7mgte miss fire!!

[rollsy]

hi guys!

Well my lux has finally gone to be dyno tuned but as always nothing is simple

firstly here is the rundown

its got a single turbo supra engine (7MGTE) running a wolf3D version 4 ecu in a 90 model hilux.

it has a bad missfire underload anywhere between 3-5000 RPM ranging from 3 - 7 pound boost

it has a good crank angle input signal to the computer and is running a rb30 optical crank angle sensor

the computer is registering a missfire code but we cant figure out wat the problem is.


any ideas???? throw any ideas at me no matter how stupid they may sound.

cheers
rollsy

[Vios-GT_07]

are your cams on right? is timing good?

[rollsy]

yes timing is good..
wat do u mean by cams on right?

[Vios-GT_07]

cam gears erm.. could have skipped a tooth?

[EldarO]

it could be tuned like dog shit.

because its a standalone computer, the spark/fuel maps might be up the shitter.

check that, you could be leaning out, or drowning it in fuel.

heaps of black smoke pouring out the arse end under load?

Eldar.O.

[rollsy]

nah because i just dont the head gasket and they are spot on!
any other ideas?
and its a very random miss.. only happens under medium load..
but we put new spark plugs in.. and they were gaped at 1.1 and are meant to be 0.8 would that matter?

[rollsy]

we tried leaning it right off and richining it up but made no difference either way it does blow lots of black smoke when it misses even blows flames of a night (plenty of unburt fuel)

[thechuckster]

'sounds' unrelated to amount of fuel, therefore look at spark system...

mechanical:
dud plug leads
cracked spark-plug connectors
poor earth to ingiter(s)

ECU:
dwell correct?
is timing consistent (e.g. what do the logs say)
is something pulling timing out (knock sensor, dodgy input from optical sensor, etc)

plug:
rumour suggests smaller gaps for turbo engines... set gap to what the TSRM says not the back of blister pack

[rollsy]

the wolf3d ecu is not smart enough to register a code from an output signal this is wat leads me to belive something other than the basics is a miss

the wolf 3d can only really register a code from the input signals hence crank angle ant temp ect ect but wont register a code from any output signals hence coil leads plugs ect.

the input signal from the crank angle sensor is perfect its a fine crisp signal measured from both the sensor and the input to the computer
cheers rollsy
p.s
timing is consistent! i will also try reseting plugs at proper gaping!

[thechuckster]

i don't expect a code to be returned - but if a sensor is providing noisy data or occaisionally dropping out you might see a dropped spark or injection event - viewing log files will show you this, you wont see it staring at a real-time display.

i'd suggest you re-check cabling, connectors, etc... most electrical problems are mechanical in nature.

[EldarO]

sounds like a dud plug or lead to me, the spark plugs can crack around the ceramic part along the top, especially if they receive a slight knock, or are dropped during installation, and even the slightest crack, that you can barely see, can cause problems.

the main things with 7M's is that the cam covers can leak like a bitch, and fill your plug wells up with oil, resulting in a miss/loss of power.

so, check your leads, plugs, make sure the leads are seated properly on the plugs and coils, and that the wells arent filled with excessive oil (theres always some in there, this engines a bastard.)

Eldar.O.

[Vios-GT_07]

i don't expect a code to be returned - but if a sensor is providing noisy data or occaisionally dropping out you might see a dropped spark or injection event - viewing log files will show you this, you wont see it staring at a real-time display.

i'd suggest you re-check cabling, connectors, etc... most electrical problems are mechanical in nature.

which is why i never like aftermarket ECUs.. but yeh if u got a modified motor that's the only way to go..

i'm with you on that, and eldar o about the oil in the wells.. happens to 4A-GEs as well and those darn plugs in deep below the rocker covers.. it's not very hard to fix, but is darned annoying isn't it...

apart from timing consistent, maybe u can up it a bit more? considering u've got black smoke and popping fire.. also maybe lean it out a bit and see if it gets better or not..?

[1200det]

Spark Plug gapping ?

Ive also had this problem with new NGK Copper plugs and went to Denso plugs and it was spot on , The yanks also have problems like this with NGK Copper plugs if you dont gap them.

Just a thought.

.

[rollsy]

thanks for your input guys i really apreciate it

absoulutly no oil at all in the plug tubes

and i will double check all the connectors
also plug gaps are high on the priority list
thanks again will keep you informed keep the ideas coming

cheers Rollsy

[jonra23]

Is your loom from Crank Angle sensor well shielded and routed away coils and high tension leads?

regards
jon