Another rough idle post

The Devils Own Chariot

The Devils Own Chariot

Active member
Im not posting this up because Im clueless on what to check. I have checked mostly everything. Vacuum lines, replaced plugs cr43ts, gap .026, new plug wires, cleaned cap and rotor, msd coil.
If the truck is in neutral and you rev it up and let rpms fall it wants to die. Its also really cold blooded. It has hesitation on the throttle initially but then cleans up when its fully warm. It will not make boost well until its fully warm also. After everything is warmed up throttle response is better and it spools smooth and fast. After its warm it still has a funny idle. WOT is great when warm.
Im looking at the DM file and you can see the fuzzy idle. ECM voltage looks good. TPS sensor seems to be reading right. No codes. Do I need to make my plug gap bigger? Mods are in my sig. Thoughts.....
 
KDBL1TY

KDBL1TY

Member
Re: Another rough idle post

Let it get to operating temperature, then drive it around above 35mph.This will reset the IAC. If this doesn't restore your idle it might be time to buy a new IAC.
 
S

syty9933

New member
Re: Another rough idle post

im having the same problem sometimes ,mine almost dies when i start it up and rev it a lil to stop it from dying then when i let off it drops too low, and then sometimes when i hit the gas it has crappy throttle response
 
The Devils Own Chariot

The Devils Own Chariot

Active member
Re: Another rough idle post

syty9933 said:
im having the same problem sometimes ,mine almost dies when i start it up and rev it a lil to stop it from dying then when i let off it drops too low, and then sometimes when i hit the gas it has crappy throttle response
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Exactly. The IAC looks clean I took it off last year. What fails on them?
 
The Devils Own Chariot

The Devils Own Chariot

Active member
Re: Another rough idle post

Looks like my idle is lean. It sure smells rich. Look at the LT and ST counts. Also look how fuzzy the rpm line is.
Snap1-2.jpg
 
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syty9933

New member
Re: Another rough idle post

i dont think he figured it out the problem ,his just fixed the info, i think its the throttle body because it started doin all of this after i adjusted it, but even when i adjust it by the book it still does this
 
KDBL1TY

KDBL1TY

Member
Re: Another rough idle post

TPS and IAC controls idle, If you adjusted the small set screw put it back to stock position. Do you know how to code it with a paper clip ? Don't over think this. Read the codes and go from there. these trucks are really fickle when things are a little outta place.
 
Don W.

Don W.

Stab it and steer it
Re: Another rough idle post

To answer your question I would definitely try 0.035-6 on the gap. Lots of folks say 0.026 but my truck likes the big gap. I'd give it a try.

OK one thing here. Pull the throttle body and check for butterflies closed completely, Hold it up to the light, should be almost no light coming through yet not binding. If the adjustment screw is not sealed then someone may have messed with it.

What is the PLX telling you? You could also switch back to the stock chip and 2 bar for a test.

If all else fails and I was to place a bet I'd bet on a blown lower intake. Only because after much BS that's what I found on mine.

Keep us posted.
 
The Devils Own Chariot

The Devils Own Chariot

Active member
Re: Another rough idle post

The PLX says 14 to 15 at idle. It jumps around between those numbers a bit. Im going to try the .035 gap. I experimented with the throttle body screw using a small screw driver wedged in there. Its seems to like where its at more than anything.
Im also wondering if the alternator is weak. I should be getting better than 12v at idle right?

KDBL1TY said:
Do you know how to code it with a paper clip ? Don't over think this. Read the codes and go from there. these trucks are really fickle when things are a little outta place.
Click to expand...

I have datamaster. There are no codes/DTC errors.
 
M

Mike

New member
Re: Another rough idle post

I was having a similar problem and it turned out that one of my injectors had a slight crack on the tip
 
WyoSyclone

WyoSyclone

Active member
Re: Another rough idle post

Rookie said:
The PLX says 14 to 15 at idle. It jumps around between those numbers a bit. Im going to try the .035 gap. I experimented with the throttle body screw using a small screw driver wedged in there. Its seems to like where its at more than anything.
Im also wondering if the alternator is weak. I should be getting better than 12v at idle right?



I have datamaster. There are no codes/DTC errors.
Click to expand...


But you've still got .8 TPS at idle..... I'd sure get that fixed first.... :D
 
WyoSyclone

WyoSyclone

Active member
Re: Another rough idle post

Rookie said:
Do you really think .8% tps matters?
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Yup, you've gotta remember that's almost 1%.... if you look at the size of the throttle bores and calculate how big of an open area that represents, I would bet that it exceeds the flow/control of the IAC.... so, you've got an IAC/ECM trying to control idle when there is a huge leak past the throttle body butterflies.
 
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