YJ stumbling

[Atlas]

This sounds very accurate. How do I find the leak!
Should I just replace every line? At this point I'll replace all the vacuum lines and not look back

 

[luis]

This sounds very accurate. How do I find the leak!
Should I just replace every line? At this point I'll replace all the vacuum lines and not look back

You can try spraying the lines with carb cleaner and listen for an idle change. That what I did on my older vehicles and it work well for me

 

[Atlas]

I did that three times already. He is saying at high idles and speeds

 

[superj]

he thinks you have a ported vacuum leak, which is very possible. ported vacuum only comes open at a certain rpm and stays open above that rpm so you would not find it while at idle. that, or you have a cracked line or loose fitting that expands as it heats up and seals the leak on its own, which is possible also. like maybe on a plastic tee or something like that or at the threads where something screws into the intake or is bolted down.

 

[JPNinPA]

Looked back through all of this.
You could start you jeep with the IAC unplugged and it idles fine?? Sounds like a leak somewhere.


Items reviewed and comments:
The post where you mention the high idle at start when cold and warm is normal. RPM's ~1100 for a min when dead cold and a few seconds when warm is typical.

If the Crank sensor or TPS was failing you may not throw a code. Bad TPS has spots when you depress the pedal the rpm's don't increase then it all catches up at once.
Bad crank sensor starts with rough idle and may end up leaving you stranded by killing the engine.

If your Cat is bay you will have soem shuttering issues and you timing will change based on the O2's feedback to teh PCM. If you want to see if your Cat is a problem Remove the upstream O2 and run the jeep normally to see if the issue goes away.

 

[Atlas]

Will sensors read when the engine is just started and not warmed up?

 

[superj]

Resistance increases with heat so it's possible that a bad sensor or wire reads fine cold but cannot over come the mechanical resistance of corrosion or a something once it gets hot

 

[Atlas]

I'm referring to the o2 sensor. If I had it unplugged when the engine is fully cold will it still read?
Anyways I remembered when I got a cel it was because the o2 was unplugged. It did the same problem so I dunno

Regardless the work the guy did on my muffler sucked. Gobs of muffled goop fell off and it's loud at the cat connection. The end is all mangled up so I'm getting one put in Friday.

That will rule out that converter

Question. Are the vacuum nipples on the intake replaceable? Need to know invade I break one

 

[JPNinPA]

If you look back through I linked a post where a guy had a rough idle after heat soak and it was the upstream O2. You may throw a code but the idea is to see what the engine is doing.
By pulling the O2 to check if a clogged cat is the issue I mean remove the sensor from the pipe not just unplug the wiring.

 

[superj]

some of the nipples are. depends if you break a screw in one or not

 

[Atlas]

I'm very frustrated with this all. Out of patience and money

New cat put on today
They said it was plugged. So I'm all happy and soon as I pull out from getting it all done it still does it. Stopped and did a computer reset and still the same

Now I idle lower then before BUT I have more power. Had no problem doing 75 on the interstate. Before I could barely do 65

Also it seems my new muffler resonates loud. Anyone suggest a quiet one. I have hearing problems.


Also I rechecked the vacuum lines and I can't find anything. I do have a exhaust leak on the manifold.

 

[superj]

I don't know man. You are not the only person I have heard of having trouble like this. I knew girl here in town with a 4 cylinder yj, back when they were new in 94 or 95, and she had the same type of trouble. No one could fix it so she got rid of it

 

[Atlas]

Yuck. Ill buy another engine before I get rid of mine

I'm going to run it with the O2 unplugged and see what it does. I did some reading about someone with a GC that has similar issues

Also going to do some wire wiggling.

We I needed a new cat anyways and oil pan and we can say I needed a new timing chain

 

[Atlas]

JPNinPA IS RIGHT!!!


Stumbled upon an article for a grand Cherokee that gave this theory

The O2 heats faster then the engine. O2 is heated by the exhaust. A bad O2 will cause a bad signal until it warms up. A minute or do later the computer starts reading signals and changes the fuel air mix. It does not always give a code for a bad O2

So my theory is that the plugged cat messed up the O2.


So I unplugged it.


Dude.

Throttle is there
Idle is up
No more stutter

Lol


So the next day I noticed a small drip in an odd spot under the xj

Yup. Blown brake line.....

Seriously.........

What brand of O2 should I get. Garage can fool with that line.

 

[JPNinPA]

So glad you found the answer. Don't miss this one: Use OEM O2 sensors. There are many people that experienced issues with aftermarket O2 sensors.

When you cleaned the TB did you take it off and remove the IAC and clean this as well? If not you should. This will give idle issues. hot or cold.
TPS will have flat spots when they go bad, so when you gradually step on the gas you will not increase RPM for a bit then it will jump and catch up. TPA should be OE brand or else early failure.
What plugs do you have? Autolite AP985?
What brand O2's Bosch brand seem to have issues. Slow up stream O2's will cause rough idle until at temp. Check the part # to be sure you have the correct ones in and in the correct locations.
Cold the temp sender should be high res. At 210 it should be low like 9 ohm or 90 ohms. I'd have to look it up.
You really need a 195* thermo. At cooler temps your waisting gas and slowly killing your CAT. Not to mention poor heat. The fact you added coolant and started to overheat is either the wrong % mix or another issue you need to fix.

A weak battery could cause a rough idle but it wouldn't matter what temp.

Slow O2's cause rough idle when cold. Believe it or not.

Cleaning IAC and Throttle body write up (for dummies) - JeepForum.com

http://www.jeepsunlimited.com/forums/showthread.php?t=536698&highlight=Birdo+O2+sensor&page=4

Looked back through all of this.
You could start you jeep with the IAC unplugged and it idles fine?? Sounds like a leak somewhere.


Items reviewed and comments:
The post where you mention the high idle at start when cold and warm is normal. RPM's ~1100 for a min when dead cold and a few seconds when warm is typical.

If the Crank sensor or TPS was failing you may not throw a code. Bad TPS has spots when you depress the pedal the rpm's don't increase then it all catches up at once.
Bad crank sensor starts with rough idle and may end up leaving you stranded by killing the engine.

If your Cat is bay you will have soem shuttering issues and you timing will change based on the O2's feedback to teh PCM. If you want to see if your Cat is a problem Remove the upstream O2 and run the jeep normally to see if the issue goes away.

If you look back through I linked a post where a guy had a rough idle after heat soak and it was the upstream O2. You may throw a code but the idea is to see what the engine is doing.
By pulling the O2 to check if a clogged cat is the issue I mean remove the sensor from the pipe not just unplug the wiring.

FOUND IT


Stumbled upon an article for a grand Cherokee that gave this theory

The O2 heats faster then the engine. O2 is heated by the exhaust. A bad O2 will cause a bad signal until it warms up. A minute or do later the computer starts reading signals and changes the fuel air mix. It does not always give a code for a bad O2

So my theory is that the plugged cat messed up the O2.


So I unplugged it.


Dude.

Throttle is there
Idle is up
No more stutter

Lol


So the next day I noticed a small drip in an odd spot under the xj

Yup. Blown brake line.....

Seriously.........

What brand of O2 should I get. Garage can fool with that line.

 

[Atlas]

Alright you did know the answer. I just discounted the O2 because of no CEL and I never knew the cat was plugged. It just seemed to be something different

 

[Atlas]

I will say reading about your O2 comments lead me to research it more and unplug it

 

[JPNinPA]

Not looking for credit. Or to rain on your parade. It's great that you got it fixed and you have that weight/worry off your shoulders. :beer:

Just burns when we get caught up in it and react with without considering it all. Goes for me too.

 

[Atlas]

Not looking for credit. And this comment is for anyone. *If someone throws out a suggestion and you don't agree or understand what they are talking about. Ask for more info or an explaination.

Fair enough. I just didn't understand how the sensors worked.

 

[superj]

That's great you got it fixed. The cat would have been that very last thing I considered changing and it would have messed up your new o2 again. Good call on that part too