With any unmetered or raw fuel being injested or passed through by either misfire/s or even an injector bleed, the trims are going to go to the negative as the PCM tries to correct the ratio. Vacuum leak you should see the trims go positive and the correction attempt there would be more fuel being dumped in to maintain ratio.. Think I read that your 4.6 was lower mileage, but if their original wire, their way beyond time to change. Seen a 'few' buck'n and jerk'n fom wires breaking down..

 

Valid point, Hayapower, thank you kindly! I'll be laughing at me in the mirror for the rest of my life if it'll turn out that, after sinking almost $1k in a breakout box, injectors, ICM, two PCMs and a lot of gaskets, the cables were the culprit .... as I said, new cables and spark plugs going in today or tomorrow. Will keep everyone posted. In any case, this whole thing was my greatest automotive learning experience so far, for which I'm grateful to all who contributed time and ideas.

Cheers,
Dan

 

There is such a thing as going back to basics. In this case with all the trouble you've gone through , let's hope you solve the problem with some basic reasoning and steps.

 

Ladies and gentlemen,

On my count: 1,2,3 ... everybody laugh now ... I deserve it The only freakin' little thing I could not be bothered to replace when all this started turned out to be the culprit. I replaced the spark plug cables, kept the old (6 months old, that is) spark plugs to avoid changing two things at once (BS .. actually I could not find the plug wrench in the mess I have in the workshop, and I was anxious to see what happens with new cables ...), and took the Cat for a short ride. No hiccups at all, it purrs again like it used to. Her old power and sounds are back. Just like that ... one $47 cable kit, three screws to deal with and one hour of work. Yep. While at it, since I had to take down the generator, I also replaced the (long overdue) belt.

Will take it out tomorrow for a longer test drive (now it's pretty late and I still have other stuff to do around the house), and will let everybody know. If things look good, I'll be disconnecting the BOB tomorrow and put the PCM back in its cradle. Boy, what a ride this was ...

ONCE AGAIN, THANK YOU ALL FOR SHARING SO MUCH OF YOUR KNOWLEDGE WITH ME AND THE REST OF US HERE ON THE FORUM!!

Dan

BTW: tomorrow is my birthday. Can anybody imagine a nicer present for a man who loves his car dearly? I can't. Thanks God for this ...

 

Dan, HAPPY BIRTHDAY!! Thanks to Hayapower for coming up with the cure and you for doing all the work.
I hope now that your car's problem is solved that you keep in touch with all of us.
I want to thank you for enlightening me and also reminding me to not forget the basics.

 

Thank you, Hanky! Yes, I'll stick around, I love cars and I know (now more than ever before) how it feels to see that someone, somewhere cares about your pain and helps you out when you most need it. Will do my part to keep the fire going. We all learned a lot, so the struggle hasn't been in vain ... plus, I did a great effort to support the parts industry ... bought so much stuff that I never needed

Kindly,
Dan

 

Don't worry Dan, when I think about how much money I have invested in tools, especially the ones that I only once in a blue moon, but CAN'T be without, it makes me weak. Have fun with the newly restored cougar. And keep in touch.

 

Dear friends,

I can confirm that the spark plug cables were the culprit. The car idles and runs like a dream, I took it out today for a spin. It ran flawlessly, it is screeching the wheels again when I ask her to, it is alive again. Phew ...

One thing worth mentioning: the long fuel trims continue to be slightly imbalanced (bank 1 running leaner than bank 2). Could this be caused by the fact that I only changed the LH O2 sensor? No biggie here, I was about to change the other O2 sensor anyway to maintain the symmetry.

Finally, a detail that keeps bothering me is that incredible fuel economy displayed by the scanner when the stutter happened. Why would a burst of misfires make the ScanGauge report 3-4 liters /100 km instead of the expected 8-9 liters / 100 km otherwise? Dunno ...

Thanks again!
Dan

 

Well,, Happy Birthday Dan..

Glad you got'r squared away. Won't catch me laugh'n, many times it's taken someone looking over a shoulder pointing a greezy finger, or pick'n another brain for direction, and will continue I'm sure of that, and it's true there is strength in numbers!

 

The fuel milage display would display an incredible milage, because it was seeing a ton of air in the exhaust, which means we don't need fuel, so we take it out and the milage goes up. Also, since most of the processor was seeing was garbage, it did the best it could. If you knew how diesels get their milage calculation, then you would n't even use it! (It's all inferred, and some of the inferences they make are amazing!)
I am so very pleased that you got it fixed. And don't worry, whatever brains I have left you may pick through, though it may not be much!
Take care!