: Idle is higher than normal and fluctuates



Twilightcall
10-17-03, 09:57 PM
My car has been idling perfectly at 700 rpm or so. Today I started it up and it went to 2500 rpm and stayed there then it went to 1100 rpm then back up to 2700 or so. Any ideas on this. It never really came back to 700 during this time. Thanks.

officerom
10-18-03, 05:28 PM
My car has been idling perfectly at 700 rpm or so. Today I started it up and it went to 2500 rpm and stayed there then it went to 1100 rpm then back up to 2700 or so. Any ideas on this. It never really came back to 700 during this time. Thanks.



hi it sounds like it is your idle speed senor it is located next to the throttle body. did check engine come on? you may have to see what code came up,see if it is the idle senor. the computer also controls
the idle. good luck tom

Twilightcall
10-19-03, 09:06 AM
No new codes came up. Will a code come up if it is the ISM? I will try cleaning the throttle body today. Is there a way to test the ISM?

ETC
10-22-03, 09:03 PM
Im having the same problem right now myself. I have a 1996 Eldorado that idles high (1200 to 2500 rpms). The Caddy dealer has repaced the throttle body, PCM and still no fix. My car started idling so bad it faulted out one of the coil packs and started missing. Do you think the Mas Air Meter could be faulty? Will it cause the car to idle high if its messed up. Ive replaced all but the Mass Air. Im going to take my car to another Caddy dealer next week. Ill keep all posted

miishmiish
10-26-03, 01:38 PM
Hello to all. I HAD the same problem on my 97 concours; high idle, late rough shifts and occassional revving. I went to 6 mechanics, the first told me to change the speed sensor, that did nothing. A few mechanics later I landed at the dealership changing my faulty speedometer as that is supposed to affect it. $600 later, I have a new speedometer (woo-hoo) but the same problem. I said screw these mechanics, they don't know shi* so I went to the library, checked out a service manual for my car and skimmed through it in less than 30 minutes; I decided to change my TPS (throttle positioning sensor) $30 at autozone. Problem solved. All that B.S. and it was just a $30 piece of plastic. Let me explain though: you may or may not get an error code because many times, these sensors are not made that effectively. I never had a code which is why it took so long to figure this out. Once I removed the TPS, it was filled with debris and corrosion. I removed it and drove around the block to notice the driving was the same, but NOW my check engine light came on. Once replaced with new, I noticed an instant difference. Remember, that if you remove your sensor, make sure the new one comes with an "o" ring (just a rubber surround to keep moisture out). If you have debris and/or corrosion, use an old toothbrush to scrub it clean and keep it dry. You will need a "star" shaped bit and to work on your engine when it has cooled down. I hope this has helped someone. I went through a lot of crap to fix this problem and I hope I saved someone the same B.S. Good luck.

zonie77
10-26-03, 02:38 PM
You wouldn't get a code because the engine doesn't know if it's a faulty part or the driver moving the gas pedal. A smarter generation computer may include a check at startup but if your foot's on the gas you'd get a false error.

EZROV
01-17-04, 07:14 PM
i have the same problem on eldorado . does anyone else had or having this problem?

Anthony Cipriano
01-18-04, 02:18 AM
My car has been idling perfectly at 700 rpm or so. Today I started it up and it went to 2500 rpm and stayed there then it went to 1100 rpm then back up to 2700 or so. Any ideas on this. It never really came back to 700 during this time. Thanks.
What year car and what type of engine? It makes a difference.

EZROV
01-18-04, 02:43 AM
1993 with 4.9 . is it usually the TPS need to be replaced? i lost my book . where is it exaclly?

Anthony Cipriano
01-19-04, 01:07 AM
1993 with 4.9 . is it usually the TPS need to be replaced? i lost my book . where is it exaclly?

It's not likely the TPS. I wouldn't replace it as that would just be a shotgun approach. It sounds like the idle speed control motor has failed. Either the closed throttle switch has failed or the idle speed motor mechanism itself (that runs the plunger in and out) has failed.

You can check this by starting the engine and depressing the plunger of the idle speed control motor firmly with your finger while holding the RPM at an elevated level with your other hand on the throttle lever. The ISC motor should retract when you do this as the PCM will see the throttle switch closed (your finger depressing the plunger. Try to push the plunger into the can of the ISC motor), think that the throttle is closed and try to retract to bring the idle down. If the motor retracts then the closed throttle switch may just be sticky and it is possible to tear the ISM motor apart and clean the switch contacts. If the ISC motor will not retract when you do this likely the motor is failed and you will have to replace it.

You can visually check the ICS motor closed throttle switch using the onboard diagnostics. Enter into the diagnostics mode by simultaneously pressing and holding the off and warmer buttons on the climate control panel with the engine idling in park. Once any codes display the sytem will prompt you with "PCM?". Answer yes with the HI button. Now that you're in the PCM mode the icons on the climate control panel will indicate the status of certain PCM functions. The lo fan icon will indicate the status of the closed throttle switch status. If the lo is lit the switch is closed. The switch should be closed whenever the throttle is closed ie. your foot isn't on the throttle. If the lo icon status doesn't show the closed throttle switch to be functioning then that is the likely problem. Either clean the switch contacts and lube the assembly by disassembling the ISC motor or just replace it.

carnerd
01-23-04, 10:44 AM
A quick test to see if you motor is bad get on a strait road and floor it till it gets a little higher in the RPMs and then let off really fast. If your car seems like it is going to stall or did stall its the ISC. Make sure you check the plug and the motor. The wire could be shorted out. If not then i suggest cleaning the throttle body out and the intake. Could be gunk clogging this up. Good luck!:bighead: