Isuzu Trooper Owners Club UK™

[bigbluetruck]

Hi, I have been chasing this fault for over a week and I'm at the head scratching stage and could do with some options of what to try next.

About a month a go, I noticed the engine would hesitate (only once) when going up a steep hill. Over time, this got worse and started to do this whenever the engine was put under load. The current situation is that it has deteriorated to running rough all the time. It starts fine and gets worse as it warms up. It will rev while idling (though responds sluggishly) and the gear stick vibrates excessively, so classic sign of a cylinder going down.

Here is what I have done so far:
1. Checked on Tech2, no error codes.
2. MAP sensor removed and cleaned when initially started hesitating under load. It was dirty but did not improve matters.
3. ORPS replaced as an easy first option, though it had not failed completely, I thought its response to the change in demand might have been slow. No change.
4. Control test of injectors carried out, all click correctly when selected but understand the problem could be heat related at it get up to operating temp.
5. Injector balance test carried out. Results of switching off injectors 2, 3 and 4 individually was a noticeable drop in idle speed and running rougher. Turning off injector 1 had a detrimental effect but not to the same extent as the others. I thought this was the problem, the injector has not failed completely (yet) but is operating at reduced efficiency. Time to change it.
6. Replacement injector fitted. This made no difference, but as I had bought it second hand and fully tested (honest guv) I thought maybe the replacement part was just as bad as my original so needed to confirm the injector issue.
7. I swapped over injector 1 and 3, expecting the fault to transfer if indeed it was the problem. Unfortunately, the issue is exactly the same. All pass the control test and the balance test shows a reduced marginally reduced effect of turning injector 1 off and a distinct effect of turning the others off.
8. Injector harness is in good condition (no cable ties on this one) and I have cleaned all the electrical connectors to the injectors and also the main engine plug by the oil filler. I have also con checked the wiring, no high resistances, cross connections or shorts to earth.
9. I am now thinking that the issue must now be related to cylinder 1 itself (piston ring, valves or head gasket).

Can anybody with more experience suggest something else that I can check, or anything that I have blatantly got wrong? Any help would be most grateful as the truck is all but immobile now.

Many thanks in advance.
Dave

[Google]

[wildata]

No Expert, this 4JXI terrifies me. Nothing ever seems to diagnose easily.
Pull Glow plug(s) (if of course it comes out) and compression test No 1 vs any other cylinder ?
Otherwise ECU, or injector sleeve issue ?

[wildata]

Ps: Glow Plugs are reported by lots of people as very prone to shearing off during removal.
See the posts here about them - I do not want to put you in even more grief !!!

[eithan h]

check the inlet valve clearance they do have a habit of closing up and the pistons are known to be made of chocolate in the 3.0l

[bigbluetruck]

Thanks for the input gents. I will post some feedback once I have done some extra checks

Cheers

[bigbluetruck]

Another update. I checked the inlet valve clearances and they were spot on at 0.15mm so at least I can rule that out.

I did run it again with the tech2 fitted to see if I could identify a trigger. As stated previously it starts fine with no smoke and initially runs smoothly for 3  or 4 minutes but then slowly begins to deteriorate and if left idling it eventually stalls. The only reading on the tech2 that seemed to correlate with the idling problem was the injector timing. It started at -2.2 CA while running ok, and as it warmed up and got worse there was a step change in the rough running as it moved slowly through to -3.8 CA where it was running at its worst. This might be a symptom of the ECU trying to correct a problem rather than the cause, but I don't know enough about what this measurement is, or what range is acceptable at idle.

Even once stalled, there were no error codes thrown up. I even conducted another injector control test, but all injectors clicked when activated. The engine never got up to operating temperature to meet the injector balance test entry requirements of over 80 degrees.

If anyone can suggest where else to look, or possible causes I would be grateful to hear them.

Many thanks.

[eithan h]

whats the oil pressure reading on tech2 and whats the control valve % reading?

[bigbluetruck]

Hi Eithan,

At idle I am reading 4 MPA and control v/v at 19%.
At 2000 rpm it is reading 7 MPA and control v/v at 27%
At 300 rpm I have 10 MPA  with control v/v at 30%.
The demanded and measured MPA readings do seem to match very well across the dynamic range observed above.

Once warmed up, I did achieve a smooth idle and it would rev quite freely,which is a big improvement, however when driving if I put the engine under any load it still hesitates and after a shoer distance power and speed reduced until it eventually stalled. I did note at this point that the pressure rail was at -0.3 at the time (not sure it should drop below zero). After being left a couple of minutes it restarted again once the pressure rail had built up over 5 MPA again. Should the pressure drop so quickly as soon as the HP pump stops being driven by the running engine?

I love driving the Trooper when it's running well, just hope I can rectify the problem as its unusable at the moment.

All the best.

[fithin67]

Just a thought - how long since you cleaned the Rail Pressure Control Valve?  The oil can form minute soot inside, pays to disassemble and clean.

[ivcho.vd]

[eithan h]

yes once the engine stops pressure should drop to 0mpa pretty much instantly but to go to -0.3 to me that says orps is faulty, where did you get it from?

also the orcv % needs to be when it's being driven

[Mike Rosie]

I had a slightly similar fault in that mine felt like it was missing when under load at mid range revs.
After lots of searching and trying thinks l replaced ORPCV and been spot on ever since