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Emnmem

New Member

• Dec 29, 2007

• #1

Hope someone can help, I have a very nice P38 DSE diesel. It has started to suffer with a lumpy tickover once warmed up, is fine when cold. This often causes the engine to stall when moving from drive to reverse. Also it has now started to hesitate when at steady speed on a light throttle usually around 50mph. However if you accelerate its fine. I did replace the fuel pump in the tank at around 120k (now 150k) but had trouble starting then, (air bubbles in fue line) but nothing like that now. I have replaced the ECU engine temp sensor as I have had trouble with these on V8's but no change. Would really appreciate any ideas.

Mike

 

wills

Well-Known Member

• Dec 30, 2007

• #2

hmmm, what year P38?? Does it have the MAF sensor?

-Wills

 

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irpbath

New Member

• Dec 30, 2007

• #3

BMW 6 cylinder? if so........Theres a signal injector which can cause problems on these, start of fuel injector (no 4 injector). The 6 cylinder bmw engine does suffer from injection pump problems. Its not easy to get it reconditioned either. Have you had it checked for fault codes? if not i suggest you do.

 

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LSE3.9

Member

• Dec 30, 2007

• #4

I seem to recall that the fuel lines from the tank run up and over the rear axle and are prone to corrosion here. if corroded they will allow air to enter and cause the misfire you speak about. Just a guess but worth a look I think.

 

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irpbath

New Member

• Dec 30, 2007

• #5

if the fuel lines are corroded then they will leak fuel , as you got the pump in the tank sending fuel to the injection pump. So it should be easy to spot if thats the case.

 

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Emnmem

New Member

• Dec 30, 2007

• #6

Thanks gents, its a pre egr model so has the IAT senesor not the MAF, no fuel leaks, I m not sure about the fuel lines running above rear axle as tank is located in front of the axle? I will try & get it hooked up to testbook.

Mike

 

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Emnmem

New Member

• May 19, 2008

• #7

Problem solved!!!

I have tricked the ECU into thinking the engine is colder than it is by inserting a 3000 Ohm resistor in the feed from the engine temp sensor to the ECU (grey with blue trace). This is in series with the sensor, so increasing the resiatance. The idle is now around 900rpm but the vehicle no longer misfires when ticking over, or at 50mph, it also has stopped stalling when going from drive to reverse (auto). I think the problem is down to wear in the injector pump & the resister overcomes this by increasing the fueling. the car does not smoke and the average consumption has not changed. Happy days!

Please do not hesitate to conatct me if you have the same problems & need further info.

Mike

 

SpudH

Well-Known Member

• May 19, 2008

• #8

Check out the posts on the P38 hot starting problems. There is a downside to what you have done as there is a different fuel map for hot and cold. Most of the guys put in a timed relay to introduce the resistor only when cold due to the side effects of running it full time on the cold map (I can't remember exactly what they were but I think some took a while to turn up)