Engine Miss (running microtech)

[Peewee]

My 1UZ has a constant miss (ie, its not intermittant)

When cold it happens from 3200 to 3500.
When hot it happens at almost exactly 3500.

Does not happen under light throttle.

Only happens for a split second, then continues fine to redline.
Only just started happening.
When it happens the tacho (autometer) drops 500-1000rpm then continues.


Pretty much happens every time, in every gear.


Thoughts?

Its running an LT8S btw.
My tuner is booked out for a few weeks, so I can't get him to look at it.
Nothing in the engine bay has been touched.
All I have done is reduce the idle speed from 1300 to 750, and played with the idle timing/fuel.

The fuel has been in the tank for 6 weeks, so this *could* be it.
Am going to fill up with new fuel tonight.

 

[V8Celica]

If your tacho is dropping it must have some thing to do ignition.

 

[Zuffen]

When you say you only played with the timing/fuel I would suspect a very lean spot at 3,500. The engine stumbles, so you drop revs but pass back through it once it's done it. You couldn't drop 1,000 rpm or you'd hit the windscreen.

If I wiped 1,000 rpm off third gear at 3,500 I'd be dropping 30kph (20mph) and you'd sure notice that.

Try putting the settings back to normal. I wouldn't reset the idle until you try the fuel/timing.

 

[V8Celica]

I thought even a 500 rpm drop was to big for an engine in a second therefore assumed that the tacho had lost its signal for that second

 

[Peewee]

Yeah, I think its tacho losing signal.

I didnt play with anything but the idle map, and idle timing.
But driving it tonight it feels that timing gets f****d up at 3500rpm.
The car feels like it looses power.
I will have to check the maps and make sure I havent accidently changed something.

 

[V8Celica]

Have you checked the connections to your ignition module.
Including the earth?

 

[Peewee]

Its to consistant on its miss to be wiring related.
Its definately ecu related.

 

[Peewee]

Spoke to my tuner, and showed him this

That was 2nd gear, pulling from 20ish kph to redline (100ish kph)

Tuner couldnt see anything wrong with it.
He suggests that my fuel pump is wearing out and can no longer cope with the required output.
I suppose 240,000km's of 5mge and a sudden rush of 1uz could kill it.
Sounds like its Walbro time!

 

[KDog]

If you had a fuel problem it should still show up by a drop in RPMs. Maybe the micro logger software isn't accurate enough to get good info.
I assume the problem was there during this run?
Have you disconnected your tacho and done a run? If so I assume there was still a problem. What ignitors are you using?

Did the problem occur exactly when you changed the ECU settings? If so reload the old program? If it is fine again you know you screwed up somewhere. Make you changes one at a time and see which one causes the problem.

 

[Peewee]

Ignitors are bosch 008's.

I honestly can't remember exactly when the problem started.
I just noticed it one day last week.
And I don't think microtech has the option of saving settings and reloading old programs.
I think thats on the next firmware update. (Whenever they get around to releasing it).


One thing I have noticed since that run, is that the timing there doesn't go past 32degress.
From what I can remember, its supposed to be 34degrees at 5000rpm, and 36degrees at 6000rpm (or there abouts).
But it doesn't do that.

I'll have to look around at the settings and see if I have stuffed something up.
The program did some wierd things when I was last fiddling.
It locked up and no buttons worked for about 20 secs.
Then started working again. Wierd

 

[tweaked]

Peewee
If you turned your idle down, you need to re-zero your TPS. If your LOAD switch is on TPS, not MAP, it will be out by as much as you turned your idle down. That or sparky misfire? maybe... Actually, fuel pump before that.... I wouldn't drive it again till you got another, better pump! wouldn't wanna burn a valve out now would we.
If you need a hand with zeroing the TPS feel free to give me a buzz.
BTW, did you go to and enter motorvation? My cousin thinks he saw it there...

-Troy
0439 969 502

 

[Peewee]

Yeah, I was there at motorvation on Saturday.
Didn't bother going back on Sunday though, too hot.

The car is tuned in MAP/Matrix mode, not TPS mode.
I didn't touch the throttle plate to wind down the idle, I just set the ISCV to be further closed.

New pump will be going in next week hopefully.

Until then, I'm trying to keep it under 3000rpm.
Its quite hard with a 4.10:1 diff.

 

[tweaked]

another possibility could be your voltage, had similar probs with a rotary, 13bt, voltage was at 10.9-11.2 and would misfire constantly after 4K RPM. This was at night with the lights on and thermo running constantly.
Anyway, your car impressed my cousin and all his chev mates!
BTW, you can save 4 different maps in your handset on microtechs.
-Troy

 

[Peewee]

Hehe, cheers.

Voltage has been checked, as that was one suspicsion of mine, I just didn't display it on that screen shot.
It remained at 13.8ish volts, give or take 0.2v.
With a 100-120A alternator, there should be no voltage worries.

Car came off the road last night. Will remove the tank and replace the pump this week some time.

 

[tweaked]

prob sorted?

 

[Peewee]

Installed new pump yesterday, but its gonna be another week or 2 before car is back on the road.

 

[Peewee]

Just a follow up post to say that I just fixed it.
Turns out the Crank Angle Sensor was wired backwards, which I'll go to my grave saying is something I have tried before. Embarassed

But I just played around with the cam and crank angle sensor wires in every combination possible (there is only 4, was already running one, and it wouldnt start with 2, which left the last one to be perfect)

So if anyone ever gets an RPM ERROR on a Microtech, its the cam or crank angle sensor backwards.