3176B CAT not revving well what do I do? - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 11 (permalink) Old 08-30-2009, 09:16 PM Thread Starter
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3176B CAT not revving well what do I do?

Guys I've got a Freightliner FLD120 with 3176B CAT engine double axle, 3.65 gear ratio, 365HP, not revving to more than 1500rpm while on motion and will only exceed that going down hill. But when traveling uphill, it gets below 1500rpm to as low as 1000rpm even when the throttle is floored.
What could be the problem? We have replaced the air filter, done the oil change (even when its only done 9,850Miles since the last oil change) change the oil & gas filters.
Please what's the correct thing to do or what next should we do?

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post #2 of 11 (permalink) Old 08-30-2009, 09:48 PM
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From reading your other threads, is this one of the trucks with the chk eng light flickering? Almost sounds like limp mode.

What is the fuel pressure?

"Some people are educated beyond their intelligence."

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post #3 of 11 (permalink) Old 08-30-2009, 09:55 PM
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check fuel supply line ,inner liner collapses restricting fuel supply
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post #4 of 11 (permalink) Old 08-30-2009, 10:02 PM
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Originally Posted by S-AOW View Post
Guys I've got a Freightliner FLD120 with 3176B CAT engine double axle, 3.65 gear ratio, 365HP, not revving to more than 1500rpm while on motion and will only exceed that going down hill. But when traveling uphill, it gets below 1500rpm to as low as 1000rpm even when the throttle is floored.
What could be the problem? We have replaced the air filter, done the oil change (even when its only done 9,850Miles since the last oil change) change the oil & gas filters.
Please what's the correct thing to do or what next should we do?

Thanks
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From reading your other threads, is this one of the trucks with the chk eng light flickering? Almost sounds like limp mode.
!!! Another good call bud!!
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post #5 of 11 (permalink) Old 08-31-2009, 11:24 PM Thread Starter
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Nope this isn't the one with the CHK ENG light. This one is about a thousand miles away from me. The driver complained about the low rpm last nite. Hope to get ideas for fixing it before it gets back to base. Pls pardon my ignorance, what is "limp mode"?

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post #6 of 11 (permalink) Old 09-01-2009, 12:33 AM
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Limp mode basically protects the engine when something is wrong. It limit RPMs or hp output. Could possibly shut the engine down if need be. Have seen some equipment that have an over ride switch to keep it running to get to the shoulder. You have to push and hold it.

Electronically controlled transmissions can do the same. They will limit what gears can use going forward, and allow rev only.

Can the driver get it to a shop with a computer to hook it to? Could maybe be a cam or crank position sensor causing the problem.

Any chance of having an automated transmission?

"Some people are educated beyond their intelligence."

'93 W350 CC, LE, 5spd, HTT modded H1C, 4" DE

Sold- '99 3500 Q/C, SO CTD, 4x4, 5spd.

Traded off- '97 3500 C/C, 4x4, CTD

'92 W250, LE, CC, CTD w/ tweaked pump (SOLD)


"Obama = Hoax and Chains"

If Obama is the answer, it must have been a stupid question.

Last edited by bmoeller; 09-01-2009 at 12:35 AM.
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post #7 of 11 (permalink) Old 09-01-2009, 03:17 AM
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Originally Posted by S-AOW View Post
Nope this isn't the one with the CHK ENG light. This one is about a thousand miles away from me. The driver complained about the low rpm last nite. Hope to get ideas for fixing it before it gets back to base. Pls pardon my ignorance, what is "limp mode"?
Regardless of light (which can blow or glitch etc...), if he's at a standstill and mashes it to the floor and it hits 1500 and stops like a wall, it's limp mode. If it flutters or bounces around 15/ 1600 or whatever, you'll hafta ET the TPS, which doesn't always set the light or even code, tho should definately in limp mode. Key off and on to check if the light works
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post #8 of 11 (permalink) Old 09-01-2009, 07:00 AM Thread Starter
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Regardless of light (which can blow or glitch etc...), if he's at a standstill and mashes it to the floor and it hits 1500 and stops like a wall, it's limp mode. If it flutters or bounces around 15/ 1600 or whatever, you'll hafta ET the TPS, which doesn't always set the light or even code, tho should definately in limp mode. Key off and on to check if the light works
The lights doesnt come on. Please what do you by " you'll hafta ET the TPS" ? Please once again bear with my massive ignorance. Then also what do you think about the truck doing the trip back (it's kinda roughly a thousand miles away from base) before we fix the problem?, cos essentially we might not get anywhere it could do a proper diagnosis along the way!

Thank you immensely
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post #9 of 11 (permalink) Old 09-01-2009, 01:00 PM
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The TPS is the throttle position sensor.

The ET is one of Cat's electronic diagnostic tools. Can see some of what is going on, and also change some parameters.

You should be able to test it with an oscilloscope as well. Can watch the bandwidth as you move the throttle. You'll be able to see any place there is a problem within its travel. As you move the throttle slowly one way or the other, it show a steady increase or decrease without it jumping around if it is OK.

"Some people are educated beyond their intelligence."

'93 W350 CC, LE, 5spd, HTT modded H1C, 4" DE

Sold- '99 3500 Q/C, SO CTD, 4x4, 5spd.

Traded off- '97 3500 C/C, 4x4, CTD

'92 W250, LE, CC, CTD w/ tweaked pump (SOLD)


"Obama = Hoax and Chains"

If Obama is the answer, it must have been a stupid question.
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post #10 of 11 (permalink) Old 09-01-2009, 03:59 PM
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Originally Posted by S-AOW View Post
The lights doesnt come on. Please what do you by " you'll hafta ET the TPS" ? Please once again bear with my massive ignorance. Then also what do you think about the truck doing the trip back (it's kinda roughly a thousand miles away from base) before we fix the problem?, cos essentially we might not get anywhere it could do a proper diagnosis along the way!

Thank you immensely
Not a problem. If it was in immanent danger, it would shut down. It'll make it home (slowly )
Quote:
Originally Posted by bmoeller View Post
The TPS is the throttle position sensor.

The ET is one of Cat's electronic diagnostic tools. Can see some of what is going on, and also change some parameters.

You should be able to test it with an oscilloscope as well. Can watch the bandwidth as you move the throttle. You'll be able to see any place there is a problem within its travel. As you move the throttle slowly one way or the other, it show a steady increase or decrease without it jumping around if it is OK.
Thanx again Bri. I hafta remember we're not all from here, or able to speak Texan...
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