davesmith84
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- May 25, 2009
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1972 1600 twin port engine, 34 pict 3 with a vac distributor but with pertronix electronic ignition module.
I've owned my bus for 4 years now and I've always had hesitation at low revs when warm. As you can imagine over the years I've done many services so it's extremely unlikely that it's anything simple like a serviceable item.
It runs amazingly, perfectly smooth whilst on choke. Obviously makes me think it must be running too lean when warm? But I've reset the carb when the engine is warm many times and the exhaust is black.
It seems to be at it's worst the hotter the engine is, this is what makes me think it's an intake air leak. I've tried spraying carb cleaner around the engine so many times I've lost count, no change in engine revs.
Other things I've tried (which have made no difference):
• Rebuilt the carb checking and cleaning all jets
• Recently re-bushed the throttle spindle on the carb
• Checked fuel cut off solenoid and is fine
• Tried the unscrewing of the idle/pilot jet slightly but this made it run worse. It's now just nipped up to the carb body.
The problem I have is the hesitation is so consistent and reliable, it kinda feels like it doesn't matter what I do, it will always be there. I've had it for 4 years now and counting! The bus is still very much drivable but only if you drive through the hesitation or let your foot off the pedal and then build the revs more slowly. Occasionally, when pulling away, the bus will hesitate so badly that if I didn't remove my foot from the pedal it would stall, or it feels like it will.
The only thing I can think is left to do is pull the engine, remove the intake manifold and re-seat all joints with new gaskets making sure everything is torqued down properly. It must be an air leak that just isn't showing when I spray carb cleaner around? The only issue I have with this idea is that if I cover the carb throat with my hand the engine dies instantly. I understand this normally means you have no leak? Maybe the air leak only 'opens up' when the engine is being run on the road and is hotter? Obviously the only time I can check for leaks is when the engine is idling which inherently means it's cooler than when running? Also, the hesitation obviously only happens on the road when the bus is under load. I can't make the engine hesitate by operating the throttle arm by hand.
Thanks for reading and I massively appreciate any help offered.
I've owned my bus for 4 years now and I've always had hesitation at low revs when warm. As you can imagine over the years I've done many services so it's extremely unlikely that it's anything simple like a serviceable item.
It runs amazingly, perfectly smooth whilst on choke. Obviously makes me think it must be running too lean when warm? But I've reset the carb when the engine is warm many times and the exhaust is black.
It seems to be at it's worst the hotter the engine is, this is what makes me think it's an intake air leak. I've tried spraying carb cleaner around the engine so many times I've lost count, no change in engine revs.
Other things I've tried (which have made no difference):
• Rebuilt the carb checking and cleaning all jets
• Recently re-bushed the throttle spindle on the carb
• Checked fuel cut off solenoid and is fine
• Tried the unscrewing of the idle/pilot jet slightly but this made it run worse. It's now just nipped up to the carb body.
The problem I have is the hesitation is so consistent and reliable, it kinda feels like it doesn't matter what I do, it will always be there. I've had it for 4 years now and counting! The bus is still very much drivable but only if you drive through the hesitation or let your foot off the pedal and then build the revs more slowly. Occasionally, when pulling away, the bus will hesitate so badly that if I didn't remove my foot from the pedal it would stall, or it feels like it will.
The only thing I can think is left to do is pull the engine, remove the intake manifold and re-seat all joints with new gaskets making sure everything is torqued down properly. It must be an air leak that just isn't showing when I spray carb cleaner around? The only issue I have with this idea is that if I cover the carb throat with my hand the engine dies instantly. I understand this normally means you have no leak? Maybe the air leak only 'opens up' when the engine is being run on the road and is hotter? Obviously the only time I can check for leaks is when the engine is idling which inherently means it's cooler than when running? Also, the hesitation obviously only happens on the road when the bus is under load. I can't make the engine hesitate by operating the throttle arm by hand.
Thanks for reading and I massively appreciate any help offered.