[T3] Temp sensor and MPS problems on new motor

[Jessica Chase]

I think I might have been a little unclear. We have bucking when the AFR goes lean but when we drove home yesterday with bad gas mileage and rich AFR’s (and TS1 unplugged) there was no bucking at all. The driving was smooth but the gas mileage was really bad. Plug TS1 back in and we’re lean and bucking all over again.

Today, we tested our fuel pressure and went for a drive with the gauge installed. The pressure was at a steady 28 psi under all conditions. We also tested both temp sensors under a variety of temps and conditions and they both spec out fine. We also ran tests using 3 ECU’s and 3 different pressure sensors so 9 tests all told pairing each sensor with each ECU: two B units (neither of which ground our fuel pump) and one A unit. Each pressure sensor with each ECU did the same thing: idled lean and then leaned out so much under load that we bucked and could barely accelerate. The fried unit has been out of commission since late November and it’s sitting in a box waiting to be sent to WI for a post mortem as soon as we get our lazy butts to the post office. 

Finally, we ran a 10th test. We re-calibrated the pressure sensor we took the epoxy out of the other day. We were so fraught being 300 miles from home and needing to get back that we didn’t reset the screw to it’s correct depth. Anyway, it also idled lean but we were able to adjust it about a half turn counter-clockwise to get it to idle at 13.2. We took it on a 15 mile drive and the AFR #’s were sane and there was no bucking or hesitation. We’ll do some more extensive driving and testing tomorrow. The sensor is well marked as to the original position though the adjusting screw on all of our sensors (both with and without epoxy) seem to be at the exact same position….on a diagonal like so   /   with the upper part at 1 o’clock and the lower at 7 o’clock. 

We do have one of Joe’s harnesses and the injector grounds are at the center of the case. We also tightened up the injector connectors before we installed the new motor. We’ve had issues in the past with the connectors getting loose so we periodically retighten them as a precaution. We did the same to the injector grounds. 

Jim….we want to get a B brain from you because at the very least we want to be safe and be able to ground our fuel pump and we’re happy to re-try everything with a known good B unit, but out of curiosity, why don’t you favor adjusting the pressure sensor?