AU 4.0L 1 - 6 miss.

[Bob Valdez 136]

It's home now and that miss is really bad. No way this is electrical. Driving it on and off the trailer, it shook and carried on like a dog shitting razor blades. I suspect this is likely to be a head gasket blown between 2 cylinders, as my brother's Bronco was very similar and had blown the head gasket between #1 and #2. When I get time, I'll do a full comp test and leak down and pull the valve cover to have a look why there is bugger all oil around the rocker gear. The comp test will give some indication as to WTF is going on.

[SPArKy_Dave 8,881]

6 hours ago, Bob Valdez said:

It's home now and that miss is really bad. No way this is electrical.

 

Keep us all posted, I for one am keen to see what's causing the issue!

[Bob Valdez 136]

So, today I decided to try a trick I learned from a guy who used to do my radiators years ago. I put my radiator tester on with an extension on the header tank and filled it completely with water after I warmed up the engine. I started the engine and sure enough, bubbles formed in the top of the tube. Dad and the Bro are visiting on Sunday, so we will do a complete compression test and check the valvetrain, but I'm pretty sure it has a leaking head gasket in #1 and possibly into #2. The bubbles and the fact that it won't build pressure in the cooling system point to that logical conclusion. If that is the case, the engine will come out to repair it, go back in to be tested and if that cures the problem, it's going up for sale and the 302 and 5 speed from the XR8 are going in. 

[Bob Valdez 136]

Well, I've had a day of unusual results. Got Ol' Blue out of the garage, warmed her up and pulled spark plugs, fuel pump fuse and coil pack plug and started the compression test. For correct results, the engine should be at operating temp, the throttle needs to be wide open and the test gauge accurate. This one is brand new (and a good one I've used else where), so away we went. My brother got the key and accelerator duties, with Dad watching on, I started at #6.

#6: 155 psi

#5: 120 psi (squirted oil into the cylinder and 145 psi). I'll attribute this to a broken top ring.

#4: 145 psi

#3: 145 psi

#2: 150 psi

#1: 165 psi

The rocker cover was removed and the valve train inspected thoroughly for loose/broken rockers, broken valve springs and/ or sticking valves: Nada. All is as it should be and very clean (thanks to Dad's meticulous schedule of servicing every 10k without fail). At 335,xxx km, the compressions are about what I'd expect, except for #1.  Next, put it all back together, it still misses on #1. Put a clean plug in #1 lead, started the engine and we have sparks. Put a globe in #1 injector plug and we have light, but when re-assembled, it still misses in #1. Disconnected the alternator to do the diode failure test (again) and it still misses. However, due to a lack of time, we ended the session there, packed up and went to my block to have a walk and see if we could whistle up a fox or two.

 

So, the last 3 things I will do is:

1/ Completely disconnect the alternator (it does not appear to be charging, either) and remove the belt to make sure that any AC current frequency cannot be any possible interference.

2/ Fit a set of normal OHC spark plugs.

3/ Bypass the #1 injector wiring in the engine harness directly from the injector to the ECU right at the plug with a 2 core to eliminate any broken/intermittent connections there and see what happens.

 

If the miss is gone, I'll replace the harness/alternator/whatever to fix the issue and get the car back together, either to sell or use.

If the miss prevails, then I'm going to split the intake manifold and see if there is an obstruction in the intake or the bypass butterfly hasn't fallen into and blocked the intake tract (or something stupid like that, which might account for the unusually higher comp pressure and/or the miss). If I find nothing wrong, the engine and harness will go to junk and I'll put a V8 and 4 speed into it and go club racing. It will be carbed or use a FiTech with a seperate wiring harness, so the gremlin won't bother me again.

I can't see the dash or it's harness being a factor in this, because there are only a few critical wires in the ECU to dash connector and without them, it will not run at all. The others are for water temp, tacho and oil pressure, TC enable (disconnected anyway), ECU enable from the BCM and that's about it.

When I have time during the week, I'll try again and then make a decision.

Cheers all.

[SPArKy_Dave 8,881]

I actually have this issue, with the non-matching number engine in the XF SVO project ute...

(crossflow six on LPG)

Doesn't bother me, as I have a Windsor engine conversion waiting to go in.

 

In my case, the engine runs perfect when cold, but gradually develop's a steady miss, as it warms up.

It happens like clockwork.

 

A compression test early on, yielded two cylinders with high compression relative to all the rest, plus oily plugs on cylinders 2,3,5 and 6.

(no.2 the worst by FAR)

These new plugs, had barely a handful of hours run-time.

 

1 - 155

2 - 152

3 - 170

4 - 156

5 - 169

6 - 148

 

Could the issue be caused by valves not opening fully?

I'll soon know, once I dissect the engine and measure all the clearances - to hopefully learn something myself

 

My theory is, (in my case at least) it could only be caused by either -

1. a faulty lifter (HLA in the case of OHC engines)

2. a partly wiped cam lobe

3. and/or a very slightly bent/sticking valve stem? (possible but unlikely IMO)

 

[Bob Valdez 136]

Mine misses from the get go.  The HLA's are working, oil is flowing from their bleed holes, valve springs in #1 are good, no sticking valves. Cam lobes and rockers and bearings are perfect. However, the spark plug is clean, whilst the others are sooty from the short running on cold start it's been doing lately. No valve gear noise of any kind, so that rules out the rocker gear.

 

Your oily plugs are likely bad or broken valve stem seals, quite common in crossflows. You also could have an exhaust valve seat recessing, taking up the lash adjustment in the lifter and holding the valve off the seat as it heats up and expands. Mine? Still working on it.

[SPArKy_Dave 8,881]

8 hours ago, Bob Valdez said:

the spark plug is clean, whilst the others are sooty

Still working on it.

 

Sounds like it could be fuel related (or lack thereof)?

(either injector, or injector control?)

 

Have u tried swapping Injectors?

 

[Bob Valdez 136]

Yes, fitted a brand new set of injectors. I even swapped a few around on Sunday (I didn't include that in my post), just for shits and giggles, however, samy same. I'm making up a jumper to take the pulse direct from the plug at the ECU to the injector, bypassing the entire harness. I just have to isolate the injector power feed and the #1 wire pos on the ECU plug to tap into and run the injector in remote mode. I'll also run it with the belt off, to make sure there is zero interference from the alternator. If it still misses it's got to be the driver in the ECU which grounds each injector in the correct sequence.

When the weather allows, I'll get into it this week, as I'll have to collect the XF from the farm and start work on that.

[ZKFairlane 235]

Had something similar with the young blokes BF Turbo; it kept triggering a coil pack error in number one cylinder and running like a dog.  Put nos plugs, coils, sensors etc in it to no avail (similar to your situation).

 

Took it to an old school mechanic and he changed the inlet manifold gaskets and removed the engine hook and all is good.  The old gaskets were so hard and perished that they would leak air when the motor heated up but were ok when it was cold.

[Bob Valdez 136]

I've considered that, too. Yesterday, I sprayed WD40 around every gasket joint in the manifold to see if it picked up, but to no avail. That doesn't mean that's not a problem, because the fuel is injected at the inlet port, so a manifold leak won't affect it. A carb engine, yes, it will.

[Bob Valdez 136]

That actually is the next thing to do, and the last. If it doesn't come good, it will go out the back until I have more time, or go to a new home.