Cold Idle Problem
Ditto. Lower intake manifold gaskets are the most likely culprit. Common problem this time of year.
Ditto to your Ditto......
I got tired of my '99 SOHC 4.0 idling rough on these cold mornings so I changed spark plugs last weekend along with oil and air filters. No change in rough idling. So I happened upon this site and bingo, fixed this weekend. What did I do? After changing the plugs last weekend, I got a CEL a couple of days later and figured I knocked a vacuum line loose somewhere. After driving a couple of days like that ( after checking my oil level to be sure of that ), I stopped by Autozone and had them read the code. P0147 -- lean on bank 2. They said its probably an O2 sensor and quoted me $57. I told him to print it out and I did buy a PCV valve for $2.99 and a candy bar, along with some MAF cleaner. I was leaning towards a dirty IAC from posts here, but I dug a little deeper and found out about the leaky intake manifold gaskets.
I picked up a set of gaskets at the local Ford dealer ( $24 ), could've saved 7 or 8 bucks at AZ but I didn't mind spending a little more for Ford parts. I followed the couple of well-written gasket changing procedures and the whole thing took me about 5 hours -- I'm slow and deliberate.
What I found : Dirty/stuck PCV valve, slightly dirty but operational IAC, a lot of carbon build-up in the throttle body and both the upper and lower intake manifolds. A little carbon on the top half of the head intake too.
The intake manifold gaskets had definitely taken a set and were surely leaking air. After cleaning the manifolds as best I could everything went back together pretty well. One note -- I removed the large plug and ground wire from the stud on the firewall on the passenger side to give me a free run at the back two upper manifold torx bolts, made the PCV valve change easier too. The plastic retaining ring holding the original PCV valve broke off but I couldn't see that it was doing much good. I used a hose clamp on the lower PCV hose there.
It fired right up on the first crank!! And it ran pretty smooth for 5 minutes for the most part. It snorted a couple of times but I had sprayed a good amount of carbeurator cleaner in the head intake to loosen up some of the gunk. I took it out on the road and it drives like it was new. First stop sign I pulled up to was a very smooth idle. Then take off was smooth and even and peppy. Next was the interstate and it really accelerated on the ramp like it hasn't in years. I ran it for about 20 minutes and its great and no CEL. I'll report back if something comes up but I think I've got it covered. Mileage -- 154,000. Hopefully the only time I have to replace those gaskets.
