engine stall/ no pedal response

[Dingo76]

1993 318i M42
About 5 minutes into a fresh trip...i will suddenly have no response at all to gas pedal and will coast to a stop..and have to pull off the road. I cannot pull away in 1st at all..the engine does not die or stall..just does not respond to gas pedal..the only way i can get motion is to somehow rev very high with a sharp punch of the pedal and keep the revs high...eventually the problem dissappears and will accelerate in 1st and 2nd quite normally. Other than the car runs just fine, but this is a scenario that repeats predictably. and can be sketchy if nowhere to exit the road. Engine code is 1222
I have been addressing this for afew months but no luck, so i have to start fresh from the begginning.
Any ideas and advice is very welcome
Thx
D

[bmwman91]

When the car starts doing this, and you open the throttle, is there ANY noticeable change to how the engine runs? It is a mechanical throttle, so if you start pressing the pedal, more air goes in, and it'll either rev or stall. The "normal for 5 minutes" thing is often indicative of a bad O2 sensor. That sensor is ignored until the engine has warmed up a bit. I know that a crapped out O2 sensor can make the car run poorly, but I have never heard of it causing a loss of throttle response.

The only other item that I can think of is the air flow meter. If it is having a major intermittent fault, then MAYBE it could cause what you are observing, although I would expect a stall. If you can reproduce this issue multiple times from a cold start, then it is not all that likely to be the AFM, and it points more to the O2 sensor (which 1222 is also an indication of, although 1222 comes up for a bunch of issues that are caused by other things).

[nando]

Is the main relay original? I had something similar, the pedal would go "dead" but the car was still on - turned out, the main relay was dying, which cut power to the ECU, but not the rest of the car, the instrument cluster, etc. It's confusing because with a name like "main relay", you don't think about it, but it really only controls power to the ECU - it doesn't directly affect anything else.

[Dingo76]

Thanks for the replies.
in normal conditions u can see the Tach needle respond to even pressure on the pedal.
in this failure mode, a steady push on pedal causes brief rise of needle but then as your foot co tinues the needle just drops down to the bottom and stays low...no forward motion at all
with multiple attempts I can sneak it to very hi revs and keep it there just to move
once out of this failure mode, pedal and engine are very normal

this repeats every trip after car parked for a few hours or overnite


not sure if main relay is original or not...I have not looked at it..is it in the main relay box under hood?

[nando]

it's in the 3 relay box next to the airbox usually - it's been a long time since I had a 318is in my possession, but I think it's similar to the M20. One is the main relay, one is the fuel pump, and the last one is for the o2 sensor heater.

[roguetoaster]

Look at the three relays on the firewall, beneath a black plastic cover. Two relays are physically identical, but different colors, the other is the main relay.