idle problem, very difficult to find problem

[calais s2]

i own a vs calais series 2 v6 auto.
it is a dual fuel car, it has a idle problem on petrol, less so gas.
the list of things i have changed an had done to my engine are (please note some things werent changed cause of the rough idle).
the heads had been reconditioned with new valve seats an valves, injectors brand new, valley seals replaced, lifters replaced, water pump, O2 sensors (both of them). TPS, ISC valve. air temp sensor, base idle reset, cleaned out throttle body, fuel pump, fuel regulator, leads, plugs.
an i still have not found the problem with the idle, sounds like an imtermitent miss, not with every engine revolution it will miss, but none the less misses all the time on just idle, put on to scan tool, found no codes. read live data an found the O2 sensors signal very rich on both banks, the timing is i retardard like hell, did check the specs with another engine that ran smooth on idle and would not run as rich or as retardard as mine, the good engine ran a -30 advance an mine is running a -71 advance as it sez on the scan tool.
i havn´t changed the knock sensors, coolant temp sensor or the crack sensor an the timing chain sensor. carried out comp tests and leak down tests an had shown 165-170psi in all cylinders, with no leaks from valves an rings, computer was swoped, swoped air flow meters, made no difference, so must be a sensor telling the computer to run rich an retard.
i get 450k´s to a tank no matter how i drive the thing, hard, soft, doesn´t seem to make a difference, mind u i only get that same amount on freeway!!!!
i´m thinking i will change the coolant temp sensor next as it controls both ignition timing an injector pulse for cold start up and tuning for operating temps. i did not notice anything abnormal about the coolant temp sensor on the scan tool but i´m running out of options here
just wondering if anyone else has had this sort of problem with there car????
what is that small sensor that is located next to the coolant temp sensor???

[moff_man]

coil or lead, you did plugs maybe the leads are cactus
dfi controls the coils which gets the signal from the cas, not uncommon for a cas and dfi to be half faulty and cause a miss also the leads are renowned for breaking down in side and defiantly the ends where they brake down

also are the plugs gaped at 1.1 not the std 1.5mm

[calais s2]

DFI module was swopped i remember as well as the coil packs, it made no change to how it ran. the leads are good, believe it or not it´s my 4th set, i was un-lucky when taking then off for plug changing. why do u say to re-gap the plugs to 1.1mm???, on the passenger side strut tower is standed 1.5mm it sez on the placard. the spark gap couldnt cause a problem since thats what it´s suppost to be running at and running smooth

[calais s2]

is there anyway to test the CAS????, or is that something u just replace and hope for the best???

[Brett_jjj]

what is that small sensor that is located next to the coolant temp sensor???

The other single wire "sensor" near the temp sensor is actually the sender unit for the temperature gauge on the dash.The other temperature sensor with multi wires is for the ECU.

[hako]

Re plug gap - this should be 1.1mm on a car running on gas. The reason is that it is harder for the spark to jump across the plug gap when running on gas than running on petrol....and because electricity always takes the shortest path to earth, it will sometimes punch thru the plug lead as that's a shorter path to earth.

[calais s2]

well it runs nice on gas but shit on petrol so that wouldnt be the problem for the intermittent miss, i put gas plugs in it, the gap i think is standard to the car i think an just the cold-hot plug range is different. does anyone kno how to test the CAS if there is a test

[RX25SE]

If your sure it's not ignition then look at fuel.

Maybe the injectors are partly blocked due to running on gas most of the time?

[calais s2]

done that, they are brand new along with the fuel system (sender, fuel pump, regulator, injectors, filters, including injector filters)

[calais s2]

Might do the crank angle sensor first, new one of course, but after that i think knock sensors, but they cost a bit, never heard of the knock sensor failing in a commodore

[MrSirWantalot]

Im not 100% into Commodores but dont they have an IAC & TPS sensors on the throttle body???