Misfire, running on three cylinders now won't start

[172_Tom]

History of events as follows:
1. Drove to work this morning, occasional stuttering/hesitation/misfire particularly below 3000rpm when accelerating on part throttle.
2. Seemed to go down to three cylinders but I managed to limp it to work. Engine management light flashed for a bit.
3. No faults showing when doing this.
4. Fitted new coil pack from GSF during my lunch break. Would have fitted ignition leads too but ECP seem to have given me ones for an F7R engine, not F4R.
5. Car turns over but won't start.
6. Checked plugs connected to the right terminals on the coil pack, they were.
7. Re-fitted old coil pack.
8. Car turns over but won't start. Sounds like it is trying to a little though!

The replaced the spark plugs on the service before last using the correct NGK plugs. There was no oil/water down with the spark plugs. I'm sure I have clicked the ignition leads down onto the spark plugs correctly as I've done that before when I changed the spark plugs and on other cars with no issues. Fairly sure the TDC sensor is OK as I checked it before and it was clean. Car is low on fuel (light not on yet) but I always put super unleaded in it.

Really bad time for this to happen as I'm supposed to be going to Donington tomorrow!

Just tried Wests Renault and they don't have coil packs/leads in stock today so looking like I might have to cancel the trackday and get AA recovery home so I'm not in such a rush to fix it.

 

[Martin J]

Injector ?

 

[Gus]

Get the plenum off and pull the Ht leads off each spark plug in turn look down the hole to see if there is any water or oil down where the park plug is.

You should buy one of these to keep in the glove box - http://www.ebay.co.uk/itm/Mini-V1-5...748?pt=LH_DefaultDomain_3&hash=item3cd6e5f62c
and then use "torque" on your phone to read the error codes. Also see if you can get a mini socket set to keep in the car for times like this.

 

[Gus]

But yeah, call the AA and get them to sort it whilst your working.

 

[Gus]

From reading your post again im almost certain it is a spark plug/ht issue my money is on water in the sparkplug hole. If you have an airduster at work use that to blow any water out along with a rag.

 

[172_Tom]

Sorry - didn't make it clear - I removed the inlet to replace the HT leads then realised ECP had given me the wrong ones. The spark plug holes were all clean and dry. Car was running fine up until today - did a wet trackday at Brands just under 3 weeks ago.

Edit: could well be injector and will be something I'll try if not ignition/coil pack related.
Code reader is a good call and would come in handy for my other car too! If I can't get it fixed today I'll buy an adaptor. If there was an injector fault I'm guessing that would probably show it up...

 

[172_Tom]

Called the AA out - cause of not starting was a dodgy wire to the TDC sensor (I think that sensor - under the TB). Thanks previous owner!
Once that was sorted it started but wasn't running right - traced the misfire to cylinder four so I now suspect an injector fault or ignition lead fault.

 

[172_Tom]

Finally got some parts and free time to try and fix this...

I took spark plug 4 out and it looked exactly the same as number 3. They are the correct NGK ones which I replaced earlier this year and it was running fine from then until 21st November.
I took the fuel rail out and all four injectors are spraying fine. After putting it back together the car started but runs on three cylinders. Unplugging injector four made no difference.
I then replaced the ignition leads with a used set of original Renault leads. Same as before - runs on three cylinders. Issue still on cylinder four.

So to summarise:
Fault: Car runs on three cylinders (issue on cylinder four)
Things I've tried/checked:
Spark plugs are good. No water down holes.
Tried two coil packs.
Tried two sets of ignition leads.
Tested injectors are spraying fuel

Any advice - where do I go from here?!

 

[bloke]

measure resistance on the injectors

 

[dann2707]

Try unplugging the HT lead for cylinder 4 to see if that changes anything? Even though it won't really prove anything

Out of interest are you naming the cylinders as how they actually are named? 1-4 starting from the gearbox back.

 

[Raymond_11]

Surely unplugging injector 4 and it made no difference could mean that it's the injector at fault ?

 

[dann2707]

Surely unplugging injector 4 and it made no difference could mean that it's the injector at fault ?

Not at all. Could still be the lead, plug etc

I'd be looking at swapping an injector with a different one. Maybe number 3 or something. Then unplug injector number 4 and see if the engine note changes. If it does then it's your injector that is dead.

 

[172_Tom]

Cheers for the replies. Yeah I'm naming the cylinders right they are numbered right to left.

Should have time to do more fiddling around new year and hopefully get to the bottom of it. So far does seem quite odd given that I've checked the injector is spraying fuel and with recent ish plugs and replacement leads/coil pack mean there should be a spark in there!

 

[172_Tom]

Measured the resistance of the injectors, 1-3 were about 13. something ohms and 4 was 11. Replaced the fuel rail with a second hand one with all injectors measuring 14.3/14.4 ohms and she's now firing on all four cylinders again.

Odd that it was misfiring so badly even though the old injector was spraying fuel.

Anyone know what the resistance of the injector actually means? Will the one with low resistance have normal resistance and work again if I get it cleaned?

 

[bloke]

nope, it's knackered. bin it.
just because an injector sprays doesn't mean it's good, as you've discovered.

 

[172_Tom]

Now need to clear the engine mangement light on the dash... I have two fault codes showing up with Torque (free phone app) but it couldn't clear them. There are no faults showing when holding the button on the end of the wiper stalk and turning the ignition on.

Will the faults clear on their own or if I disconnect the battery for a while?
Thanks!

 

[JamesBryan]

Just buy the Torque Pro app for £3, it's pretty handy.

 

[bloke]

what codes?

 

[172_Tom]

Can't remember the numbers for them, one was for a misfire and I think the other was for injector 4.

 

[bloke]

if you only had an injector fault then changing the injector would clear the light. get a proper reader plugged in and see what it pulls up.

 

[1hpclio]

Does it crank? If so crank for a while then take out a spark plug make sure its wet with juice and check spark if not electric fault somewhere, then crank sensor would be a good start, take it put make sure the tip is magnet at least.. If you dont get spark and plug js dry the something else is wrong.. Good luck

 

[172_Tom]

Does it crank? If so crank for a while then take out a spark plug make sure its wet with juice and check spark if not electric fault somewhere, then crank sensor would be a good start, take it put make sure the tip is magnet at least.. If you dont get spark and plug js dry the something else is wrong.. Good luck

You missed the rest of the thread - it's running now

In case anyone searches and finds this - my EML cleared itself after a while without disconnecting the battery. I think it just takes the car a little while to realise the fault is definitely gone after replacing the injector.

 

[dablk]

Good to hear your sorted mate.
for future info.
However I agree with the comments above. If you unplugged an injector and nothing changed...then you have found a knackered injector. When you unplug a healthy one the engine should noticeably die in my experience.

I have had two knackered injectors recently. First one MUST still have been spraying as the car didn't feel "that" bad but eml was warning of a problem, code reader indicator cylinder no 3. and pulling injector lead didn't change anything on the running.

Just to prove it I swapped two injectors around. Car ran just the same, not "that" badly and code reader indicated that the problem had shifted with the injector swap.

2nd Time, one failed totally suddenly and we were well into 3 cylinder sounds like a Scooby territory.

In both cases pulling the healthy leads made the car try and stall completely and pulling the knackered one made no difference.

Like said pleased your up and running again.

Chris