406oc.co.uk

I'm currently suffering a bout of chronic turbo lag and am working my way through the usual suspects:
1. Fault codes, (none, bar an old intermittent overboost message).
2. MAF - looks OK on PP2k - around 400mg/impulse at idle and seems to rise progressively with engine speed / throttle position, (bit I will swap it with my bro's at the weekend to be sure).
3. Vacuum leaks - can't find anything so far
4. Turbo solenoid valve - swapped it with the EGR e/v, made no difference.
5. E/v filters - cleaned both of the above, to no effect
6 Boost leaks - can't find anything
7 TPS operation - goes progressively from 0 to 99%
8. (Still to do), check vacuum restrictors aren't blocked
9. ? Have I forgotten anything?

It drives reasonably OK and cruises normally, but there is a distinct lack of go until you reach 1500+ rpm and have had your foot on the accelerator for a few seconds. Once it goes, it's every bit as quick as ever. Bit of a nuisance, since it's Pugfest next week.
FWIW mine has no EGR, air dosers, or swirl flap actuator

I'm assuming no slack in the throttle cable up to the TPS?
Is the vac reservoir still fitted? a symptom of the vac leak on mine was a lack of servo assist if you did 2 heavy stops in quick succession, any open stretches near you to give it a try?

How long have you been running with the swirl fixed on 16 valve setting? I assumed it ran 8 valves at low revs for better torque but I'm basing that assumption on the fact I couldn't think of any other reason to have an actuator in the first place if thats not the case.

Intercooler full of sludge

no idea really

Hi Eric, I would be tempted to check the vacuum levels going into and out of the turbo ev. If you swapped with the egr one, it may be stuck from lack of use.

The Maf seems most likely if the turbo vacuum is okay - I can check it for you at Pugfest if you like.

gumby6371 wrote:I'm assuming no slack in the throttle cable up to the TPS?

Nope

Is the vac reservoir still fitted? a symptom of the vac leak on mine was a lack of servo assist if you did 2 heavy stops in quick succession, any open stretches near you to give it a try?

Still fitted, I'll check the brakes / try it without. Been meaning to remove some more surplus plumbing anyway.

How long have you been running with the swirl fixed on 16 valve setting? I assumed it ran 8 valves at low revs for better torque but I'm basing that assumption on the fact I couldn't think of any other reason to have an actuator in the first place if thats not the case.

About 9 months - it dawned on me that I was doing most of my motoring at 1900/2000 RPM since fitting the 6-speed and the swirl flaps open at 2100......
I think it did have fractionally more 'edge' at low revs with the flaps working, but it was marginal and the improvement from losing the EGR more than made up for it

Intercooler full of sludge

Hmmm. Mine has a minor leak & I have a spare so will swap it anyway

Many thanks for your suggestions gumby.

GingerMagic wrote:Hi Eric, I would be tempted to check the vacuum levels going into and out of the turbo ev. If you swapped with the egr one, it may be stuck from lack of use.

Possibly, but it's exactly the same. Thinking about it, I guess I have two more 'spares' to try......

The Maf seems most likely if the turbo vacuum is okay - I can check it for you at Pugfest if you like.

I may take you up on that Kelv, thank you, but I'm really hoping to get it sorted in time for my annual foray up the hill

Thanks for the suggestions, I'll try the MAF swap first because it does feel awful like that to me, then work through the others.

Have you properly bypassed the swirl ev, or just unplugged and bunged the diaphragm?

The swirl ev is prone to leaks too....

I only have 2 feeds from my vac pump now, turbo and servo - nothing else.

GingerMagic wrote:Have you properly bypassed the swirl ev, or just unplugged and bunged the diaphragm?

The swirl ev is prone to leaks too....

I only have 2 feeds from my vac pump now, turbo and servo - nothing else.

just unplugged and bunged the diaphragm, as far as I remember.

Thanks for the tip.

In effect, I only have the turbo & servo, but I've still got the vacuum reservoir and some* redundant piping....

....but not for long.

Loan of MAF arranged for tomorrow afternoon, (tyres, alignment & purhase of service bitz in the morning).

Have a peek at this, young man.
http://www.406coupeclub.org/PHPBB3/view ... 45&t=49159

It's oh-fish-hell, I haz naf MAF.

Borrowed my bro's MAF and it went perfick.
Then dropped one of the screws refitting his.
Then tried cleaning mine and snapped one of the sensing wires
....Hello Aunty Pollution, it's been ages.

To summarise, before I tinkered wiv it, I had a huge delay, then loads of oomph. Now I have an inifinite delay and no go at all.

Oh well, least I know what's up.

Anyone know where I can get an OE MAF for less than 90 sheets?

You have mail......

Forgot to say, I used a kiddies paintbrush and carb cleaner to clean my MAF- did it work? - no idea as my vacuum was at fault.....

When I fitted a new MAF I used a Hella one which was around £80 with my trade discount, not OE but still a decent brand. Never gave me any problems.

Thanks gents.

"Premium" MAF ordered from GSF with 35% w/end discount. Still £73+.

Had a leisurely* trip to work this morning, (with Aunty for company).

Patience, it seems, is a virtue. Unfortunately it's not one of mine.

I replaced mine with a Siemens/VDO one for about £80 about 6 months ago. Pricy

All sorted now.

GSF's 'Premium' MAF turned out not to be a Siemens, but it is VDO marked, packaging says Made in Germany and it certainly seems to work.
Car seems smoother and more responsive than it has for a while, guess it had been deteriorating for some time and I hadn't really noticed.

Siemens own(ed?) VDO, so you've got an OE one there, good job