[T3] An FI stumper?

Keith Park topnotch at nycap.rr.com
Wed Oct 7 17:07:05 PDT 2020




Ok, when my last engine was pulled out everything was working perfectly,


Since the new one has gone in, there is a miss, sometimes slight, sometimes
jolting under light and moderate throttle, idle is always perfect and there
are no issues with heavy or 

Full throttle.  Leaner mixtures make it worse, but even when a bit rich
under light to moderate throttle you can feel it miss from time to time.


What Ive tried:

Switching in and out the Mark 10 makes no difference, spraying up the dist
and leads with water does not change anything.

Switched out each injector, no difference.

Replaced head temp sensor with a 100 ohm resistor for testing at temp, no

No apparent vacuum leaks

No wire-wiggling issues

Swapped out pressure sensor, same issue

Tends to be worse when colder, better after a good warm soak, but in a long
drive it did get worse again after it got better

It HAS at times, RUN PERFECTLY, so I don't think it's a setup problem with
anything in the system, and I don't think its mixture calibration.

Acted just like a sticky injector but it isnt that, ignition SEEMS strong,
but?  It does feel like that could be it.  Everything checks OK though.


I did find a broken wire at the manifold air temp sensor, and fixing that
made a BIG difference, but it only shifted the mixture curve lean, once
adjusted back to where it should be,

Same issues with occasional miss.


What am I Missing? Or WHY am I missing?



BTW, THIS build, without the slop between cam and crank seems to have
considerably MORE power and a distinctively different sound when floored!
Remember, with the old build

it "sounded" fine above 2000 RPM but when you really get into it on the
highway now.... Swwwwwwwwwwwwweeeeeeeeeeeeeeetttt!!!


and it SEEMS to be running cooler too, although so is the weather around
here now that its fall.  Some of my tuning headaches may have been variable
valve timing that I DID NOT WANT!


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