[purple145]

Hi, I have been getting somewhat erratic running from my JTD for a while, plugging in ECUscan seemed to point to the MAF (duly replaced) but I am still getting a difference in the demanded air quantity and the actual which then suggests an air leak somewhere. (EGR blanked off with a plate with a hole and no swirl flaps).

Both main hoses are silicone and are good, I did find a twist in the vacuum pipe connector, and that improved performance now end but there are now times when it will not rev up then burst into life after a minute or so typically after being stuck in traffic or after hitting a bump. I went to investigate air leaks and found air being forced out of the air intake box through a pre-formed hole in the base, I am guessing this hole should be plugged somehow......?

Would this be the cause of my issues? And if not, any ideas where else to look.

Cheers

 

[Cuore_Sportivo_155]

is the measured airflow higher or lower than demanded?

to me it sounds liek you have egr issues

 

[purple145]

Hi, it varies, it typically demanded 300 and was drawing in 500 when I fitted the new MAF a few weeks back, but today during an unresponsive phase it was asking for 1200 and drawing just 300. The EGR is blanked off bar a small hole on the plate to allow the engine light to remain off. I am getting no warning lights at the moment.

This pressured air from the airbox puzzles me though, does not sound right to have air coming out? Gertting sucked in yer, but out?

 

[Cuore_Sportivo_155]

that partial blanking is useless.

300 is likely demanded when egr is active. 500 is about right fora 1.9 engine using NO EGR Similarly, when the engine wants 1200 but egr is stuck open you would only get around 300 (and no power).

seriously, check the egr or blank it completely as a test.

Yes, air moves in pulses so some will get back out. The MAF can read the direction of the pulses and distract the air going out from the ar going in. Again, faulty egr can mke this worse

 

[Pud237]

Does it have swirl flaps or is it a pre-swirl flap engine?

 

[purple145]

pre swirl flap

 

[purple145]

right, the mystery gets deeper.

I found that the connector to the vacuum pipe had a twist in it, which presumable meant the vacuum to the VNT valve was insufficient, I disconnected it, removed the twist pushed it back and was feeling confident I had found the problem, the car ran well with lots of power and good low end pick up.

However when I came to start it the next day it would barely tick over, stalled when under load, eventually after a minute or two I was able to get it moving gradually building the revs up. During this time there was a lot of smoke, then after a further minute or so the car flew, but again high smoke and low mpg, around 20mpg.

I have inspected both turbo hoses to ensure I had not disturbed anything, all fine, air filter still clean. I forgot to add I put on a new genuine (from Alfaworkshop not ebay!) MAF a couple of months ago. No MCSF light on the dash. Still getting that blowing out of the air intake box which does smell strongly of diesel fumes which is a puzzle.

Any ideas what is going on?

 

[halftone]

As Cuore_Sportivo_155 said at post #4, EGR sticking open. Seems to explain everything (except why there's a hole in your airbox).

 

[purple145]

if it is blanked off, which it is bar a 6mm hole, why should it? Further more it has been blanked off for months and the erratic running has only recently started.

 

[Pud237]

if it is blanked off, which it is bar a 6mm hole, why should it? Further more it has been blanked off for months and the erratic running has only recently started.

"Blanked off" to me means fully blanked, zero gas can pass through. A plate with a hole in it, I would call that a restrictor plate. If you have a restrictor fitted but your EGR valve is stuck open, the pressure in the exhaust manifold is going to be forcing exhaust gas very quickly through that 6mm hole and depriving the engine of oxygen. Reduced air mass measured will reduce injection quantity and further reduce power.

 

[halftone]

^^ What he said. And it's easy enough to check, just cut a bit of beer can to slide into the joint between the restrictor plate and EGR, so the 6mm hole is blocked. If that fixes the symptoms, it's the EGR. Don't leave the bit of beer can in there though, it will quickly burn/blow through. Either fix or replace the EGR, or get a proper blanking plate + map out.