420SEL runs lean on over run
 

G'day guys hoping someone can shed some light on this. Airflow meter packed it up a couple of months ago leaving me stranded. So I replaced that along with new fuel injectors two new pumps, new pressure regulator, accumulator, plugs and leads and new coil. Temp sensor was out of limits so I replaced that and did a new oxy sensor why I was at it. Car was running great now here is the weird bit.

I changed the throttle sensor, but now I have this weird fault when you lift your foot off the gas it seems to lean off too quickly like the fuel supply is cutting off. Now I have tried a different fuel distributor and two EHA valves with no change fitted original throttle switch and problem remains.

Car pulls well, idles so smoothly you wouldn't know it was running and starts perfect. It's something weird because if you engage the cruise control, it gets jerky because it's cutting off and back on when loosing speed related to the initial fault. Now if you disconnect the EHA and force it into limp home mode cruise works perfect and car drives fine so it's something on the electrical side is a miss. Could a poorly adjusted throttle linkage cause this?

I've checked all elec readings as per factory manual and they all come up good what on earth could cause this? Simply if your doing 100kph and take your foot off it drops speed instantly almost like drag, disconnect the electronics and it runs fine but all the electronics check out fine help???????????

I know it's supposed to cut off on the overrun mate but it has never been so obvious before it's clearly got something small wrong with it but what I have no idea?

Cheers Mat.

True mate but not because of that fault. My mate has a 560 and a 420 and neither of them do this the local Merc dealer says it's not right but are scratching their heads too. Originally it was flooding hence the overhaul and all was good till recently I'm borrowing an ECU of a mate next week to rule that out but I doubt it will cure the problem.