check injection warning light and engine become sluggish

[tarky41]

my renault megan 1.9dci is coming up with a message saying "checking injection" and the service warning comes on and then the engine becomes sluggish. also on and off there is buzzing noise coming from the engine. the garage has investigated and said it could be the air flow sensor and or the turbo solenoid. they changed the air flow sensor yesterday but the problem is still there.

any ideas?

[almcgrail]

My solution, take it for a run down motorway for a couple of junctions, however I am no mechanic.

[AlexB]

Replace the garage, unless you are a DIY person. In the latter case start with OBD.

Avoid driving meanwhile, because the engine is trying to minimize the damage by reducing its power on purpose.

[davecoyle]

hi , I had the same problem I had the turbo boost sensor replaced all is fine now regards

[l111fsh]

Get hold of a volt meter, 10mm socket + ratchet.

The engine does not need to be running or ignition on for the test.

Take off the rocker cover-cover (lol) if fitted by removing the 2x 10mm bolts and unclip the black connector.

You should see the glow plug connectors (long black protective hose with white + white/red wires inside leading to a black connector with a long plastic handle coming off the top) just in front and left of the injector carefully pull the connector off by the handle or the connector NOT THE WIRE.

Set the voltmeter to Ohm (omega symbol).

Put the black lead of the tester on the negative of the battery / any good earth point on chassis and place the red side on the tip of the glow plug.

This will measure the internal resistance of each glow plug. The value shown on the tester should be very low.
Test all the glow plugs in this manner and if any are showing a high resistance or open circuit (often shown as O/S) that one will need to be replaced.



To replace any, get a 10mm Deep socket and some WD40. Give a little spray, and be gentile with the glow plug when removing. They squeak and creak on the way out but don't give it arms of death, if they snap they can be a bugger to get out. when in doubt, a little more WD40 and 5 mins to soak goes a long way! When replacing the new one a dot of copper slip on the threads wont go amiss.

[AlexB]

In this case the glow plugs are irrelevant.

To the previous comment, the glow plugs are always removed on a hot engine, installed without any anti-seize and torqued to the rated value.

[craigyt]

Never never remove glow plugs or spark plugs on a hot engine! The engine is hot, thus makin the everything metal expand and will nip onto the threads! Sorry but necer do it on a hot or warm engine

[l111fsh]

AlexB, well pointend out for the removal in a warm engine, it does make it easier, but only install in a cool engine. That's what the torque settings are set in. As for anti seizure compounds on threads, as long as its a small amount on the threads only it is good practice, improves sealing and makes future repairs a little less troublesome.

Also, I suggest checking the glow plugs as I had some similar effects from my glow plug being dead on no4 cylinder. Replacement and fault code wiping ended the problem and now runs lovely.
All the best,
Fish

[AlexB]

Here we are again on the subject of using anti-seize.

It is normally used where the mating surfaces are prone to very intensive corrosion, whatever causes it. The glow plugs from decent makers have protective coating which works well with aluminium - there is no risk of corrosion.

Anti-seize applied to the thread reduces friction while torquing the plug, and the friction is the major component of the torque. I've quoted the studies of the wheel bolt threads recently - anti-seize results in reduction of the torque to about 1/3 of the rated figure while (this is important!) achieving the same tension in the fastener.

In our case this means that instead of 15Nm torque with dry thread, you will have to apply about 5Nm to fit the plug with anti-seize. I doubt that you would feel comfortable with such a low figure. Furthermore, if there is a small irregularity in the thread, such a low torque may not be enough to flatten it. On the other hand, if you apply the full 15Nm, then the thread will be experiencing 3x tension, which means trouble the next year.

Well, cars are designed to be serviced by people with limited knowledge in the field. Very broad margins are introduced everywhere, and it is possible to tighten most fasteners without using a torque wrench and reading the manual. However, I wouldn't call this a good practice.

PS: there exists yet another threat when removing glow plugs. There can be carbon deposits sitting on the very tip of the heater, which may catch the hole in the course of removal. To avoid the tip breaking off and falling into the cylinder wiggle the plug clockwise-anticlockwise while applying plenty of penetrant. This will detach the deposits and let the tip through the hole.

[AlexB]

It is a common misconception. The holes also expand with temperature (their diameter increases), not only the shafts. Aluminium is known to expand much more than steel - this will make removal of the glow plugs easier. On top of this, don't forget that the thread can be contaminated with polymerised oil, which softens with temperature.

Never never remove glow plugs or spark plugs on a hot engine! The engine is hot, thus makin the everything metal expand and will nip onto the threads! Sorry but necer do it on a hot or warm engine

[LydonJohn]

my renault megan 1.9dci is coming up with a message saying "checking injection" and the service warning comes on and then the engine becomes sluggish. also on and off there is buzzing noise coming from the engine. the garage has investigated and said it could be the air flow sensor and or the turbo solenoid. they changed the air flow sensor yesterday but the problem is still there.

any ideas?

My megane has done this 3 times now. i turned it off for 20 mins, turned it on and the message had gone. then i took it for a drive for about a mile at 3000rpm going up to 3500rpm then back down (repeated for the mile) and it seems fine.

hope it helps

[almcgrail]

Thats why I recomended taking it for a run. I had same messeage but then also had regenerate soot filter mesage aswell a bit later. I bought a boost sensor which I never got round to fitting, did some motorway driving and all was cured