Performance Issues and Confusion

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May 15, 2020 | 07:19 PM

#16

coreywt

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Quote:

Originally Posted by 99f350sd

.................................................. ..

Two options: make sure the 12volts is stable with a test light or some kind of 1 amp load 12 ohm resistor? Next check signal wire back to computer for breaks. That wire on scope should be 12v then zero during pulse with coil plugged in. Check resistance of coil? compare? Connector for corrosion. They corrode bad..

Good luck.

Dick

so. We swapped the pcm today. In addition we checked resistance on coils. Connector is in good shape. I had a spare wiring harness from the engine swap, so I pulled a connector off and we wiring a new wire from directly off the PCM connector over to the #2 cyl. We did see some stuff on the scope, however it was faint. we did not see anything change in terms of performance. Same symptoms. We tried a engine balance test by unplugging #1 and heard the engine rev down. Did the same for #2 and no difference. Ugh.

truthfully I am beyond frustrated with this.

May 15, 2020 | 08:01 PM

#17

99f350sd

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Joined: May 2003

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From: Lyndonville, Vermont

I feel your pain. Few years ago I had same issue with a 2000 5.4l..
So no blockage in intake or exhaust manifold?
Maybe do a leak down test on 1 and 2.....and compare.
Pull the plug and look at it.
I'll be thinking

May 15, 2020 | 08:21 PM

#18

Djosbun

Fleet Mechanic

Joined: Oct 2017

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From: Southwest Ohio

I previously suggested that a leakdown test be performed but he said his compression test was good.

He'll figure it out eventually.

-- Dave

May 15, 2020 | 08:23 PM

#19

99f350sd

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From: Lyndonville, Vermont

Should be good. But the more data the better.

May 15, 2020 | 08:29 PM

#20

Djosbun

Fleet Mechanic

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From: Southwest Ohio

I was being sarcastic.

-- Dave

May 15, 2020 | 08:43 PM

#21

coreywt

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Quote:

Originally Posted by Djosbun

I was being sarcastic.

-- Dave

It’s on the list. We talked about it today, just more tools to go get. Leak down set is one of the few we don’t have. Based on all the other data we have it seems less Likely to me, but at this point clearly anything could be the problem. With so few options left, it seems leak down is next on the list.

May 19, 2020 | 03:59 PM

#22

coreywt

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Quote:

Originally Posted by Djosbun

You need to test, using a noid light, to see if injector #2 is working.

-- Dave

Quote:

Originally Posted by Djosbun

Either do a leakdown test (to see if the #2 cylinder holds pressure) or pull the valve cover and see if there's a broken valve spring or rocker arm on the intake valve.

Either the intake valve isn't opening.

-- Dave

ok, we did a noid light test and a leak down test. Both showed positive results. Leak down was about 5psi lower than the air I was sending in. Noid light flickered as i would have expected.

additionally I pulled spark plugs and did a test just to make sure I visibly saw spark, which I did. Compared to multiple other plugs and COPs on multiple spark circuits and same result.

is it possible the fuel injector port is clogged just on cyl 2? I swapped cyl 1 and 2 previously which did not seem to change anything.