Question about 1991 Cadillac DeVille
Not using oil but front plugs shows signs of running too rich.
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Posted on Jan 02, 2017
it can be engine temperature sensor, map sensor or oxygen sensor. what happen here is when your engine cold, it run on a limp mode. it ignores all the inputs from sensors but when it warm up to the operating temperature the computer will take over and at this time if one of your sensor is bad it will give the computer wrong data
Posted on Feb 25, 2010
SOURCE: rough idle after warm up
I'd take a look at the temp sender...the engines computer may be
"thinking" the engine is still cold when it's not. That would cause it
run rich (and rough) after it's warmed up. Generally the sender can be
tested with an ordinary volt/ohmeter but you will need the
specifications available in most inexpensive manuals. As with any
complicated electronics system, I can only give you my best guess,
without the luxury of doing any hands-on testing myself.
Posted on May 28, 2009
Did you have battery disconnected or dead recently?
Try to place ignition in run without starting engine for 3 minutes (shut off all accessories and lights etc..). Then shut it off and then start it. Should relearn the idle.
If this doesn't fix the problem, unplug the MAF sensor, if it runs fine with it unplugged, its the MAF sensor.
Exactly what happened on my wife's 01'.
Posted on Jul 25, 2010
The combination of heat and missing tells me that you have an ignition problem. Warm the engine as much as possible and take a water mister and mist the exhaust manifold with the water mist at each cylinder where the exhaust comes out of the cylinder. The cylinder(s) that doesn't evaporate as quickly as all the others is the one that's missing (no combustion = no heat out the exhaust for that cylinder). The next thing to do is to pull the spark plug. examine it for dirt built up around the electrode. If it's dirty then just replace all your plugs. If the plugs look good ( not worn - no contaminates around the electrode) then suspect plug wires. If all the cylinders evaporated the water pretty much the same, then your coil wire to the distributor cap or the cap and/or rotor itself is faulty. Examine the rotor cap and rotor for thin black lines running along the inside. If you find evidence of arcing (the lines inside) then replace the cap and rotor at the same time. The data you gave though sounds more like plugs or plug wires if I were to guess... For best results you should plan on replacing plugs/wires/rotor/distributor cap at the maintenance intervals suggested in the owners manual. But now that you're having these issues you should have some kind of concrete evidence before replacing these items - that is unless you've never replaced them ever before. In which case it's high time to have replaced them.
Posted on Oct 01, 2010
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