One of my sensors isn't 100% and I can't work out which one it is.
The beast takes some cranking to start (which I've narrowed down to the initial fuel pump "flash" signal being absent) but once it's started it idles really smoothly and seems fine.
When cold, it's generally fine... but as you accelerate, it has a bit of a flat spot off idle... though almost so you don't notice it.
When it's warm it's also fine.. but it has a teeny bit more flat spot (around 1500-1750rpm) and if you lift off the gas, you get quite a lurch on and off the gas. Occassionally, if you wind on more gas, you can feel a lurch (misfire) but only for a split-second.
The rear pipe is very sooty.. so it's obviously "missing" when it has the problem.
I disconnected the throttle position sensor and the Idle control valve one after the other .. and both times the engine went unstable.. so these fellas are doing *something*...
I didn't disconnect the MAF as the plug is next to the battery where I can't reach it without lifting the MAF slightly (unbolting stuff required).. but it's dead clean in there and the sensor doodah is undamaged.
The TDC sensor and fuel pump relays killed the engine when I un plugged them.. so they're all working... (not expecting them to be the problem anyway) but the Lambda didn't affect the engine at all when I disconnected it? Notmally when the lambada dies, the idle goes all lumpy, so I was surprised.. engine runs okay without the lambda connected...
Everything (connection wise) is clean and tidy. I didn't check the coil pack as it's a "hiccup" type of problem not something affecting all the cylinders all the time. I'm sure one of the sensors or the ECU is occassionally having a moment.. so I need to know who the most likely culprit is.
Everything is OE part (1994 vintage and 190,000 miles) apart from the TDC sensor, the fuel pump relay and the lambda sensor which are 2-3 years old... so it could be any of it to blame.