Hello all. I am at this point desperately seeking assistance. I've been working on this bus for 2.5 days straight, just about literally with about 3 hours of sleep and I can't figure out the fix I need. At present my bus has been surging at idle, very unusual rpm fluctuations. If it's not idling high, it's surging and about to bog out. If I hit the gas it stops but clearly experiencing misfire. When I drive and give it gas, pressing the gas pedal down makes a sort of whistling noise. Sometimes I need to use both feet on brakes and gas to switch from park into drive, seems a little bit better to start in neutral. Also, when I take off the oil cap, there is a clear change in rpm. This all has lead me to try a few things.

I cleaned the idle air control valve, cleaned the throttle body, changed exhaust manifold gaskets, bled the air out of my coolant reservoir and power steering, cleaned the MAF, got a new PCV valve, reset the computer. I even made a little smoke machine using a soldering iron, mineral oil and a bike pump, but I'm not so sure how effective this was i couldn't find any leaks and in almost certain there is a vac leak somewhere. I can hear it. My girlfriend also said that when she tried to put gas in that the gas pump was acting like the tank was full and topping off. I've added some octane booster to the fuel which seemed to help a small amount to get to the O'Reilly's im currently at. Their scan tool doesn't seem to work on this bus and I'm just about stuck here at this point. I don't want to drive the vehicle in this condition but I can't stay here forever.

What I'm about to do now is patch a pressure hose leak to what I believe is to my oil cooler. Seems to be leaking from the threads. I've got some silicone tape I'm going to wrap that up with for now. I'm then going to pull the EGR valve and clean it then figure out how to test the pressure in the fuel rail.

Any suggestions would be great. Everything I've learned about fixing cars I've learned over the last year so I'm by no means a mechanic and I'm halfway to panic mode.

Thanks y'all,
​​​Chad

 

Sounds like your vehicle has an intake manifold leak.

 

what did you say about my mama? I mean Jeeze hank, thats definitely not what I wanted to hear. When I did my smoke test, I attached to the PCV valve hose and saw no smoke coming from the area.... Is this something I can fix myself, being a noob? Is there a way I can maybe patch the issue for now or temporarily on the cheap/free? Its really important I get this fixed as im currently living in this thing and quite honestly im broke as a joke right now. I only really drive between 25 and 50 miles per week my situation being what it is and I'm working on replacing the carb for my 76 e250 as a more affordable ride. Appreciate your quick response brother. I'm going to do a little propane test in the suspected area and will fill you in on the results, perhaps take a little video.

 

So I did try to release some propane in the area, but with the fluctuations in RPM being what they are, it's difficult to tell. Is it possible propane could have made it seem like it ran better? Haha. Along with a hissing sound and other symptoms, I'm thinking @hanky is right. It's gotta be the intake manifold. At the moment I'm a bit short on cash and was wondering if there was a way of repairing the issue aside from buying new gaskets. is there a known easy way to seal from outside? Can I make a proper seal with a gasket maker in a tube? Also, any tips or extra know how would be insanely appreciated. I'm very much so still learning and could use a little help. Thanks y'all!

 

Hi Chad,
The fact that you were able to get a reaction when applying propane externally tells us some of the problem is external,but,,,,,,,,,,,,from your earlier description I am inclined to believe there is some leakage at the mounting inside also. These type problems usually require manifold removal,replacing the gaskets and mounting bolt gaskets also.
When removed the gaskets look fine , but still leak, and replacement was the solution.