auto repair forums

[Rob30]

Anyony know a good auto repair forum?
I have been having an ongoing problem with my GMC 1500. 5.7L auto 2wd.
It has a miss at hgh way speed. I'll be cruising along them it just misses, sometimes for a few seconds but usually just for a second. The check engine sign comes on if it is a long miss. The code says its the throttle position sensor. Changed it and it still misses. Changed the fuel pump, filter. I have changed the cap, rotor, plugs, and wires.
I need to know what would cause a throttle position sensor code besides the sensor?

[Red Devil TN]

www.fullsizechevy.com

What year? The early vortec v8's had poppet injector issues. I'm going through the process of finding a miss myself in my '96 2500 'burban. I'm avoiding thinking it's the injectors. lol!

[agmantoo]

I had the similar symptoms with a GM vehicle and the problem remained very eratic. The dealer attempted to read the code but was never able to identify the exact source. The mechanic told me he "thought" it was the EGR valve and for some reason he looked at the valve and put it back on. Afterward the car did not exhibit the symptoms for a good number of miles but as always the problem resurfaced. I realized the mechanic's looking at the EGR valve did have an impact on the problem so I bought an internet sourced EGR valve and installed it myself. That fixed the problem. If your vehicle has a EGR valve that is controlled by the magnetism of a solenoid valve working against a spring, common reasoning will conclude that as the vehicle ages and the spring changes characteristics from use and temperature that the ---- thing will fail to seat or accurately meter. That cut out/miss is an overdose of the inert combustion gases being introduced into the gas/air mixture causing the engine to misfire. What the engineer was attempting was to cool the combustion in order to reduce the polution. I suggest that you removed your EGR valve and attempt to clean it by using compressed air or brake cleaner and then run it to see if you notice an improvement. The EGR valve is rather expensive.

[clovis]

I am not an auto mechanic, but did you "read" the old plugs when you pulled them?
Wear and engine problems sometimes show up on plugs.
I had an old four cylinder that developed a miss. A mechanic told me to pull each plug and look for abnomal wear/signs. Sure enough, one of the plugs was super clean, like it had been steam cleaned. It was the first sign that I had a bad head gasket, leaking antifreeze at the #3 cylinder. You might be able, if you use a flashlight, to peer into each cylinder when the plugs are pulled. I am told that a leaking HG will often look like the cylinder is also steam cleaned.
Again, I am not a mechanic, but thought this post might be of assistance to you. Most generic repair manuals, like Chiltons, has a page of this info on spark plugs and their respective wear and problems.
While my info may not be relevent to your problem, this type of detective work can often help determine where the problem lies.
Clove

[Janon]

http://www.automotiveforums.com is one of my favorite sites for all things auto repair.

cheers,

[John Hill]

Generally speaking, any indication of a sensor malfunction should throw suspicion on the wires that connect to the sensor. It is a hard life for a little push on connector in the hot engine space with oil fumes and continual vibration.

[Rob30]

When the engine has a real hard miss it messes everything up. The tranny starts shifting bad, 1-2 shift is real hard, other gears are seem to shift rough. The truck is a 96. I have checked the plugs. They are all good.

[Theront]

there is a website called http://67-72chevytrucks.com. From this site they aslo have a 47-98 chevy truck page. Very good links and a lot of information here. I have used it a lot.

Theront