I've had a persistent problem with my 92 Bonneville SE (3800, 3.8L V6
engine, 4-speed tranny with overdrive, 221000 miles [no typo]) that
has me perplexed. When I have been driving a while (at least half an
hour), especially in slow traffic, I lose power when accelerating.
That is, I can accelerate gently and the car will operate normally. I
can get it up to 95mph with no problem, if I accelerate gently enough.
However, if I try to accelerate harder, the car gives me no power at
all, except for a few intermittent bursts where the car will
accelerate. These bursts last under a second, and are separated by
several seconds with no power at all. This situation occurs at about
3000 rpm once the problem is fully developed. On its way there, the
car will start to accelerate unevenly around 5000 rpm. The longer I
drive, the lower the threshold becomes until it reaches about 2900
rpm. At one point, on a long road trip, it got to the point where it
started doing this at about 2000 rpm, and I couldn't enter the freeway
or maintain speed up a hill.
Once this happens, I can turn off the car and leave it for a while.
The longer I let it sit, the better it runs, but it takes about six
hours for the car to be in good condition. (Until it heats up again,
In neutral, I can rev the engine as high as I want with no problem,
and the engine behaves very well when power braking. (But the RPMS are
relatively low when power breaking. This phenomenon occurs at high
rpm.) Before I replaced the spark plugs, the car began stalling at low
speeds or when decelerating.
I've replaced the plugs, wires, MAF sensor (it was cracked anyway) and
fuel filter. Starter had to be replaced at 205000 miles.
The car performed very well after I replaced the plugs and wires, but
it was back after about 2000 miles. I pulled the plugs today, and
there were in almost-new condition.
I don't know if this is related or not, but the transmission fluid has
begun to smell burnt, especially after driving a long time. Also, in
this condition, when I'm idling at a light and I release the brake,
the car doesn't creep like it normally does for a second. Then I hear
(and feel) a loud pop and the car begins to roll again. Oh, and the
main driving belt (whatever it's called) is shorter than it should be
because it bypasses the air conditioner compressor. I'm told the AC is
broken anyway. I bought the car like that. (All the problems appeared
after I purchased it, when it had 200000 miles on it.)
I've brought this car to several garages, but none of them have been
able to reproduce the problem. As luck would have it, I drove past a
garage one day while it was doing this and a mechanic was able to deal
with it right away. However, leaving the car off long enough to go
inside and get him was enough to let the car operate normally while he
The oil pressure gauge behaves interestingly. Normally, it's at about
40psi, but when I accelerate, it VERY quickly goes to maximum, then
returns to 40psi some unpredictable time afterwards.
The problem became worse after a recent oil change, but I have no idea
what kind of oil was used for it. (*Grumbles about people not owning
my car doing service on it*
I have no idea what to do now. I've read that it could be my ignition
system (this model uses a DIS system. There are three ignition modules
that the plug wires connect to. I've examined each of them, and they
all seem clean and secure. I can borrow a multimeter if necessary.
I'd greatly appreciate any advice. Thanks!