Hey guys, I replaced the TPS (Niehoff) to fix the choppy roughness a few weeks ago. That Problem solved, totally.

Yesterday the TFI module (Niehoff) went out and left us stranded, no big deal. I replaced it and runs even better than it did before.

BUT, now I'm still getting the high idle at random times. Especially whenever the A/C is on, the motor will rev way up, then go back down, and repeat. I'm still getting 16.5mpg though, but hoping for more.

Does anyone have any idea what's left to check?

Maybe clogged exhaust? The exhaust does have a hole in the pipe maybe from getting too hot from lack of exhaustation? It's all in good shape which surprises me the hole in the pipe. It's got the duel factory cats then flanged into a Y-pipe. I was hoping to pull the cats off and gut them and check for cloggage, then from the existing flanges go into some duels.

 

Still no check engine light. Now the Cig lighter won't work or the Cruise Control. Anything? Thanks

 

Ok, it's not the exhaust as I just duel exhausted the car.


What about a sensor of some kind? Anyone?

 

Cig lighter and cruise not working... wiring or fuses.

The random IDLE issue very well might be a map sensor, or a vacuum leak.

 

Ok, I'll check into the fuses first on the cig ligher and cruise control.

I've onced over the vaccum hoes and didn't find any, but I'll go over it again. Where can the Map sensor be located for inspection?

Edit: On my first post I meant I replaced the IAC not TPS.

Thanks a bunch!

 

I took of the air filter/lid off and took it for a drive, the car seems to run better. When I turn on the A/C the IAC opens and sucks a lot of air causing the motor to rev up. Then when I put my finger over the IAC hole (in the throttle body) it revs the motor back down to where it should be.

I looked at the fuse box, there are a few empty slots where a fuse could have been for the Cruise and cig. I'm searching right now to find a fuse box chart (I don't have the owners manual).

I still can't find a vaccum leak.

 

its normal for the AC to cause the engine to rev up a little.

 

In my experience in most vehicles when the A/C kicks on it pulls the idle down because of the added load, or am I mistaken? But in this case, the IAC auctally opens up and sucks air in causing high idle. Is that supposed to happen?

 

The IAC should open when the compressor kicks in to keep the idle speed up. Do you know exactly how much the idle is increasing? The computer does this so that the load from the compressor doesn't pull the idle down. Have you checked the computer for codes? I don't really know anything about crown vic's but all the computer stuff is fairly similar.

 

EPN, no, I don't know how much it's idling up but it's a fairly big increase. I need to get a diagnostic tach and see, I'll work on that today. No, I haven't checked the computer for codes either.

I timed the motor to 10BTDC but I couldn't find where the "spout connector" was. So, I found what I thought was it, unplugged it, rechecked it and found that i was 3 off, so I put it to 10 and it calmed the idle down just a hair.

I read that a clogged PCV might cause idle problems so I'm going to inspect that today.

 

try joining www.crownvic.net

A good bunch over there and very helpful.

 

DenDanger, thanks for the great link. I signed up but I'm still waiting to be 'verified' by the admin.

I still can't find the PCV on this car! It's buried behind the huge intake and I've crawled up on the motor and still can't see it. Even the book shows it to be right behind there, what a bummer. But I might be on the right track to the looks of things - sounds like most 5.0 vics have them clogged up as well as the crankcase screen behind it.

 

I had an 88. LOVED that car!! Gave it's life to save my kids. Was hit by a cubevan-TWICE!! He kept his foot in it.

Anyways, been awhile but I think if I recall the PCV on the Crown was screwed right into the intake? Even if it don't solve the problem, it probably needs to be replaced anyways.