Rough idle

[aaronr]

It started doing this when it got cold outside. When the truck start up it idles really rough and the whole truck rocks like it has a cam. To me a sound like it has too much fuel and sounds like missing on the exhaust. When it idles why is the spark all over the place? Here is the log file.

[Biggsy]

Welcome to the forum

Dud spark plug/lead?
The PCM is raising/lowering timing possibly to try and keep the idle rpm from falling/raising.

[aaronr]

It only started this when it got cold outside. The truck got tuned this summer.
spark plugs were change 5 months ago and plug wires 1yr ago. I think this what your asking?

[Biggsy]

I think this what your asking?

Correct.
Ive had a relatively new (less than 12 months old) spark plug lead fail on me.

[aaronr]

Correct.
Ive had a relatively new (less than 12 months old) spark plug lead fail on me. I'm not sure I know what a spark plug lead is? Wouldn't you get a random misfire code?

[joecar]

Yes, I have had new spark plug leads fail, so check each one (you can see each of them between each coil and spark plug).

Also, other possibilities:
- air leak due to failed hose (would cause positve LTFT like your log shows);
- failed fuel pressure regulator (may go either way).

[joecar]

I'm not sure I know what a spark plug lead is? Wouldn't you get a random misfire code?Best thing to do is have someone diagnose the problem.:cheers:

[aaronr]

Yes, I have had new plug leads fail, so check each one.

Also, another possibility is: air leak.
Why only when it is cold like 50 degrees or so?

[aaronr]

Yes, I have had new spark plug leads fail, so check each one (you can each of them between each coil and spark plug).

Also, other possibilities:
- air leak due to failed hose (would cause positve LTFT like your log shows);
- failed fuel pressure regulator (may go either way).
I think pressure regulator is bad. I was told when the truck is hot and you let sit for 2hr or so it was hard to stat in the summertime.

[Biggsy]

Why only when it is cold like 50 degrees or so?
Are you talking outside temperature?
Post your tune, someone might see a problem.

[joecar]

I think pressure regulator is bad. I was told when the truck is hot and you let sit for 2hr or so it was hard to stat in the summertime.This could also be a bad crank position sensor; or a bad ignition module if it's a V6.

[aaronr]

Are you talking outside temperature?
Post your tune, someone might see a problem.
Yes, that is what i'm talking about. Here is my tune.

[joecar]

I'm not sure I know what a spark plug lead is?Aaronr,

Due to the nature of the engine compartment ->
- moving/hot components pose health hazards to humans and wires;
- some "delicate" components may be prone to breakage (oil pressure sensor, spark plug leads, plastic parts/tubes, electrical connectors, etc);
- over-torquing/stripping of fastener threads;
- fire/chemical/electrcial hazards;

...it may be wise to have an experienced technician look at your idle problem (or a friend who is comfortable with cars)... for your safety and for the safety of your vehicle... this is not for the faint-of-heart nor for the casual car person.

As a moderator of this forum, and at risk of sounding like a nag, I ask you to please don't do anything to injure yourself or your vehicle... that would make the rest of pretty darned sad... :bawl: ...the well-being of all forum members is our concern.

Physical idle problems are tough to crack... if it just started happening, then something broke or partly broke... it requires diagnosis using various test equipment (scantool, scopemeter, leak testers, etc), thorough functional knowledge of the the system, and some amount of experience in chasing down problems like this.

Regards and Keep Safe,
Happy New Year,
Joe
:cheers:

[aaronr]

Aaronr,

Due to the nature of the engine compartment ->
- moving/hot components pose health hazards to humans and wires;
- some "delicate" components may be prone to breakage (oil pressure sensor, spark plug leads, plastic parts/tubes, electrical connectors, etc);
- over-torquing/stripping of fastener threads;
- fire/chemical/electrcial hazards;

...it may be wise to have an experienced technician look at your idle problem (or a friend who is comfortable with cars)... for your safety and for the safety of your vehicle... this is not for the faint-of-heart nor for the casual car person.

As a moderator of this forum, and at risk of sounding like a nag, I ask you to please don't do anything to injure yourself or your vehicle... that would make the rest of pretty darned sad... :bawl: ...the well-being of all forum members is our concern.

Physical idle problems are tough to crack... if it just started happening, then something broke or partly broke... it requires diagnosis using various test equipment (scantool, scopemeter, leak testers, etc), thorough functional knowledge of the the system, and some amount of experience in chasing down problems like this.

Regards and Keep Safe,
Happy New Year,
Joe
:cheers:
I never heard them called lead. I've always heard them called spark plugs wires. I just make sure there wasn't something I was missing. I know I don't know all the technical terms. I had done all the work on it my self. This problem has come about when the weather starting gets cold. The truck runs great doesn’t have any other prombles than this.

[joecar]

If I misssed the mark, then please accept my apologies... :)

[joecar]

You need to check spark plug wires, air hoses, and anything that may change with temperature...

also, can you think of anything that may have happened prior to the problem showing up (moving a wire, backfire, etc)...?

[aaronr]

You need to check spark plug wires, air hoses, and anything that may change with temperature...

also, can you think of anything that may have happened prior to the problem showing up (moving a wire, backfire, etc)...?

The only thing that has changed is my tune. I went from diablosport to EFIlive. So I’m still learning EFIlive there is allot to this program and so much to take in. I though maybe it was in tune. I am going to load my old tune tomorrow to see if still it does. I will check the leads and hoses. The only time it does this first thing in the morning and when 60 and below. It does idle smooth in till it drops down around 800 rpm. If you make idle at 1000rpm for few seconds more when it kick down than it idle fine. May be this will help little more.

[SV8346]

i think i would be looking more towards a cracked air hose somewhere, with the LTFT as hish as what it is and also running leaner than it should be i would be assuming it has an air leak somewhere.

[aaronr]

i think i would be looking more towards a cracked air hose somewhere, with the LTFT as hish as what it is and also running leaner than it should be i would be assuming it has an air leak somewhere.
I'm looking at some of my old files and you are right. There is leak some where. I will start looking at my intake and any hose.:bash: