Al Stokes
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From: Huntsville, AL
Al Stokes
18,000 lbs motor home, 140,000 miles, new plugs!
I have a hard miss at 40MPH, up hill, 3 gear, 2500 RPM. Not at idle!
Vacuum gauge readings, start engine-17 inches (cold or hot).
Run 20 seconds or so, than 7 inches. Stays same on light acceleration.
If I turn off Ignition, 2 seconds, returns to 17 inches, than 0.
I suspect the Vapor Management Valve (VMV). But I do not know what the vacuum gauge should read under these conditions. I have no MIL or DTCs on my OBII reader.
The VMV appears to go directly to the PCM, so signals/info come directly from the PCM.
I do not expect not see 7 inches at idle and light acceleration!
Please help an old man with his troubleshooting!!!!
Al Stokes
256-539-2058
I have a hard miss at 40MPH, up hill, 3 gear, 2500 RPM. Not at idle!
Vacuum gauge readings, start engine-17 inches (cold or hot).
Run 20 seconds or so, than 7 inches. Stays same on light acceleration.
If I turn off Ignition, 2 seconds, returns to 17 inches, than 0.
I suspect the Vapor Management Valve (VMV). But I do not know what the vacuum gauge should read under these conditions. I have no MIL or DTCs on my OBII reader.
The VMV appears to go directly to the PCM, so signals/info come directly from the PCM.
I do not expect not see 7 inches at idle and light acceleration!
Please help an old man with his troubleshooting!!!!
Al Stokes
256-539-2058
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Do you mean that when you turn the engine off, the vacuum gauge goes UP to 17, and then falls back to 0?
Definitely sounds like a clogged catalytic converter. Once you turn the key off, no more combustion, pressure disappears from exhaust side, so as the engine spins down, it generates vacuum once again.
Definitely sounds like a clogged catalytic converter. Once you turn the key off, no more combustion, pressure disappears from exhaust side, so as the engine spins down, it generates vacuum once again.
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Joined: Dec 2015
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From: Huntsville, AL
I shot myself in the foot with the Vac readings. I placed a “T” in the vac line to the purge valve causing a restriction in the 3/8” line! Replacing with a 3/8” pass through, the readings were normal.
Idle, 800 RPM @ 21“ through 3000 RPM @ 21.5“.
In reverse, 800 RPM @18”, 1,500 RPM @11”, 2,000 RPM @ 0”. These look OK!
Ran five minutes in reverse @ 2,000 RPM and measured temperatures front and rear of Catalytic Converter: My laser “OH” at 600 Deg. On the front and rear. As things cooled down, I measured, 470 Front and 600 rear.
Is 130 degrees enough to change the converter?
Thank you for your patience!
Al Stokes
PS Having trouble finding my posts and replies.
Idle, 800 RPM @ 21“ through 3000 RPM @ 21.5“.
In reverse, 800 RPM @18”, 1,500 RPM @11”, 2,000 RPM @ 0”. These look OK!
Ran five minutes in reverse @ 2,000 RPM and measured temperatures front and rear of Catalytic Converter: My laser “OH” at 600 Deg. On the front and rear. As things cooled down, I measured, 470 Front and 600 rear.
Is 130 degrees enough to change the converter?
Thank you for your patience!
Al Stokes
PS Having trouble finding my posts and replies.
Thread Starter
|
New User
Joined: Dec 2015
Posts: 7
Likes: 0
From: Huntsville, AL
I shot myself in the foot with the Vac readings. I placed a “T” in the vac line to the purge valve causing a restriction in the 3/8” line! Replacing with a 3/8” pass through, the readings were normal.
Idle, 800 RPM @ 21“ through 3000 RPM @ 21.5“.
In reverse, 800 RPM @18”, 1,500 RPM @11”, 2,000 RPM @ 0”. These look OK!
Ran five minutes in reverse @ 2,000 RPM and measured temperatures front and rear of Catalytic Converter: My laser “OH” at 600 Deg. On the front and rear. As things cooled down, I measured, 470 Front and 600 rear.
Is 130 degrees enough to change the converter?
Thank you for your patience!
Al Stokes
PS having trouble finding my post and replies.
Idle, 800 RPM @ 21“ through 3000 RPM @ 21.5“.
In reverse, 800 RPM @18”, 1,500 RPM @11”, 2,000 RPM @ 0”. These look OK!
Ran five minutes in reverse @ 2,000 RPM and measured temperatures front and rear of Catalytic Converter: My laser “OH” at 600 Deg. On the front and rear. As things cooled down, I measured, 470 Front and 600 rear.
Is 130 degrees enough to change the converter?
Thank you for your patience!
Al Stokes
PS having trouble finding my post and replies.
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Joined: Dec 2015
Posts: 7
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From: Huntsville, AL
Just sharing my latest troubleshooting adventures!!
1999, F53, V-10, 140,000 miles, OBI system, Motor Home @ 16,000 lbs.
Engine miss under load, uphill, 2,500 RPM, 3 rd gear.
Feels like more than one cylinder. No DTC’s.
Installed Ford plugs and new coil boots.
Installed crankshaft sensor, New 297 ohms, Old 343 ohms.
Touch magnetic tip w/metal, 343-0-343 ohms.
Measure vacuum at idle, 19 in., at 2,000 RPM, 22 in.
Test catalytic converter, 20 min drive, Inlet 470 degrees, Outlet 600 degrees = +130. Rear should be at least 80 degrees hotter. Cat OPEN!!
INNOVA 3160 Reader:
P0300 random misfire. SOMETIMES.
P0309 and 10 misfire. Switched coils, 9 to 4 and 10 to 5. No change. No codes.
Drove 75 miles to weekend camping. No “Service Engine Soon” or MIL.
P0300 random misfire.
P0305 misfire cylinder 5.
Replaced cylinder 5 coil and drove home. Hard miss gone. There was a slight miss that disappeared as I drove.
Before the 75 miles, it ran smooth as a kitten. I guess the PCM learned new parameters.
Thought all of you would want to know what happened. Al
1999, F53, V-10, 140,000 miles, OBI system, Motor Home @ 16,000 lbs.
Engine miss under load, uphill, 2,500 RPM, 3 rd gear.
Feels like more than one cylinder. No DTC’s.
Installed Ford plugs and new coil boots.
Installed crankshaft sensor, New 297 ohms, Old 343 ohms.
Touch magnetic tip w/metal, 343-0-343 ohms.
Measure vacuum at idle, 19 in., at 2,000 RPM, 22 in.
Test catalytic converter, 20 min drive, Inlet 470 degrees, Outlet 600 degrees = +130. Rear should be at least 80 degrees hotter. Cat OPEN!!
INNOVA 3160 Reader:
P0300 random misfire. SOMETIMES.
P0309 and 10 misfire. Switched coils, 9 to 4 and 10 to 5. No change. No codes.
Drove 75 miles to weekend camping. No “Service Engine Soon” or MIL.
P0300 random misfire.
P0305 misfire cylinder 5.
Replaced cylinder 5 coil and drove home. Hard miss gone. There was a slight miss that disappeared as I drove.
Before the 75 miles, it ran smooth as a kitten. I guess the PCM learned new parameters.
Thought all of you would want to know what happened. Al
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