Topic: weird idle problem

[tallrugbyguy]

hmm, would the screw do it? it seems like its somthing electrical since it only happens when its a cold start up. mine dosent vary too much at idle, my problem is more the starting. usually takes two tries...

[TrailsLessTaken]

That more how mine is.  If I don't give it gas right after if fires up it will die

[lax22]

I have no problem at start up its just at idle after warm-up. like sitting at a traffic light in neutral.

[Jeffy]

Any CEL Codes?

[lax22]

I have not seen and check engine lights and the dash button trick dose nothing, I have a 97 by the way.

[tallrugbyguy]

ill let ya know as soon as i get my new computer in. in the cold weather right now il waiting for 6 minutes just for it to start.!

[Sidscan]

I did my 4.0TB swap this past summer and i have a weird idle as well. With the stock TB and TBS it idled smooth and steady at 700rpm. I took off the TBS and the 2.5l TB and as soon as the new 4.0l TB went on the RPMs jump up and down between 700 and 800 rpm at idle. I have replaced the TB gasket and even checked the 2.5l IAC housing and everything is sealed and tight. I would like to fix it without switching back but its starting to get annoying. I have a new TPS and IAC. The only thing i can think is that the engine is getting too much air if that even makes any sense since i am running the 4.0l intake tube with an arrait intake. Any suggestions? I would assume that the computer would have readjusted by now.

I went back to the stock air intake with the 4.0tb and a TBS - after about 500 miles everything runs great.  I was struggling through a lot of the same problems this is what the computer likes best.  For the first 500 miles or so my Firewire plugs would work its way off the distributor, now that they are not moving everything seems to tie togther. 

[Jeffy]

I went back to the stock air intake with the 4.0tb and a TBS

That's exactly what I run...

[stan98tj]

im lookin to upgrade to the 62mm TB and maybe a spacer on as well..i currently have an AEM intake that id like to keep-wonder if all that air would cause a problem. ideas anyone?

[lax22]

I will throw the stock intake back on and see if that helps. I though that the Arraid might have been giving it too much air which is throwing off the sensors a bit.

[Jawbonz]

I have something along these lines and wonder what might be the cause.

Symptoms:

On most COLD days, it starts fine, but idle is horribly low...in the almost stalling range of probably 200-400RPM, and it runs rough.  If I put it in gear and give it just a bit too much gas, it stalls right out.  Sometimes, I'll sit and crank for anywhere from a second to 30+.  As soon as the motor starts to warm, the idle/rough run goes away.  If I don't stall and get moving, it's just fine until I let off the gas prior to warming up completely.

After reading through some of the 4banger yahoo threads, it could be either the CPS or the IAC.  I've been running the 4.0L TB with a cold air can for a few years, and this just started when the weather began cooling off for the winter.

Now, with the 2.5L, I'll need to replace the IAC with the 4.0L due to the TB, correct?

[lax22]

Just a little update. I put my stock TB back on afte rtrying the 4.0 TB with the stock intake and no change in my idle problem. After putting the stock TB back together and installing it the idle returned to normal and is smooth and consitent now. I wonder if there is something leaking causing a vacume leak somewhere. I am going to try cleaning up the mounting surfaces and see if that fixes it. pretty frusturating though.

[chardrc]

I could be wrong but don't you have to use the2.5l sensors with the 4.0l tb???...

[FourbangerYJ]

I could be wrong but don't you have to use the2.5l sensors with the 4.0l tb???...

Yes you do.

[lax22]

New 2.5 TPS and IAC sensors and 2.5L IAC housing were also swapped over to the 4.0 throttle body when it was swapped.