Wednesday, 17 March 2021

Damn Car's Haunted

Well it's all got a bit sad I'm afraid. The car still won't run properly & due to an ongoing lack of work at work, I've had to pull out of the road trip I've spent six month organising. I am still trying to fix the car, I swapped the Mass Airflow Meter (MAF) to no avail & my brother came over this PM & we tried some things I couldn't try with just one of me.

I'd taken the Throttle Position Sensor (TPS) off & checked it on a meter & it seems fine, so with it off the throttle body, turning it with a screwdriver, my brother was in the car & started the engine & pushed the throttle & we got it running OK, but found we didn't need to open the Throttle body butterfly, it'll run just fine up to 3-4k just on bypass air - so there's no restriction in my adaptor block & it responded to the TPS just like a throttle pedal - though the butterfly stayed closed.
BUT, put the TPS back on the throttle body & it doesn't want to run at all.

ALSO with the engine like that (TPS de-coupled from the butterfly), if the MAF is plugged in it runs on - off - on - off - on, engine rocking one way as it's on, the rocking back when it goes off, it's a hard on - off cycle, not a sine wave. Unplug the MAF & it's OK. The frequency of the on - off cycles could be controlled with the TPS.

Current thinking (see what I did there?) is that something in the loom is picking up interference from another wire, corrupting the signals to the ECU. The wires from the Crank Position Sensor are a twisted pair, so someone was concerned about interference. Next step is to strip the car again & unwrap the loom, separate the wires & see what happens then. Worst case is that I fit the Omex ECU from a previous car - which needs me to unwrap & separate the loom anyway. I may find the solution before I resort to the Omex, I may not (sigh).

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