LT35 bogging down when cold

[Mike_AA]

Could anyone suggest why my 2005 LT 110hp bogs down when cold. It starts well hot or cold, but I have to really rev it hard when cold to take off otherwise it will stall. It feels like it's not running on all cylinders, I also get a fair bit of blue smoke from the exhaust as I rev it to get going when cold. After being run for a few minutes it's fine. The van has only done 60K miles, only 4000 of those in the last 5 years, so it has spent a lot of time sitting idle - that may be a contributing factor. A local garage turned off the immobiliser light after the battery had gone flat but they couldn't see any other error codes. Have tried searching but couldn't find any similar threads. Any pointers to possible causes would be really appreciated.

Many thanks
Mike

[Mike_AA]

No one able to offer any ideas? Or am I unlikely to get a response while I'm a 'One Post Wonder'? :-(

[niall campbell]

you need to change the diesel filter for a start

My guess is that the diesel filter has water in it, the filter may or may not have a drain plug at the bottom of it.

The water is more than likely freezing

New filters for new car range have started phasing out the drain plug, it costs money to put them on ................................... and no one seems to know nowadays to actually drain the filter

So change the filter first, I do mine every 20,000 miles regardless and I don't freeze in the winter

Then report back if it doesn't help

[Mike_AA]

Hi Niall,

Many thanks for taking the time to reply. I will change the filter in case there's water present but I should've mentioned, this problem existed prior to winter, in fact, it's existed for the best part of a year, but as the van was hardly used, I didn't worry too much. Now that I'm using it most days and live on a steep hill, it's more of an issue as I have to rev pretty high to get off the drive. In less than a minute though (before it's had chance to warm up properly) it's fine.

Thanks again
Mike

[Rob69]

I'm thinking that it is a pd engine, 2 litre or 2.5 litre 5 cylinder? . You say the mechanic scanned for faults but it depends what tool he used, not all OBDII tools pick up everything. A lot of folks (including myself) use VCDS for diagnostics. This would be best in your case, if no immediate faults come up then run logs during engine warm up monitoring the MAF, temp sender unit, glow plug status etc. A common failure is the temp sender unit, which could be fooling the ECU into thinking the engine is hotter than it really is giving you the poor running while stone cold. Someone must have also changed the timing belt at some point on that age engine, the camshaft setting or 'torsion' values should also be checked in case the cam is slightly out. Look for tippex marks as dead giveaway the proper locking tools were not used! That is low mileage on a van that age !!

[Mike_AA]

Hi Rob,

Ah, that could well be it, the temperature gauge has never worked since buying the van 5 years ago, it's the AVR 2.5TDI engine. I noticed a post on here a while back regarding a fairly common fault with one of the wires connecting to the temperature sending unit resulting in the temperature gauge not working. I'll get a VCDS diagnosis, the previous diagnosis was done using VCDS but they were only looking to turn off the immobiliser light after the battery had gone flat.

Thanks
Mike

[Rob69]

For the cost, just change the cts first, use a genuine vw òne and use a new o ring, get a new horseshoe clip as well, as you will break or lose the old one. pity they didn't spend a few more minutes while vcds was plugged in and make a few more checks!

[Mike_AA]

Have ordered the cts, I'll also do full service incl timing belts / water pump while I'm at it. Will report back whether problem solved or not.

Cheers
Mike

[Mike_AA]

Sorry to be stupid but what are the 3 temperature sensors? I have one with two wires above the thermostat, one with four wires below the thermostat and one with a 4 point terminal but only two wires connected in front of the battery? Don't suppose anyone knows of a service manual or diagram available online? There seems to be so many variations of the LT, it's difficult to search for relevant data.

So far, I've done an oil and filter change, attempted to change the fuel filter but backed out as it's so inaccessible and I wasn't confident that I'd secure the fuel hoses back on correctly, read a few horror stories on here and other forums about leaks after changing so just drained it instead - fuel clean with no water present. Flat spot still present but haven't done anything that would improve it yet.

Cheers
Mike