I’ve used injector cleaner in the past with petrol cars when they started to run a bit lumpy.
Now got a diesel (Renault 1.5 DCi 100) and its a bit lumpy on startup, but once its warmed up its ok.
Is it worth running some injector cleaner through it to smooth it out?
I’ve used Wynnes as it usually seems to work ok.

Your thoughts please.

Works – *IF* your problem is dirty injectors. Could be a range of things, including dodgy/dirty MAF I think.

The Forte stuff is supposedly the best. You’re not meant to be able to buy it retail but it’s all over ebay. Get the turbo cleaner and injector cleaner, use as per instructions together.

Plenty of ignorant people will say snake oil but I’ve used BG244 or Archoil AR6400-D on my diesels for the last 9-10 years and it works very well in removing the deposits. First used in my Mondeo which scrapped a smoke test pass of 2.97 (fail 3.00) at its MOT. After using the BG244 it went down year after year to just 0.14 and the MPG and throttle response were much better too.
If the injectors are bust though no amount of fuel system cleaner will fix them.

Could be the glow plugs (or myriad other things). FWIW, my wife has the 1.5 DCi in her Qashqai, and it’s a bit rough when cold. Don’t think there’s actually anything wrong with that.

I’ve read that injector cleaners can damage some designs of fuel injectors.

I’d be more inclined to try a few tanks of good quality fuel and an ‘Italian tune-up’ to see how that affects it.

It starts fine, so it cant be glow plugs.

It gets a semi-regular “tune up”. Great fun when some clown is tailgaiting you and you boot it in second. Breathe my shit, scum!

Great fun when some clown is tailgaiting you and you boot it in second. Breathe my shit, scum!

Hang on – if it smokes on hard acceleration then something is wrong. Could still be MAF related. If the MAF is over-reading then it’ll put in more fuel, which won’t get burned. I think rough idle is a symptom of dodgy MAF. You can try unplugging it, which will cause the engine to revert to a default value which should at least be consistent.

Will this work on petrols too?

Again depends what you mean by ‘work’. Will it clean your injectors? Yes. Are they dirty? Probably not. Will it solve X Y Z? Depends.

My experience of running Renault DCi engines on a shoestring taught me that if in doubt, it’s the EGR valve that’s causing the problem.

Did all sorts including Forte cleaner (worked to a point, and is way better than the other brands), taking the EGR valve off and giving it a proper clean (again worked to a point but it was over 10 years old and way past its best anyway), and even spraying a fine mist of carb cleaner in whilst the engine was running (don’t recommend this at all, I knew what I was doing and was ultra careful, you can risk hydraulic lock in your engine though so do not do it!)…

Gave in and bought a new (genuine, the pattern ones don’t last very long) EGR valve in the end. Cost about £120 inc VAT which was a lot less than I expected. Fitted it and suddenly the car ran like a dream, economy went up 10% and black clouds of smoke out the exhaust were history!

[video]https://www.youtube.com/watch?v=KMic_78PaT0[/video]

Just thrash the living daylights out of it for a bit. That should do the same job. 🙂

Will this work on petrols too?

Try BG44K for petrol engines. Lad at work bought an Audi A3 1.4 recently and wasn’t get more than 36mpg over his first 4 tank fulls. Told him to try some BG44k and now up to 44mpg.
You use it by putting the cleaner in a near empty tank before filling up and then drive around like Miss Daisy trying to make the tank last as long as possible and allowing the cleaner to dissolve as much as it can. When it gets to 1/4 tank refill and then drive normally.

Giving the car an Italian tune up is good for clearing EGR and exhaust soot buildup but not cleaning the fuel side.

Glow plugs are used for more than just starting on modern diesels…

Has it only started running rough when cold since the mornings have turned chilly or was it doing so during the Summer?

Glow plugs are used for more than just starting on modern diesels…

Yes but it would struggle to catch, cos then it’s at its coldest.

drive around like Miss Daisy

Miss Daisy doesn’t bloody drive!

In order

molgrips – Member

Great fun when some clown is tailgaiting you and you boot it in second. Breathe my shit, scum!

Hang on – if it smokes on hard acceleration then something is wrong. Could still be MAF related. If the MAF is over-reading then it’ll put in more fuel, which won’t get burned. I think rough idle is a symptom of dodgy MAF. You can try unplugging it, which will cause the engine to revert to a default value which should at least be consistent.
Only when I really boot it and its soot. Mostly because it trundles about during the week on local short runs. A couple of blasts and its mostly fine.

mboy – Member

My experience of running Renault DCi engines on a shoestring taught me that if in doubt, it’s the EGR valve that’s causing the problem.
Probably, thats why mine is in the engine bay still connected (so as not to throw a fault code) and the hole where the EGR was is plugged by another EGR valve that isn’t connected, thus blanking it off.

Tallpaul – Member

Glow plugs are used for more than just starting on modern diesels…

Has it only started running rough when cold since the mornings have turned chilly or was it doing so during the Summer?
It started doing it at least a month ago, so its unlikely to be temp related. When I say rough, theres just a little more vibration noticeable on start up, it pulls fine. Feels similar to when I had an almost solid engine mount (temp fix) which transmitted a bit more vibration through the chassis than usual.

Miss Daisy doesn’t bloody drive!

Miss Daisy does drive until she wrecks her car and her son makes her take on a driver (Morgan Freeman)

Probably, thats why mine is in the engine bay still connected (so as not to throw a fault code) and the hole where the EGR was is plugged by another EGR valve that isn’t connected, thus blanking it off.

Personally, FWIW, I think you’re best off just buying a brand new EGR and connecting it properly. I know and understand the reasons for removing it, but the problems thrown up from their removal (even if correctly mapped out, or as in your case, still connected to the ECU) are numerous and far more annoying than just buying a new £120 part every 100,000 miles.

EGR cleaning kits also work especially if used regularly.

When I say rough, theres just a little more vibration noticeable on start up, it pulls fine

Engine mount perhaps?

Engine mount you would feel every time you came off the power.

If it starting rough on a morning with an erratic idle it sounds like a worn injector.
Sluggish to start up could be glow plugs or battery. Shouldn’t really need the glowplugs to get the engine started at the moment.

As I said starts fine every time (well since I replaced the crank position sensor anyway), so Im fairly comfortable with saying its not glow plugs.
Im pretty sure its not the engine mount. It has 2 upper mounts either side of the engine / gearbox and a lower mount. The lower mount basically stops it swinging backwards and forwards (which it used to before I replaced it).
With regards to blanking off my EGR, I cant see how it would have any detrimental effects, other than an increase on NOx. All other things I’ve heard about EGR deletion are positive. e.g. increased MPG, slightly more power (not noticed that), less oil contamination. Besides its been like this for a least 6 months with no issues.
Its almost like a low idle vibration.

Engine mount you would feel every time you came off the power.

Depends which one it is I’d imagine.

All other things I’ve heard about EGR deletion are positive. e.g. increased MPG, slightly more power (not noticed that), less oil contamination.

Yeah, from grumpy old git DIY mechanics who wish everything was the way it used to be. I bet if you talked to an actual VW engineer you’d get a different story.

slightly more power (not noticed that)

That’s because the EGR shuts off when you boot it.. see they talk bollocks, they really do.

It also doesnt operate when the aircon is engaged (at least on Scenics it does).
My main reasons for removing it is to stop mucking up the engine oil and also not having to de-crud it every 6 months.

Hmmm, bloody thing took several attempts to start this morning. Was about 12 deg C, so not cold really.
Might be time to look at the glow plugs, although if it was only firing on 3 it would be down on power and really rough I’d imagine.

If it is struggling to start with the current temperatures it won’t be the glow plugs as it’s not cold enough for them to be required yet. They will still be on until the car gets up to operating temperature to help with the emissions.

Archoil AR6400

Great stuff this.

I had an engine management light that used to come on put the car into limp mode whenever I was doing around 60-70 on the motorway. Put some Archoil in ahead of a big run to Scotland and the car has been absolutely superb ever since.

If it’s struggeling to start it’s worth checking the flywheel. When the dual mass type start to fail this is one of the first symptons.

How so?

I can still remember Redexing my dads Capri .. dripping directly into the carb … that was fun!

Used Reddex a couple of times on my old 300TDI Defender.
Mechanic friend of mine suggested half-filling the fuel filter canister with it when I changed the filter – initially loads of smoke but afterwards it seams to run better.

Try new air cleaner as well that works wonders for smokey diesels