UKC

Had a quick word with a mechanic concerning my poor fuel economy and an EGR fault code and he suggested "deleting" the egr- not strictly legal but would likely improve fuel economy/performance? Any anecdotes to share? Or just try cleaning/replacing the egr valve first as it maybe stuck/bad?  Just replaced battery so hoping may solve. (has stopped economy mode and esp light coming on which is a good start..)

In reply to magma:

using my friend's driving as a test (same 1.6 hdi engine), she got just over 40mpg over a few 60mile trips with my Citroen C4 GP yet she's just recorded an admirable 55+ with her Peugeot 308..

In reply to magma:

If you delete the EGR remember never to complain about any environmental issues again.

It's there for a reason, people who delete it are part of the problem, it's not really a solution to anything.

In reply to magma:

How many miles per year do you do in your diesel?

In reply to magma:

I would find a new mechanic, someone who will actually fix things rather than shortcut with dubious practices 

In reply to Andrew Lodge:

it's there for a reason, (marginal reduction of nox at startup?), but if it's not working properly it's worse than useless/deleting..

In reply to magma:

A working EGR has an insignificant impact on mpg.

It will reduce it a tiny but, as it's cooling cylinder temperatures, and displacing oxygen, you don't quite get as thorough combustion, but I don't believe you would notice the difference in mpg.

If it's stuck open, and the EGR allows too much exhaust gas into the cylinder (some can pass a lot through, not sure about yours) then under higher loads, you could be running rich and basically throwing fuel down your exhaust unburnt.

Not sure where the EGR only working on start-up comes from. They are effective mainly under partial throttle (not that your diesel uses a throttle in the conventional sense, but you know what I mean). At full throttle, they close off so they don't impact performance when you want full power.

A new EGR is about £120 (you can get cheap aftermarket ones for £30 but no idea if these are a waste of money or not). Since a blanking kit will cost something, the work to fit is similar to an EGR, may as well just get an new EGR and be done with it.

If it's the EGR motor that's gone, as the code suggests it's likely something else (injector?) that's causing the fuel efficiency issue.

In reply to magma:

Would this count as an engine modification that you’d need to declare to your insurers so as not to invalidate your insurance?

In reply to magma:

The suggestion to delete it, feels a bit like putting black paint over a warning light to "fix" the problem.

If you think there's only a few miles left in the vehicle and you want to use it a little longer, then delete away. But if you think the vehicle is worth fixing...

Edit: and clean your injectors!

In reply to magma:  Maybe buy some alcohol and give your mass airflow sensor a clean.  We have a 2005 diesel and I’ve just replaced the turbo to keep it going for a few more years until we go electric or similar and the fuel economy has jumped.  We try and avoid short journeys at all costs as they are not great for diesel engines especially modern ones.

Good luck

Toby

In reply to Blue Straggler:

It's illegal so it would absolutely invalidate your insurance, if found

In reply to magma:

No idea how similar the compared vehicles actually are but a reported 40 vs 55mpg is a reasonably significant difference, probably big enough to indicate a real phenomenon. Assuming similar vehicles, loads, conditions and usage, also assuming they run the same electronics so the dash/metering can be ignored I'd check the basics like tyres and brakes before messing with the engine.

Speed, wind, hills, bendy or wet roads, soft or threadbare tyres, draggy brakes, gearbox, aircon and heavy loads can all make a noticeable impact on economy and a big one cumulatively.

If your EGR might be broken get it properly diagnosed then if necessary fixed or cleaned.

jk

In reply to jkarran:

got as far as the EGR fixing bolts. think they're puny torx 27 and someone seems to have had a go at removing as can't get any torque. luckily seems to be enough access for drilling/bolt extractor, or would you suggest something else?

In reply to magma:

hammer and chisel at an angle to get them turning. 

In reply to magma:

T27 is what, M3, M4 at most? If you cut the heads off, will you ever get the threaded portion out? Are they really rounded or clogged with crud? Drilling M3 screws out without a mill will be a nightmare, they'll be way tougher than the body they're in, even getting the heads off with a drill won't go that smoothly, they're usually pretty tough.

Obviously penetrating oil, some axial smacks to break any stiction. I can't see a spiral screw extractor working at that scale but could be wrong. Assuming you can't turn the heads with pliers or mole grips? If you're sure they're already trashed see if you can pound in the next size up hex/torx driver or even a flat if it fits across lobes. Or you could cut a slot for a flat bit. If there is space to get the angles you could try knocking them round with a sharp chisel/punch. Or you could weld a screw on.

Also, does it actually have to come off, are you sure it's not working? All of it?

jk

In reply to magma:

I'd just look carefully first, a lot of EGR's (Beemers, Fiats, McCormick are ones I know) are installed with Torx TR (Tamper Resistant) commonly called Torx with a pin as there is a central pin to prevent a normal bit engaging fully. You'll find them on power tools, domestic appliances and stuff you aren't supposed to open. The bits are commonly available, just look for a hole in them.

In reply to jimtitt:

thanks jim, didn't know about them. no, they're defo normal torx. just ordered a damaged torx removal set to try first - some sort of hybrid of torx and screw extractor..

In reply to jkarran:

PO0490 error (possibly due to failing battery- now replaced)

if it's stuck then some sort of vacuum gizmo may release it, but perhaps easier to remove and inspect/test/replace?

In reply to ianstevens:

yes, was surprised the mechanic suggested it, but said it would be cheaper than replacing it (~£300 for delete). that's when i decided to do it myself- easy access on the DV6C engine- and a new one is only £60. just the pesky bolts. will need reprogramming tho?

In reply to magma:

Have you checked your tyre pressures recently?

In reply to wintertree:

tyres slightly overflated, new air/fuel filter. i'd like to give the engine a good thrash (meant to clear the soot/increase mpg if car has been used conservatively) but not sure of the timing belt..

In reply to magma:

Once you have removed it you can clean it and put it back on. Nylon bristle brush, carb cleaner, oven cleaner for the stuborn hard to reach places, rinse and repeat. Half an hour elbow grease and ideally new gaskets is all it takes.

Chances are the cooler is also blocked which takes a fair bit longer to do. I should know as i have to do it at least one a year.... (Thanks Volvo you useless clueless gits)

In reply to magma:

You’re welcome 

In reply to Mr Lopez:

It's almost certainly the EGR motor that's gone based on the code. 

In reply to magma:

Your mechanic is a cowboy. Go to someone that doesn't recommend illegal modifications.

In reply to magma:

Since it's putting up a fight, clear the error, leave it alone for a while see what happens.

jk

In reply:

this is a really good explanation of the EGR valve and delete..

youtube.com/watch?v=Bnpj4eIo6nI&

wonder how many people are driving around with high fuel consumpion due to bad ERG valves/MAF etc. don't think MOT emission tests would detect..

In reply to montyjohn:

Not necessarily. 0490 indicates that the voltage measured indicating the valve position is higher than the expected value that should be received from the commanded position. I.e. the valve is not opening/closing as directed.

I get 'control circuit high' codes when it's time to remove and unclog my manifold/swirl flaps and egr 

In reply to Blue Straggler:

my pleasure not sure how many MOT stations/insurance claims are going to go routing around behind the engine.. anyway, i'm determined to keep things legal. Thanks for your concern

In reply to Mr Lopez:

thanks. my circuit high code was in conjuction with cylinder 1 contribution balance. low mpg would suggest stuck open? hoped a new battery could provide enough voltage to get it moving, but prob not. error codes have not returned tho. there's a resistance test you can do without removing?

In reply to Toby_W:

thanks. will try that as well. electrical contact spray should do? although no MAF error codes..

In reply to jkarran:

^ This. 

In reply to magma:

Not really. The voltage referred to by the code comes from a potentiometer within the body. The valve/stem has a wiper that sweeps up and down on the potentiometer as it moves open/closed. Nothing to do with how much 'power' the battery provides.

 Depending what software you are using, you can read the 'valve position' and 'commanded position' and play around with the throttle see what happens and if you see any changes or.patterns. With more advanced software you can command the egr yourself to diagnose.

If your software allows you to read egr flow that's another way to figure out if it's moving, open, closed, or stuck somewhere in between. Playing with the throttle it should be commanded open in neutral with light throttle with a cold engine and should be closed if you touch nothing after start

​

In reply to Ridge:

i did get 43 on a hypermiling 10 mile journey from cold over some hills. need to do a longer journey myself really, but going from friend's driving over 60mile, fuel consumption seems to be about 20% up compared with peugeot 308sw with same engine, so something is up.. best get it sorted soon to save the earth?..

In reply to Mr Lopez:

i thought you'd be able to test in situ by applying a voltage and listening for something moving? 

In reply to magma:

Don't fall down the emissions conspiracy rabbit hole and just fix what's actually broken on the car. If you're concerned about exactly how the engine is running get a reader that'll show you live sensor data and you can review it for any anomalies that might not trigger an individual error code.

also 1.6 HDI isn't a specific engine if you want to compare expected figures between your car and your friends try these (or correct the years):

https://www.honestjohn.co.uk/realmpg/citroen/c4-2011/16-hdi

https://www.honestjohn.co.uk/realmpg/peugeot/308-2014

In reply:

I'm just about here with bolts removed so just a matter of twisting/pulling it out. unfortuately my attempt with a crowbar has cracked the solenoid cover. looking for a tool that can clamp onto the metal housing to rotate atm- a g clamp perhaps?..

https://youtu.be/RusnWja78ik?si=0iTlLoragWjToMqf&t=526

In reply to Nick1812P:

mine at the very low end of real world mpg, along with the other drivers who don't bother to replace their egr valve

In reply to montyjohn:

rather like that stuck injector, it can now rotate by hand (as far as valve will allow), but haven't managed to pull out yet..patience.. got a pry bar set on order as per video above

is carb cleaner better than wd40 for this sort of stuff?

In reply to montyjohn:

halleluja, it's finally out thanks to lots of soaking, twisting, and finally twisting and pulling with a trusty mole grip

https://photos.app.goo.gl/CRAHPuvYSs53qvHu9

new one would need reprogramming?

In reply to magma:

I did mine (VW 1.9tdi), along with the throttle body a couple of years ago. Cycled the ignition a couple of times, cleared the fault code off and went for a drive. Engine management light has never come back on and the problems with boost and power were sorted. My van's 2007 though and about as sophisticated as a house brick.

In reply to montyjohn:

Got the new EGR fitted but now getting PO0489 (circuit low instead of high), so ECU probably needs telling about new valve?

In reply to magma:

Flipping heck. 

Assume you've checked all the basics. Clear code. Take for a drive, clear again and see if it starts behaving.

Double check wiring connectors at EGR. A bad connection would give that error.

I assume the rest of the wiring is good as it was resulting in current high before.

Other option if it's a cheap aftermarket is it's got a bad potentiometer in it. Can you look up what the resistance should be and check it with a multimeter. Think I would be tempted to get a cheap £20 second hand one off eBay that they claim is from a working car to try and rule that out.

In reply to magma:

I think you need to find a competent technician, you've been wrestling with this for nearly two weeks. Diagnosis by UKC is going to do your brain in!

In reply to nikoid:

yeah, needs a proper live diagnostic test being done now by a competent technician i trust. hopefully the new egr valve just needs recalibrating, although dunno if it even works (hard to test outside engine) . also getting a new auto parking warning light to go with the esp light- all can be related eg youtube.com/watch?v=73qogaPVcrM&

of course all this maybe unrelated to my poor fuel economy. some components eg the maf and o2 sensors can cause this without generating fault codes?

In reply to montyjohn:

this week i've learnt about the 'swirl diaphragm actuator?'. the plastic rod was broken when i replaced the egr (possibly me or someone else meddling with old egr). decided to test the vacuum to it by cutting and plugging the hoses for now (couldn't pull it off). the diaphragm seems to be holding a vacuum so have kept it 'closed' for now ie rod pulled in as for most conditions? shouldn't effect diagnostic tests?

In reply to nikoid:

all warning lights off for now after recalibration of egr valve (was related to esp/parking brake lights). yet to find out effect on fuel economy..

In reply to magma:

...however the warning lights came back on after a while- on the way to have the timing belt replaced (P0489 again). cleared them but now have some new codes stored after belt replacement- P0405, P0335 (crankshaft position sensor- related to timing belt change?) as well. seems like the crankshaft error was cleared leaving just the 2 EGR errors now. Cleared again, will take back to first guy to explore further. I love car diagonsics starting to think it maybe a duff aftermarket part..

In reply to magma:

only P0405 remained today- no limp mode, but P0489 just returned (esp+autobraking lights, limp mode)

looking at the freeze frame data for the first time the P0405 has a MAP (kPa) of 101 with 0 load/rpm, and the P0489 has pressure at 99 at load 42%/rpm 789

think i know where to look next..can anyone guess?

In reply to magma:

not what i first thought perhaps. i thought MAP pressure would go down at idle but apparently not on turbos (atmospheric pressure is normal).

next line of enquiry is the DPF pressure sensor as a low voltage from that can cause a low in the EGR circuit..one of those connection that can't be back probed tho.

i'm thinking of getting a more advanced diagnostic tool - a bi-directional bluetooth thingy that should allow me to read all the sensor voltages? and fuel trim data?

also MAF sensor readings seem high- about 10g/s at idle, rising to 40+ with revs. could be a boost leak apparently, and MAF sensors most often fail low?, but freeze frame of latest P0405 showed >200g/s with engine off!

also fuel load_pct is >40% at idle..

In reply to magma:

I think it'd be easier just to torch the car TBH.

In reply to magma:

Gremlins.

Engine off MAF reading is probably meaningless because the engine is off! Not sure how your particular MAF sensor works but types with heated elements presumably misbehave with no flow or (at least partially) shut down to avoid overheating.

Have you considered a bad earth.

Surely you'd hear a boost leak, they are hard to ignore.

jk

In reply to jkarran:

got myself a more advanced obd scanner that reads all (or most) of the data.

MAF and DPFE sensors seem to be in range and increase with revs.

However looking at live data from the EGR position sensor i noticed it was all over the place at idle. when i revved up it suddenly switched to a more stable reading of ~20% (should be 0%-closed). Also had noticed a clicking for several minutes after engine off (should only be a few secs), but suggesting EGR was accuating.

Decided to check connections/valve again and as i was removing air box (while the egr was clicking) i noticed a change in sound and sure enough, when i wiggled the wire at the connector, the clicking frequency changed and was able to make it stop. multimeter voltages confirmed intermittent voltage at connector according to wiggle

A breakthrough at last! Cut wire and replace connector i guess. Or check the wiring near the connector first?

In reply to jkarran:

also ordered a new ambient temperature sensor for the wing mirror as gave an error code (no value on dashboard). you'd never guess what that could trigger..

https://youtu.be/Vra67yTVjrI?si=__slGv7TEkm6zilH&t=1254