Jump to content



Recommended Posts

long running issue ive been having, i have a missfire at 5800/6000 rpm ive upped valve springs, dropped plug gap from 1mm to .5 played with dwell, put capacitors on the coil trigger wires but same issue every time. hoping someone can provide some insight.

im running a v6 ecotec ls1 coil on plug

Log 2016-12-9 12;35;17 pm.llg

Link to comment
Share on other sites

Couple initial thoughts.
You are running almost 24 degrees timing. I dont know the engine you got but isnt that alot? And this is at 1.7 bars of boost and rising. What fuel?

Also you are at 10.5 afr... this isnt by any chanse a rich missfire?

Knock signals seems to top out. Sure it isnt knocking? Knock control is effectively turned of by some of the settings.

Edited by Steve
Link to comment
Share on other sites

The knock sensors arnt accurate and it seams to like the timing so thats what i give it, e85 fuel so pretty safe. Its been 10.1 @139 but im hitting this limiter before i cross. I tried pulling timing, tried pulling fuel till egts on other cylinders were to hot. Its rich because of the miss fire. I went back to gate pressure (16lb) same issue. Ran another ground to motor same issue. Everything ive read say the ls1 coils are about 4ms for full charge, ive tried them as low as 2ms same issue.

Link to comment
Share on other sites

High 900s.

It does it when i pull 10lb of boost out of it as well. lean while there is extra unburnt fuel going past the 02?

Idle is terrible with the moran injectors and hardly concerned about that atm

Coils are all individual from ecu, coil ground to front of head, ecu ground to back of head. i now have capacitors on the trigger wires incase it was noise. positive is a heavy gauge cable splitting off just infront of coils

Link to comment
Share on other sites

  • 1 month later...

So ive leaked down no5 and 25% so not bad, cleaned injectors and tips were black on cyl 5 and 6, 5 being the worst.

Ran it on weekend and cyl 6 drops out during the burnout stays at 300, during the run 5 and 6 are down 100 deg as it gets in to revs, kept pulling fuel and made no difference really struggled to get mixtures in the 11s. Ill post the log later

Link to comment
Share on other sites

Its logged under something else, its an ecu log file so not all things logged. No fuel pressure but. 

This is a pic of injectors after 6 passes at track. Im getting a black sticky buildup on injectors 5 and 6 everytime. Any injector in those cylinders do same thing


Edited by jervies
Link to comment
Share on other sites

Hi ,

looking at the deposit on that injector tip to me suggests possibly oil.

What does the deposit smell like.

Oil coming back past the intake valve due to backfire, incorrect firing order, valve overlap which should be evident on all injectors.

If hydraulic camshaft to much pre load on that lifter, pumping up holding valve open at rpm, bent valve, poor valve seating.

If solid, too little or no lash causing valve to ride.

Intake manifold has poor underside seating or blown gasket, this leaves an opening directly into the floor of the inlet runner.

Any excessive blow by or poor crank case scavenging can lead to excessive crankcase pressure which can be seen normally at the front crank seal, rear main at times or if the intake has an issue as described.

As you can see there are many possibilities, first we need to address the BLOODY OBVIOUS, WHAT is the deposit on the injector tip consist of.

As for your leak down if i had 25% i would be concerned. (PURELY MY OPINION).

How do the other cylinders compare.

I have been looking at your logs.

Can you please give me a brief run down on what your engine combo is etc.

Does the intake manifold have an EGR crossover passage or anything strange like that.

Do you have a PCV fitted or any type of crank case vacuum scavenging devices. 



Edited by Dave Kriedeman
Link to comment
Share on other sites


 still taking into consideration of the above mentioned things to be checked and confirmed,

i have also analysed your LEAN spot PCL FILE and the corresponding data log.

Please take no offence to the following, i am just trying to help out.

Both the FUEL and IGNITION tables really need some work as far as the entered values etc.

Not much makes sense in there when doing a comparison in relation to the data log.

May i also suggest running some finer resolution via more load and rpm points if tuning via data log or make sure the dyno can sustain the load cell  accurately if load cell tuning on the dyno.

If the dyno is holding the load nice and steady then you will get away with fewer load points as the ECU can very easily and accurately INTERPOLATE between the cells.

However if there is a mechanical issue with the engine it could be the reason for such strange fuel table numbers.

The IGN timing table using, E85, METHANOL or what ever are also extreme at some points, with quite large changes,from some adjacent cells.

Just remember that all TABLE cell values influence the cells around it which has a snow ball effect to a degree.

So for example the very large fuel cell numbers at low RPM and high Boost values in your MAIN FUEL TABLE even though you wont see that boost at that rpm , the values will still influence those around them through INTERPOLATION.

Does the rear of the intake manifold leak oil.






Edited by Dave Kriedeman
Link to comment
Share on other sites

Yeah my map is shit at the min, everytime i go out im changing things on the fly, and have been for 12 months with this issue. I checked lifter preload and there's heaps, im working on a fix to go solid, i might try fix preload in the meantime. Ive got decent breathing and no oil leaks, ive had the manifold and head off double checked everything and still same issue. My deadtimes are completly wrong so ive been working on fixing that aswell.

Its a series 2 v6 buick motor, gt35/40 turbo, 1600cc morans, e85, ls1 coils, c4 transmition powering a 1580kg vt commodore. Its being tuned on the track no dyno.

Im not 100% sure on the deposits, they seam to be oil. I think i really need to fix the preload issue and eliminate that first. 

Thanks for the help 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...