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Secondary Idle Adjustment?

2K views 29 replies 11 participants last post by  Millionmiles 
#1 ·
I've read up on the posts about adjusting the motor's idle using the throttle linkage rod, but what else can be done beyond this?

I've maxed out the length of my linkage on both ends (threaded rod almost unscrewed from the female ends), but my idle is still on the low side, right about at 500 in Drive w/ A/C on. Want to get it up to about 650 here as it's hard starting at the current level.

When I installed my new p-pump, I recall there was a plate on the side of it towards the back of the pump where the linkage connects. Can this be adjusted too? It looked like it was possible to change the angle of it, thus taking up some of the slack in the linkage. Now that's it's installed in the truck facing downwards, it's hard to see much.

What's even more bizarre, my linkage rod was capable of conventional idle adjustments right after I installed my new pump. The truck at first idled too high, so I backed it off quite a bit. Now I need to increase it, but the linkage is all maxed out. Any ideas what caused this? :confused013:
 
#2 ·
You shouldn’t adjust your linkage. If you follow it all the way to the rear of the pump, it all rests on a cap screw. There’s a jam nut on the underside you loosen and then spin the cap screw up to increase throttle. 10mm I believe.


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#3 ·
Ooofff you should of left that alone. That rod is not meant to adjust idle. It is used to make sure the TPS, TV, and cruise control are all in proper alignment. There is only +-1mm adjustment allowed there and that is used for TPS adjustment.

The proper way to adjust idle is at the low idle stop on the pump.
 
#4 ·
Gosh darnit.

Ok, thanks guys. I'll give that a try. Hopefully the linkage isn't too messed up. I'll try to reset it towards somewhere in the middle for now.
 

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#5 ·
I suggest you open the factory service manual and adjust both the linkage rod and the idle by the book. Not much point in having a correct tool if you don't use it.
 
#6 ·
Do you guys back off the locknut a ways down the screw, and then turn the screw by hand from its tip underneath? I'm having a heck of a time getting two 10mm wrenches down there.
 
#10 ·
It isn't in the easiest place to get to, but using a 10mm wrench from the top is how I do it. Having a helper to hold the throttle full forward would make it a bit easier. The bolt goes up to increase idle. A little bit of adjustment goes a long way.
 
#7 ·
Yes, get it about where you want it and then tighten the lock nut. The idle will adjust up or down (Cant remember) a little when you tighten it down.
 
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#8 ·
Hope you’re taking GAmes advice on the manual and setting your linkage by the book. You can take the tranny out in short order with the wrong settings.
 
#9 ·
Yes, I'm going to address this tomorrow. And goodness, I did not realize it was that critical. I appreciate the warning.
 
#13 ·
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.
 
#14 ·
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?
 
#15 ·
Why don't you test drive it before you take it out of spec again?
 
#17 ·
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.
 
#16 ·
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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#18 ·
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.
 
#19 ·
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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#20 ·
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.
 
#21 ·
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.
 
#22 ·
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.
 
#26 ·
You do know there is a free factory service manual download in the stickies don't you? If you prefer not to get your computer greasy there is my go to, the printed version.

https://www.genosgarage.com/product/dfsm97-print/dodgeram-factory-service-manuals

Since you are a customer of Oregon injection you must live close to Eugene? So does one of our other members, who I see almost every time I go to visit my grandkids in Salem.
 
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