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Intermittent stalling and rough idle

8K views 8 replies 4 participants last post by  Short Bed 94 
#1 ·
Greetings, I'm a first time user and need some help with my 2wd '94 Ram which I have had since new. The truck has 200,000 miles and I've been trying to solve an intermittent problem for the last several months. The truck has a 5.9 and has been very well taken care. The truck is having a problem with stalling/stumbling at highway speeds, and then a rough idle when coming to a stop. I can go for a week, accumulating 250-300 miles with no issues, then unexpectedly it will start acting up. It has never actually stalled out and shut down. It most generally acts up for 25-30 miles and then it is perfectly okay for another 200 plus miles. I am getting no check engine light, not sure if it is even working. I have replaced the the TPS, MAP sensor, EGR valve, and thoroughly cleaned the IAC. The battery checks out okay along with the fuel pump and ASD relays. Plugs look excellent. The problem never happens when the engine is cold, always at operating temperature. If I sit long enough at a traffic light while it is having problem idling, it will eventually stall out, I smell a lean burn, and there is a air suction sound coming from underneath the hood. I am not able to find any vacuum leaks. Gas mileage is good and has not changed. Fuel pump was changed a few years ago. Again, this is an intermittent problem that always seems to work itself out. However when it happens I am not in a position to take it somewhere to analyze what is happening. Thanks for your help and assistance!
 
#6 ·
Thanks for the response, symptons of a bad intake manifold plenum gasket is excessive oil consumption. I would also think that an issue with the manifold gasket would be consistent day in and day out which is not the case. Oil consumption is not an issue and the spark plugs look fantastic. I'm leaning towards something in engine management that is controlling fuel supply or possibly choking the engine for some reason. Thanks again!
 
#7 ·
Using THAT logic one could say that fantastic-looking spark plugs would be inconsistent with a fuel management issue.
Maybe it's not the gasket, but a failing gasket doesn't start causing massive oil consumption over night, and it's more than just that sympton. The vacuum problem will throw off fuel management. I also agree with O2 sensors if they've got that much time on them. Looks like you've already shotgunned it with other parts to no avail.
 
#9 ·
The O2 sensor was replaced at the 120,000 mile mark and I believe a bad O2 will result in poor gas mileage which is not the case. The condition of the plugs indicate all is well with the ignition however it is still possible that an irregular fuel delivery could be possible and the plugs would quickly recover and not show any wear. Plugs on the other hand that are carbon or oil fouled will need attention. Thanks for the input!
 
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