Weird idle after JLT install

[ctrlraven]

Well I installed my JLT intake the other day and didn't notice any problem with "bog" or any issues because my engine was still nice and warm from just getting to work until later that day when I left work. The car started right up fine but after the rpms drops to their normal idle in P I could feel the engine shaking and hear a lil rough of an idle but didn't see the rpms moving. So the past few times when I started the car up when it has a cold engine the idle is rough and just barely seems like it wants to cut out but doesn't. I read all the post on the JLT section on the site and don't have a bog problem, car has better accel with the intake than the OEM intake but it only does it when it's cold and after a few mins once the engine starts to heat up everything is nice and smooth just like before I did the install. I can live with this little qork until I get some more parts (full exhaust) and take it to have it dyno tuned but has anyone else noticed this on theirs?

[DEFYANT]

Any vaccume leaks?

[ctrlraven]

Well I do have a breather filter on the driverside valve cover and I didn't hook up the little tube that was on the JLT intake to it cause it wouldn't reach but its caped off. I'll try and get a small piece of tube to connect it and to the intake and see if that fixes it.

[Drock96Marquis]

IAC supply on nice and tight?

[merc6]

Reset the pcm(ecu) as well and see what happens.

[Black_Noise]

it happened on mine, when my filter fell off, the heat shield and filter just wouldnt stay, so i took the heat shield off and tightened her down good, fixed it

[merc6]

Oh thats right the JLT did have that freak filter issue...

[magindat]

1) Get that valve cover vacuum hooked up.
1a) Make sure that PCV valve is still good.
2) Make sure the JLT is tight and on well. It settles a bit and needs re-tightening.
3) Make sure there's no gap between the MAF adapter and MAF (common).
4) Make a short bracket to go from the stock airbox stud (front inside of wheel well directly under MAF adapter) up to the MAF adapter. This will prevent any vibration of JLT.

If the intake is sucking any air the MAF doesn't know about, the car will run 'funny' depending on just how much air is unknown to the ECU.

[ctrlraven]

I'll do that stuff today. It's just weird to me that it only does it when the engine is cold but once it warms up its fine.

[SID210SA]

Mine ran fine the first time I put the JLT on and I took it off to got the the dealership for a couple of thousand miles and put it back on...I had the rough idle as well but mine was all the time....I put the stock airbox back on again and still had the rough idle...took it to the dealership to have it checked. It was hardly noticeable but I noticed it....dealership said it was nothing to worry about so I put back on the JLT....So I dont think the rough idle is due to the JLT. JMO. I had a friend of mine in the Marauder after I recently put the JLT back on and when I oppened her up on the frontage road he had a grin from ear to ear and mentioned how much he missed that awsome sound and the seat of the pants feel....he swears he can feel it...and so do I.....Glad to put a smile on peoples faces!!!

[SID210SA]

I'll do that stuff today. It's just weird to me that it only does it when the engine is cold but once it warms up its fine.

Your JLT should have come with an extension tube.....mine did.

[Breadfan]

You could do a MAF relearn since it's now getting more air. Disconnect battery for 20 minutes, and then plug it back together and go.

Is there a set MAF relearn procedure from Ford? I know GM has one for the LS1 that's pretty detailed on how to properly do a MAF relearn...

That couldn't hurt...

Also just curious but did you recently switch to gas that has 10% ethanol? Alot of stations are changing to this formulation, there was talk about a minor idle rumble when using the 10% ethanol fuel (not sure if it was every truly attributed to it though).

[ctrlraven]

I'll un hook the negitive terminal and see what that does. No I have been running the same type of gas since before I even got my flash tuner. It's almost like the feeling of a high powered 5.0 and it has that real rough idle with a shaking engine like its about to die because of the shortage of fuel at idle but not as bad. It does it for about maybe 5 mins then goes away but it didn't start until I put the JLT on and engine was cold. I had done anything else to the vehicle that day and it didnt move anywhere.

[merc6]

besides the issue(s) did you like the new feel when you barely tapped the accelerator? :)

[ctrlraven]

Well they wernt really issues cause it didn't bother me was just wondering what it could be. Yeah I can defenitley feel the mid range power difference. I unhooked the battery for about 45-50mins, re-tighten everything and found the OEM breather hose got that hooked up. I'll see what it does later tonight and tomorrow morning when I start her up. Thanks for the input fellas.

[DEFYANT]

You must use the oem PCV system. ANY unmetered air in the system WILL make a lean condition. I tried that fnacy lil breather thingy.

Didn't work.

[ctrlraven]

I've had that little breather thing on for months now lol. Yeah I hooked it back up and ran the car after it cooled down and everything seems back to normal expect for my gas mileage but I think thats due to the heavy right foot syndrome I'm having right now lol. Next step is to hook up a oil/air separator.

[djbruce26]

It actually sounds like the computer is just needing to adjust itself to the difference in airflows... and when you put a stock box back on it would likely have the same problem since it would be learned halfway to your new tube... and halfway from the stock box. Whenever I change anything on my car I've adopted the policy of unplugging the batter cable and then doing a MAF relearn.

Is there a set procedure? Yes... there is. It needs to learn the new air settings for the engine at varying throttle ranges, idles, and load levels. I'm not sure this is everything but if memory serves on our cars you just need to:
Sit in park a few minutes.
Sit in park with AC on.
Sit in neutral.
Sit in neutral with AC on.
Drive.
Drive with AC on.
Try to vary speeds and acceleration levels when driving. Start with soft accels and work your way into higher speeds and harder accels.

I might have missed something but it always works for me... Takes me about 15 minutes or so (maybe 20) and it runs smooth and flawless again.

Post note: I do drive a 2001 CVLX, not marauder... but computer should be similar in relearning the maf settings.

[Tucker]

Sounds like you got it straight, but just wanted to chime in.
The PCV hose supplied doesn't replace the entire PCV hose, but connects to the existing hose with the factory fitting that's in the factory hose.

Clearing the computer is a good idea for a first thing to do if any odd issue happens when parts are installed.

I also run breathers without any of the effects talked about on the internet. 100's of dyno runs with A/F checks and never a lean spike. So it's not a problem.
Thanks and remember, any questions feel free to call.

Jay