Odd 'soft' miss on Blacktop 4AGE / Megasquirt (video inside)

[Talkiet]

Hi guys - I have a 4AGE (Blacktop with Megasquirt) in a 7 replica and the engine is giving me troubles. I lack the skills, tools or time to really dig into this any more than I have already, but if there's something simple I have missed I'd love some pointers.

Symptoms - miss at anything over 2000ish revs - seems most pronounced at about 3500 RPM. Seems much worse when car is sitting still in neutral and not under load. Misfire seems quite 'soft'... Car SEEMS to be ok at wide open throttle as well (!)... I have a Wideband O2 (not running closed loop - just for logging) and it seems to be running a little lean as well although this MAY be due to a small leak in the exhaust (not confirmed or fixed yet)

Youtube video of engine, already warm (out of warmup enrichment), and me holding the throttle at about 3500rpm - eventually)

http://www.youtube.com/watch?v=H9IV9MYzufM

What I've looked at:

- Plugs seem ok, maybe running a little hot



- plug leads all seem ok. Misfire is NOT isolated to one cylinder (removed all leads one at a time and misfire stayed)

- Cleaned and reoiled air filter

- unplugged and replugged the ECU and checked grounds

- Voltage is ok while car's running, but the battery itself is tired.

- Wideband O2 isn't involved (open loop system)

- TPS gives good solid readings (through datalogging from ECU - no jumps and it moves smoothly)

I am beginning to suspect that the fuel system may be the culprit or MAYBE an air leak on the inlet side but I have reached the limit of enjoyment tracking down this issue.

I'm after a recommendation of a good honest mechanic in Chch that knows 4AGEs and isn't scared by the existence of the aftermarket ECU - or as I mentioned, what have I missed that as a non mechanic I could troubleshoot myself?

I should note that I could probably mask the issue by screwing with the tune, but I'd rather fix what changed... There have been NO CHANGES made to the ECU or tune between it running really well and it running not quite so well at the moment.

Any simple insights or recommendations on where to go greatly appreciated.

Cheers - N

[d1 mule]

my best mate Beau has just started a workshop in CHCH (woolston across from the Brewry), he did his time at Miles Toyota and has played with mine and many other 4ages so he is pretty clued up.

his cell number is 0273677368 (i dont know the work number cuz im in Perth)


Tell him Shannon sent you, he will sort you out a mean deal / i just messaged him so he knows about it.


cheers

[Talkiet]

my best mate Beau has just started a workshop in CHCH (woolston across from the Brewry), he did his time at Miles Toyota and has played with mine and many other 4ages so he is pretty clued up.

his cell number is 0273677368 (i dont know the work number cuz im in Perth)


Tell him Shannon sent you, he will sort you out a mean deal

Sweet! Thanks for this - Exactly the sort of recommendation I'm after. I have someone hopefully coming to have a quick look on the weekend but I'll give Beau a call early next week if I have no luck with one final attempt at home.

Cheers - N

[QikStarlie]

i'd say its the tune. or the megasquirt itself. unless of course it was running fine and just started doing this?

wideband will show lean soon as it missfires, as the unburnt mix is entering the exhaust.

[iOnic]

Are you using Tunerstudio?

I'd check your trigger signals in the diagnostics tab using the composite logger (or it may have been tooth logger - been a while). Sounds like you've got noise in your crank position/cam position signals.

[YeMs]

Iv had issues with them in a standard vehicle, getting small carbon build up in the throttles, but more carbon in one or two than the other (essentially unbalancing the engine by allowing a little more air to the other cylinders) and would cause a horrible harsh engine vibration around mid rev range more so under a little load and light throttle, could be considered a soft miss.

Fixed it on all occasions by removing the air box, manually cleaning the throttles with a rag, the running the motor and blipping the throttle while spraying throttle/intake cleaner directly into the throttles.

Of course with the addition of a megafart there could be other issues to do with that