: 99 Deville starting idle issue



arctic_man
06-11-10, 07:12 PM
So, after doing plenty of troubleshooting on this issue... and have it get progressivly better... I am down to what I hope is the last bit.

Right now, most of the time... well, every other start it seems now, my car will start at a very high RPM, anywhere from 1500 to 2100. But, when I turn off my car, wait roughly 3 or 4 seconds... and turn it back on, the idle is normal. I have been tracking down this problem for weeks and have come across a few other issues and have fixed those as well. I have cleaned the TB 3 times, replaced the vacuum lines at the "T" line, and also verified that they all have vacuum, fixed the vacuum diaphram thing under the dash so now my parking brake disengages when I shift out of park (and I have air coming out of my front vents respectively) No codes except that my AC is off due to low refidgerant. I have had some lines identified thanks to some members here, and have verified that they are secure and not leaking. I have done the WD 40 test and soapy water test to find leaks on the vacuum lines and have come up empty. What it is doing as well that makes me think it isn't a vacuum line is if it starts fine it will drive fine, the idle will not get worse. And same thing for when the idle starts at 1500, if it starts there in park, then at stop lights it sits at 1100 or somewhere around there, depending on what it started at. It never seems to get better when driving it.

A side note that happens every once n awhile as well, that may be related; it will start fine, idle perfect and drive fine. But when I reverse in to a parking spot, the idle seems to get a bit higher with each shift. So if the rpm is 750, right around idle, easing into a spot, shifting into reverse will bring it to say 850, then to straighten it back out and shift into drive, it will bring it up to say 900 or 950. And again to reverse right around 1000. Not sure if that is a separate issue or co-related.

But thank you if you read all that. Any suggestions or comments are great. I still have yet to clean the TPS, not sure of that would even make a difference, but I thought that it was worth a shot. Not like I am throwing money at the issue yet... a 2 dollar vacuum diaphragm and 3 dollars in vacuum line.

Submariner409
06-11-10, 07:32 PM
You're due for a thorough throttlebody and idle speed control cleaning. Maybe EGR cleaning (a sticky EGR valve really screws up idle speeds......). Many, many threads on these down in Northstar Performance, Tech Tips.

Your normal cold start idle sequence is: 1200 rpm for about 30 seconds, ramp down to 850 or so, 650 at open loop changeover (160 degrees coolant temp).

Idle should increase at no other time - even A/C operation instantly compensates for changing idle loads.

Please study and learn the cleaning techniques before you start squirting fluids into your intake, EGR, and TB.)

arctic_man
06-11-10, 09:26 PM
You're due for a thorough throttlebody and idle speed control cleaning. Maybe EGR cleaning (a sticky EGR valve really screws up idle speeds......). Many, many threads on these down in Northstar Performance, Tech Tips.

Your normal cold start idle sequence is: 1200 rpm for about 30 seconds, ramp down to 850 or so, 650 at open loop changeover (160 degrees coolant temp).

Idle should increase at no other time - even A/C operation instantly compensates for changing idle loads.

Please study and learn the cleaning techniques before you start squirting fluids into your intake, EGR, and TB.)

The normal cold start is exactly what happens usually every other start up if it is cold, otherwise when warm it usually drops much quicker. And trust me, I have viewed every document at least twice on TB cleaning and ect. lol. I also make sure I only use TB cleaner or when I cleaned the IAC valve I used some electronics safe cleaner. I plan on using that for the TPS as well.

I guess before I go clean again... is that what it sounds like it is? (Granted, totally understand that without actually looking at it ect ect no one can be 100%) But just thought I would ask! Thanks