Confusion.

**Disco Muppet** · 18th July 2014, 05:06 PM

Hia folks.
Chasing a confusing issue on my Td5 auto.
Problem started a while ago, with fairly lack-luster performance.
Hooked up to Slunnies nanocom which showed a MAF reading of around 40 at idle so pretty reasonable to say it's carked it.
It was still quite drivable though so I persisted with it, didn't want to rev past 3000RPM though (As in, it would, but only when very severely motivated)
Driving home from uni one day I started getting the kangaroo experience above 2500RPM, along with a hissing sound, which pointed me to a boost leak.
Fair enough, replaced the hoses to the boost modulator with some new hose, which was smaller in ID than normal.
Back to a level of performance best described as 'meh'.
Disconnected my MAF and we're back to 'zoom zoom', whizzing past 4000RPM happy as larry.
Next time I drove it, back to meh. Persisted for a while and got crap boost again so bypassed the modulator with some new vacuum line, 6mm ID I think.
First drive, again zoom zoom, no worries getting past 3 grand.
Now we're back to meh.
My fuel pump makes happy noises for a while with the key in the ignition waiting for the glow plugs to go out, then goes silent, which I understand to be normal.
Will still get past 3000rpm with 'encouragement'.
Gentle driving is okay, but if you kick it in the guts it doesn't do much, whereas it used to be off like a rocket.
So it appears I need a new boost modulator and a new MAF.
Are there any other things I should be checking? Are my lack-luster performance issues going to be solved with a new MAF?
If I plant it from stand-still it doesn't shift out of 1st until about 3800rpm, but I understand that a disconnected MAF will mess with auto shift points.
Any input appreciated.
Cheers

Muppet

**PhilipA** · 18th July 2014, 08:04 PM

1-2 change at WFO is 4200RPM, so maybe you have a sticking wastegate causing lower power and less airflow through the MAF.

Regards Philip A

**EvilGTV** · 18th July 2014, 08:32 PM

Sticking wastegate is a pretty fair call, especially being easy and free to check out.

I discovered that even in a manual car (remapped), they move along fairly happily with no boost at all until you ask for more than light acceleration, or higher revs. If I hadn't had a boost guage on my dash failing to move off the stop, it probably would have taken me a while to figure out.

I was really surprised at how punchy a non-turbo Td5 actually is, I would have thought you'd struggle to get to 60-70k, but cruising (and casual acceleration) at 100k was no problem at all, just with EGTs about 100 degrees higher than normal. The torque multiplication of an auto would hide the fact even better.

**Disco Muppet** · 18th July 2014, 08:46 PM

Had considered a sticky wastegate, but that's normally an issue of them being driven sedately....
Not a term that fits my driving habits

I'll check it anyway

**EvilGTV** · 18th July 2014, 08:57 PM

Originally Posted by Disco Muppet

Had considered a sticky wastegate, but that's normally an issue of them being driven sedately....
Not a term that fits my driving habits

I'll check it anyway

Sed-ate-ly? Nope, don't understand a word you're saying...

**Disco Muppet** · 18th July 2014, 09:31 PM

Originally Posted by EvilGTV

Sed-ate-ly? Nope, don't understand a word you're saying...

Tried that excuse with the cops.
Didn't work

**rangeyrover** · 20th July 2014, 07:42 PM

When my old mans TD5 did this in the UK it turned out to be a collapsed cat, ie blockage in the exhaust system.
Worth a check. Manifested itself as a reluctance to rev, but everything else seemed normal.

**Disco Muppet** · 20th July 2014, 08:57 PM

Hmmm interesting.
I don't have a cat, I'll check the centre muffler. I know my flex joint is fubar so maybe that's something to do with it

Sent from my GT-S7500T using AULRO mobile app

**Redback** · 21st July 2014, 08:58 AM

How are your intercooler hoses, and when was the last time you checked the oil in the harness, I'm assuming you have bypassed the EGR??

Only other things I can think of is air and fuel filters, but I would think the Wastegate mod and MAF will be the culprit.

2500 to 3000rpm is fine for checking your MAF and 40 at idle is too low, should be 60.

Baz.

**Disco Muppet** · 21st July 2014, 11:39 AM

Yup, EGR is gone

Filters have less than 2k on them.
Intercooler hoses seem fine, IC itself was flushed <15k ago, no plumes of black smoke.
I'll check the red plug.

Thread: Confusion.

Thread Tools

Confusion.

Collapsed Cat?

Bookmarks

Bookmarks

Posting Permissions