Lean air/fuel mixture on 95 Eagle Vision (difficult cold start)

Hi, all,
Here's my current suffering, and I'll try to keep it short. Bought
this 95 Eagle Vision 3.5 ESI (Intrepid clone) about 1 1/2 yrs ago, 79k
miles on. Currently at 92k.

Ever since I bought it had a rough idle (shudder, trembling when in
idle). Back then, tried to fix it, replaced plugs, wires, battery, air
filter, PCV valve, intake manifold gasket. Nothing gives, shudder
still there today, but note that allthose items are barely 1 year old.
Occasional history of not starting in cold weather (teens and below)
but I attributed that to fuel line freeze.

To top that, in the past couple of weeks due to extremely cold weather
car won't start again, this time had a full tank of BP 93. Tow the car
to my garage, heat up the garage, nothing gives, car would turn, crank
but not start. A few days later still very cold in the garage, but I
floored the gas pedal, keep cranking the key(suggestion from the
group), some 20-30 secs later car starts in a cloud of smoke (probably
flooded). Still starts and runs today, but with an apparent loss of
power, check engine light on. I did the key trick, read the codes, 51
twice (lean air fuel mixture).

So I figure it's the O2 sensors (also from reading the group), bought
2 new ones and proceed to replace the old ones. BEFORE taking the old
ones out, I just disconnected them, and I crank the key again, fully
expecting not to start. Wrong! Car started as if nothing has happened.
So, I postponed changing the sensors. Now, car is running but still
sluggish, still check engine light on, still code 51. I'm afraid it
won't start again in cold.

Would welcome advice: could the O2 sensors still be bad and in need of
replacement? If so, how come the car started with them disconnected?
(Granted, car was warm at the time). If not, any other suggestions on
what might be wrong? I only mentioned the shudder because I think it
may be realted to the lean air/fuel mixture. Your help is greatly
appreciated.

Sorin

Note: due to bad experiences with local shops, I'm reluctant to take
the car to a local shop, until I find one trustworthy and
knowledgeable, so I welcome suggestions in that department as well (I
live in NE Ohio, Cleveland/Akron area). I found an excellent local
mechanic for my Passat but he won't touch anything NOT European.

 

Certainly. If they're shorted low, they're going to report back
to the PCM a lean fuel condition, the PCM is then going to
erroniously add more fuel possibly carboning the sparkplugs, the
addition of an erronious lean condition is going to skew the fuel
trim strategy so that even during a cold start when the O2
sensors aren't being monitored, too much fuel is injected.
What you get is a flooding condition from compounded problems.

Because simply, the O2 sensors are not a necessary component to
whether the engine will start.

Ideally you'd want to scan the engine data with the appropriate
tool to see what is actually happening, as an alternative, you
could back probe into the O2 sensor signal circuits with a DVOM
and watch the sensor response as a way to confirm whether they're
stuck low giving a false lean report to the PCM.

In addition, you may want to check the fuel pressure regulator
and verify the cam timing because these three items (O2 stuck
lean, fuel pressure regulator, cam timing) have been the only
causes that I've seen that create a hard start condition on the
3.5 engine.

Perhaps you can get recommendations from friends, cow-orkers or
family??

 

Suspect leaky manifold gasket, very common on 3.5L engines.

 

And maybe the lower intake manifold gasket.... it might leak enough to
lean the car out enough that it would be hard to start.

Completely O/T- I had a GM rental this week. 3.4L, only 8200 miles, but
that thing was a hard-starter (in only 48 degree weather, no less). Ran
great once fired up (well, not as good as a Chrysler 3.5), but took
several re-tries to get going. By the way, I noticed that GM cars no
longer put the driver in control of the starter directly- once you bump
the key over to 'start,' even if you release the key the engine will
keep cranking until the engine starts. If the engine doesn't start, it
gives up after about 5 seconds. Really surprising the first time you let
go of the key and the sucker keeps merrily cranking away!

 

Except that the OP already mentioned that he had the intake
gaskets replaced a year ago, and that there was no change in the
rough idle condition, although that doesn't mean that it was done
correctly.
(job is pretty gravy, so I can't imagine how one might screw it
up)

Hmmm. copying Mercedes?