Hesitancy under heavy load

[silverbullet]

I'll join in this one as I have always had the same symptoms an Andy, with a very early EJ22 (1990?) in a T3 - now much improved with the correct AA190 brown label MAF - that has a full-load misfire/stutter when pushing 95mph in 5th gear which would disappear if the throttle is backed off slightly. Not running a VSS but considering fitting one.
I appreciate that this is anecdotal as opposed to Andy's hard data but it does suggest something's going on. I though it was just my crummy inherited conversion...

[ScoobySplitLtd]

Andy

What year car did your engine come out of ?

Also, do you have the load figures logged from your runs ? Just wondering if perhaps the load is higher than is held in the tables in the ecu. There could be a 'max load' parameter or something in the ecu that you are exceeding, is the VW a heavier vehicle than the Subaru that the engine came out of ?

One other thought, could it be a fuel surge related issue, ie fuel running to the back of the tank on the climb so causing air to be introduced into the fuel lines ? This sort of thing is common Subaru cars when the fuel level gets low. A fix for this is to modify the return feed to squirt directly on to the fuel filter on the in-tank fuel pump (I realise you have a different setup but the principle may be the same).

Ken

[silverbullet]

Ken,
T3's are typically around the 1600kg mark, give or take, so they are a bit up on a Legacy but not wildly heavier. A camper would be more like 2000kg with a pop-top and fittings, but they are a bit compromised aerodynamically
What's the max GVW for a Legacy btw?
I'd have thought that Subaru would have made the ecu go rich at full load to prevent a burned valve or holed piston (I'm told that turbos are always very rich under load as standard) rather than cutting injectors like a crude rev limiter?
Fuel surge could be a possibility in my case (very long and flat 85 litre South African spec fuel tank) but not in Andy's syncro (well-designed fuel sump point and return in tank) but it wouldn't explain his injector data though. I took it that the ecu assumes that fuel delivery is adequate from the pump, regulator and pressure switch or am I missing something?
Ian

[rjes]

I agree that the biggest correlation between the injector puls width dropping seems to be with throttle position, although, it doesn't look 100% consistant to me. i.e always at a similar amount of throttle opening, but not exactly the same.

Try plotting throttle position against time, and watching the trace as you repeatedly open and close the throttle (you don't need the engine to be running, just the ignition on). Andy, do I remember you have an oscilloscope? If so, use this as it'll probably be capable of sampling the output voltage much faster than the relatively slow OBD II data. I've found throttle position sensor faults and MAF faults on the earlier engines this way before. Just look for anything oither than a nice, smooth voltage change as you move the throttle.

Does your software show throttle position as a percentage as well as a voltage? If so, does the reading ever go beyond 0 - 100%? I doubt it, as this would probably cause an error code, but it's worth checking.
_________________
Regards,

Richard,

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