93 bonneville AGAIN!!!

hi everybody, I posted the other day on this car with no response...The plot thickens... My 93 bonneville se has several of us here totally bafffled...Just replaced
the engine with a low mile used one..engine sounds great...Here's the problem. ..The car runs horrible for the first few minutes on a cold engine...it idles around 2000rpm and nearly dies when you try to accellerate..once running approx 2 minutes, it's drivable but has a hesitation from a dead start. Once your moving it runs pretty well. The check engine light is on intermittantly and was initially producing a different code every time I scanned it. Thinking at this point that I had a bad computer, I replaced the computer. Light's still on and off, problem's still there but now the only code info I'm getting is "fault in ESC circuit" and my scanner shows 0 deg timing advance...sometimes? New development I think may be related----Now the engine temp guage will not reach more than 150 deg f.---Replaced thermostat...again...no change, stll says it's not warming up fully, but I think it really is...{good heat, fans cycling properly} I'm beginning to suspect a bad ground problem somewhere as I have had a few other wiring problems crop up with the pwr windows and seats which required running a new grond wire to correct. Has anyone seen a problem like this and any suggestions where to look? thanks to all Gonz
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Go back thru all the engine grounds in particular, make sure temp sensor reads accurately on a cold engine, check tps on the scanner not accurate as it would be with a scope but give it a try. Any codes now besides esc, which is controlled by the icm, swap witth the one from your old engine, grounds here are important!

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thickens...
replaced
problem.
idles
Once
producing a

a
circuit"
will
heat,
a
look?
Grounds are very important. Double check those. Check what the engine temp sensor is showing. It's a primary input for fuel mixture, timing advance, etc.
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-Mike-
snipped-for-privacy@alltel.net
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Like Mike advised above, check what the engine temp. sensor is showing AND conmpare it to a manual check using a suitable thermometer--CAREFUL TO NOT GET BURNED!!! I use a cooking therm. to check them with, but I have been removing radiator caps for y-e-a-r-s and know how to do so carefully. If you're not completely familiar with how to do so, pay a mechanic a couple of dollars to check it with wife's cooking therm--he should do it cheap. Reason for double-checking: these thermostats are tricky to install, & if not done properly, using outer o-ring, it'll merely float around in its housing & let water bypass it and run too cool. HTH, s
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