jtcaddy Posted February 10, 2004 Report Share Posted February 10, 2004 Hello I have a problem with my 1999 cadillac sts when i start the car up sometimes it shakes a little and has a little hesitation, but when the car warms up the shaking and hesitation goes away. I recently have changed the O2 sensor any other suggestion would greatly be appreciated. Thanks Jae Thompson Link to comment Share on other sites More sharing options...
Bob D Posted February 10, 2004 Report Share Posted February 10, 2004 "FPR" (Fuel pressure regulator). It very well may be causing the symptoms you are describing. It's kind of a normal 'wear and tear' item, on cars approaching 100k miles. On your year NS, its a small 'can' external to the engine cover, with a vacumm hose going into it. If you unplug it after a drive, and it has fuel in the line it's a sure sign of it failing. There are some posts here last night on this subject with pictures. Look up "fuel problems" or some string with that association. ** Look up last night's string on "Fuel Diaphram". '93 STS.. opened, dropped, wide...fast. Link to comment Share on other sites More sharing options...
Maximln Posted February 10, 2004 Report Share Posted February 10, 2004 My car does the exact same thing (98 STS). I have been told the same thing--to replace the FPR but I haven't done it yet. I think I will do it within the next couple of weeks. If you do it before that, let me know how it works or I will post the results as well. Max Link to comment Share on other sites More sharing options...
98Concours Posted February 10, 2004 Report Share Posted February 10, 2004 On another post in this forum, jadcock said you can buy a rebuild kit for your FPR. Might want to try that as it is alot cheaper than buying a new FPR. Jeff 98 Concours 90 Seville 04 Corvette Link to comment Share on other sites More sharing options...
JasonA Posted February 10, 2004 Report Share Posted February 10, 2004 True -- but I would further diagnose your rough running first. You said "until the car warms up" it ran rough. Symptoms of a leaking FPR would likely disappear after 10 seconds at the most. I think you're looking at a problem where something's not reporting properly to the computer, and cold operation is compromised. Possibly a bad sensor somewhere (O2, etc). There are no trouble codes I assume? Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
rjhat Posted February 10, 2004 Report Share Posted February 10, 2004 Do the O2 sensors immediately report to the pcm at startup on caddys? I thought that the cars ran on a default program until the car reached operating temp. Link to comment Share on other sites More sharing options...
rjhat Posted February 11, 2004 Report Share Posted February 11, 2004 I saw this once on a 300zx. Although it may not pertain tou you, its worth checking out. On the ZX, the sparkplugs were beginning to foul out. One of them was not firing while the engine was cold, but as it heated up it began to function. I would check them if they haven't been changed in a while. If so it would be a cheap fix! Link to comment Share on other sites More sharing options...
Dloch Posted February 11, 2004 Report Share Posted February 11, 2004 Do the O2 sensors immediately report to the pcm at startup on caddys? I thought that the cars ran on a default program until the car reached operating temp. Generally the PCM ignores the O2 sensors until the coolant reaches a PCM determined temp. Dennis Dennis Link to comment Share on other sites More sharing options...
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