Bad MPG/Rough Idle

I have a 99 Escort SE with about 79000 miles on it. I cannot figure out what the problem is. I had a diag done on it and it said it was the IAC/TPS. I have replaced both and has changed nothing. The funny thing about it is I can't plug the IAC in, other wise it idles excessivly for about 5-10 sec. before finally dropping down to normal idle. As long I keep it unpluged it does fine but still has a rough idle especially with the A/C on. Plus gets terrible gas milage ('bout 20MPG).

I have not installed mods of any type, only general maintance. Just for future reference

Maybe an oxygen sensor or bad vacuum leak.

I have a 99 Escort SE with about 79000 miles on it. I cannot figure out what the problem is. I had a diag done on it and it said it was the IAC/TPS. I have replaced both and has changed nothing. The funny thing about it is I can't plug the IAC in, other wise it idles excessivly for about 5-10 sec. before finally dropping down to normal idle. As long I keep it unpluged it does fine but still has a rough idle especially with the A/C on. Plus gets terrible gas milage ('bout 20MPG).

I have not installed mods of any type, only general maintance. Just for future reference

You know I had the same problem with a 97. I cleaned and oiled the IAC and it didn't help. I disconnected the wiring clip to the IAC while the motor was running and I could feel no vibration from the motor at all.
Stupid me. The motor quit when I unhooked it. Anyway, to make a long story short I replaced the PCV valve. I thought the old one was all right because I could shake it and hear it rattling and I could blow through it one way and not the other. It was the best 3 bucks I ever spent. The
car idles smooth regardless of whether I have the lights, blower and air conditioning on. My fuel mileage has increased by 3 mpg. Replace your PCV valve. They say look for the simple things first. This is simple!

You know I had the same problem with a 97. I cleaned and oiled the IAC and it didn't help. I disconnected the wiring clip to the IAC while the motor was running and I could feel no vibration from the motor at all.
Stupid me. The motor quit when I unhooked it. Anyway, to make a long story short I replaced the PCV valve. I thought the old one was all right because I could shake it and hear it rattling and I could blow through it one way and not the other. It was the best 3 bucks I ever spent. The
car idles smooth regardless of whether I have the lights, blower and air conditioning on. My fuel mileage has increased by 3 mpg. Replace your PCV valve. They say look for the simple things first. This is simple!

I have seen that also too dave. Poster should also look for vaccum leaks. BTW Dave is your pcv hose bent ? mine is I didnt know if thats normal.

Thanks for the reminder! My PVC hose is collapsing. Need to replace it today.

Thanks for all the advice! I'm gonna start working on it in a couple of days. How do I trace down a vacuum leak if that ends up being the problem. Hopefully it won't be a leak, but I figured I'd ask just in case.

Thanks

I have seen that also too dave. Poster should also look for vaccum leaks. BTW Dave is your pcv hose bent ? mine is I didnt know if thats normal.

The hose itself isn't bent, but where it goes into the intake manifold there is a plastic connector which is bent at a right angle. The other end goes straight into a hose coming from the crankcase. Then, there's the hose going into the breather box.