Down On Power and Black Smoke

1.4 HDi, car runs normally on light load, but on fuller throttles, down on power and lots of black smoke coming out of the exhaust. Car sounds a little noisier, like it has an exhaust blow. Fuel economy seems ever so slightly worse, but not significantly down.

I've removed the EGR valve and the attached pipe for cleaning, they are a little coked up but not as bad as I've seen on other cars. Mechanic has fault read the car with a generic code reader which has come up with an EGR fault code but can't remember the exact code number.

I'm cleaning everything in petrol and carb cleaner, am I going in the right direction, any tips, comments, things I might be missing?

Also am I OK to soak the EGR valve in petrol for a time to clean it, or will that harm the vacuum bits inside?

matk wrote:1.4 HDi, car runs normally on light load, but on fuller throttles, down on power and lots of black smoke coming out of the exhaust. Car sounds a little noisier, like it has an exhaust blow. Fuel economy seems ever so slightly worse, but not significantly down.

I've removed the EGR valve and the attached pipe for cleaning, they are a little coked up but not as bad as I've seen on other cars. Mechanic has fault read the car with a generic code reader which has come up with an EGR fault code but can't remember the exact code number.

I'm cleaning everything in petrol and carb cleaner, am I going in the right direction, any tips, comments, things I might be missing?

Also am I OK to soak the EGR valve in petrol for a time to clean it, or will that harm the vacuum bits inside?

Hi matk

For a quick way to diagnose EGR faults, just use an EGR blanking plate from ebay for a couple of pounds. With the EGR blanked, you can drive the car and see if the fault continues. The HDi C3 will very happily run with its EGR blanked and no other changes need to be made (like ECU).

This can save quite a bit of searching for faults as it proves the EGR in one hit and allow you to move on to other systems.

Reading the codes is very important as this can also save a fair bit of time, guessing, use Lexia Tool and a laptop to do that.

For a black smoke problem with your mileage, other than the air filter, I would be suspicious of the injectors

Thank you for the quick reply. Like an idiot I've dropped the EGR gasket into the engine bay and can't find it, and also I need a new clip to replace the one time use original clip on the pipe.

I'll get these on Monday, put it all together, and see where we go from there.

Thanks for suggesting the blanking plate, no idea it was so easy, thought it might need an ECU code or something else. Would I need to blank off the vacuum pipe as well, or is it literally just put the blanking plate in?

Thanks for your help and advice.

matk wrote: Like an idiot I've dropped the EGR gasket into the engine bay and can't find it,

Not all the engines have a gasket between the EGR valve and its mounting point.

matk wrote:Thanks for suggesting the blanking plate, no idea it was so easy, thought it might need an ECU code or something else.

It really is as easy as slackening the EGR bolts and dropping the blanking plate in place, then re-tighten the bolts.

matk wrote:Would I need to blank off the vacuum pipe as well, or is it literally just put the blanking plate in?

If the vacuum side of the system is OK and not leaking at the EGR (its not often found to be a problem on the C3), then a blanking plate will stop the problem of a partially or fully open EGR when it should be shut (usually partially jammed with coke so it won't fully close). Just dropping in the blanking plate is enough to diagnose a stuck EGR valve.

If you have a leak on the vacuum side, you will probably notice it in the brake servo assistance before the EGR as the EGR will stay shut but brake assistance will be reduced.

Lol I know mine did as I heard it tinkling as it fell downwards when I removed the EGR!

Thanks again for the advice and reply, I'll check back after I've got the EGR cleaned and re-installed and let you know how I get on.

matk wrote:Lol I know mine did as I heard it tinkling as it fell downwards when I removed the EGR!

Thanks again for the advice and reply, I'll check back after I've got the EGR cleaned and re-installed and let you know how I get on.

Not a problem, Thanks.

Hi all .
I don't know if this problem was resolved but I have a c3 with exactly the same fault. Mine's a 1.6 and I am trying to fix it but I wondered if anyone on here could pinpoint the fault instead of me just stabbing around in the dark. Cheers. John

Johnali1997 wrote: ↑Tue Dec 06, 2022 1:31 pm Hi all .
I don't know if this problem was resolved but I have a c3 with exactly the same fault. Mine's a 1.6 and I am trying to fix it but I wondered if anyone on here could pinpoint the fault instead of me just stabbing around in the dark. Cheers. John

Hi

Its a fuelling fault.

This could be caused by a number of things and it is not always due to the same parts being faulty, even if the description sounds similar.

It is a question of diagnosis. Doing the EGR test is an easy thing to try and you don't need to boot up lexia to read the codes to try it.