I have a 97 Buick LeSabre 3800 Series II 105k miles. Since the temperature dropped here in mid-Michigan about three weeks ago to between 10 and 20 degrees fahrenheit, my previously good starting/running car has become a nightmare to start. After five to ten attempts to start the car each time, I have to 'feather' the gas pedal at a rate of 3-presses per second or so to try to get the car up to around 1000rpm where it runs VERY rough. After around 20 seconds of this procedure, the motor will usually "catch" andclimb to around 2000rpm where I can maintain the rpm to warm the engine up for a few minutes. If I try to take off too soon down the road, the car will not accelerate and may stall if I try too hard to speed up. The big kicker on this whole scenario is - after five minutes of the car running, it just starts to run perfect for the rest of that driving session. When I get to my destination, shut the car off, I can come out ten to infinity minutes later, and the whole nasty process repeats with the very hard starting. After it's warmed up, it never stumbles, hesitates or stalls. It accelerates great on the highway. To me, this rules out the fuel filter completely and most likely rules out the fuel pump. I always try to keep about five gallons of gas in the tank to prevent premature death of the fuel pump. In the past month, I've put in a new crank sensor (had set crank sensor code), new alternator (bad bearings), new battery (bad cell), new plugs/wires (rule out misfires), oil change (rule out low oil sensor), tranny fluid/filter change and radiator flush/fill. Car is clean stock, no wiring mods or any hack jobs. The only consistent DTC is P0171 (Lean to Bank 1). Whenever I pull the vacuum lines from the fuel press reg, I never get any fuel spitting out. The vacuum line to the FPR does have a strong smell of fuel, but perhaps I'm just smelling the fumes in the lines from the Evap/EGR systems that feeds back to be reburned? I dunno... I'm a long time electronics tech who's usually successful in my own auto repairs. I have an Actron CP9185 for what that's worth. Again, the only DTC that keeps the Check-Engine light on is the P0171. Please help, Dan Gibbs :)
Okay first question i would ask would be if this car has a plastic upper intake,, if it does then i would take a good lokk at it make sure there is no coolant from throtlebody gasket entering intake and also leave line to fuel reg unhooked before starting in cold weather and then start the car and see if there is any fuel coming out of it .. with the tool you have are you able to look at fuel readings, long and short trem readings and last would be to install a fuel pressure gauge to line and watch your readings......
Hey Johnny, yes this is a 3800 Series II with the plastic intake. I have pulled the fuel press reg vacuum hose several times and have never been able to get any fuel on my finger from fuel passing the diaphragm not ever seen fuel spurting out when motor is running. I just found my fuel pressure guage and will check fuel pressure shortly. My Actron 9185 does show realtime long and short fuel trim numbers but I don't have any data to tell me what is actually good or bad for this 3800. The fuel trim things are new to me and I only vaguely understand the concept when I looked into it last year after I bought the car used and the SES light P0171 code kept coming back after clearing the codes.
I'll go test the fuel pressure, after I clean 6-inches of fresh snow off of the car...sheesh :) The car actually might start better as it's warm enough to snow this much up here in mid Michigan today :)
Here's the skinny on the fuel pressure measurements this evening. Before cold start, no pressure. Begin to crank, pressure goes to just above 10psi and within 5-10 seconds goes up to 20psi. Once car was able to idle on it's own, I let it sit for an hour running in the driveway. Fuel pressure after an hour in park is a solid 20-22psi both at idle and with revving the engineup to around 3000rpm and also during throttle snap.
(continued from previous) I turned the car off for a minute, and then tried to restart...won't restart, only turns over but will not try to fire as when the engine is fully cooled down. Outside air temp is still around 20-deg F. Dunno what the fuel pressure specification is supposed to be but when trying to start again this last time, the fuel pressure red 15psi solidly. I'm now inside and letting the car cool off and waiting to see if the fuel pressure is going to drop from the 15psi.while the car is off. I also pulled the vacuum line off of the fuel pressure regulator and could not get and fuel on my fingertip.
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SOURCE: Engine runs rough after about ten minutes /idles really low
Just trowing some suggestions out there, but, I would check the idle air control valve (solenoid) or the throttle position sensor. If they check out then my last guess would be the map sensor or the vaccuum to the map sensor. Hope I was able to help. Best wishes.
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