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#4722608 - 04/10/18 10:39 AM Misfire at idle??
Darwin1138 Offline

Registered: 01/07/14
Posts: 399
Loc: Slimy Mudhole
The car is a Peugeot 207 1.6, over the last year it has started to consume oil to the point where it now drinks one litre of oil every 3000 kms. Last week started to misfire only when hot and only at idle, I got a code P1337 "Cylinder 1 misfire."

The car makes plenty of power and the coolant level hasn't changed.
Fuel pressure is OK.
Coil and injector pulse are present during misfire.
Changed coil to cylinder 2, spark plug to cylinder 3 and fuel injector to cylinder 4. Still misfires on cylinder 1.
Checked compression and every cylinder makes 150 psi dry and wet.

Since only 1 cylinder is affected, I highly doubt it is related to a timing problem, to a plugged exhaust or intake or to a deficient MAP or IAT sensor.

The best explanation I can come with is that the valve guide seals are broken. And when the oil is hot there is enough leakage to produce the misfire at idle.

I am currently waiting on delivery of the tools to remove the camshafts and further inspect the valvetrain and the valve stem seals. But in the meantime I wanted to know your opinions.

Do you agree with my diagnosis?
Is there something I have not ruled out?

I don't own a leak down tester, but maybe I could procure one without too much hassle.
Do you think it will be wise to perform a leak down test to get a more complete analysis?

Thanks for all your help.
0W-20 or death!

#4722650 - 04/10/18 11:30 AM Re: Misfire at idle?? [Re: Darwin1138]
MasterSolenoid Offline

Registered: 09/26/17
Posts: 130
Loc: One Step Beyond
First,,,, I'm not a mechanic.

I had a misfire code once (cylinder one, I believe).
I ended up changing the spark-plugs and then the wires.
Been fine ever since.

At night (when it's dark) start the engine and check the wires.
I was seeing pin-points of arching along the wires.

Always try the simple fixes first.

Edited by MasterSolenoid (04/10/18 11:32 AM)

#4722671 - 04/10/18 11:56 AM Re: Misfire at idle?? [Re: Darwin1138]
meep Offline

Registered: 02/20/07
Posts: 3508
Loc: Southeast
inspect the spark plug and you will see if it's oil-fouled or not

I had a stretched timing belt cause rough idle and misfire.
2018 F150
2015 crv (wifey!)
2009 s60 2.5T

#4722686 - 04/10/18 12:06 PM Re: Misfire at idle?? [Re: Darwin1138]
OTCW Offline

Registered: 05/07/17
Posts: 49
Loc: Tennessee
Cars tend to idle at higher rpms when cold, so maybe the misfire 'only when hot' really means only at low rpm. I would change out the pcv valve as one that sticks open can cause misfire in the cylinder it is closest to. Is that cylinder one for you? Also, if it is sticking shut, it can cause oil consumption. It may be doing both in its transition from operational to fully inoperational, thus explaining both symptoms.

Anyways, it is a really inexpensive part and usually a really easy change out.
2017 Nissan Sentra 1.8L 11k miles
2004 Nissan Frontier 2.4 L 199k miles
2012 Yard Machines 21 in 140 cc
2001 Weedeater Featherlite Plus 21 cc

#4722705 - 04/10/18 12:25 PM Re: Misfire at idle?? [Re: Darwin1138]
mk378 Online   content

Registered: 09/27/15
Posts: 1338
Loc: USA
Is the valve clearance adjustable? Make sure they are not too tight.

Don't trust the PCM to tell you which cylinder. While it is obviously idling badly, do a cylinder drop test by unplugging the injectors one at a time.

An air leak near one cylinder will lean out that cylinder and make it misfire.

#4722715 - 04/10/18 12:31 PM Re: Misfire at idle?? [Re: Darwin1138]
Trav Offline

Registered: 11/20/06
Posts: 18268
Loc: MA,
As you say the coil, plug and injector were moved and the misfire remained on the same cylinder its time to look for something that effects just that cylinder, a vacuum hose broke, loose, intake leak, etc.
You can spray a little carb cleaner or starting fluid around that area or use propane to see if there is any change in the idle.
ASE L1, Master. Deutsch Meisterbrief.

#4722716 - 04/10/18 12:33 PM Re: Misfire at idle?? [Re: Darwin1138]
WobblyElvis Online   content

Registered: 09/23/14
Posts: 1277
Loc: Toronto Canada
If after the coil and plug were changed over, the misfire occurred immedatley on cyl #1, I doubt it's oil fouling. Oil fouling should take at least a few minutes. If the intake manifold has a small leak only where cyl #1 meets the manifold. This could cause the problem. At idle, blow propane or WD 40 around the manifold where it bolts to cyl #1. If it smooth's out you found the problem.

great minds think alike..and fools...well

Edited by WobblyElvis (04/10/18 12:33 PM)

#4723251 - 04/11/18 12:01 AM Re: Misfire at idle?? [Re: Darwin1138]
Darwin1138 Offline

Registered: 01/07/14
Posts: 399
Loc: Slimy Mudhole
Thanks to all for your replies.

The engine is a coil over plug design, so there are no HV wires. I was hoping that the problem would be one of the coils but swapping them make no difference at all.
The spark plugs look a little oily but there isn't any difference between them and they are fairly new, perhaps 10,000 kms.

The timing chain could be stretched, I am waiting delivery of the tool that I need to measure it. But I think, that in that case the misfire would be in multiple cylinders. I am going to measure the chain and report back.

Valve clearance is not adjustable. the misfire could be because of a broken return spring or a collapsed lifter, although there isn't any weird noises coming from the engine. In any case, the plan is to disassemble the valve train for further inspection.
I did the drop test and it confirmed cylinder 1 as the problem.

This engine uses the valvetronic system, which means that there is atmospheric pressure inside the intake manifold, since it doesn't generates any vacuum with the throttle plate.
So there isn't any PCV valve, just a breather, and cylinder 1 is the furthest from the point where the breather attaches to the manifold. Even so, I disconnected the breather and the misfire is still present.

Similarly, because it doesn't generate any vacuum, a vacuum leak can not be the cause of the misfire. Besides, even if the valvetronic system was not operational, this is a speed density engine, which means that it doesn't have a MAF sensor and only uses the MAP and IAT sensors for the operation of the engine. A vacuum leak, no matter how big, can not produce a lean misfire in a speed density engine.
0W-20 or death!

#4723383 - 04/11/18 08:24 AM Re: Misfire at idle?? [Re: Darwin1138]
Trav Offline

Registered: 11/20/06
Posts: 18268
Loc: MA,
Have you done a compression and leak down test?
ASE L1, Master. Deutsch Meisterbrief.

#4723734 - 04/11/18 02:31 PM Re: Misfire at idle?? [Re: Darwin1138]
SteveSRT8 Offline

Registered: 10/10/08
Posts: 18864
Loc: Sunny Florida
Originally Posted By: Darwin1138
A vacuum leak, no matter how big, can not produce a lean misfire in a speed density engine.

Ahem, that is not a truth. Perhaps on your ride, but I own 2 different Hemis that would...
"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix

#4723746 - 04/11/18 02:37 PM Re: Misfire at idle?? [Re: Darwin1138]
mk378 Online   content

Registered: 09/27/15
Posts: 1338
Loc: USA
MAP controlled engines are immune to global leaks, that will just cause the idle speed to rise out of control. But a local leak putting extra air mostly toward only one cylinder is a problem.

#4739131 - Yesterday at 11:29 PM Re: Misfire at idle?? [Re: Darwin1138]
Darwin1138 Offline

Registered: 01/07/14
Posts: 399
Loc: Slimy Mudhole
The misfire is present when there is no vacuum in the manifold. Even if the misfire was somehow the result of a vacuum leak, wouldn't the problem will be more evident when the car is cold??

Or at start up when the valvetronic system is not enabled???

I tried to get a leak down tester but apparently no one at the auto parts store knew what I was talking about.
So the only sensible option was to make one, I used some gauges I had laying around and some plumbing connections from the hardware store. To make the restriction orifice I used a 3/64 drill bit.

I did the leak down test and there wasn't any difference between any cylinders. After that I disassembled the timing components and couldn't see anything wrong with the camshafts, dephasers, followers or lifters and the timing chain is not stretched. So I think that the theory of the valve stem seals is the only plausible explanation.

Right now I am looking at the way to replace the seals without removing the head. I bought a spring compressor but it was too big for the valve springs, I need to modify it and hopefully I will be able to order the valve seals on Monday and finish it by the end the week.
0W-20 or death!

#4739313 - Today at 07:48 AM Re: Misfire at idle?? [Re: Darwin1138]
mattd Offline

Registered: 10/03/10
Posts: 652
Loc: RI
Run a dynamic compression test , that will tell you if there is a valve train issue or not, and will tell you if itís intake or exhaust valve related.
2007 Ford F-350 4x4 6.0 PSD

ASE Master, L1