Hesitant / Stmbles on quick but not slow acceleration

[SpudgunBlunder]

I swopped the ECU from another MX-3 and it cured it.

How could the ECU fail like this? Could I have caused it by cranking/running the engine without the resonator hose?

[SpudgunBlunder]

It seems I did'nt touch wood.
The ECU swop seemed to fix the hesitant behaviour but it seems to be limited at 5k rpm? The rest of the time it's fine.
Is the ECU limiting the revs? (cutting the fuel)
Would it be something to do with the advance timming? or is that just on quick increase in revs? (i.e. near the low end)

This car's driving me

Would really appreciate any advice.

[kiwi_MX3]

Its a bit of a novel but worth the read however.

limited to 5k? if you sit in neutral and just nail the accelrator to the floor
the engine limiter should be 7500 - 8000

The k8 ECU's have a habit of dying lot like DSM ones do.
The O2 sensors from memory
( please excuse this as im a long way from home and my libary )
run in parralle to the ECU , so the ecu just reads it as the motor in total
not from or rear bank.

Drain your fuel tank and flush the system out with clean fuel
( eliminates the bad fuel side of things )

last but not least ( and i know this is a bugger of a job ) but pull the front
cambelt covers and check all the timing marks line up as this sounds
likea classic case of the timing belt has jumped a tooth.

this to me would explain hesitation and backfiring and lack of hp.

[SpudgunBlunder]

Hi guys. I haven't posted here for a while because I've been busy looking for a new job to earn some £ (to spend on this car) and I've been trying diagnose it a bit more.

I'll try to recap on what's been going on:

Did compression test, after which caused engine to stumble (loose all power) on quickly opened throttle.
After some diagnostics (above posts) I replaced ECU and seemed to be cured. It seems it's not cured but a lot better than it was.

Replaced disty cap, fuel filter.
Tested
Air Filter
Air Leaks
O2 Sensors
Crank and Cam sensors
MAF
Water Temp Sensor
All Solenoids
Resetting ECU's doesn't help

Timing - Checked at about 6-7k rpm idle and is set at 10 degrees BTDC.

However when I jump GND+TEN and adjust the timing it isn't saved by the ecu. Also when GND+TEN are connected the revs drop very low about 0.2-0.3k rmp and rise and fall. But this doesn't happen when GND+TEN are NOT connected.

I also noticed that the timing RETARDS before it advances on quick open throttle. And also when using the original ECU and quicly reving the engine and it stumbles the timing drops to TDC.

When accelerating over 5k rmp (only when travelling) the engine seems to be "limited" except when in 1st or 2nd or if the throttle is open very slightly.

I haven't checked the cam belt for a slip yet but would that not effect performance continuously? rather than what I'm experiencing now which is more of an intermittent problem.

I also didn't change the disty rotor cos I thought it was ok. But I'm getting one tmw just to make sure.


What the heck is going on?
What could cause the change between different ECU's?

[JM1EC-V6]

I would check the timing belt.

[SpudgunBlunder]

I have noticed that although my timing advance is at 10 deg BTDC that is INTERMITTENTLY FLUCTUATES. Some times by a few degrees either way and sometimes by 5-6 deg.

Also when I quickly open the throttle the timing RETARDS and then advances when the revs pickup. This happens when the engine stumbles and it retards past TDC (ATDC) as my timing light "cuts out".

Should the timing retard slightly at 1st on accel?

What the hell could cause this?

Really need some help on this please.

Thanks in advance.

PS. I wanted to check the cam belt for a slip but it's a big job and I want to exhaust this timing issue first.

[ariesdude]

If you have access to another good running mx-3 or even junkyard parts - test the sensors first - like TPS, VAF, CPS etc and definitely try a new distributor...

[SpudgunBlunder]

Sorry to dig this one back up but the solution to my problem was replacing the distributor!

DESPITE having tested the coil and cam sensor (to the book) in the disty I think it must have been a faulty ignition module in the disty which was causing the bad timming/miss fire.

I've read that there is a common fault with these modules going but I expected it to just cut out.

Thanks for all the help with this. Very much appreciated.