7MGTE miss while cruising

[Jin~Jah]

Hi all,

I've got an auto 7mgte in an x83 cressida.

Recently it's been behaving oddly at cruising speed (say 70-80k's) with light load. It seems to start missing a little bit, sometimes it's bad, other times it's as if it just drops a cylinder for one revolution and then is fine.

fuel/air wise, It's got an HKS VPC, a 255lph walbro, standard injectors, ~9psi, NA cams, and it behaves fine under load, no problems there. The idle is usually fine, although sometimes it wanders. Doesn't overheat, water temp stays around ~90deg (thermofans).

The bottom end is an apparanlty rebuilt GE unit, after the GTE threw a leg out of bed. We drilled the bungs for the 2x knock sensors used on the GTE, and they are in and i've noticed them work before while testing the car.

It has stalled after missing before, and once it was hard to start afterwards. Slope doens't seem to make a difference, although the first couple of times it happened, i think i was going downhill, but i heard it hesitate today on a flat sitting around 70ish.

Whether the torque convertor is locked or not seems to make no difference, although it's more noticable with it locked since it transfers the hesitation right through the drivetrain.

It will sometimes stall after missing if you knock it into neutral and let it idle while rolling along. If it hasn't been missing, then it usually has no problem what so ever.

There is some oil between the cam covers. I have not had time to clean it out yet, but will do so especially if general consensus is that it could be a contributing factor.

Engine Codes:
14
"Ignition signal - No 'IGF' signal to ECU 3 times in a row"

-I still have to work out exactly what surrounds this, eg where it gets IGF from, and what triggers the signal to be sent

21
"Oxygen Sensor Signal/Oxygen Sensor Heater"

after pulling this I had a look and found the oxygen sensor was unplugged
It's entirely possible the sensor is dodgy anyway... turbo was dumping oil into the exhaust at one point.. replacement sourced, now fine

34
"Turbocharger Pressure"

I presume this is basically overboost, which did happen a couple of times accidently after the innards of my ebay boost controller fell out onto the road somewhere. (this happened while it was raining too )

The reason I'm including it in this post is that I pulled the codes while out one night after it missed/stalled, and it was just 14 and 21. Was driving again a bit later on and noticed the check engine light flash going round a corner (i'm pretty sure) so pulled over a bit further up and pulled the codes again. This time it included 34. Between code-pulls I don't believe i went above 6psi, let alone 15 or whatever it the code is triggered at. At the time (and still now) It has a turbosmart bleed valve on there, and that has never had a problem, and I've never noticed the boost spike while using it.



Re: code 34, I wonder if the VPC is playing sillybuggers and has a loose connection somewhere in the wiring. The plugs all seem fine, and the map sensor and airtemp sensor plugs had not fallen out.

The Map sensor is mounted at a slight angle, probably 30degrees off vertical. Would this have an effect? it's been at this angle since installation, and it's been fine going up and down the F3/M4 a few times since then

Also i just had a thought - the ECU might not be getting a water temp signal. This should just make it think it's cold all the time right?


Any thoughts/suggestions/opinions/help greatly appreciated

-James

[BeRad]

It gets igf from the coil.

Ive had similar problems, and one of the coils was rooted, but only under certain load, would drive perfect with no boost, would drive sometimes ok with boost.

Pull a lead off the plug and put a spare plug on it and earth each lead out, see if one is firing a weak spark, if it is, theres your problem.

O2 sensor, if youve reset the ecu and its still throwing the o2 sensor code, replace it, it could be causing the engine to run rich on cruise, which fouls the plug/s. When you give it a boot full, it burns the carbon off and continues on its merry way until next time.

No water temp sensor would think its cold all the time which puts in more fuel depending on how the ecu see's it.

[BlackSupra]

Have you pulled the plugs to check if they are fouled?

Ignition leads are another thing to check.

[Jin~Jah]

well that was an interesting trip home from work...

it did it once while puttering along, and I figured I'd give it a boot to clear out any potential whatever that might be in there. This time it stuttered under load too

went along a bit further, and then while braking the check engine light on, and then the car stalled. Started it again, stuttered and stammered around the corner to a sidestreet where it stalled as i turned the wheel to go left. I'd printed out the VPC manual at work, so pulled the glovebox out and checked that everything was all good. Didn't seem to have any troubles.

Pulled codes, came up 14 by itself. checked wriring and plugs again, then was poking around in the engine bay looking at the ignitor and such. Found that one of the loom plugs that goes to the ignitor, the actual metal contacts had practically come out of the plastic housing!

tried to unplug it, but it wouldn't come, so something else might be amiss in there. I pushed the contacts back in until they were where they should be, then threaded a cable tie through to hold it all together.

car started ok, took it up the street and back, and under very little load it seemed fine. Set off to continue trip home, and it was ok, even sat on 80 in overdrive with no troubles

I'm guessing that plug has the IGF signal coming off it, and the inertia of the car moving was having an effect on the contacts, which almost fell out when I touched them.

Either way it seemed fine on the way home, and later on tonight i'll go test it at cruise speeds/loads

Intend to check plugs at some point soonish, I have a sneaking suspicion that the compressor housing oil seal is ever so slightly leaking

edit: +rep for quick replies!

[LeeRoy]

Had the same problem code 14 on my 4age corolla, turned out to be the wires earthing out on each other at the plug for the distributor. The plug was not supported and with heat, vibration, movement or whatever the stuff around the wires had cracked and come away for a few mm right in the plug just after the connectors. Once i fixed that it was fine but when it was stuffed it had the same symptoms dropping cylinders and missing. Would only throw a code up every now and then though as it takes 8 (from what ive heard) continuous missed signals to trip the code.

[Jin~Jah]

ahh ok... how long did it take you to work out what it was?

mine's been doing it intermittently for probably 2 weeks

and with 7m's it's "6-8" continuous revolutions for the GE, and 3 continuous revolutions for the GTE

[LeeRoy]

Well it had me stumped for ages. Went and bought another ecu, ignitor, and coil, none of which fixed the problem. I had initially noticed the wires being damaged but thought that they should be fine.

Didnt really have time to fix it so took it to 2 auto elecs who the first one was a bunch of idiots telling me my dizzy was stuffed and my coil was rooted which was bs and they said to but new dizzy ($600 from toyota) so i got the car back and went to another place who couldnt find it either but gave me some direction on to what it probably was.

In the end i got my dad to have a look with me and we sorted it out. From when it originally played up it took about 3 months before i rectified the fault but since then it hasnt missed a beat.