PAU can't idle below 950 rpm
doorunrun
09-22-2008, 07:28 PM
Hello All,
I've had a few threads going trying to solve it poor idle on my 1992 Park Avenue Ultra. There's been a lot of good advice. I've tried tracking every suggestion down but I still at square one, at least I think. Thanks for the help and patience.
I just got a scan tool to observe live data. But I should review the symptoms. At startup the idle is somewhat high, 1300-1400 rpm, and then after a few moments, it will start to drop down. as we get a little below 950 the engine starts cutting out almost as if it was going to stall. Then it will accelerate back up above 1000 rpm for a while and then drop again. The car seems to be fine while driving and has lots of power.
I have replaced the IAC valve and the TPS. These did not help. Vacuum is good. Fuel pressure is good and steady. Over the weekend I pulled the fuel rail and checked the injectors and cleaned them up a little; I also had a look at the fuel pressure regulator and it was pretty clean, no gas in the vac line. I've tried the unlit propane torch method to hunt for leaks but haven't found any. I've checked the grounds under the Ignition Control Module, cleaned them and they should be good.
I picked up a used OTC Monitor 2000 scanner and it does a pretty good job of displaying data. What I do see that at idle, the car is running lean, I almost never see the rich LED come on. From what I understand, at idle the PCM should vary the mixture, too. So, this means I'm getting too much air.
The integrator value, this is short-term fuel adjustments to the fuel mixture, goes between 128 and 150 which should mean rich, yet the lean/flag stays on lean. The air/fuel mixture ratio value seems to be what's listed in the manual.
Sorry to go on and on. But, now that I can see some data, does anyone want to hazard a guess of there to go from here. Is there something in the data stream I should be looking for? While writing this, I'm suspicious of the 02 sensor, but I just replaced it a few months ago with a ACDelco unit; and under normal driving conditions, the rich/lean flag is flapping back and forth, so to speak.
Thanks.
I've had a few threads going trying to solve it poor idle on my 1992 Park Avenue Ultra. There's been a lot of good advice. I've tried tracking every suggestion down but I still at square one, at least I think. Thanks for the help and patience.
I just got a scan tool to observe live data. But I should review the symptoms. At startup the idle is somewhat high, 1300-1400 rpm, and then after a few moments, it will start to drop down. as we get a little below 950 the engine starts cutting out almost as if it was going to stall. Then it will accelerate back up above 1000 rpm for a while and then drop again. The car seems to be fine while driving and has lots of power.
I have replaced the IAC valve and the TPS. These did not help. Vacuum is good. Fuel pressure is good and steady. Over the weekend I pulled the fuel rail and checked the injectors and cleaned them up a little; I also had a look at the fuel pressure regulator and it was pretty clean, no gas in the vac line. I've tried the unlit propane torch method to hunt for leaks but haven't found any. I've checked the grounds under the Ignition Control Module, cleaned them and they should be good.
I picked up a used OTC Monitor 2000 scanner and it does a pretty good job of displaying data. What I do see that at idle, the car is running lean, I almost never see the rich LED come on. From what I understand, at idle the PCM should vary the mixture, too. So, this means I'm getting too much air.
The integrator value, this is short-term fuel adjustments to the fuel mixture, goes between 128 and 150 which should mean rich, yet the lean/flag stays on lean. The air/fuel mixture ratio value seems to be what's listed in the manual.
Sorry to go on and on. But, now that I can see some data, does anyone want to hazard a guess of there to go from here. Is there something in the data stream I should be looking for? While writing this, I'm suspicious of the 02 sensor, but I just replaced it a few months ago with a ACDelco unit; and under normal driving conditions, the rich/lean flag is flapping back and forth, so to speak.
Thanks.
doorunrun
09-22-2008, 08:37 PM
I'm going to mark this fixed. I came across another Automotive Forums thread:
http://www.automotiveforums.com/vbulletin/showthread.php?t=900530
inside this is a link to a video of someone spraying carb cleaner near an injector followed by a subsequent improvement in idle.
I got inspired and tried it on mine and voila it ran better. In my case, it turns to to be the the area just under the left front of the supercharger where it meets the intake manifold. I found the supercharger mounting bolt kind of loose. But I can't get the torque wrench on it or the other mounting bolts very well. I got them tighter, but there's still some leakage. So, maybe another gasket is in order. (I'll bet it work with a unlit propane torch, too!)
Although, I can't figure out why the bolts are loose. I torqued 'em good when I installed the rebuilt supercharger. Maybe I should have used Locktite?
Oh well, no biggie. I've got a date with a gasket job. Woo woo! :smile:
http://www.automotiveforums.com/vbulletin/showthread.php?t=900530
inside this is a link to a video of someone spraying carb cleaner near an injector followed by a subsequent improvement in idle.
I got inspired and tried it on mine and voila it ran better. In my case, it turns to to be the the area just under the left front of the supercharger where it meets the intake manifold. I found the supercharger mounting bolt kind of loose. But I can't get the torque wrench on it or the other mounting bolts very well. I got them tighter, but there's still some leakage. So, maybe another gasket is in order. (I'll bet it work with a unlit propane torch, too!)
Although, I can't figure out why the bolts are loose. I torqued 'em good when I installed the rebuilt supercharger. Maybe I should have used Locktite?
Oh well, no biggie. I've got a date with a gasket job. Woo woo! :smile:
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