2000 Buick LeSabre running rough....

Hello all, I'm new to this forum. Currently own a 2000 Buick LeSabre with the 3800 S-II K-code engine. The engine idles great, but part throttle and above is "spotty" and "bucky". To date the following things have been done to this vehicle:

1) replaced the cat converter (old one was clogged)
2) replaced the MAF and TPS
3) replaced the heated O2 sensor
4) replaced all three ignition coils
5) tested the fuel pump - found it to be in spec (48 at idle with reg vac line on/55 at idle with vac line removed)
6) tested exhaust back pressure - less than 0.5lbs at all RPM's
7) replaced the EGR valve
8) Cleaned the MAF (looked clean before and after cleaning)
9) Scanned the PCM/ECM for codes (none)
10) Replaced plugs/wires
11) Replaced brake vac elbow on intake
12) Removed, cleaned, re-installed throttle body

I'm beginning to believe that the intake manifold is cracked or the fuel pump is acting up when I'm not looking/measuring. The idle is perfect - not a stumble or shake. Possibly bad/clogged fuel injectors? :confused:

My thoughts are leaning toward getting rid of this vehicle if I can't get it running right. I suppose that 3800 series 2 is not a very robust engine. :disappoin

Any ideas, thoughts, and/or experiences on this beast? :banghead:

Thanks in advance!

(Sorry - please move this to the appropriate thread/group)

Welcome to the Forum.

The 3800 series II is imho one of the better engines out there.

I think you have done a great job in looking after many possible issues....

I don't think its a cracked intake... that would give you a high idle, but otherwise the car would run okay.

Try changing the fuel filter.......

Replaced the fuel filter about 3 days ago.... problem remains. I'm leaning toward bad PCM/ECM and/or fuel injectors.

Not going to hurt and it's realitively easy. Don't forget to get new O rings. ($2) but you could just have some shitty gas. If fuel filter wasn't clogged and your getting good supply I would wait until you burn that tank of fuel and throw in some dry gas in case you have some water/moisture.

Rob

How about the PCV valve and it's rubber O ring?

I've just received a new upper intake in the mail today. It included new fuel injector o-rings, new gaskets, new PCV valve+o-rings, and new EGR tip. I'll try to install it tonight. I've run several tanks of various brands of fuel with no change... Idle is great, cruise is great, acceleration is jerky. I'll finally figure this one out sooner or later. Thank you all for your suggestions, they are all taken under serious consideration.

Wish the Buick ran as well as my two old Town Cars (1992 and 1997).

(Also thanks to the Mod for moving this into the correct forum)

FYI... This vehicle has about 62K miles on it... shouldn't be acting up like this so soon.

One quick question, what brand of plugs and wires did you put on?

Used AC Delco wires and AC Delco plugs. Engine when revved to 4K RPM while in park begins to stumble badly. Engine seems to lack power, almost like when the cat converter went bad. Wonder if my cam sensor is starting to go bad and causing the injectors to fire badly. Also, ran a compression check, all jugs build pressure to 210 PSI quickly (4 revs). Oil changed every 3K miles using full synthetic 10W-30 (yes I ignore the silly oil change minder).

My next step; I will unbolt the cat and see if the stumble remains.

This is my first GM since my 1982 Corvette. The Corvette is a nice car, but this Buick is really irritating me.

Oh, a couple of additional items; replaced the oil pressure sender. It read 130 PSI all the time. Now back to normal 65PSI at idle. Also replaced the thermostat with 180 degree as Florida summer temps easily exceed 100F each day. Replaced the upper intake/gaskets/PCV valve, etc. Still no change. PCM/ECM no codes!

Any news/updates on your problem? I have a sporadic rough idle (almost like a miss that I can't seem to get rid of.

My problem is deffinitley my fuel pump. It read good psi but when fuel in low it has hard time getting primed. Not sure if that's the right termonlogy but I've kept it above half a tank full and haven't had a problem. I will replace it as soon as I"m done with my Ford. Sorry I can't be of more help.

Rob

Thanks for updating me. I just replaced my fuel pump about 6 months ago. It's not too bad a job. Good luck.

"Part throttle and above". Does this mean sitting in park, or driving down the road?

The problem happens while either sitting in the driveway, engine running, and in park, part throttle. Also happens, and appears to be much worse when running down the road part throttle in drive at 30mph or above. Unexplainable issues.. wish I could track it down. No "check engine" lamp illuminated. Suppose I will take it to a GM specialist and have them pick my pocketbook. Last GM I will ever buy.

Last GM I will ever buy.
No matter what car you buy, you can have problems with it. After you get this fixed, it's possible you can have it run for years and years, without any major problems.
Chris.

Last GM I will ever buy.
You must have gotten a bad one. Everyone makes a lemon now and then. Our 2000 had over 200,000 on it, and all we ever replaced were plugs, wires, and left front wheel bearing (other than brakes, air filter etc..[never changed fuel filter] .and we only changed the oil when "it" said it needed one. It was the best GM we ever owned, and sorry we traded it for our new lemon.