Fluctuating Idle RPM -Diesel P38

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Removed n measured resistance of CKP, 1328 ohms. Is it right?
Idle value changed to 130 to escape fluctuations but did not help. Now it fluctuates at RPMs up to about 2000.
 
Thanks Grrr for that excel sheet. Is it the 4th injector playing up?
When I say fluctuations even at 2000 RPM, when in gear , engine @ 2000 RPM, foot off accelerator then the engine shakes.within a range of +/- 300 RPM.
I have not gone beyond 2000 RPM to observe. But below 2000 RPM it's there up to idling.
I'm going to recheck static timing. Waiting for the CKP from rimmers.
 
kapilamuni said:
Thanks Grrr for that excel sheet. Is it the 4th injector playing up?
When I say fluctuations even at 2000 RPM, when in gear , engine @ 2000 RPM, foot off accelerator then the engine shakes.within a range of +/- 300 RPM.
I have not gone beyond 2000 RPM to observe. But below 2000 RPM it's there up to idling.
I'm going to recheck static timing. Waiting for the CKP from rimmers.
Click to expand...

That makes sense do it. Stop buggering about until you have a known good CPS fitted. When you check static make sure the lock pin is engaged in the hole in the flywheel, so that the engine is locked solid and will NOT TURN in either direction. It is very easy to miss the timing hole and get hung up on the timing pip 20 degrees after TDC. Which would give you off scale high modulation. Last movement of pump to achieve 0.95 mm lift on cam should be towards engine.
 
kapilamuni said:
Thanks Grrr for that excel sheet. Is it the 4th injector playing up?
When I say fluctuations even at 2000 RPM, when in gear , engine @ 2000 RPM, foot off accelerator then the engine shakes.within a range of +/- 300 RPM.
I have not gone beyond 2000 RPM to observe. But below 2000 RPM it's there up to idling.
I'm going to recheck static timing. Waiting for the CKP from rimmers.
Click to expand...

Beyond my ken. I'm just watching what Wammers is typing!

As far as I know it uses the crankshaft sensor and number 4 to work when to inject the fuel. Wammers will correct me if I'm wrong but I think it uses the crankshaft sensor to work out where the engine is so it can inject the fuel at the right moment and then the number 4 injectors tells it when the injection actually occurred. Ideally the 2 shouldn't be too different. If there is a difference it can modulate the timing using the electrickery in the top of the FIP, to a certain extent - this is your timing modulation. However, if it goes too far out of whack then it cannot adjust it far enough, it throws an error and your engine stalls.

Given your values are quite far apart something is clearly wrong! Wammers thinks the crank position sensor which would make sense. How he knows it is that one and not the number 4 I don't know. Maybe if you unplug number 4 injector it would just run with some sort of default value? DON'T TRY IT! Not until one of the diesel gurus says if it would be safe.
 
Grrrrrr said:
Beyond my ken. I'm just watching what Wammers is typing!

As far as I know it uses the crankshaft sensor and number 4 to work when to inject the fuel. Wammers will correct me if I'm wrong but I think it uses the crankshaft sensor to work out where the engine is so it can inject the fuel at the right moment and then the number 4 injectors tells it when the injection actually occurred. Ideally the 2 shouldn't be too different. If there is a difference it can modulate the timing using the electrickery in the top of the FIP, to a certain extent - this is your timing modulation. However, if it goes too far out of whack then it cannot adjust it far enough, it throws an error and your engine stalls.

Given your values are quite far apart something is clearly wrong! Wammers thinks the crank position sensor which would make sense. How he knows it is that one and not the number 4 I don't know. Maybe if you unplug number 4 injector it would just run with some sort of default value? DON'T TRY IT! Not until one of the diesel gurus says if it would be safe.
Click to expand...

I can only go on the info as reported by the OP. I am not stood by the car and was not when the work was done. I do not know for sure that the static has been done correctly. I do not know if the chains have been fitted correctly. I can only assume they have. If all is correct then the CPS is the cheapest option to try first. The CPS reads engine RPM, there are two timing pips one 40 degrees BTDC and one 20 degrees ATDC. The CPS reads these as they pass it and the ECU then extrapolates where TDC is. The needle sensor measures the point of injection. The ECU then modulates the timing solenoid to increase or decrease internal fuel pressure pressing against the timing devise piston to rotate the cam set in either direction to adjust point of injection to TDC. When all is correct the point of injection should be at idle warm engine within a couple of degrees of TDC and the needle RPM and CPS RPM should be within 40 RPM of each other. If he is getting 96% modulation and static is indeed correct something is seriously wrong, under normal circumstances that would indicate a grossly retarded static setting. The needle RPM is sensible the CPS RPM is not from his readouts.
 
kapilamuni said:
Guys, it happened again. The engine cut off while parked and idling. Luckily I was in a parking bay near kids school.
Got it started after waiting about two hours. Checked faults with Nanocom after coming home, nothing there except the usual 'timing value out of expected range...'
Also, checked gear box faults assuming it could be the torque converter lockup issue, but nothing.
Noted that 'fuel quantity current' value is floating around 0.00 to 0.50 mg/s @ idle and rarely goes to 2.25 mg/s while 'fuel q/feed back' gives steady 63.25 or 63.00 mg/s.
If I accelerate to 2000 RPM 'fuel quantity current' value moves to about 17 mg/s. Is this a valid set of values for fuel quantity current?
Appreciate your quick responses as this is my daily runner and scared to take it out again.
Click to expand...

0 to 0,5 mg/stroke at fuel quantity current is way too much fuel and quantity actutatar cannot correct that, you won't get steady timing modulation when RPM are jumping like that.
loosen four middle section bolts and tap it towards front of engine to achieve around 5mg/str on hot engine.
5 mg/str is less fuel than 0 mg/str because it's only a reading from quantity actutator voltage map. Idle control only tries to achieve steady rpm, and it can't be done when fueling is not set right.
 
N2O said:
0 to 0,5 mg/stroke at fuel quantity current is way too much fuel and quantity actutatar cannot correct that, you won't get steady timing modulation when RPM are jumping like that.
loosen four middle section bolts and tap it towards front of engine to achieve around 5mg/str on hot engine.
5 mg/str is less fuel than 0 mg/str because it's only a reading from quantity actutator voltage map. Idle control only tries to achieve steady rpm, and it can't be done when fueling is not set right.
Click to expand...

The fact that he may have not replaced the pump mid section correctly has been mentioned several times, he ignores it.
 
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Last time I've done some experiments with incorrectly adjusted quantity actutator and finally it idles and drives well with my 11mm pump. Someone messed with internal adjustment(arm and copper plate) and it would't react to change of load like it should, revs were dropping when selecting gear or when AC compressor cut in. Increasing SWG voltage and adjusting fuel quantity completly cured it.
 
N2O said:
Last time I've done some experiments with incorrectly adjusted quantity actutator and finally it idles and drives well with my 11mm pump. Someone messed with internal adjustment(arm and copper plate) and it would't react to change of load like it should, revs were dropping when selecting gear or when AC compressor cut in. Increasing SWG voltage and adjusting fuel quantity completly cured it.
Click to expand...

Revs are supposed to drop momentarily when engine is put under load but be returned to 750 by quantity servo increasing fuel subject to signals from CPS. Cannot speak for your bastardised pump but idle fuel quantity is set electronically when the pump is set up on the calibration machine. If pump centre section is removed and not replaced correctly initial idle fuel will be changed. He says his car ran well after he did this. He may have been lucky. This problem arose after he changed chains and re-timed the pump. I think it is more to do with that than the pump centre section being a little out. He has either timed the static wrong or has a failing sensor. If the CPS fails engine RPM is taken from needle sensor. If the needle sensor fails the engine will go into limp mode and mil lamp will come on. If there is a vast discrepancy between needle sensor RPM and CPS RPM timing solenoid will modulate to try and correct it. He says modulation at idle varies between 40% and 90% or more. That would indicate to me a CPS malfunction.
 
I guess it is possible that when the chains were worn and he replaced the pump top he compensated for the worn chains by fettling it to run smooth. Now he has the chains etc all setup correctly the pump-to might be giving issues as it is correcting something that isn't there anymore?

Can the readout from the CPS be picked up in any other menus on the Nanocom?
 
Grrrrrr said:
I guess it is possible that when the chains were worn and he replaced the pump top he compensated for the worn chains by fettling it to run smooth. Now he has the chains etc all setup correctly the pump-to might be giving issues as it is correcting something that isn't there anymore?

Can the readout from the CPS be picked up in any other menus on the Nanocom?
Click to expand...

Pump top was marked before removal and replaced accordingly. Did not make any adjustment as I was only trying to cure a leaky pump. Also, I did not know about chain stretch, until recently thanks to this forum.

I have redone the static to read 0.95 and got the starter motor serviced. Still the hot start n idle fluctuations remain but I can start it immediately after shutdown.
I,m waiting for the new CPS.
Also, could it be the worn throttle pot at the idle position, on n off seeing idle switch?
On park or neutral idling, when the fluctuations start, I can put into gear and stop fluctuations. When on the move, if I take foot off the acceleartor, fluctuations start but stops when the car comes to a complete stop or accelerated again.
All the fluctuations happened randomly but since last two weeks , more frequent.
 
Don't know, to be honest. This is beyond my experience. It is hard enough trying to diagnose something you cannot see from someone's description even when you've seen it before. Throw random into the mix and that's the icing on he cake. Random does sound sensor / electronic-like though, especially if doing mainly when hot.

Let's see how it behaves with the new CPS. One thing at a time.
 
You cannot put pump middle section based only on previously made marks, tens of milimeter makes significant change in fueling. Adjust middle section position, and it will work. Fluctations start when you remove load from motor and it cannot lower fueling anymore. Trust me, i have done it many, many times. Maybe middle section bolts aren't torqued properly and it moved.
:D
 
It's not only when hot. Even at startup when cold it's there. Basically, engine temp has no bearing on this.
Can the throttle pot wiper make this kind of fluctuations?

With the horror stories around, I'm scared to do what N2O suggests. I was very lucky two years ago and do not look so at the moment.
 
kapilamuni said:
It's not only when hot. Even at startup when cold it's there. Basically, engine temp has no bearing on this.
Can the throttle pot wiper make this kind of fluctuations?

With the horror stories around, I'm scared to do what N2O suggests. I was very lucky two years ago and do not look so at the moment.
Click to expand...

Wait until you get the CPS. See what you get with the new one fitted. The pump mid section position CANNOT cause the modulation to flop about between 40 and 93%.
 
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Yes,will wait for the CPS.
It does about 5-6 Km/l in town but can't remember what exactly appeard on the display.
Will check it tomrw morning n post here.
 
Last edited:
To be fair the marks are already there. You can always put it back again.

As N2O says it is tens of millimeters. When I did mine the act of tightening was enough to take it out. In the end I left the bolts ever so slightly loose and with a piece of wood just tapped ever so gently so it just moved then tried again. In fact in the end I did it with the engine running and a mate in the cab to turn the engine off as soon as revs went too high.

CPS is probably safer to play with though!
 
Message centre says 5.4 L/100KM (without AC- I don't use AC since this idle problem), which is absurd. Even my small Toyota 1.5 Dturbo was doing 10L/100KM under similar conditions with AC.
Actual usage is about 18-19L /100KM which is in fairly heavy traffic. I figure this is too high but has been the position for the 8 yrs of my ownership.
 
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