Secondary Idle Adjustment? - Page 2 - Dodge Cummins Diesel Forum
94-98 Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission Ect...NO ADVERTISING

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post #13 of 30 (permalink) Old 03-06-2019, 09:42 PM Thread Starter
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Here's a question - chicken or egg sort of deal.

The manual says set the low-speed idle first before adjusting the linkage. I did that.

Then went to adjust the linkage to 5" (I was actually closer to a half inch off as I wasn't including the 1/8" steel plate, was measuring from the front of the plate instead).

Anyways, when I put the linkage back to spec, it then throws off my low speed idle. To the point where the truck won't even start.

So now it's time to turn up the idle screw, but then that's going to lengthen the throttle linkage once again.

What's a guy to do here?


Edit: After some more tinkering I think I've just got about, just took some adjustment back and forth.

Now I just need a buddy to press the accelerator so I can observe the linkage rod & throttle lever operation.


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post #14 of 30 (permalink) Old 03-07-2019, 02:51 PM Thread Starter
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I now have the linkage within spec & the idle set where I want.

It seems my accelerator pedal has lost some range, however. While I haven't test drove it, just pushing it, it seems to have a noticeably shorter travel to reach the floor. I still need a friend to step on it while I inspect the linkage, but I suspect the throttle lever isn't maxing out.

Please correct me if I'm wrong, but the solution to me seems I need to lengthen the throttle linkage to get this pedal travel back? Then adjust the low speed idle too, all the while trying to maintain that 5" gap?

'97 2500 Laramie 4x4, 60-lb Valve Springs, 4K GSK, PDD Stage 3 P-Pump, MBRP 5" Exhaust, PDD AFC Live, Built 47RE, Thuren 2" Coils, Bilstein 5100, Synergy track bar, RedHead Steering Gear
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post #15 of 30 (permalink) Old 03-07-2019, 03:38 PM
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Why don't you test drive it before you take it out of spec again?

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post #16 of 30 (permalink) Old 03-07-2019, 07:37 PM
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You will want to watch for breaker. You should see the governor arm hit the high idle stop right before the pedal reaches the floor. You'll know then you have full throttle range.

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post #17 of 30 (permalink) Old 03-07-2019, 10:58 PM Thread Starter
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Quote:
Originally Posted by GAmes View Post
Why don't you test drive it before you take it out of spec again?
Took it for a drive earlier tonight and sure enough she wouldn't reach full throttle.

I lengthened the linkage to get more pedal travel. I'm a hair under 5 1/8" of gap so it isn't drastically off.

I'm now concerned about the TCV cable though, which I think is the most critical part of this whole deal (with regard to damage anyways).

The FSM is only somewhat helpful. It says get the cable's end to within +- 1mm of the stud on the throttle body lever. I'm in the ballpark, though it's very hard to measure down there and know for sure. It mentions nothing about the TCV's cable tension, and I'd think this would be a more reliable measure to go by.

Maybe I'm overthinking it, but does anyone know if the TCV cable should have any tension? Or should it rest freely with no tension, but also no slack, on the stud? As mine sits right now, I have the ever slightest bit of tension. I would think you wouldn't want any tension here at all, so I'm inclined to lengthen it 1-2mm.

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post #18 of 30 (permalink) Old 03-08-2019, 03:36 PM
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One simple trick I did: paint the idle nut head with a criss cross. I used yellow and blue for contrast. You can now put a visual on fine turns of the adjustment.
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post #19 of 30 (permalink) Old 03-08-2019, 03:44 PM Thread Starter
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One simple trick I did: paint the idle nut head with a criss cross. I used yellow and blue for contrast. You can now put a visual on fine turns of the adjustment.
That's a fine idea. I'll do this next time I need to fool with it.

I took a bit of tension out of the TCV cable, so it now has the slightest amount of slack when the throttle lever is at idle position. I think this adjustment was necessary as the truck is back to shifting like it did prior to me messing with the linkage. After I screwed up the linkage spec, it seemed to raise the shift points to a higher RPM even under only moderate-slight throttle, and it also didn't shift as smoothly. My guess is the tiny bit of tension on the TCV cable was the culprit here.

As always, thanks for the help everyone.
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post #20 of 30 (permalink) Old 04-08-2019, 11:24 AM
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My 97’ 12v is constantly needing this done. I take it to Oregon fuel injection for fuel filter changes and any thing else connected to the fuel system because they are supposed to be specialists. They rebuilt my injectors and did the trimming on my fuel pump at 200k. Could a dirty fuel filter cause this kind of low idle? Last time they adjusted it they said they might not be able to adjust it again. Said my pump might have to be rebuilt? It starts up immediately and runs great. Has 337,000 miles and the motor sounds better then my 2004 that has 124,000.

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post #21 of 30 (permalink) Old 04-08-2019, 11:36 AM Thread Starter
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Originally Posted by Millionmiles View Post
My 97í 12v is constantly needing this done. I take it to Oregon fuel injection for fuel filter changes and any thing else connected to the fuel system because they are supposed to be specialists. They rebuilt my injectors and did the trimming on my fuel pump at 200k. Could a dirty fuel filter cause this kind of low idle? Last time they adjusted it they said they might not be able to adjust it again. Said my pump might have to be rebuilt? It starts up immediately and runs great. Has 337,000 miles and the motor sounds better then my 2004 that has 124,000.
As for a dirty fuel filter causing low idle: yes, I would think this could be a cause. Dirty filters can lower your fuel pressure, and if bad enough, might affect idle.

Your pump should not have to be rebuilt from adjusting the low-speed idle if done correctly. Are you sure they are adjusting the low-speed, external idle screw at the lower firewall side of the pump? There is a tamper-proof high-speed idle screw that exists as well, though this shouldn't be messed with.

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post #22 of 30 (permalink) Old 04-08-2019, 12:22 PM
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In addition to what @SFGiants posted, if they are adjusting the rod like the OP did you will have the same issue. My IP is the original.

97 3500, 2 WD, G56, slightly bombed, 1.3 million miles. Started the second million on 8/24/13
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post #23 of 30 (permalink) Old 04-08-2019, 03:47 PM
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Quote:
Originally Posted by SFGiants View Post
Quote:
Originally Posted by Millionmiles View Post
My 97’ 12v is constantly needing this done. I take it to Oregon fuel injection for fuel filter changes and any thing else connected to the fuel system because they are supposed to be specialists. They rebuilt my injectors and did the trimming on my fuel pump at 200k. Could a dirty fuel filter cause this kind of low idle? Last time they adjusted it they said they might not be able to adjust it again. Said my pump might have to be rebuilt? It starts up immediately and runs great. Has 337,000 miles and the motor sounds better then my 2004 that has 124,000.
As for a dirty fuel filter causing low idle: yes, I would think this could be a cause. Dirty filters can lower your fuel pressure, and if bad enough, might affect idle.

Your pump should not have to be rebuilt from adjusting the low-speed idle if done correctly. Are you sure they are adjusting the low-speed, external idle screw at the lower firewall side of the pump? There is a tamper-proof high-speed idle screw that exists as well, though this shouldn't be messed with.
Quote:
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In addition to what @SFGiants posted, if they are adjusting the rod like the OP did you will have the same issue. My IP is the original.
I will change the filter and go from there. If it’s still low idling I’m gonna take it to someone else. Get that second opinion. Thanks guys.

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post #24 of 30 (permalink) Old 04-08-2019, 03:50 PM
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I will change the filter and go from there. If itís still low idling Iím gonna take it to someone else. Get that second opinion. Thanks guys.
Does that mean you don't do any of the work yourself? Adjusting the idle only takes a 10mm wrench and a bit of contorting your body. Measuring the length of the throttle rod requires a ruler.

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