Help, I'm a little confused here....
working on a 1992 Chevy Lumina APV minivan 3.1 Engine
The temperature normally is about 185 - 195 degrees,, and idles at about 775 rpm
Recently my temperature gauge started climbing up to 220 and then dropping back
which is a little less than 200. Climbing again to 220 and dropping back to
again. The engine started running roughly and stalling out when idling at a
The thermostat had been replaced... cooling system pressure checked. There are
No water in oil, no oil in water. Nothing coming out the tailpipe.
No error codes have been set. An ODBI scan shows all sensors to
be operating normal.... however it did note temperature increases
to about 220 degrees ( normal running temperature was about 185 - 195 range. )
I put an inductive timing light on all spark plug wires. Looks as if all
plugs are firing pretty evenly.... light stobes pretty evenly, no drop outs.
Pulled the plugs out of the front 3 cylinders...all look normal no deposits or
white. Ran a compression test on one head with a screw in tester...
cyl # 2 read 150
cyl # 4 read 165
cyl # 6 read 190 lbs
I have a Helms Service manual which (surprisingly did not give an
expected compression value. However it does state that the weakest
reading should be at least 70 percent of the strongest and a minumum
of 100 lbs.
Could not check the rear cylinders because of the diffculty of access.
Squirting about 1 tablespoon of oil into cylinder #2 brought the cylinder
reading up...Not only in #2 but also in adjacent #4.
Is this indicative of a blown head gasket between adjacent cylinders 2 and 4 ??
Is there anything else that should be checked to complete the diagnosis ???
Thanking you in advance for your help !!!