Isuzu Trooper Owners Club UK™

[mikeburton]

Hi all,

As you will know from my post entitled "3.2 V6 Lambda Sensor", my old girl is giving me some problems.
Despite the best efforts of the Tune-Up man in Penrith (I Recommend this guy if anyone else has problems - he's like a terrier after a rabbit - relentless! ) we have been unable to trace the fault. See bottom for further info on area's tested and parts replaced.

Well today the old cow finally gave a "Check Engine" light and I pulled the following fault codes out of her - Can anyone tell me if the fault code meanings I have are correct or not and what the most likely cause of the problem may be;

Fault Codes:
12 - No Fault, ECM Handshake
21 - Throttle Position Sensor circuit, low voltage
44 - Oxygen (O2) Sensor Circuit (Lean Exhaust Indicated)

Chassis Number: JACUBS25GR8102357
Vehicle: Trooper 3.2 V6 1995

Symptoms

Started off with a light hesitation at light throttle and tick over dropping off when engine running down i.e at road junctions.
Developed into heavy hesiation, lack of go and uneven running with an obvious occasioanl missfire.
Developed into the above WITH engine unable to maintain revs i.e. press throttle and engine speed would immediately rise to say 3000rpm. Hold throttle position steady but revs would die and only anti stall would keep it running.
Developed further into engine driving OKish when stone cold, but above symptoms arrising when warm. This was later reversed to running poor when cold but OKish when warm....now it's *beep* ALL the time!

Current situation is:

When stone cold it will drive like a car with a cold engine, but as it warms after say 40-60 seconds running, it kangaroo's violently, will not respond to anything other than full throttle, back fires, misses and generaly cause as much fuss as possible.
As the temperature rises to normal full throttle becomes like reverse thrust on an aircraft accompanied with exhaust smoke (unburnt fuel I assume), back firing etc. Light throttle becomes easier to use but still not good and the best way to progress is to pulse the throttle through about 10mm right in the middle of the throttle pedal's range.
If climbing any incline engine struggles, full throttle causes the car to die and only lighter throttle opening will allow progress. Going down hill once engine revs above 3000rpm full throttle will work but it's not exactly accelarion you get, more of a mediocre increase in speed.
Under no load i.e. parked up, holding throttle WIDE open will produce 5000rpm and not a jot more. A light throttle opening causes a stall.

So there you go, whats wrong with it??

The following areas have been tested and so far produced what appear to be normal results:
Throttle pot - tested with an osciloscope and actuation of throttle produces a corresponding line on the scope
MAP sensor - tested OK
Fault Codes read - #12 (no faults prior to today)
Anti Stall - tested by removing unit and running engine. Piston actuates when engine revs fall. Produced a reading on a multimeter when valve should activiate.
Lambda Sensor output - 200mv at idle, 400mv at approx 3000rpm
O2 output - Significant reading on crypton type tuner - no obvious blow in exhaust anywhere
Lambda Value (??) - NIL

Replaced:
HT Ignition Leads
Fuel Filter
Plugs
Air Filter
De-waterd fuel tank
Ran engine with STP 5000mile de-coke fuel treatment stuff - twice.



Any Help with this would be greatfully received.
_________________
If it aint dirty you ain tryin hard enough

[Google]

[jocten]

Hello Mike,
There are not many of us on here that can help you, but most of us know a man that can..................Come on down Markyboy.
TTFN, Jock.

[suzu]

it sounds to me as though it's a fueling problem of which i have changed quite a few temp sensors, these make it difficult to start with lots of smoke. when checking it on the tech1 the engine temp is the giveaway because the ecu reads it at something like 180 degrees when it should be around the 88-90 mark. this could also throw up the o2 sensor as it would be way out of range and also cause bad running due to the mixture being too rich due to it only running with throttle wide open.
the sensor is down the back of the heads and to get at it you need skinny hand and arms and unbolt the rear gearbox mounting and jack the back end up to tilt the engine forward, this would be the first thing i would try as i know they do cause all sorts of trouble

[mikeburton]

Thanks for that. I will see if we can get at it enough to test it. Nice of 'em to put these in such easily accessible areas eh?
_________________
If it aint dirty you ain tryin hard enough

[suzu]

it's not so much testing it as you will get a reading of sorts but it's how the ecu is decoding the resistance. it may be giving the wrong resistance for the temp of the engine best bet would be to change it completely and be done with it, after what you have shelled out so far it won't cost much to buy and it's peace of mind then that it's ok.

[mikeburton]

Well after much faffing about and probing every damn thing I could find to poke, I found the problem:

After testing the less than 2 year old Lambda (o2) sensor, I found the voltage to be ranging from 400mv at tick-over to 900mv WOT (Wide Oped Throttle), and according to...well everybody, the reading should range from 100mv at tickover to 900mv at WOT.

So after consulting more fault code translations ( and proving my initial information on the fault codes was correct) I decided to replace the sensor.

Genden Ltd supplied the direct replacement part (Manufactured by Fuel Parts) and I fitted it in just over 15 minutes. Plugged her in , cleared the fault codes, started her up.....sweet as honey!

So there you all have it, all the fuss and bother was down to a £50 sensor. The one that was fitted previous was a universal one that had been BADLY spliced onto the existing wiring. Water was getting into the joints and causing the duff readings - hence the problem being all over place.


Thanks to all who offered solutions
_________________
If it aint dirty you ain tryin hard enough

[denis]

A related question if I may Mike - can one get the fault codes from the Trooper with out any equipment ?

If so how ?

Denis

[mikeburton]

Yes indeedy,

If your Trooper is pre 1996 and therefore pre OBD2, there is a specialist piece of equipment that will read your fault codes easy peazy......a paperclip!

Let me know what model you have inc year and I will tell you where and how to read the codes and what they mean!
_________________
If it aint dirty you ain tryin hard enough

[denis]

This sounds like removing a cdrom from a cdrom drive without power !!


Back to your question - I have a 93 Bighorn import 3.1 diesel (without CD player )

Denis

[mikeburton]

In the drivers side foot well somewhere near the clutch pedal there should be a 3 pin connector. A three-terminal connector (ALDL), located near the ECM connector, is used to actuate the Engine Control Module (ECM) trouble code memory within the module.
Two terminals (A and C - the outer pins) of this connector are used to activate the diagnostic trouble code system in the ECM. With the ignition switch turned Off, connect a jumper wire between terminals A and C then switch the ignition On with engine OFF.
The "Check Engine" lamp will begin by flashing a DTC 12. DTC 12 = flash, pause, flash, flash.
There will be a longer pause and a code 12 will repeat two more times. This code indicates the self-diagnostic system is operating. Each code is repeated 3 times in total. The cycle will then repeat until the engine is started or the ignition is switched Off. In most cases, DTC's will be checked with the engine running since no DTC's other than DTC 12 or 51 will be present without the engine running. However if a fault has been stored previously it will be reported with the engine off. Remove jumper wire from ALDL connector before starting engine. Reconnect jumper wire after engine is running.

BE CAREFULL WHEN YOU DO THIS, CONNECT THE WIRES WRONGLY AND BYE BYE ECU !! Make sure to use terminals A+C or 1+3
_________________
If it aint dirty you ain tryin hard enough