'00 5.0L misfires OBD $06 data access

[TestPoint]

Got the engine running after installation in a 30 year old Volvo but am having misfires.

Both coils are firing. Compression is excellent on an 11K mile engine. New plugs. New injectors. 02 sensors not installed yet, tomorrow afternoon.

Of course, no OBD II codes as the Volvo fuel sender is not connected to the PCM.

(for Ford vehicles) •The Fuel Tank level must be above 15% for misfire monitor operation. It’s not uncommon to be working on a vehicle that’s low on fuel, but if the fuel level is less than 15%, misfire monitoring is suspended.

I know all the fault tracing items.

•Faulty spark plugs or wires
•Faulty coil (pack)
•Faulty oxygen sensor(s)
•Faulty fuel injector(s)
•Burned exhaust valve
•Faulty catalytic converter(s)
•Stuck/blocked EGR valve / passages
•Faulty camshaft position sensor
•Defective computer

I am going to do it the old fashion way and pull the plugs this morning.

Two questions:

Should I just wait until 02 sensors connected and see what happens?

Anyone know how to access the OBD $06 diagnostics on an Innova 3100 code reader? That is supposed to supply raw data of misfires by cylinder but is not mentioned in the on-line manual.

 

[TestPoint]

The ignition system seems to be working. All the plugs are evenly colored. I guess it is just running rich because of the open loop fuel trim, or lack there of.

 

[TestPoint]

The missing has gotten worst rather than better.

Story update:

Got it running well enough that I drove it 15 miles to the local Ford store for an alignment after my complete front suspension rebuild. Ran poorly, perhaps on only 6 cylinders. Misfires and small explosions in the exhaust system. Pulled all the plugs . . . again . . . and #1 and #3 looked suspicious. Number 1 had slight trace of oil and looked much darker than the others. Number 3 looked as if it wasn't getting gas. Verified that I am getting spark to plugs 1,2,3. Put it all back together and slept on it.

This morning I drove it 15 miles, in the other direction, for an exhaust system. Ran like crap. Gotta be running on 6 cylinders . . . or less. When we were testing the finished system the guys showed me that apparently there is an exhaust valve stuck open as every second it will suck a piece of paper back into the exhaust instead of continually blowing out.

Well . . . that is discouraging. The engine is represented as only having 11k miles on it and I have not seen anything to call that into question. It is not even dirty, just a little dusty. As I was installing the engine I did a compression test and all were perfect.

I pulled the right valve cover since that is where the suspicious plugs were. All of the valves are fully up and level. I assume that is because the hydraulic lifters collapse when the engine shuts off.

Guess I am back to pulling the plugs, verifying that all are sparking, and doing the compression test again.

Any thoughts would be greatly appreciated.

 

[TestPoint]

Inspiration . . .

. . . . . desperately needed.

I have to admit to thinking more than doing but I pulled all the plugs today and checked the ignition. Blue spark at all plugs laying around on frame/engine ground. Yes, I have a big ground strap from the block to the firewall and a #2 copper cable from the firewall to the battery ground strap at the rear.

Compression is perfect:

1 200
2 190 and these could be from a short spin.
3 190
4 200
5 205
6 200
7 200
8 200

That is with all plugs out and the throttle plate open.

Engine runs well at idle, better at start up than a minute later. No O2 sensors. Misses and small backfires into the exhaust on acceleration. Checked throttle position sensor both resistance and electrically. Really sound like an exhaust valve stuck but . . . with that compression there cannot be a bad valve or lifter.

No clue from OBD II as misfires monitoring is disabled with less that 15% fuel in the tank and since the tank sensor is not connected to the PCM that is not going to happen. That will be one of my future modifications . . . to provide a voltage to the PCM to represent a half tank of gas. Bet Converse never thought of that.

That leaves at least three things to think about:

1.) Crank Position Sensor - Why would it mainly work to provide spark but cause misfires?

2.) Cam Position Sensor - Same. Why would it provide injector pulse but cause misfires?

3.) Injectors or injector wiring - Newly professionally tested injectors. Wiggled all the injector connectors that I could reach. I put a dab of silicone grease on each connector and connected/disconnected each several times when reinstalling the new injectors.

[edit] perhaps a fourth . . . while the small backfires and a stuck closed exhaust valve is sorta mutually exclusive perhaps I should look for a valve lifter that is not getting oil pressure or is gummed up.

Just make me a list and I will try them all.

 

[Runnin'OnEmpty]

......
Engine runs well at idle, better at start up than a minute later. No O2 sensors. Misses and small backfires into the exhaust on acceleration......

I think the engine is good with those compression numbers, and don't believe a lifter is sticking because
there's no noise. Also it starts and idles too good for
anything mechanical to be wrong.

How are you running it without a MAFS or O2 sensors?
It almost sounds like the problem starts when the
transition to closed loop should occur. There's a
'time elapsed since engine start' parameter built into
the PCM; which comes to mind since you say it runs
good for about a minute after start-up.

The only thing I can think of to check is maybe
disconnect the temp sensor that controls open/closed
loop changes and force the engine to stay in open
loop operation...?

 

[TestPoint]

I do have a MAFS. Would be a little difficult without one. At the moment there are not O2 sensors as I wanted to make sure I was not blowing flame out the headers and frying them before installation. So it is running in open loop all the time and not affected by the coolant temp, which stays low anyway since the thermostat is out. Perhaps time to try it at real operating temp. I am at a loss to explain the perceived change in running. Maybe it just feels better at idle.

One more thing to do before putting it back together; observe the rocker arm operation while my able assistant spins the starter. The right side is off which was easy. Left side requires removing the manifold. Last time I tried that, on a '56 Chevy, I blew oil all over the engine compartment.

I will get the cover on and the plugs back in today and try again. Guess it is time to try it with the sensors also.

 

[TestPoint]

I am down to only the #1 cylinder not firing. Got spark, got compression, getting little raw gas explosions in the exhaust system. Number 1 header tube reads 140 degrees on an IR thermometer while all the others peg the meter high.

The #1 cylinder is one of the 3 -4 that you can get to the injector connector with the manifold in place. Upon pulling the connector the little backfires went away. Now, the engine just runs like it is firing on only 7 of 8 cylinders. That eliminates the injector and forces the problem back into the harness or PCM.

Oh Joy!

Done for the day. I will check the injector to PCM wiring tomorrow. Hope it is as simple as I cut/reused the TAN circuit 555 wire for something else. If it goes inside the PCM I am in at a loss . . . again.

 

[Runnin'OnEmpty]

I'm betting it's #1 injector sticking open. That would
account for the cooler #1 header tube, the exhaust
backfires, and the sooty #1 plug.

Congrats on narrowing it down to the #1 cylinder.