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Old 07-01-2022, 08:16 PM   #1
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Unhappy Low Power, Rough Idle - MAF? Spark? Compression?

I am once again asking for your support lol. About 2 weeks ago, I was driving my HB on a rural road and noticed I was pretty low on power. Couldn't hold any speed up a hill, etc etc. Pulled over to check for something obvious, loose vacuum line, etc...found nothing. Did notice the engine was shaking more than usual. Turned around and beetled it back home so I didn't get stranded.

Fast forward to now, here's what I've tried to diagnose and fix it.
  • Removed passenger seat, pulled codes - 12 and 33. I believe these are MAF sensor and O2 sensor. O2 sensor was replaced with new one in Fall 2021, so I'm doubting that alone is causing the issue.
  • Truck had a rough idle, low power, bad throttle response, etc, and was throwing that MAF code. Unplugged old MAF, very small change in idle. Plugged MAF back in, truck almost dies for a second and then recovers.
  • So I went and bought one cheap MAF ($50 CAD on Amazon) and one other MAF ($120 CAD on RA). Don't ask why I bought two...I'm just dumb lol.
  • Installed the Delphi MAF from RA...no change. Installed the Chineseum Amazon MAF...no change. Fk
  • Time to check for vacuum leaks. So I made my own smoke tester out of a soldering iron, pasta sauce jar, bic pen, etc. Only leaks were from behind the new Amazon MAF and the smoke tester itself. Swapped the original MAF back in, and tightened up the tester...no vacuum leaks. Fk
  • Time to check each cyl while running. Pulled the wire from Cyl 1 spark plug, truck almost died. Cyl 1 working fine. Pulled Cyl 2 plug, no change at all. Pulled Cyl 3 plug, no change at all. Pulled Cyl 4 plug, truck almost died. Ok so Cyl 2 and 3 are basically not working...this explains the low power.
  • Time to check for spark. Checked spark on Cyl 2...almost electrocuted myself even wearing gloves and work boots. Guess you're not supposed to plug in the inline spark tester while the engine is running. Whoops. Did the same thing for Cyl 3, tons of spark as well. Well shit...both are getting spark but they don't seem to be doing anything.
  • While the truck is idling in my garage, I also noticed the garage is starting to smell like fuel. This makes me think Cyl 2 and 3 are getting spark and fuel, but no compression.

What else am I missing? Anything else for me to test aside from a compression test? If a compression test is next, can someone please link me a good HB compression test thread/guide? It's been about a decade since I did a compression test and I don't want to be the idiot turning the engine the wrong way via the crank or something. As well, if a compression test is in order, what results should I be expecting?

Thanks for your help!
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Old 07-02-2022, 12:56 PM   #2
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Sounds like you're not getting power to the cylinders ... you check the wires?
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Old 07-02-2022, 01:19 PM   #3
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Did you check timing? That a big one. A shift in timing can affect power greatly.
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Old 07-02-2022, 03:11 PM   #4
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Quote:
Originally Posted by Balkins View Post
Sounds like you're not getting power to the cylinders ... you check the wires?
I mentioned above that Cyl 2 and 3 are getting spark.
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Old 07-02-2022, 03:13 PM   #5
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Quote:
Originally Posted by Deerhurst View Post
Did you check timing? That a big one. A shift in timing can affect power greatly.
Haven't checked timing lately. Not sure how a few degrees of timing would make it so that unplugging Cyl 2 and 3 spark plugs would make no difference. That would be a LOT of timing to adjust, no?

Also the truck has been running fine for months. The timing would just change in the middle of a drive?
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Old 07-02-2022, 03:57 PM   #6
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Check the resistance across the injectors. Each should have about 10 to 12 Ohms.

I bet 2 and 3 are either 0 or Infinite. Replace all of the injectors and the o-ring seals that they sit in at the same time.
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Old 07-02-2022, 04:04 PM   #7
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Quote:
Originally Posted by hstuder View Post
I mentioned above that Cyl 2 and 3 are getting spark.
You saying that 1 and 4 are not getting power?


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Old 07-02-2022, 04:08 PM   #8
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Quote:
Originally Posted by Balkins View Post
You saying that 1 and 4 are not getting power?
I think they are all getting power, but 2 and 3 show no change when they are unplugged.

My guess is that 2 and 3 are either dumping too much or not enough fuel.
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Old 07-02-2022, 04:10 PM   #9
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Quote:
Originally Posted by Balkins View Post
You saying that 1 and 4 are not getting power?


No I'm saying that I mentioned unplugging 1 and 4 and the truck almost stalled when I did that, so obviously those are working. I only checked Cyl 2 and 3 with the inline spark tester cause those had no effect when I unplugged the plug wire.
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Old 07-02-2022, 04:12 PM   #10
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Quote:
Originally Posted by jp2code View Post
Check the resistance across the injectors. Each should have about 10 to 12 Ohms.

I bet 2 and 3 are either 0 or Infinite. Replace all of the injectors and the o-ring seals that they sit in at the same time.
I will check that today. I do smell a lot of fuel when it's idling in the garage, so I'm thinking some fuel is not being burned
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