: 2002 N* Deville occasionally idles too high



cheeko
02-05-07, 12:57 PM
I recently purchased a fine 2002 Deville with N* of course.(135,000miles) It had some bad oil leaks so I had a mechanic pull the engine and seal it all up. Since then it does not appear to leak oil but it has been occasionally idling very high (1350at times) When in drive at stop lights it just wants to go and this high idle causes it to shift into R and D hard. Most times it idles perfect. When it is idling high, I can usually shut the car off and wait a sec then start it back up and seems to idle fine again for a while. I have not tried the carb cleaner spray on hoses or intake, trick yet. Also, in the morning it has had trouble starting sometimes. I would try it several times and no go. Then I decided to give it a little throttle at startup and it started right up and I noticed a gasoline smell. It has been very cold weather here lately (0's) if it has anything to do with it. The first time this high idle thing happened, the service engine soon light came on after I noticed it was running poorly. This was just after the engine oil fix so I brought it back to the mech. and he read the codes. There were two of them. It said high idle and something else. He also said that those codes were in the history so he cleared them and then told me to come back again when the light comes back on. He also pulled the vacuum hose from the fuel pressure regulator? for 15 min. and it never leaked fuel. It's been a week since then and no lights have come on yet but the high idle problem has occurred several times. It has been starting up fine lately also. Any help would be greatly appreciated !! :worship: :bonkers:

eldorado1
02-05-07, 01:56 PM
There is a rubber hose that connects your plastic intake to your metal throttle body (actually the water crossover housing). I've read a few threads here where people have had them crack and leak. I'd probably start there.

Ranger
02-05-07, 04:27 PM
It also might not hurt to clean the TB (Throttle Body) and IAC (Idle Air Control) valve.

ewill3rd
02-05-07, 07:18 PM
I would follow Ranger's advice and if you still have problems, replace the Idle Air Control valve. I have seen them get sticky and bind periodically.
I went round and round with one for 6 months before I caught it acting up.

2manyhotrods
07-01-13, 08:50 AM
I'm curious about this thread too.
Although I haven't attacked all my oil leaks to the extent you did, my 1999 Eldorado ETC displays similar symptoms your Deville has, alert lights, hi idle .......I'm also presently dealing with a hi speed surge or miss in the engine at a steady cruising speed, 65 mph range.
TPS? IAC? EGR, or any number of ideas traveled thru my brain but I'm not a technician so I'm leaving it to the profesionals.
Mine is at Olsen Cadillac now being diagnosed.
I'll let you know later what they encounter.

Submariner409
07-01-13, 09:07 AM
This thread has been dead for 6 years. The only members left are ewill3rd (a registered Cadillac/GM shop Tech) and Ranger - both are advisors to the forums, not members with problems.

Your 1999 engine is quite different from a 2002, so some of the old advice does not apply to your situation.

You could have run your own basic diagnostics in your driveway, using the car's built-in system, and saved the first $100.

Ranger
07-01-13, 11:14 AM
WOW! Talk about a resurrection.

2manyhotrods
07-01-13, 10:30 PM
I'm curious about this thread too.
Although I haven't attacked all my oil leaks to the extent you did, my 1999 Eldorado ETC displays similar symptoms your Deville has, alert lights, hi idle .......I'm also presently dealing with a hi speed surge or miss in the engine at a steady cruising speed, 65 mph range.
TPS? IAC? EGR, or any number of ideas traveled thru my brain but I'm not a technician so I'm leaving it to the profesionals.
Mine is at Olsen Cadillac now being diagnosed.
I'll let you know later what they encounter.

Picked my '99 Eldorado ETC up from the dealer tonight and for $270 they took a shot in the dark, and with my permission and input, they replaced the IAC for a racing idle.
No codes were stored, (I know, very odd), no vacuum leaks, normal operating temperature, all systems normal.
Traffic was too heavy to go very fast or very far tonight so tomorrow I'll run the snot out of it it on the turnpike and hope all goes well.
Next educated guess would be to change the TPS but the dealer feels that item and the EGR would throw conflicting symptoms from what my Eldorado displays.
A little puzzling still.

2manyhotrods
07-06-13, 07:37 AM
I've put about 200 miles on the Eldorado since Olsen Cadillac replaced the IAC. Functions are fine now, no more runaway fast idle.
Next week the hi speed surge is on the punch list.
This Caddy had ZERO maintenance for about 4 years although it was rarely driven. The prior owner kind of gave up on it and moved onto a truck for his daily ride.
I enjoy a challenge and this keeps me very sharp.

RippyPartsDept
07-06-13, 09:26 AM
do a coolant exchange NOW if you haven't already