Where are my Ford experts at?

Discussion in 'The BS Topic' started by AllensaurusRex, Aug 6, 2019.

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  1. Knuckle Dragger

    Knuckle Dragger Mayor of Simpleton Staff Member Lifetime Gold Member

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    You can check the cat like Fbird describes or with a vacuum gauge. If you drop the exhaust you can cause the O2 to see a lean condition and it would throw fuel control off. The vehicle should still run a hell of a lot better. When it was just cylinder 4 missing the cat seems unlikely, with all three on bank two misfiring it seems possible. The pending p0316 kind of discounts that possibility because the misfire seems immediate to start up and it usually takes a bit for a clogged cat to build pressure. I'm completely baffled so IMO it can hurt to check it.

    https://www.aa1car.com/library/converter.htm

    EXHAUST BACKPRESSURE CHECKS
    To diagnose a plugged catalytic converter, you can check intake vacuum or exhaust backpressure. To check intake vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Then increase engine speed to about 2,500 rpm and hold steady. Normal vacuum at idle for most engines should be 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is 10 percent lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust. Remember, though, that intake vacuum can also be affected by retarded ignition timing and valve timing. What's more, some engines are much more sensitive to small changes in intake vacuum than others, so checking backpressure rather than intake vacuum may give you a better indication of what's going on.
     
  2. danbrennan

    danbrennan Veteran Member Lifetime Gold Member

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  3. AllensaurusRex

    AllensaurusRex Veteran Member

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  4. Knuckle Dragger

    Knuckle Dragger Mayor of Simpleton Staff Member Lifetime Gold Member

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    Yeah, you should see it in the O2. IF we had a fuel restriction it would be adding fuel to both sides.
     
  5. AllensaurusRex

    AllensaurusRex Veteran Member

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    So at this point, I'm leaning toward a few different thoughts:
    1. Timing: I have never messed with the timing of this vehicle. I pulled both heads at 250k and there were valve seat issues that I resolved. Lucky for me, this isn't an overhead cam, so I didn't have to deal with timing...nor have I ever replaced the water pump. Long story short, it is possible that the timing chain could be stretched a bit after 300k and jumped a tooth. Regardless, I would imagine that would affect both banks...
    2. Catalytic Converter: I haven't received any o2 related check engine lights. The only reason I did the upstream o2 in the first place was because I was running out of ideas, and I knew that it helped regulate the driver side bank (cyl 4, 5, and 6). I guess it could be that it is clogged. I might try running it around town and see if it is glowing after ~ 30 minute drive.
    3. Fuel Injectors: I replaced the #4 fuel injector back when I was only receiving a misfire check engine light for that specific cylinder. No change. I might try flipping fuel injectors from the other bank to see if anything changes. I have put a screw driver up to them as the hillbilly stethoscope, and I do hear all of them clicking/firing.
    4. Spark Plugs: This was the first thing I did when I received the # 4 misfire check engine light. I'm usually working on Chevy's so I bought AC Delco's (DOH!). I installed them anyway (gapped correctly) with no change. I then bought a single Motorcraft plug and installed it on cyl # 4. Still no change. Maybe it needs a whole set of Motorcraft plugs, but again not sure why it would be only affecting one bank.
    5. Bad ECM: I know this one is rare, but who knows...
     
  6. danbrennan

    danbrennan Veteran Member Lifetime Gold Member

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    I think we generally spec our ECMs to last 10 years, with some very low failure rate. I imagine Ford's specs are similar. But unless it's been replaced, yours is getting pretty far past that. Still, I rarely hear about an ECM going bad. But I have heard of it. Grounds and connectors are the most popular electrical problems, I think.
     
  7. AllensaurusRex

    AllensaurusRex Veteran Member

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    So I piddled around a little bit this weekend. I made sure the ECM ground was secure and it was. No corrosion, etc. I also looked at all hoses and connections. I didn't find anything that was loose or not connected. I know when cats get clogged they usually have a really rotten smell to them. I don't smell that here.

    I was thinking I might be able to test if it has a clogged cat by removing the o2 sensor and driving around. Although it would be loud, if it ran well...I can assume it was a clogged cat. I just don't know if it would run...like at all...since the o2 sensor usually regulates...
     
  8. Knuckle Dragger

    Knuckle Dragger Mayor of Simpleton Staff Member Lifetime Gold Member

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    Unplug the O2 sensors, don't let them hang. The ECM should use substitute numbers and run OK. O2s aren't quite as influential as people make them out to be. You won't be fine tuning the fuel but you'll be fairly close. IMO, reset the KAM before you drive it this way so the ECM isn't adapting for a no longer present issue. Disconnect toe battery for 10-15 minutes.
     
  9. AllensaurusRex

    AllensaurusRex Veteran Member

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    So I don't have to remove the o2 sensor from the header? I can just simply unplug it?..and zip tie it up so it doesn't get burned up.
     
  10. Knuckle Dragger

    Knuckle Dragger Mayor of Simpleton Staff Member Lifetime Gold Member

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    You'll have to pull it out of the exhaust to release the restriction (if there is one). I was referring to not leaving it plugged in to the electrical in the open air to have the ECM see a lean mixture. If it's unplugged the ECM will default to a known value.
     

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