94 850T check engine light while accelerating

henrysin44 · Post by **henrysin44** » 12 May 2020, 16:45

My check engine light comes on only during acceleration, the light turns off once off the throttle/just coasting. Its almost like the throttle is a check engine light switch lol. It doesn't always come on during light acceleration but always under medium to full throttle.
Whats weird is theres no codes set at all, not even pending codes, the light doesn't flash, and the car runs perfect with no loss of power or hesitation.

Post by **misha** » 12 May 2020, 16:53

Does this happens only in high rpms(5-6k rpms) or even on lower rpms with full throttle?

Did you read the codes from instrument cluster?

henrysin44 · Post by **henrysin44** » 12 May 2020, 17:49

misha wrote: 12 May 2020, 16:53 Does this happens only in high rpms(5-6k rpms) or even on lower rpms with full throttle?

Did you read the codes from instrument cluster?

Most of the time it happens in around 3K and above and no I haven't checked the instrument cluster codes, ill check them now. My car has an upgraded ECU so its OBD2 only for engine trouble codes.

henrysin44 · Post by **henrysin44** » 12 May 2020, 17:53

misha wrote: 12 May 2020, 16:53 Does this happens only in high rpms(5-6k rpms) or even on lower rpms with full throttle?

Did you read the codes from instrument cluster?

1-2-2 and 1-3-2 was stored in A7 inst cluster

Post by **misha** » 12 May 2020, 18:13

Did you had this problem before ecu upgrade?

1-2-2 temperature sensor interval too long
1-3-2 engine speed sensor signal incorrect

How did you upgraded ecu...swap from a newer model(which year) or flashed?
Clear the codes,go for a spin and check will they come back.

EDIT...i just saw the signature...it's a custom M4.4 tune.
Anyway...clear the codes and see if they comes back.

How do you check OBDII codes since '94 doesn't have OBDII port?
Did you added it?

henrysin44 · Post by **henrysin44** » 12 May 2020, 18:32

misha wrote: 12 May 2020, 18:13 Did you had this problem before ecu upgrade?

1-2-2 temperature sensor interval too long
1-3-2 engine speed sensor signal incorrect

How did you upgraded ecu...swap from a newer model(which year) or flashed?
Clear the codes,go for a spin and check will they come back.

I flashed a 1998(maybe 99) Turbo ECU (M4.4) about a year ago, its a stock 850 T5 BIN for manual transmissions, have not had any problems with it, even have working A/C. I'm pretty sure these codes are new as I had the battery unhooked for a few hours last week. Although my RPM sensor is a knock-off from AutoZone so I'd bet that code is genuine sense the sensor is not BOSCH.

EDIT: I have no idea why my 94 has an OBD2 and OBD1, but it is factory. I think the very late 94 models introduced the OBD2 port

Post by **misha** » 12 May 2020, 18:37

So...are you saying that CEL thing during acceleration appeared AFTER battery was disconnected?

Aftermarket sensors are usually out of range from the factory and they can't be trusted.
Code is for it....incorrect signal.

That can be the source of your problems.

henrysin44 · Post by **henrysin44** » 12 May 2020, 18:49

misha wrote: 12 May 2020, 18:37 So...are you saying that CEL thing during acceleration appeared AFTER battery was disconnected?

Ya wasn't comming on prior to that, actually I disconnected the battery to pull the cluster, odometer gear needed replacing and there were also a few bulbs burnt out so I replaced every single bulb (don't want to be back in there again). Don't exactly know how that could cause a CEL after a week but the cluster has always acted up for years now.

As a side note not all the lights come up when key is in position 2, or while starting, but all are functional. Video: https://www.youtube.com/watch?v=eDVhA78yTyI

henrysin44 · Post by **henrysin44** » 12 May 2020, 18:50

henrysin44 wrote: 12 May 2020, 18:49
misha wrote: 12 May 2020, 18:37 So...are you saying that CEL thing during acceleration appeared AFTER battery was disconnected?
Ya wasn't comming on prior to that, actually I disconnected the battery to pull the cluster, odometer gear needed replacing and there were also a few bulbs burnt out so I replaced every single bulb (don't want to be back in there again). Don't exactly know how that could cause a CEL after a week but the cluster has always acted up for years now.

As a side note not all the lights come up when key is in position 2, or while starting, but all are functional. Video: https://www.youtube.com/watch?v=eDVhA78yTyI The rattling bang sound is my exaust pipe

Post by **RickHaleParker** » 12 May 2020, 18:57

henrysin44 wrote: 12 May 2020, 18:49 Don't exactly know how that could cause a CEL after a week but the cluster has always acted up for years now.

Cracked solder joint, path or connector got aggravated when you pulled the cluster.