Join Date: Mar 2017
Location: East Lansing, MI
Exhaustively checked continuity between ECU and primary o2 sensor. NO FAULTS detected. All wires correctly connected and not grounding out or broken connections. Doesn't rule out an intermittent fault as I cannot easily test with the car running. I also did not exhaustively check every pin on the same wiring loom fore connectivity issues with neighboring wires (hopefully I don't regret this in a year...we all know these decisions...).
After talking w/ Andrew @ BoE I didn't have much faith it'd work - but I paid a visit to Auto Europe in Birmingham MI. They were not exactly enthusiastic to solve my problem. To be fair on the rough SE MI roads the problem was hard to detect. So I re-created the problem, showed the data, talked w/ the technician. Long story short - I spent 8hrs in a waiting room and all they did was re-set my ECU (reverted back to original ECU after testing the new one I swapped in). Didn't appear they attempted to trouble shoot the issue at all beyond reading the write up I gave them. In the end they agreed to reprogram/reset the ECU. Unfortunately according to the tech my ECU was up to date, and he could not reload the software (ehhh - really?), only reset the ecu's memory. So 8hrs waiting and $260 later I tested the now re-set car - immediately the problem was present. Before leaving I was assured it was fine and the car was meant to be driven all out, not at partial throttle... right.
Not phased I proceeded to dig a little deeper into the Toyota service manuals. The procedure for testing the fueling system is to prime it and verify the pressure is held. If the pressure drops it basically tells you to inspect all things fuel. As all lotus owners know - the pressure did drop. So I caved and decided to attempt every 2005 Elise owner's nightmare: fuel pump and basket bits (pressure regulator, sock, and filter). Unlikely as it seemed there's still a chance it was failing partially due to a clog, electrical issue, etc. A week later the nightmare is over and the new parts are in. I let the car idle for a while after I adjusted the base idle speed (had to remove all the cables to get to the shear panel). Problem persisted... ouch. So what else could be leaking? Well the entire system by design could have leaks. I don't smell fuel - but having had longer / hard starts before I do suspect my "flow tested and cleaned" injectors... but I feel that's just throwing more money at the problem with no conclusive reason to suspect the injectors. What are the chances an injector could fail at partial throttle and instantly be fine at WOT or at high speed cam? There's a chance, but it seems fairly low... probably as low as the fuel pump being to blame in this scenario...
Shot off several emails to Lotus and Phil @ BoE. Curious what inputs are used for the short term fuel trim (STFT)... Does anyone here definitively know?
My problem is very specifically boxed: any scenario where the STFT is adjusting
30s after warm up
partial throttle very detectable
disappears at wide open throttle
disappears when the high speed cam lobes engage
Problem does not exist: any scenario where the STFT is flat lined
All sensors read normal - including the o2 sensor which then behaves in a more normal fashion in a steady state..