Erratic idle qeustions

[jasonh]

My car does not like to run...It starts up fine but then surges between high idle and low idle until it stalls. It starts right back up again and does the same thing. Even holding my foot on the gas or working the throttle by hand it still idles up then down, almost stalling, then back up again, like a wave at the beach LOL. Eventually it smooths out, still slightly rough, but it stays running.
I tried unplugging the IAC and it just stalls, I cleaned it anyways,it wasn't really dirty though. There is no check engine light. I fixed some vacuum leaks on the passenger wheel well thing and I think I can still hear one coming from under the upper intake. I can't see a vacuum leak causing this problem, could it? I'm gonna change the plugs/wires/cap and rotor/coil this weekend but I doubt they will fix the problem.
The thing is this idle problem got worse after I cleaned the engine, with Castrol Super Clean and water. It used to surge for about 60 secs or so on startup then smooth out. I believe I aggravated the problem Any ideas?

[gadget73]

Check the calibration on the TPS. It should be 1.0v on the green wire. This is one of those annoying Ford SD problems that I think everyone has dealt with, unfortunately lots of crap causes it. Vacuum leaks, coolant and air temp sensors out of range, bad oxygen sensors, bad connections at the big engine harness connector just to name some. My car does it, and I haven't managed to chase it out yet either, low vacuum plus what I strongly suspect to be a failed oxygen sensor play no small part in it though.

[FastGallopingPonies]

Yeah I've been having the same problem described, Checked my IAC, Checked Vac Lines, Did Complete tuneup... Still no Avail...

[mrltd]

Vacuum leaks will make it do that. The coolant temp sensor and the intake air sensor can also make it run rough.

[gadget73]

Mine fouled the intake air temp sensor because I didn't put the stupid PCV screen under the PCv valve. The whole intake was full of oil. I installed a new filter, ran it for a bit, then seafoamed the crap out of it through the PCV valve. I also replaced the air temp sensor, and it seems a little happier now.

[87_crown_vic]

i saw you guys say that there is a PCV valve on the EFI 5.0 where the hell is it since i have been told it has one.

[Ape]

my surging and stalling problems seamed to have stopped when I took off my cats (Knocks on wood). Now my car just revs up supppper high when ever its to wet outside

[87mefull]

i saw you guys say that there is a PCV valve on the EFI 5.0 where the hell is it since i have been told it has one.

Its underneath the upper intake and its a bitch to get out. You can try to use needle nose pliers to get it out since you will most likely have to replace the PCV screen also. Mine was clogged but running seafoam cleared it up for the most part. I'm just going to pull my upper intake to do it since I'm putting an HO upper intake and TB on my car.

I also noticed that most of my surging and hesitation problems went away as soon as I removed the smog pump and plugged the vacumm lines. It runs very smooth and quiet, only stumbles a little bit when it comes to a stop with the engine still cold which it has allways done since the day I bought it. I know it will shorten the life of the cats, but at 129k it doubt it makes a difference.

[gadget73]

its BEHIND the upper intake, not under it. Its directly behind where the upper and lower bolt together. lay on top of the motor and look straight down, you'll find it.

[RobClark]

I had this.

Fix was simple - assuming you have an EFI engine.

Pull off the Idle Speed Motor thingy on the side of the throttle butterfly valve. See if it is gummed up. If so - carby cleaner spray will work.

With EFI engines, at idle:
- Butterfly valve (i.e throttle) is 100% closed (or nearly)
- there is a bypass that goes along the side of that valve
- the amount of air that passes throught the bypass is computer controlled - and that adjustment is based on the idle speed
- there is a thing called a pintle in there - which is like a needle valve (or bigger). The computer moves that valve in/out as needed.
- It can get gummed up - and the poor computer drives it in and out so the idle speed goes up/down/up/down/etc

[RugerP97DC]

Its underneath the upper intake and its a bitch to get out. You can try to use needle nose pliers to get it out since you will most likely have to replace the PCV screen also. Mine was clogged but running seafoam cleared it up for the most part. I'm just going to pull my upper intake to do it since I'm putting an HO upper intake and TB on my car.

I also noticed that most of my surging and hesitation problems went away as soon as I removed the smog pump and plugged the vacumm lines. It runs very smooth and quiet, only stumbles a little bit when it comes to a stop with the engine still cold which it has allways done since the day I bought it. I know it will shorten the life of the cats, but at 129k it doubt it makes a difference.

Ditto on that. I took the upper intake off my firends 88 TC, (He wrecked it, death by cheesewagon). Even with the upper off it was a CAST IRON BITACH! But perseveance and a shotgun can conspire to get things done!

PS We installed a intake spacer.

[gadget73]

Not to be argumentative, but I don't get whats so bad about the Pcv valve removal. The screen can be a bitch, but taking a nice long wood screw, threading it in, and grabbing it with a pair of pliers makes it come out much easier. Its not in the most convenient location though, I'll absolutely agree with that much. Getting it out with needle nose pliers is almost impossible tho. Nothing to grab on to.


Oh, I got a chance to actually drive around some tonight with lights (had to replace the headlight switch, it blew earlier in the week) and it seems like my idle crap is fixed. Must have been a combination of the gunked up intake temp sensor and all that oil in the intake. Once I ran the magic juice through the pcv system to clean all that crap out, it runs just fine.