MikeFl4

Active Member
Hello everyone,

Taking a break from my recent exploration in the V8 world, today we are back to the hard slog that is slowly chipping away at my diesel P38 in order to make it “as good as possible”

I have been having an engine issue that’s just a bit strange, but I think it all stems from a timing issue (unless one of you guys has another idea!)

The engine runs good, starts instantly after a single cycle of the glow plugs and runs nice and smooth (if you don’t touch it, more on this later)

It really seems to be an injection timing issue just based on that modulation read out. Unfortunately, from what I have read, it seems in order to set the modulation correctly I need the engine to come up to proper temperature! (Note: I have swapped the thermostat and although this finally brought my temperature up from below C all the time – It only gets to about 1/3 the way there)

Since my car has 230K miles, would it really be worth getting all of the proper timing equipment in order to set the timing correctly? I have read its possible to adjust the timing "by ear", this type of adjustment is more common on high mileage engines which are too worn to be adjusted using factory measurements.

The actual problem:

Inconsistent idle and a lumpy/bumpy return to idle while being driven… Let me explain in this video:




**Stuff to mention below to narrow down the problem**


Jobs that have been done:

Full service of every single oil and filter in the vehicle

Refurbished injectors x 6

Intake manifold gaskets (1999 model so rubber type)

Cleaned/flushed intake manifold

New glow plugs

New leak off pipes

Cleaned / swapped MAF (for testing purposes)

Cleaned / swapped MAP sensor (for testing purposes)

Pipes free from crap going from manifold to MAP sensor

EGR bypassed – one of those straight through pipes

Intercooler swapped (original one was leaking oil so I assume had a hole in it)

Note: Ac system has been removed from the car.

No CEL but often gives a code of “ignition timing deviation”



Things ive tested:

Turbo wastegate – I was able to move the rod so I assume its not stuck

All hose clamps are tight and pipes seem to be good with no obvious splits

Engine power is O-K, I’ve never driven a “good” M51 so I don’t really know what to base it off of

Removed cam cover and cleaned the oil sponge thing (engine seems to have high-ish top end pressure – no pressure from crankcase testing through dip stick – only what I would consider as slightly excess pressure coming from the cam breather hose


Things to note / im not happy with:

I have swapped the thermostat and although this finally brought my temperature up from below C all the time – It only gets to about 1/3 the way there. I have another thermostat that im going to swap in when I get a chance as having the engine running at the correct temperature is always a good thing.

Engine still seems what I would consider as excessively smoky when accelerating – very very much so at full throttle, it will cloud out the whole road behind you!
 
Sound like its drawing air ,your tank is lowish and if you have a duff in tank pump it will draw air ,check the see through pipe at the filter n see if its got bubbles ,;)..
 
What diagnostic is that you are using. as the P38 is very specific to what can read it?
I have been using an Autel Maxidiag, The Nanocom has been on the "to buy" list for a long long time, but ive had a pretty good experience so far with the Autel so ive been spending the money on parts instead of diagnostic equipment. I believe I can be pretty confident in the read outs from the Autel as its not given me any false readings yet, it helped be diagnose and fix the needle lift sensor & narrow down a lot of ABS faults.
 
Has the fip been touched at all, New seals etc.
From what I can see, the FIP has been changed at some stage in the past. Its far more shiny than the rest of the equipment in the engine bay and its got little yellow marks on all the bolts (signs somebody has taken it apart to be refurbished etc)
 
Sound like its drawing air ,your tank is lowish and if you have a duff in tank pump it will draw air ,check the see through pipe at the filter n see if its got bubbles ,;)..
Thanks for this suggestion, I can see that yes my fuel was kinda low in this video but unfortunately I have filled the car a few times since and its got the same problems - just that inconsistency etc. I believe the in-tank pump is fine as it starts instantly, half turn of the engine, no matter how long its been standing - and it never seems to drop in power or any fuel starvation type issues.

I might just have a check of that pipe at the filter, always good to make sure!
 
With a Nanocom and a steel rule the FIP timing can be set very precisely.
...

You know what! Screw it!

I just ordered a Nanocom, apparently the order has to be paid manually so waiting on an email...

So - anyone reading from here down (in about a week) I have a Nanocom!
 
...

You know what! Screw it!

I just ordered a Nanocom, apparently the order has to be paid manually so waiting on an email...

So - anyone reading from here down (in about a week) I have a Nanocom!
When you have it contact datatek as his method for setting timing does work and is quite simple to do. He sent me the instructions and I got my timing modulation to 52%
 
When you have it contact datatek as his method for setting timing does work and is quite simple to do. He sent me the instructions and I got my timing modulation to 52%

Excellent, that would be great (especially if it’s easy!)

Do you remember if the engine had to be at correct operating temperature in order to do this method? If so, I’ll work away at trying to get mine up to the correct temperature on the gauge.
 
Excellent, that would be great (especially if it’s easy!)

Do you remember if the engine had to be at correct operating temperature in order to do this method? If so, I’ll work away at trying to get mine up to the correct temperature on the gauge.

It does but is your temperature sensor reading correctly? I cannot remember if there are 2 or 3 on your engine but one a different one feeds the needle guage than the one used by the engine management system.
 
It does but is your temperature sensor reading correctly? I cannot remember if there are 2 or 3 on your engine but one a different one feeds the needle guage than the one used by the engine management system.

I believe it is reading correctly, I have very slightly "overheated" the engine twice in my ownership (Once with viscous fan explosion, other time just with a massive air bubble in the system) - Both times it only went about one notch over the middle of the gauge so I believe that - if it was reading low - it wouldn't have shown this (I also of course would not keep the engine running to see if it would actually overheat just to prove the gauge is right!)

But anyways, yeah, the gauge seems to be capable of reading correctly - Also, on a big, long uphill stretch - before I put in the new thermostat, it would reach middle on the gauge and go no further, once over hill would cool back down again (Just like the symptoms of a bad stat, but yeah I changed it and its still acting funny so hopefully its just a faulty part)
 
Excellent, that would be great (especially if it’s easy!)

Do you remember if the engine had to be at correct operating temperature in order to do this method? If so, I’ll work away at trying to get mine up to the correct temperature on the gauge.
Warm engine is essential for correct reading. Removing cooling fan can help achieve this
 
I believe it is reading correctly, I have very slightly "overheated" the engine twice in my ownership (Once with viscous fan explosion, other time just with a massive air bubble in the system) - Both times it only went about one notch over the middle of the gauge so I believe that - if it was reading low - it wouldn't have shown this (I also of course would not keep the engine running to see if it would actually overheat just to prove the gauge is right!)

But anyways, yeah, the gauge seems to be capable of reading correctly - Also, on a big, long uphill stretch - before I put in the new thermostat, it would reach middle on the gauge and go no further, once over hill would cool back down again (Just like the symptoms of a bad stat, but yeah I changed it and its still acting funny so hopefully its just a faulty part)
The gauge is not relevant, you read the engine temperature on Nanocom. It's best done with the viscous fan removed as you need to get the engine up to 95C. You then read the modulation figure and write it down. When the engine has cooled, you can use my method to adjust the FIP. With practice I can get it right first time, but with care anyone can get it very close first time, closer than is possible using the DTI method. I need an Email address to send the info too.
 

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