ECU thinks wrong cylinder misfires

trobers2 · **Posted:** Mon Jun 18, 2018 12:12 pm

Hello Lost!
I've picked up a gem of a Liberty and am working the bugs out. This last bug has me stumped.
I'm getting P0303, misfire on cylinder 3. Yet, my troubleshooting leads me to believe it is cylinder 4 that is misfiring. It is drivable but grossly under-powered. The skip is consistent. I'm down to three possible causes but am stuck as to positively identify which it is - 1) ECU could be confused in some way, 2) mechanical trouble on top end like busted rocker arm, stuck intake valve, etc, or 3) Crank Position Sensor.

History:
PO let this Liberty sit for roughly 2yrs because he had an underboost code. He replaced several parts with new. Some of these may have nothing to do with my trouble but I'm listing them anyway: Replaced both intake hoses with Samco, fuel filter head, fuel line from tank to filter head, fuel filter, air filter, and tires.

Since my purchase just a couple of weeks ago I've replaced: Turbo with latest edition of New Garrett and related gaskets, alternator from china, AGM battery, oil sending unit, and cleaned both MAF and MAP. Each of these is getting me closer to road worthy.

To troubleshoot the skip I've unplugged injector wires:
#1 unplugged causes motor to nearly die
#2 unplugged causes motor to nearly die
#3 unplugged causes motor to nearly die
#4 unplugged = no change = maintains the current skip

I've then moved #4 injector to #1 and vis-a-versa. Injectors were marked before removal to avoid confusing them. Skip remains with #4 cylinder using the same unplugged method as before.

I've ohmed the injector wires from injector side to ECM. There is continuity with ~3ohms. Neither wire is shorted to ground, neither wire is shorted to any other wire in the ECM wiring harness.

I am blowing a lot of white smoke out the tail pipe - think 007 style smoke screen. It's a lot. I suspect much of this is from the previous turbo failure leaving oil in the exhaust system.

This Liberty is nearly bone stock except for the Samco hoses. I'm aware of mods listed in the NOOB post and will get to those but first I'd like to work the skip out so I can get it registered and on the road.

The skip is real and everything I see points to #4 yet code is for #3. Any ideas? Anyone near Woodstock, GA willing to let me borrow an O'scope to poke around on some of these ECM signals?

trobers2 · **Posted:** Mon Jun 18, 2018 3:07 pm

I hate to start throwing parts at this thing but I'm going to go ahead and replace the crankshaft position sensor since it's only $50. I should have it in by tomorrow evening.

GordnadoCRD · **Posted:** Mon Jun 18, 2018 4:38 pm

I'm assuming your new vehicle is a CRD.
(sorry, was looking at the post thread rather than your sig...)

Sounds like you've done the pin test for #4 correctly, and it sounds like there is no problem with wiring.
Before dismissing this chain of investigation, I would first suggest replacing the #4 injector connector and pigtail. The vibration of these engines can eventually cause the connection to loosen and connection fail. Less likely is check the appropriate pin at the C1 connector. Not so vibration sensitive, but check if the female wire end has backed out and is not connecting with the ECM pin.

I really hope this fixes your issue, because if these are all good, and all your grounds are good, you've proven that any injector put at that location has the same problem, the next culprit is the ECM.

If it fixes your issue, before driving much, remember to get and install all new injector o-rings and seals.

trobers2 · **Posted:** Mon Jun 18, 2018 9:41 pm

Oh no...
I was able to do a compression test this evening and found cylinders 1, 2, 3 had very similar compression.
You're probably way ahead of me by now. #4 had no measurable compression at all.
What have I gotten into?

GordnadoCRD - yes, I've got the CRD. Thanks for the insight. After the compression test I wish I was looking at an ECM reflash/replacement.

Since the vehicle was sitting for ~2yrs without being ran I'm wondering if #4 cylinder valves became stuck open somehow. Could I load the cylinder up with something like carb cleaner and let it sit? If course I'd do it without the injectors in, remove the fuse for injectors, and disconnect the glow plug. Maybe I'd let it sit overnight then turn it over to push all the cleaner out. Thoughts?

Or should I start preparing to pull the valve cover off?

flash7210 · **Posted:** Mon Jun 18, 2018 9:59 pm

Time to pull the valve cover off.
You will likely find that one valve spring rests higher than the rest.

IOW, you probably have a broken valve.

GordnadoCRD · **Posted:** Tue Jun 19, 2018 1:17 am

x2

I guess the best you can hope for at this point is that the valve head is cracked or something and not separated, but the main mass of data here would suggest the valve head is embedded in either piston or cylinder head. If you know someone with a small camera bore-scope you could pull the injector and peek inside. But like flash says, the valve cover and cams are coming off. Time to get all of the timing belt stuff at least.

trobers2 wrote:

2004 Volvo S80 5cyl turbo - why does the teenager drive the fastest car in my fleet?

Because he hasn't experienced a properly running liberty CRD that kicks the volvo's booty.

trobers2 · **Posted:** Sat Jul 14, 2018 1:24 pm

Just wanted to update you all on progress...
Valve cover & cams are now off as you suggested!
There are a couple of rocker arms sort of laying over to the side like I knocked them with the valve cover when removing it. Weird.
The intake port on #4 is completely clogged - as in it is holding cleaner fluid like a cup.
My initial look at the valves suggest they are all the same height.

I'll be doing a search to learn process for testing rocker arms & springs.
I'll also be cleaning the air intake ports.

My goal today is to get parts ordered. Wish me luck

Of course, any thoughts are certainly appreciated!

trobers2 · **Posted:** Sat Jul 14, 2018 1:46 pm

I'm going to pass on testing each of the rocker arms and just order the set.
Right now I'm sitting on a cart with IDParts for:
Rocker Arm set,
Valve Cover Gasket,
Timing Belt kit w/ all the goodies from IDParts.

May I reuse the valve cover bolts?
I'm going to hold off on the thermostat and fan clutch for now.
Is there anything else I'm missing that should be ordered?

Regards,
Troy

trobers2 · **Posted:** Sat Jul 14, 2018 2:43 pm

Glow plugs!
I've just removed the original glow plugs to find #3 is broken off and presumably still in the cylinder.
Any chance the tip was busted up and pushed out the exhaust?
Assuming valves are still good - If I remove the head to inspect am I required to have the surface machined?
Does this motor require new head bolts?

Uhg - I am way deeper on this project than I expected.
Thanks for taking this journey with me!

Regards,
Troy

papaindigo · **Posted:** Sat Jul 14, 2018 4:12 pm

Comments:
1. if you have pulled the valve cover you pulled the injectors in which case you can snake a small bore scope/camera in the injector holes and a) look for the missing glow plug tip and b) inspect the piston tops for any dings caused by a dropped valve.
2. look at the broken glow plug tip. If it's sooty it broke off long ago and the tip passed safely thru the system but if it's shiny it's a recent break.
3. yes you can reuse the valve cover bolts.
4. if you do #1 and all is good you don't need to pull the head.
5. If you do pull the head then a) you should NOT machine the surface but it's worth having a good shop inspect it for cracks and straightness and b) you MUST use new head bolts. In fact whether you pull the head or not you should install ARP studs instead of head bolts (can be done 1 at a time with the held installed if you don't pull it).

Fan clutch and tstat can be done independent of the other things you are doing but:
1. consider saving up for an HDS tstat rather than an OEM replacement.
2. cut the bottom half of the fan shroud off just below the mounting bolt tabs and throw the bottom half away. No impact on cooling and makes future access easy. NOTE be very careful not to a) misplace the fan shroud bolts as their length is critical to avoid puncturing the radiator and b) consider zip tying the nuts for those bolts in their retaining slots so you don't lose the nuts.

rankom · **Posted:** Sun Jul 15, 2018 4:44 pm

the way i did it is , at 100.ooo miles , i pull cylinder head send it to machine shop get them to to there job . 2nd send injectors to bosch got them to do there job , then i got parts from ID parts and sasquach parts and GDE tune and so on ,,, so so far so good that was back 4 years ago , so yes pull the head is my advice .

trobers2 · **Posted:** Mon Jul 16, 2018 8:01 pm

Thank you Papaindigo and Rankom for your thoughts!
The $140 bore scope really sucks. Even with the light at the tip and brightness turned all the way up, it does not display dark colors in low light - like the inside of the cylinder. Fortunately, this is only a rented unit.

Tip of broken glow plug is sooty. Just for grins I ran a thin cooper wire through the glow plug hole to make sure it wasn't just stuck in there.

At this point I'm going to leave the head on and continue cleaning the air intake ports. Parts should be arriving Wednesday

Regards,
Troy

trobers2 · **Posted:** Fri Jul 20, 2018 6:23 am

Great News! I pulled an all-nighter and completed the job this morning. She spit & sputtered, blew a ton of smoke in the garage, then began purring like a kitten. Oh, such a sweet sound.
Cylinder 4 had low/no compression.
Cylinder 3 had broken ceramic glow plug tip.
The entire air intake was severely gunked up. I suspect all the build up was preventing valves from closing all the way in cylinder 4.
Replaced:
All rocker arms.
7vdc steel glow plugs
Timing belt kit from IDParts
all related gaskets/seals/crush washers.
And spent hours upon hours cleaning the intake. At one point I used paint stripper and seem to make good progress with it.

Thanks for all your help!
Regards,
Troy

WWDiesel · **Posted:** Fri Jul 20, 2018 12:26 pm

Always good to hear some Good News! :wink:

ECU thinks wrong cylinder misfires

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