TD5 "limp mode" and enginelight mystery : What to do?

In short, 2004 TD5 Defender 110, 180k km.
Engine was "rebuilt" 500km ago after head gasket went, AMC cylinderhead in place.

Weird problem has come up : Engine goes into a "Limp Mode" now and then. Engine stays on but throttle stops responding and amber engine light comes on. Turn the ignition off and back on the car starts normally and runs normally...Until the next episode, which might come after 5km or 100km.
No clear logic when the limping hits, maybe a bit more often when the engine is cold. Usually it goes limp straight away or preceede by a bit of coughing.

Engine feels relatively ok, a bit sluggish maybe. And has perhaps a bit "harder" valve rattle than before the rebuild, maybe..

Have tried the following :

- MAF sensor on or off. No effect, still goes limping.
- Turbo wastegate actuator checked & lubed, moves normally.
- Fuses checked, all ok.
- No apparent problems in the engineroom.

Will clean tomorrow MAP to see if that helps.


But, dear gentle(wo)men : Any suggestion what to troubleshoot??

Will take the car back to the shop next week for the checkup but would love to solve the problem by my self if possible.

Put a Hawkeye or Nanocomm on and read the fault codes

I had the same issue with one of those Jap vehicles, which I bought in error. I never managed to get to the source of the problem, or at least the main dealer could only give me three possibilities! Each of the three fixes was going to cost €1,000 plus. I sold the car to a dealer and let hime live with the problem.

The most likely, was the mass air box, or that's what they thought

Oh, I forgot to welcome you to the Zoon of Loonie lovers

as far as i know theres only 2 faults that the ecu puts the engine mil lamp on for on the td5, one is crank sensor, other is throttle position sensor, diagnostic reader will tell you stored codes, but when throttle position sensor is at fault the car will idle but not respond when pedal is pushed.

Thx Ac!

A quick recap : 600km since the last warning light..."problem" seemed to have remedied itself...

Actions taken :

- First disconnected the MAF, problems continued.
- MAF+MAP+Airsensor checked and cleaned (MAP was clean, others were ok), problems continued.
- Checked and lubed the turbo actuator (was a bit stiffish), problems continued.
- Checked the throttle and attachments, seemed fine.

But.

I also realized that the car had stood outside for a month in december waiting for the engine repairs (blown gasket), with only a 1/4 of diesel in it.
After that it was transferred to a garage for 3 months where it stood. So, filled up the tank and checked the throttle and avot...problem is gone.
So the actual problem might have the the condensation of water in to the fuel (winter diesel) tank, 4 months of immobility does no one any good, apparently.
There seemed not to be water in the fuel filter as I checked it out way too late, only after I filled up the tank.

Oh well, will take the car for a checkup anyway to get the codes read. Car seems to run quite well but (imho) the throttle response is a bit lacking on the lower revs.
Will check if the TPS is actually crapping out, the symptoms fit to the symptoms Johnlad described above.
Afaik it shouldnt be crank position sensor as what I heard that malfunctioning sensor would make the ECU prevent the engine to even start?
Or is it so that that if the sensor gives a misread the engine light goes unresponsive (yet leaves it running)?

The saga came to conclusion finally. Problems continued, intermittently.
Read the codes and there were two faults, crankshaft sensor and throttle position. Garage decided to change only the crankshaft sensor as it looked that someone (previous owner?) had already changed the throttle pedal not so long ago. Well, after few days the problems continued...
Back to the garage, new throttle pedal and voila = Problems gone.


Well...some problems are gone...and new surfaced.

Front right wheel bearing decided to go suddenly (within 10km) and took something with it in the front diff. Hopefully only some bearings.
Was nice to limp back home 500km without the front driveshaft.

#winning