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A collection of helpful articles based on reader submissions
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  Jim Grant's Tech TipsJim Grant's Tech Tips
Below is a collection of Jim Grant's Tech Tips sorted by Vehicle Make. These Tech Tips were answers to questions submitted to Jim by ALLDATAdiy.com users over the course of many years.
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  Jim Grant's Tech Tips

96 Chevy Astro, Check Engine Light and Plugged Exhaust

Q: My '96 Chevy Astro with 109k does not have any power and the check engine light is on all the time. If I leave the AC off I can go up to 50mph, if it's on I can only go to 30mph. Also it has a hard time climbing hills, the transmission slips and shifts erratically. I took it to the dealer and he says he is seeing a misfire code and wants to do a major tune-up. One month ago the car was in for a 60k mile service and nothing was wrong then. I took it to another shop and he says it's the transmission and won't even bother to tune it. I took it to a third shop and he saw the same code plus another one, but says I need to replace the exhaust system (Catalytic converter and muffler) first and then possibly do a tune-up. He says the exhaust is clogged and that's why I am getting the misfire code.

A: The answer is technician # 3, but I would ask him to prove it first. Proving a restricted exhaust is relatively easy but very annoying. To prove a restricted exhaust only requires unbolting the exhaust. We have a Plymouth Breeze in the shop that was lacking power with a check engine light on. The computer had 2 codes; misfire detected in cylinder #1 and the engine operating at too low of a temperature. Initial inspection found the engine to be in good condition, starting and running well. Out on the road it was a different story; the Plymouth would be in the way of any kid on a tricycle. The exhaust pipe was unbolted from the manifold and secured for a second test drive. It was the Jekyl and Hyde syndrome, the Breeze roared to life. The conclusion? The exhaust is restricted. Now many will jump to the conclusion that the catalytic converter is plugged and they are most likely right. But a word of warning, the inlet and outlet pipe to the converter should be cut open to allow for inspection. Why? Many exhaust systems use a dual walled pipe at the front of the system. We have seen the inner wall of this pipe collapse and create the same condition as a plugged converter. Have tech #3 unbolt the exhaust and test drive the vehicle. If power returns, the exhaust is restricted and needs to be inspected. If the converter is the cause then the cause for the converter's failure must be found. In the case of the Breeze it's likely due to the second computer code. The thermostat is opening too early, causing a lower coolant temperature. When coolant temperature is low the computer adds more fuel. Operating an engine under this condition for too long of a period will cause converter melt down.

 
     
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