Poor running

[drew.h]

Shunting getting worse, can stall easy just after starting, then take ages to start again (possibly flooding), and flat spots galore. Switched to the none cat map today and its a totally different story.

What ever is faulty is used buy the cat map but not the none cat map. So faulty lambdas presumably. However is there anything else it could be?

[blitzracing]

If the ECU does not get a lambda signal it will run the catalyst map, but without making the fuelling trim, so its odd its that bad, frequently you wont even notice if a lambda probe is out. More generally the non cat map tends to run a bit richer, but it leans off more under crusing conditions. Bad snatching can be the ECU trying to control the mixture rich or lean, but it hits the limits of adjustments, so something else may be out to cause this in the first place. Usual storey, put a test meter on the probe outputs to see whats going on.

[drew.h]

I've connected my VU meter to the Lambdas and one is reading lower than the other. If I swap the Lambdas the same one still reads low, so I think I need a new one.

Range on the VU meters is 0-1.2v:
VU meter video

[Drinky1]

Hi i'm getting 12v direct to the lambda with the ignition on or off any ideas ? When you say shunting what do you mean ? Mine will run fine for about 5 miles then its like the power is being turned on and off it coughs and splutters then clears runs fine then starts all over again is this shunting sorry if this is a stupid question but its my first trever

[blitzracing]

drew.h said:

I've connected my VU meter to the Lambdas and one is reading lower than the other. If I swap the Lambdas the same one still reads low, so I think I need a new one.

Range on the VU meters is 0-1.2v:
VU meter video

One probe is noticably slower in response and low, so yes time to change that probe. That is unlikely to be the cause of the poor running though, as it is switching, so the mixture should be near correct, as the ECU just looks for the voltage change, not its level, its not that smart. You need to run the test again when the cars not running correctly.

[blitzracing]

Drinky1 said:

Hi i'm getting 12v direct to the lambda with the ignition on or off any ideas ? When you say shunting what do you mean ? Mine will run fine for about 5 miles then its like the power is being turned on and off it coughs and splutters then clears runs fine then starts all over again is this shunting sorry if this is a stupid question but its my first trever

You have three wires on the lambdas, red, which is a 12 volt supply to the heater, white, that is ground, and black which is the output, so dont confuse this with earth! The 12 volt heater supply should only be there with the ignition on. If you have 12 volts (to ground) on the Lambda probe output, then the probe has failed internally, or the wiring has shorted out. The shunting is a snatching in higher gears at around 1700 rpm.

[Drinky1]

Hi thanks for that well i've changed one of them and it's still getting hot so off now to find out where it has shorted out from cheers