: 1998 Northstar throttle sticking.



burns3
02-03-11, 10:45 PM
1998 Deville 126k miles. Headed home today I noticed the throttle was kind of stiff when depressing it, not that alarming I just got spun the tires off a few starts. Then I noticed that headed down the road the RPMs weren't coming down after I let off the gas, and the speed just kept climbing. I turned off the cruise control which did nothing, put my boot under the pedal and physically pulled it up which didn't help, finally I stomped the gas as hard as I could, let off, and it started slowing down. Had to do this several times headed home. Is this do to the throttle position sensor? Or should I hit up something else? I'm headed to autozone tomorrow either way I can't drive the car like this.

JoeTahoe
02-03-11, 11:12 PM
my 99 did this after setting at the body shop, there is a pivot on mine at the throttle pedal that is just above the pedal. I just lubed it and now it works fine.

Submariner409
02-04-11, 09:59 AM
He put his boot under the gas pedal and pulled the pedal up - the car didn't slow down.

Why go to Dead Zone?? Your car already has a perfectly good built-in code scanner/reader/memory. Read the sticky post ^^^ "How to pull codes", study and practice. Write down any trouble Codes fond, noting whether each is Current or History. Return to the sticky and open the link to your car's year group - this will take you to a Master Index of links for P,B,C, and U codes. Write down all the definitions and come back here.

Just for grins and kicks, with the key OFF, operate the accelerator pedal throughout its full travel a dozen times. Now start the engine and see if the accelerator seems to function normally. No ? You may be in the throttlebody cleaning mode (piece of cake) or TPS (Throttle Position Sensor) replacement - another easy job. Google "cadillac forums 1998 deville throttle position sensor" or "cadillac forums northstar throttlebody cleaning".

"Turned off cruise control........." - the TPS is a variable resistor. Over time the wiper and/or resistance strip can develop poor contact "flat spots" from the sensor remaining in the exact same position - the pedal operation exercise described above MAY clean off that "dead spot" and/or free up the sensor. Not saying that's the fault, but it's a home start.

mhamilton
02-04-11, 10:16 AM
I'd almost guarantee the TB is dirty and gummed up... pulling up on the accelerator pedal won't release the throttle plate because the cable just slides through the linkage (hard to explain in words, you'll see when you look). A TPS problem won't cause the engine RPM to stay high, that would be an extremely dangerous function for that style of sensor. The only thing that could keep RPMs high is the IAC, but that's not usually enough to chirp the tires or keep you from braking safely.

Anyway, it won't take 5 minutes to pop off the air duct and clean out the throttle bore. Just hold the throttle open and clean the back side the best you can. Be sure to spray out where the shaft goes through the body to clean the gunk. Just be sure to use Throttle Body cleaner, not brake or carb cleaner (some say TB and Carb, that's okay).

Ranger
02-04-11, 11:55 AM
:yeah:
I'd bet money on it. There is a good tutorial in the Tech Tips section.

burns3
02-04-11, 12:15 PM
I pulled the codes, they hadn't been cleared in some time, they were all marked history. I've also been having trouble with the car dieing while coasting between 25-35 MPH.

P0603 - Control Module Long Term Memory Reset
P1527 - Transmission Range to Pressure Switch Correlation
P1579 - P/N to D/R at High Throttle Angle - Power Reduction Mode Active
P1599 - Engine Stall or Near Stall Detected
B1348 - Very Low A/C Refrigerant Pressure

burns3
02-04-11, 12:16 PM
Here's a link to my other thread, sorry for the double post but I must post 5 times before posting links. http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/220276-98-deville-northstar-dies-while-coasting.html

mhamilton
02-04-11, 01:16 PM
P1579 - P/N to D/R at High Throttle Angle - Power Reduction Mode Active

This is telling you the throttle is stuck open. Get a can of TB cleaner and a rag, it's a cheap and quick fix.

burns3
02-04-11, 02:44 PM
Awesome. Thanks all.

JoeTahoe
02-04-11, 09:18 PM
sorry had a memory fade read thread wrong

burns3
02-05-11, 11:06 AM
Update: That was the fix. It took a couple guys to get the airbox cover off, it hadn't moved in a while and the freezing temperature didn't help at all. The throttle body was really gummed up, a few sprays with the cleaner did wonders. Thanks again.

Submariner409
02-05-11, 11:13 AM
Update: That was the fix. It took a couple guys to get the airbox cover off, it hadn't moved in a while and the freezing temperature didn't help at all. The throttle body was really gummed up, a few sprays with the cleaner did wonders. Thanks again.

If you were not able to do a 100% job of cleaning, when you get a break in the weather, remove the air intake ducting and the MAF in order to get a clear shot at the throttlebody and blade. Prop the throttle wide open, and using rags, TB cleaner, and a toothbrush clean as much of the inside and both blade sides as you can. Don't get an excessive amount of raw TB cleaner into the manifold - just scrub out and wipe the TB bore. When you finish it will (should) look brand new inside.

Take a look at Post #47 in ^^^ General Discussion, Item Specific Discussions, Cadillac Technical Tips, go to the thread "How to clean the throttlebody............................"

burns3
02-05-11, 11:21 AM
I didn't mention it but I did take the duct off. I almost didn't but I'm glad I did because there would have been no way to do a good job without it. I had my buddy manipulate the pedal while I scrubbed, it did take some time.

00 Deville
02-05-11, 02:06 PM
Cleaning the TB is one of those things that should be done about once a year.

Ranger
02-05-11, 02:19 PM
:yeah: :yup:
It's part of my spring cleaning and doing it once a year all it needs is a light spray and wipe.