Poor running

hi again,
I've got a 55 plate td4 with a running issue. Cold starting has always been bad with smoke & lumpy idle. If you hold revs at 2000 when cold you can't see behind it & misfires like a good un! It's always felt to surge a bit when cruising at 50-55, like dabbing the brakes now & then, so when I started to smell diesel I thought bingo! It was the high pressure fuel pump leaking, so had this replaced. Only thing it did was stop the leak, still running as above. As the wheel arch pump has always sounded like a banshee I replaced that with a Bosch one, quiet now but still runs the same. It then began being very hesitant at junctions, unplugged Maf & bingo, surging gone, pulls like a train but very rattly/smoky. Replaced Maf tonight with brand new Bosch unit, nice & quiet & plenty of power but surging has returned!!! Pulling my hair out now, any suggestions? I'm thinking maybe injector, done 103,000 miles. Cheers guys.

my 53 plate td4 does exactly the same ,has done for nearly 3 years but as i dont hold it at 2000 rpm that often it doesnt present that much of a problem as for surging with normal driving i hardly notice that now ,many people on here have changed allsorts of things and still have the same problem, trouble is it can be a multitude of things ,have a good search and you will come up with a solution eventually , hope you sort it out soon .
Trev

Thanks for your reply. Sounds like it's a very common fault! Think I'm going to run with it & see if it improves, towing the caravan to York this weekend so will give it a good run. To be honest, it's one of those things that gets stuck in your mind & you find yourself looking for it happening I think! We will see.

Crankcase filter or EGR valve ? Have you checked / changed / cleaned these ?

Crankcase breather is the bmw modified one. The egr was a bit gummed up, cleaned it out & it moves freely. I've only had the car 2 months & know the previous owner, he bought it in 2008 at 60k & only changed oil once! It' had 98,000 when I got it. It was cheap so thought I'd risk it despite the neglect, fully serviced it straight away, but the manifold & engine is really carboned up thanks to the long oil changes.

Replace the fuel rail sensor first, then injectors. Unfortunately your going to have to methodically replace 1 item at a time until you find the issue. Is the fuel tank dirty?have you tried taking the battery off for half an hour? All sound daft ideas, but as nobody has come up with a definite fix for this fault, try everything. Mike

The injectors are a bit expensive to replace as a punt at fixing a problem.

GrumpyGel said:

The injectors are a bit expensive to replace as a punt at fixing a problem.

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True, could try taking the car to your local bosch diesel place and get them tested, they'll refurbish faulty ones as well. Mike

Clean out the manifold, clean the MAP sensor with carb cleaner do not spray directly into the MAP sensor breather hole, wipe off any gunk, check all the EGR hoses leading to the solenoid and those coming from it, check the injector leak back T connectors these are plastic and can go brittle and leak, also try a leak back test for the injectors, but deal with the easy items first.

Thanks for your replies. Been out on a long run tonight & it ran like a piece of ****! When you go to accelerate in any gear at any speed it hesitates followed by a cloud of smoke, also if trying to hold steady speed it gradually slows itself down. Feels like running an older petrol with the choke out.

I know very little about diagnosing these TD4 faults - but its obviously a fuelling or airflow issue.

Having changed the pumps on the fuelling, I suppose that does just leave an injector issue. Might be worth getting them tested - and wait for a silly price for replacements.

However, I'm wondering if this might be a turbo issue. Unlike the injectors, this could have been affected by poor maintenance. I presume you have checked all the hoses & made sure the intercooler is clear. I don't think I've seen MAP sensors causing this much trouble.

Don't think you'll be taking the caravan away this weekend!

Lets hope its not the turbo!

I presume that was caused by the turbo.

GrumpyGel said:

I presume that was caused by the turbo.

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Yep. Turbo compressor oil seal failed. Thankfully it's not that common. Most modern diesel engines now have a throttle plate in the inlet which closes at engine shutdown. This makes a diesel engine stop more smoothly in normal use but additionally will help reduce runaways.

GrumpyGel said:

I presume that was caused by the turbo.

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Poor crankcase breather maintenance, infrequent oil changes lead to poor turbo seals and lots of oil being rebreathed by the turbo and sent into the intake, acting as a fuel supply. Engine can't be switched off as it's using the oil as fuel. Only chance is to put it 5th with handbrake on and dump clutch, or stuff a large rag into intake.

And that, kids, is why we service our cars every six months, rain or shine.

I had a diesel runaway really briefly a few years ago just after I'd serviced it. It was one of those things that takes you by complete surprise. All I did was start that car up and off it went at full chat. Luckily I had a big rag on my roller cab so stuffed it into the air intake. The engine slowed to a complete stop, thankfully without any long term damage. If you can't stop it by stalling or blocking the inlet, it'll run until the oil runs out. Normally stuffing the engine up in the process.

Booking it in with pk automotive in Lincoln for a full diagnostics. He has a four wheel drive rolling road so can connect all his gadgets & see what's going on. Meanwhile, my boss is very kindly lending me his car to tow the caravan. It's a Range Rover sport 3.6 tdv8, so think I'm going to enjoy this weekend!! Thanks again for all your replies, I'll report back after I get it checked out.

That has 2 turbos to go wrong, and needs the body off to change them.... #JustSaying

Danclif said:

Meanwhile, my boss is very kindly lending me his car to tow the caravan. It's a Range Rover sport 3.6 tdv8, so think I'm going to enjoy this weekend!! Thanks again for all your replies, I'll report back after I get it checked out.

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Remember, don't get too giddy with the fast pedal while the caravan is hitched, you can damage the chassis on the caravan. Have a great time. Mike

try the fuel water trap just in front of the rear drivers side wheel and replace the thr fuel filter.
£18 might just solve your problem