Posted: 4/23/2012 7:54:07 AM EDT
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I have a 2001 Chevrolet Malibu with just over 103,000 miles on it. A year or two ago (I forget the exact mileage, but I think somewhere around 90,000) it developed a coolant leak, which I understand is a known issue with some of GM's V6 engines. I put off fixing it, and just kept topping off the coolant whenever it got low. Well last month, I decided to fix the problem. After doing some research, I concluded that it was due to a leaking lower intake manifold gasket.
Over the weekend, my dad and I tore down the engine and replaced the lower intake manifold gaskets, upper intake manifold gaskets, spark plugs, thermostat, and fuel injector O-rings and seals. We then took the car to a mechanic, who flushed the coolant and changed the oil, then checked the coolant system for leaks. He was unable to locate any. We then ran a tank of gas with fuel system cleaner through the car. Unfortunately, a new problem manifest itself after the repair. After the engine has warmed up, and has begun to idle at around 700 RPM, I will hear a slight "pop" sound come from under the hood every few seconds, which is accompanied by a drop of about 50 RPM, and a slight shudder. Also, sometimes upon acceleration, the car will stutter slightly, until the RPM gets above about 1,000. When the engine idles cold (about 1,200-1,400 RPM) or is at cruising speed (RPM about 1,500 to 2,000,) it runs perfectly. Unfortunately, I do not have a code reader, but the check engine light is not on. Anybody have any ideas? Doing some reading, the most common suggestions I have come across are to use carb cleaner to check for intake leaks, and to fiddle with the spark plug wires to make sure they are seated properly. Also, I suppose I should mention that aside from the aforementioned replacement parts and the serpentine belt, all of the parts of the engine are original. |
| I would pull the covers and double check the rocker arms. The pushrods are of 2 different lenghts for intake and exhaust, so if you had inadvertently swapped them you would have worse problems than what you describe. However, the bolts that hold the rocker arms down thread into the aluminum cylinder head. I have had a few that after tightening them down and reassembling the rest of the engine, then firing it up and getting up to N.O.T., would pull the threads up from the aluminum. This would result in excessive clearance between the rocker arm and pushrod, as well as a slight misfire. This may be what is causing your condition, and if so, the only repair is to drill out and heli-coil the bolt hole on the offending rocker bolt. |
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i've read about something better than heli coils in this application and those are "time-serts".
read here: http://www.timesert.com/ |
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Quoted:
i've read about something better than heli coils in this application and those are "time-serts". read here: http://www.timesert.com/ Timeserts work great, to install them on the 3.1/3.4 GM V6 requires a bit of work and artistry but the work is worth the effort. |