LeSabre Running Rich

Posted in Ignition Systems

Hi all, been a while since I posted but I’ve got a problem that stumping me pretty good. First, some specs:

-1989 Buick LeSabre T Type with a little over 200k on the chassis
-Vin C motor with about 70k miles on it (V6, fuel injected FWD)
-2.79 ratio transmission with about 150k miles on it

Here are my symptoms:

-Sulfur smell after a quick acceleration
-Rich gas smell on startup
-Occasional puff of smoke
-Slow acceleration
-Idles at around 550-650 RPMs but its rough-smooth-rough-smooth-rough-rough-ro… after the motor warms up
-Car seems to have better throttle response after resetting the ECM but the problem comes back after its had enough time for a learning cycle

Here are some facts and parts that I’ve eliminated:

-Flowmaster muffler about 8k miles ago
-High flow cat converter about 15k miles ago (CarSound Magnaflow)
-Belden wires wrapped in loom
-Type II ignition swap (blue on the underside of the coils)
-NGK Iridium plugs (overkill I know now but not at the time I got them)
-NTK (division of NGK) O2 sensor, less than 10k miles on it
-FWI with K&N filter (system worked great on my ’88)
-JB welded cam magnet from a code 41 about 10k miles ago
-No codes/SES light
-Correct ECM programmed for 2.79 trans and it is known to be good
-Adjustable vacuum modulator
-“fresh” rubber on the vacuum lines
-No squaling or clunking from the engine
-very slight damage to MAF screen but it has a known good MAF sensor
-I have cleaned the intake recently but the first time 20k miles back or so I did it I used carb cleaner (d’oh!) and since then the MAF has been replaced
-IAC has been swapped out with a known good one
-I don’t smell fuel in the FPR and the idle doesn’t change when I spray WD40 into it (checking for a pinhole leak)

I think the next step is to check the TPS but otherwise I’m stumped. As far as I can tell it should be running right but its not.

Suggestions would be greatly appreciated as I’m going nuts trying to fix this

I just pulled the FPR off and there was a lot of pressure behind it as it sprayed a ton of fuel everywhere… I did have a hose handy to keep anything “exciting” from happening though. I swapped in a spare and it sees better but still not quite 100%. I think I’m going to try a new one tomorrow and see what happens.

There are 6 Answers for "LeSabre Running Rich"

    1. richard m says:

      i would try some lucas fuel injector cleaner first with all those mods i could see it running a little rich,also check simple stuff like bad vacuum lines or collapsing lines,the lucas best stuff on market

    2. baldie says:

      i have a 88 olds. and it was doing something like that and i had to replace the fuel pump regulator, i think it was letting too much gas come through to the injectors.

    3. Jeffrey M says:

      I think you have a vacuum leak. Spray WD40 around throttel body and intake manifold. Also re-check all hoses (brake booster)

    4. biff says:

      Clean tps. Clean injectors, check plugs. Leakig injectors can cause this too.Check fuel pressure.

    5. d.wendel@sbcglobal.net says:

      Fuel pressure regs failure was common on these. Once vehicle is hot say on a weekend after a trip to the store, pop the hood, pull the vacuum line to the regulator and just drink a beer and sit there and watch it for 10-15 minutes or so. You will see it drip or spit fuel back out the nipple. Previous post about injectors holds true also, same symptoms, much harder to diagnose.

    6. mdk68gto says:

      i have seen situations like that where the fuel pressure regulator was just worn out, allowing excessive fuel pressure to build up. this high pressure will cause more fuel to be delivered, giving you many of the symptoms that you are seeing. replace the fuel pressure regulator and the problem should go away.