2002 Blazer Bucking, Temperature Gauge goes bonkers

Any feedback appreciated.
2002 Blazer V6
Anyone seen anything like this?
Cars bucks, usually twice, intermittently at between 15 and 70 miles highway driving. Gets worse with time. Never happens during city
driving.
Temperature gauge goes from max low to max high when problem occurs. Tach, Electrical, and other instruments remain in normal range.
Engine does not miss in neutral when the problem starts. (2000 rpms)
Turn motor off for a few minutes, restart and things are ok for a while.
No codes sets in ECM.
Has been to three dealers and no one can find a problem.
Checked transmission fluid. (Level ok, Clear and no burning smell.)
Tuned up recently.
Transmission rebuilt under warranty by GM. Warranty now expired.
Assuming it is a transmission issue, is there any explanation for the link between the temperature gauge and the bucking? Other than the ground, is there some link via a sensor or electrical connection?
Could an improper install of a satellite radio system cause electrical issues for other components? Is this worth looking at? Owner does not recall having the problem before the installation of the satellite radio.
Additional Information: Aftermarket automatic started had to be removed several years ago. It was tripping MIL.
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On Dec 6, 7:32 am, snipped-for-privacy@yahoo.com wrote:

Why do you assume that this is a transmission issue?
No, there is no way the installation of a sat radio has caused this. In all my years of installing and selling auto electronics, had the improper installation of somethng that simple, caused any such problems.
I am thinking you might have a problem with the ECU.
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Thanks for the suggestion. I found a post by someone who was having a similar problem when the radio was on. Also thought it really strange that the after-market auto starter was tripping the MIL.
Should I get a code from the ECU? Is there any link to the temperature gauge? It is an absolute predictor of the problem. Temp. gauge starts fluctuating, car bucks.
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It sounds like a bad ground problem!
There is a series of ground wires on the top of the transmission, on the bolt or on the back of either head.
Also, there are a few ground wires bolted to either the thermostat housing, or on one of the intake manifold bolts.
Another area you might want to look at carefully is, the ground wire on the battery terminal, to the body. Run your fingers over it, and carefully feel for swollen areas.
Check the braided ground straps from the firewall to the engine also.
I hope this helps.
RK

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On Dec 6, 9:32 am, snipped-for-privacy@yahoo.com wrote:

Hello
Hello
I had a similar problem that sounds like the the one you describe but it was due to a blown head gasket.
I have a 4.3L V6 that blew a head gasket recently. The introduction of coolant and oil into one of the the combustion cylinders was causing the engine to run rough due to the imbalance of forces on the engine. The cylinders must all produce an equal amount of force during the combustion cycle for it to run smoothly and this unfortunately doesn't happen when your burning a mixture of anti-freeze, oil and gasoline in one or more cylinders. The leakage became so bad that the car eventually stalled out.
So after it stalled I noticed that the temperature gauge was way high. When I went to check the coolant levels I noticed they were abnormally low. Once the head gasket goes the cooling system eventually becomes de-pressurized resulting in a temperature spike in the cooling system. You also begin losing alot of coolant. I drove it like this with no problems for a long time until it blew and I lost a hell of a lot of coolant before it went and didn't even realize it.
This may not be the cause but maybe you have a very small head gasket leak into one of the cylinders. I am not sure how you would diagnose something like that unless you had a way to check the coolant level accurately or verify the cooling system is continuously and adequately pressurized during normal operation. The temperature increase may be due to steam production inside the cylinder and the bucking you describe may be due to an imbalance of forces on the engine caused by lack of combustion in one or more cylinders. This condition would be unnoticeable if it were a very small leak and you were doing normal city driving. I usually drove mine for short trips with a leaking head gasket with no noticeable problems in engine performance. Eventually the leak became much more worse and could no longer be ignored.
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Thanks for replying. I think coolant level is remaining normal. When the temperature gauge acts up, which is followed by the car acting up, the gauge starts floating low, then spikes occasionally. I will be checking the ground wires I can find as recommended by the previous post. Really difficult problem to understand.
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