Hello, I’m a new member here and this is my first post. Six months ago, I bought a 1984 Ford conversion van. It has 35,000 original miles on it. It has a 5.8 HO engine with a four barrel carburetor and C6. When I bought it, the previous owner had contracted it a mechanic to go through it and they had installed a new battery, new plugs, a new radiator, a new distributor cap and rotor button, and oil change, and a new fuel pump. I bought it and drove it home and took it on another drive about 60 miles and parked it in my garage. The next morning, I started the van and it jerked everywhere the engine did and it was a rough idle and then it started ticking. Very long story short it had a bent pushrod (mechanic contracted by prior owner hadn’t tightened distributor and it rotated). In trying to diagnose the issue, I replaced the fuel pump and spark plugs and spark plug wires. After the new mechanic replaced the pushrod and both fuel tanks, the van drove fine and I drove it 1200 miles (trip to SC) I drove it a couple more times around town and all was well. And about a month ago, I was driving the van and it died while I was pulling up to a stop sign. It started right back up. I was driving it later that day the same trip and it died in the middle of an intersection and I was almost hit by a car. I brought it home and it had a rough idle. It also almost idled too low it seemed and when you turn the air-conditioning on the fast idle switch on the carburetor move the linkage and the engine idols at a higher RPM and will not die when you put it in gear or at intersections or stop signs. It also previously idled very fast when the air conditioning was on. Too fast as in 2500 RPMs but curb no AC idle was correct. Now, the idle with the AC on is lower probably where it should be with the AC being on.


hi took the old EGR valve off and it had carbon on it and the port had rust in it. I cleaned the port and vacuumed it out and lubricated the EGR valve. I replace the EGR valve with a new unit that NAPA had provided me but it ended up being the incorrect part number. It looks the same but it is not the proper part number for the van. So, I reinstalled the old EGR valve and test drove the van last night. With the incorrect part number EGR valve the van we’re not idol with the old EGR we installed, and it does function by pushing the plunger, I drove the van round-trip 60 miles and it idols lower than what it should while in park and the idle is rough and it died two times while coming to stops mainly when there was a downward angle or upper angle elevation to the stop sign or intersection. I’m not sure what’s going on I’ve taken the van to the mechanic further issues and I’ve tried to diagnose it myself. I’m to the point of being ready to take it back to the mechanic for this issue but would rather fix it myself if I can. I hope that someone may have experience with us and can help me. I really appreciate it ahead of time.

 

There's a decent chance someone's going to ask you to post your question on the appropriate engine subforum, but in the meantime I'm curious if you've done any testing for vacuum leaks. Vacuum line trouble in these old vans will screw up almost everything, and your AC issues make me wonder if your dash HVAC control unit is bleeding air. If I was trying to solve the problem I'd probably test for vac leaks and then maybe pull the HVAC control box and cap the lines and see if the problem goes away. If it does, you can fix or replace the control unit.

 

That's a beautiful van you have!
Wtrail is spot on about the vacuum lines and leaks..

Original post edited.
I edited this post because I missed the part about having replaced the fuel tanks.

Has anyone used a vacuum gauge to help diagnose any issues? Do you do some work yourself or does a mechanic do all of your work? A vacuum gauge is easy to connect and many auto parts stores have them in their loaner tools. HF sells them for under $20 I believe.
Here is an example do some of the issues you can diagnose with a vacuum gauge as well as just check the general health of your engine and exhaust system.
https://www.onallcylinders.com/2016/...auge-readings/

There are also lots of videos on youtube about using a vacuum gauge.

BTW, Are your mini blinds metal? I have the same windows in my van and they have metal mini blinds and you have to be very careful or they will bend... They work great to block the damaging uv rays from the upholstery. I pull mine out if I have children riding in the van... I don't know where one would find replacement parts..

 

Pull the dog house back, get the motor running and spray carb cleaner around the base of the carb and around the various vacuum lines. If the idle suddenly increases you’ve found a vacuum leak. Otherwise if the ignition is all 100% it may be time for a carb rebuild.

 

I cannot add anything to the already good advice cited.

In addition to the vacuum to be checked, I would also like to believe that the fuel supply would be to be checked. You have a magnificent Van over thirty years old with just 30K original miles. Perhaps bad residues have formed with these years of inactivity ? Perhaps these residues have come off with our new fuels ? The fuel filter should be checked and as BrnFree indicates, your carburetor may deserve a second youth, new gaskets at least ?

I just wanted to encourage you to preserve this wonderful van that you own. With these original 35K miles, all of its original documentation, original paint in good shape, the interior also seems wonderfully preserved. You have found there a pearl which is becoming rare.

Hoping that this little breakdown will not discourage you. It will be a pleasure to read the outcome of your little problem.

 

If it runs fine at idle, only stalling in gear, listen to the power brake booster, a leak there will cause that, I had the plastic angle piece crack once and suffered the same.