Fixing EGR excessive flow fault permanently.

[sepulchrave]

So it's MOT time and the Fabs being naughty, dead battery during the week (ECP £35, blinding value) and the ultra-persistent CEL with DTC 16786 which I've been ignoring for six months.

 

Time to fix it, weather forecast good, test match finished early and no other plans for the weekend so started yesterday after lunch:

 

Stripped off air cleaner engine cover, battery and complete battery box, drained coolant for reuse, disco'd and removed coilpack and lay it on cam cover, removed rad top hose from thermostat housing to allow access to loathsome 10mm bolt holding invisible EGR link pipe clip.

Released EGR link pipe from inlet plenum 2 x M5 allen screws and very tight access behind the gear linkage cables, caught steel gasket as it dropped out, released EGR valve block from exhaust manifold, 2 x M6 allen screws, dropped steel gasket and retrieved, disco'd air bleed and multiplug and removed entire EGR valve and link pipe assembly in one big lump.

Disco'd and removed throttle body, 4 x M5 allen bolts, disco'd injector loom from injectors and moved aside, removed fuel rail complete with injectors, 2 x M5 allen bolts and swung to one side.

Disconnected brake servo vacuum line from plenum, ditto EVAP vacuum line, disco'd MAP sensor, released inlet manifold, 6 x M6 allen screws, left the top middle screw until last to support assembly then removed entire manifold and plenum in one lump.

 

Ran it a bath using a dexion tub and 5L of Tetrosyl engine degreaser and proceeded to strip everything to its constituent parts, EGR valve assembly, 2 x 13mm hex screws, gave everything except the valve a bath, the valve itself and the throttle body got a stand-up wash, removed that loathsome EGR link pipe support clip and threw it in the bin.

 

Stripped the EGR pitot tube from the plenum, 2 T30 torx screws and chipped out the accretion of hard carbon stuck in the loop of the pitot tube shield. Removed MAP sensor, 2 x T15 torx screws, from plenum and cleaned separately using a fine brush and brake cleaner.

 

Stripped the manifold and plenum, removed the four curved link pipes and discovered that the presence of number 4 prevents the removal of number 3 so suggested order would be 4, 3, 2, 1, number 4 was found to have a single 2.5mm allen screw, all 15 remaining screws were T25 torx. Removed 10 x T25 torx screws from plenum and split it in half.

 

Everything was filthy, thick with sooty sticky oily residue like bitumen, everything got a bath and a stiff brush until gleaming, then everything (NOT the EGR valve, TB, fastenings, gaskets or MAP sensor) went into the dishwasher for a full 90 degree hot wash with a fairy liquid tab while I watched 'Gone Girl' (great film by the way).

 

Once everything was super clean I decided to remove any casting flashings inside the manifold and plenum parts using my trusty Dremel, there were some nasty sharp edges from the die casting on all the cylinder entries and around the injector bosses so this took a couple of hours, the curved link pipes were sand cast and needed no such attention. Bedtime.

 

Today I put everything back together, all the manifold and plenum parts got a very thin smear of RTV silicon on the mating faces to guarantee no leaks and all the gaskets were fine to reuse, the only cost was 5L of engine degreaser from ECP which I poured back for reuse today after the sludge in the dexion bathtub had settled overnight.

 

I had to recode the engine back to 00071 from 00095 because the battery had been off but it started first time and ticked over nicely so I let it reach temperature before shutting it down and clearing all the codes, I was pleasantly surprised that I didn't need to adapt the the TB or the EGR valve. I let it cool while I got the roast chicken under way then I topped the coolant back up to the max mark.

 

All done, no DTC's and no CEL after a 20 mile round trip to drop my youngest daughter back at her mums.

 

It's fixed. MOT next week so I'll give it a good wash and hoover out, I'm not expecting any unpleasant surprises.

Edited 2 August, 2015 by sepulchrave

[coskev]

You missed off the important part, surely you've gained 20 odd bhp and loads of throttle response?

 

Seems to be the norm on forums for jobs like this.........

[Breezy_Pete]

What I missed was the logic of how cleaning stuff can solve 'excessive flow'?

I can see that if debris were preventing the valve from closing fully, that might be relevant, but not debris anywhere else. Wouldn't that more likely cause 'insufficient flow'? 

:think:

[sepulchrave]

You missed off the important part, surely you've gained 20 odd bhp and loads of throttle response?

 

Seems to be the norm on forums for jobs like this.........

 

To be honest the engine feels fresher and breathes more deeply at the top end but this would be missing power restored rather than adding anything new.

 

What I missed was the logic of how cleaning stuff can solve 'excessive flow'?

I can see that if debris were preventing the valve from closing fully, that might be relevant, but not debris anywhere else. Wouldn't that more likely cause 'insufficient flow'? 

:think:

 

I believe the 'excessive flow' phrase refers to the ECU requiring more EGR despite the valve already being wide open, thus suggesting a partial blockage. I agree that the language is misleading but the PCM is Italian, the engine German and the car Czech so hey-ho.

[Breezy_Pete]

Hope you're right, and hope the dishwasher stops smelling of 'engine' before too long.

 

My missus very bravely let me put a cylinder head in ours a year or two back; it stank for about the next five washes afterward.

[sepulchrave]

Hope you're right, and hope the dishwasher stops smelling of 'engine' before too long.

 

My missus very bravely let me put a cylinder head in ours a year or two back; it stank for about the next five washes afterward.

 

It doesn't smell at all, the engine degreaser I used is completely water soluble so every trace was washed away.

[hutchysrs50]

I found anything with the slightest trace of oil on it will make the oven smell for some time.

I did a similar thing on my 1.2 recently, didn't have any faults but removed the throttle body, map sensor and egr valve with pipework to clean them all up to avoid faults in the future.

[Thisday]

 

................... went into the dishwasher for a full 90 degree hot wash with a fairy liquid tab while I watched 'Gone Girl' (great film by the way).

 

 

 

The book is much better than the film (in case you want a holiday read....)

[sepulchrave]

Quick update, CEL came on again after 50 miles with the same fault code (16786) so I cleared the code and ran the TB and EGR adaptation routines and it seems to have gone away permanently now so adaptation is necessary.

 

A bit of a dry read I know but I documented it so that the search function would bring it up for people looking for the solution to this common problem.