve springs, solid lifters, verniers, jenvey ITB`s Emerald K6 ecu etc. cam spec it may matter.

clearance [cl] 0.25mm 0.25mm

duration [0.1mm+cl] 285° 277°

duration [1.0mm+cl] 252° 244°

valve lift [cl=0] 13.25mm 12.75mm REQUIRED PARTS

cam lift - -

peak angle 106° 106° followers: CC004

timing [1.0mm+cl] 20/52° 48/16° retainers: 99317

lift at TDC [cl=0] 3.90mm 3.35mm springs: PAC-D12009

 

If you unplug injector 1 the engine speed(according to the laptop) drops by about 80-100 rpm, if you unplug any of the other injector plugs the engine speed drops by

300rpm on a 1200 rpm idle, it makes no difference if the engine is warm or cold. a list of things we tried in order of doing them,

 

1, Changed plugs around - no difference

2, Changed plug leads around - no difference

3, Changed plug leads 1 and 4 around on the coilpack (intermotor 12613) - no difference

4, Changed injector plugs from no1 to no2 to check ECU injector driver - no difference

5, Compression tested - and all are within 10% of the max

6, Changed the injector postions from no1 to no3 - no difference

 

the no1 plug fouls up as you would expect if it was a weak spark but it isnt. the only other thing we think is if it wasnt getting enough air, but after checking the butterflies they all

open together and look like they are all operating together correctly

 

anyone with any ideas please!!

 

cheers Mark

[stu8v 68 1 Cars]

I assume the T/B's have been balanced?

[markw 1]

Stu,

 

Premapping they were, could they of gone out of balance like carbs can???

[NeilGTi85 5]

Lambda?

[Anthony 1,003]

Does it miss under load / WOT as well, or just at idle and light throttle?

 

If it's just idle and light throttle, an air leak or out of balance throttle body could potentially cause this - certainly worth double-checking the balance with a synchrometer to make sure that all is OK, even though in theory (but not always practice!) Jenvey's should be balanced as a pair.

[welshpug 1,662]

we had similar issues with Dan's jenveys when we took it down to Sandy to have it mapped, the butterflies were not all central and both spindles were twisted, one thing Sandy did say was that he much prefers to use the throttle stops to set idle not the air bleed screws, and that he will usually block the bleed tracts up totally with sealant.

 

also check that you are getting true WOT, Jenvey's as standard do not!

 

the issue wasn't present on WOT and larger throttle openings at all however, only on idle and over run.

Edited January 16, 2012 by welshpug

[markw 1]

Guys,

 

Firstly there is no lambda fitted,

 

Anthony/WP

yes it does do it on wide open throttle too, didnt notice it when we mapped it but its such a small amount

who knows it may of been there.

 

going to borrow a mates carb balancer to check on wednesday, lets see what that says,

 

i did visually inspect the throttle plates and they all seem to work the same and open the same

amount together????????

[Neilpug 0]

Guess its all sorted now after your results !!

Edited May 13, 2015 by Neilpug