Engine 850: B5204S/2.0/20v: running fast

[kdan]

hi ive got a 850 2.0glt 1993/4.......... from starting whem its cold it cuts out and runs rough and once warm it idles very high 1500-1800 rpm..........ive read the codes on A1 and that came up with 2-1-3...........and on A2 there was 1-2-1.....5-1-2.........and 4-1-1??????
A6 was clear 1-1-1..


any advice would be appreciated before i go buying parts that may not need lol....

thanks

[S70 B5254T]

I'll let someone with more information give you each code name, but your physical symptoms certainly point to the Idle Air Control Valve - when I bought mine, it wasn't quite cutting out at cold, but in every other way it was behaving as yours does.
Some suggest cleaning the IACV but I just went for a reconditioned one from Ripsta33 (Chris) for an incredible £20 including fitting - I'd suggest a drive up to the north east - it's worth the petrol money!

[kdan]

Originally Posted by 854 1984cc 20v

I'll let someone with more information give you each code name, but your physical symptoms certainly point to the Idle Air Control Valve - when I bought mine, it wasn't quite cutting out at cold, but in every other way it was behaving as yours does.
Some suggest cleaning the IACV but I just went for a reconditioned one from Ripsta33 (Chris) for an incredible £20 including fitting - I'd suggest a drive up to the north east - it's worth the petrol money!

ive cleaned the idle valve out and the mech inside is moving freely... but it mite be a option to try another one

[scutyde]

A1 2-1-3 Throttle position TP. Signal too high

Condition

The throttle position TP signal is passed from the TP sensor via the transmission control module TCM. The signal tells the TCM how far the throttle damper has opened. The TCM uses the signal in its control functions, among them controlling gear–shifting and the system pressure. The signal normally varies between approx. 0.5 and approx. 4.2 V. Opening the throttle damper increases the signal voltage. If the TCM registers a signal above 4.8 V, DTC 2–1–3 is set.

Substitute value
Control Module GROUP I:
The transmission control module (TCM) "Emergency mode" program is initiated.
Control Module GROUP II:
The transmission control module (TCM) "Emergency mode I" program is initiated.


Possible source

-Short circuit to battery voltage in the signal wiring.
-Fault throttle position sensor circuit.


Fault symptom[s]
-Rough gear shifting due to maximum system pressure in the transmission
-No Lock–Up operational.
-Gear–shifting operation can change – irregular shifting.

A2 1-2-1 MAF sensor signal

Condition

Since the computed mass air flow is determined largely by the injection period, the system is dependent on the MAF sensor signal. The DTC is recorded if the control module detects that the signal is lower than 2.7 V or higher than 8 V.


Substitute value
The control module assumes a fixed load signal value (limp home) when the DTC is recorded. The adaptive and idling control functions are inhibited, and the ICM and AW 50–42 TCM load signal is adjusted to the full–load value.


Possible source

-Open–circuit in signal or supply lead.
-Signal lead short–circuited to ground or supply.
-Contact resistance in connections.
-MAF sensor faulty.


Fault symptom[s]
None.

A2 4-1-1 : Throttle position TP potentiometer signal
Condition

If the TP potentiometer signal remains steady below 0.25 V or exceeds 4.75 V, the MFI module will interpret the condition as a fault and the DTC will be recorded.

Substitute value
-The system will assume a substitute value equivalent to a throttle opening of approx. 15°.


Possible source

Signal too high:
-Open–circuit in signal or ground lead.
-Ground lead short–circuited to supply.
-Contact resistance in connections.
-Faulty TP potentiometer.
Signal too low:
-Signal lead short–circuited to ground.
-Open–circuit in supply lead.
-Contact resistance in connections.
-Faulty throttle position sensor.


Fault symptom[s]
-Incorrect idling speed.
-Impaired full–load acceleration when A/C is not switched out.

A2 5-1-2 Short term fuel trim (integrator) Lower limit

Condition

The short term fuel trim value is a measure of degree to which the injection period in the basic MFI module program must be varied to ensure that the engine is supplied with the optimum air/fuel mixture. This optimum mixture corresponds to a value of λ = 1. If the engine is running rich, the short term fuel trim will reduce the injection period to restore the optimum mixture. A DTC will be recorded if the engine runs so rich that the short term fuel trim reaches its lower limit and remains there for 166 seconds.


Substitute value
None.


Possible source

-HO2S signal lead short–circuited to ground.
-HO2S faulty.
-Contact resistance and oxidation in MAF sensor connector.
-MAF sensor faulty.


Fault symptom[s]
-Fault may cause high fuel consumption and driving problems.


My advice: change the potentiometer at the throttle. Then clear all faults, make a testdrive (longer one) then see which errors still come up.

Cheers
Cristian

[kdan]

thank you scutyde

ill try a source one today.....it does look very gunked up and the connector is also very dirty/oily....

[scutyde]

Brake / Clutch cleaner spray is your best friend

[kdan]

ok cleaned tps a throttle body best i could and took it for a run........... from cold it sort of backfires a pops through the airbox and is very hesatant and even cuts out.....when warm apart from revving high it drives ok????

[kdan]

just to update............ i put a new maf sensor in and it now runs spot on........so thanks for the info scutyde as it helped me diagnose the problem.......cheers