rough idle help
 

2001 deville reports po171 and po174. driving me nuts -this rough idle. cleaned, and replaced the the MAF and still no go. Replaced o2 sensors and still no fix. today sprayed some cleaner on the throttle body and it appeared to help so I replaced throttle body gasket...still not fixed. Running out of ideas! Car was fine until a week ago. 110,000 miles. Everyone tells me this is a vac*** issue. Need some direction.

RE: rough idle help
 

All problems will throw a code, the system assumed you have done basic mechanical checks, @110,000 mi when were the plugs & wire changed last. Vacuum leaks will fall in to the same category of basic things to check. Has gas mileage changed ??

the codes you are getting are related to fuel trim running lean on both banks,. was there a fuel rail recall on your model ??

Bill

RE: rough idle help
 

Its the intake plenum boot.

Between the intake and the throttle body housing.

The intake needs to come off to replace it.
Look it over real good, you should find a small tear in the rubber on the bottom side of the boot.

RE: rough idle help
 

To answer the first questions, plugs were replaced recently and there are no wires due to the new valve cover coil assemblies. As for fuel, it does not appear to be this either as I tested fuel pressure and it was at 41 and consistant. Though I do not know much about regulators. FL Caddy could be on to something... I will look tonight and try to see if it has the tear you mention. Don't like the idea of removing the whole manifold, drain coolant, etc. though.

RE: rough idle help
 

He often says "probably is".
But this one time with codes he said "it is"

The man knows his craft.

RE: rough idle help
 

I have yet to see the tear or whole but I sprayed carb cleaner on the rubber boot and it clearly made a difference in the way it ran. So I suspect, FL Caddy is right on. And his expert advice is highly appreciated!...I now need to gather up some nerve to tear into this project. I'll get it done and report back.

RE: rough idle help
 

you will make the job easier by getting a can of foam engine cleaner even if
it looks clean. i like to work on "clean engines" myself.

lol






.

RE: rough idle help
 

After removel of the intake (which was not that bad to do) and inspection of the boot, FL Caddy man was "right on" with his diagnosis. A 3/4" tear on the bottom causing all this to happen. Greatly appreciated! Goodbye PO171 and PO174 :)

RE: rough idle help
 

[sm=icon_cheers.gif]

RE: rough idle help
 

Hey there FL Caddytech: A toast from myself and all other car hackers out there. Is a breath of fresh air to have the knowledge and skills of guys like you to rely on for advice. The next round is on me. And the one after that. Cheers.

RE: rough idle help
 

Hey guys, I'm sorry to bump such an old post but it has such good info as to what exactly I'm talking about I figured what the heck.
I (being a Lincoln guy) just acquired an 02 deville for about 10k under bluebook. However, it runs like crap.
It has a vacuum leak, I sprayed staring fluid around where the intake manifold meets the throttlebody and sure enough the engine surges. I'm really hoping this is the only problem with the vehicle, and want to begin repairs but I'm not finding any manifolds or plenum part numbers.
Do I need the entire manifold or just an upper or lower piece? Does anyone have a part number handy? Is there anything to watch out for on the repair procedure?
I really do like the car, it's comfy and nice looking. If such a small repair would make it run good, I'll definetely be keeping it.

Thanks for your help, any information is appreciated!

The Wew