jonwalden68

Got a 95 grand Cherokee 4.0 4x4 I just got it and has really rough idle but drives good and runs good when on the gas but when you start the car it idles really rough almost cuts off and when coming to red light feels like it's idling rough to almost a surge. I checked the codes no codes showing. Since I had it I changed the valve cover gasket as it was leaking and fixed a vacuum leak on one of the hoses. I had my mechanic run a smoke test on it and it was leaking around the intake manifold near the number 6 cylinder. Would that cause a rough idle and a little stumble when you first push the gas. I ran lucas through the gas and clean the throttle body and new air filter any help be great

dave1123

Unfortunately yes. An intake leak can cause the MAP sensor to try to change the mixture to compensate. It will think the mixture is lean. Also the IAC will not work correctly. Also, make sure the elbow on the CCV is not cracked, seeing as how you had the valve cover off.

That last bolt behind #6 is the hardest to tighten and it's possible someone never got it right.

jonwalden68

I actually checked the valve cover bolt in back and had mechanic check it and that's were I got intake leak. How do you check or clean pcv? And would you try replacing iac befor putting the intake gasket on bc it involves redo the manifold gasket too correct? There one piece?

dave1123

I was referring to the last INTAKE MANIFOLD bolt and yes, replace the intake/exhaust gasket before you condemn the IAC. You might want to replace the throttle body base gasket as well because it does leak over time.

The bottom bolts on the manifold pair are the hardest to get to. When I did mine, I had to keep getting up and down to torque them in the proper order. Remember, I'm an old man, so doing this took a lot out of me. You can leave the fuel rail and injectors on it if you want, but it was easier for me to remove them and replace all the o-rings as well. If you do replace the o-rings, lubricate them before trying to re-install them so you don't cut them going back in. It's easier to install them in the fuel rail first and then install the unit into the manifold.

On the PCV, just replace it.

jonwalden68

The shop did say they there was a cylinder 6 misfire I'm looking at papers but my check engine isn't flashing and I know check engine light works but they said that fixing the gasket should take care of misfire

Bustedback

Your 95 ZJ is OBD1, it's not as sensitive as the 96 and newer OBDII. OBD1 will not set a code as easily, sometimes a code will never set a code even though there is a noticeable issue.

jonwalden68

Yea I had then pull the codes I guess I'm gonna put gasket on her

jonwalden68

I tighten 6 bolt on intake today and seems to be worse the idle but it's still leaking around it. So I'm guessing for it to be right I'll need the gasket