rough idle help
Thread Starter
Joined: Jul 2007
Posts: 4
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.
Joined: Apr 2007
Posts: 9
From:
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
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
Super Moderator
Joined: Jun 2006
Posts: 507
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.
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.
Thread Starter
Joined: Jul 2007
Posts: 4
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.
Tech Certified Members
Joined: Jun 2007
Posts: 2,701
RE: rough idle help
He often says "probably is".
But this one time with codes he said "it is"
The man knows his craft.
ORIGINAL: kaperoni
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.
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.
Thread Starter
Joined: Jul 2007
Posts: 4
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.
Thread Starter
Joined: Jul 2007
Posts: 4
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 
Tech Certified Members
Joined: Jul 2006
Posts: 424
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.