I changed the timing chain on my chevy astro 4.3l v6 2002 van.i set the timing correctly and the distributer is on right as well.when i started the van it started well but later it seemed to accelerate a little on its own and began to overheat.
I'll address your issues as if you hadn't changed the timing chain. The acceleration: I know newer cars have throttle position sensors and all sorts of other beastly things that make straight forward repairs a nightmare. As for the overheating, are you sure you refilled the coolant system completely with clean 50/50 mix? As well as running it with heater system open, then checked fluid levels afterwards. You may well have a coolant leak, bad thermostat, or a water pump that's ready to give up the ghost. I make judicious use of my Chiltons/Haynes repair manuals, and have one for each of the make/model/year of car I own. The troubleshooting guides are a great help. I was also lucky enough to receive a number or Motors Manuals after my dad died in 1980. And will grab one at yard sales and the like whenever I have the chance. Frankly, if I had been changing that timing chain I would have changed the thermostat and water pump just to keep from having to mess around in tight quarters in the near future. A final check you might make (I'm playing the really evil devil's advocate here) is to check your oil level and clarity. Best of luck.
Testimonial: "thank you very much your info was very helpful i will do all necessary checks and run scans to see if i get the problem fixed."
Check the timing again to make sure you didn't slip a tooth when you lined up the marks. Make sure #1 is at TDC and the rotor in the distributor is pointing at the #1 plug on the cap.
Testimonial: "yes i already did that and it is all correct. now i am thinking if it is possible that the problem is electrical.wat do you think?"
Overheating could be due to an air lock. Run the engine with the rad cap off and the heater on full. Make sure the level is not below the add mark in the overflow bottle when cold. If the timing is correctly aligned, you may just need to set it to the correct setting BTDC at the distributor. If that's all Ok, then I would start looking at the spark to make sure its getting good strong sparks at each cylinder.
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