86 Honda Accord stalls when accelerating

stalling
honda
accord
rpm

#1

What’s causing the car to stall when accelerating over 1700 RPM? Starts and idles fine at 800 RPM, but when I try to accelerate in 1st gear, it cuts out at about 1700- 1900 RPM. It’s manual trans, carbureted motor. Changed distributor and coil. Plugs and wires are new. Checked all vacuum lines, but it sounds like one of them is opening a thermovalve at the wrong time. Can I bypass most or all of the vacuum lines that manage the fuel system?


#2

When you say ‘cuts out’, do you mean the engine dies or just stops providing power?

If you go ahead with the ‘bypass’, you will have to be selective on what you bypass (disconnect & block) because a lot of the vacuum hosing adjusts idle speed, mixture, ignition advance and retard, timing of choke opening, etc. You might try bypassing the egr valve, the canister purge, and heated air control motor for diagnostic purposes only. I suspect that the problem may be in fuel delivery i.e. fuel filter or fuel pump or the failure of the carburator secondary either to open or a clogged secondary main jet. When the vacuum control system is working correctly it usually does a good job but it sure is a bear to trouble shoot.

Hope this helps.


#3

Good to find someone who knows carburetors, still.
Here?s the rest of the story of the 86 honda. The stalling problem is intermittent. Twice today, including the first use of the car, it stalled shortly after leaving the driveway. But sandwiched between those unsuccessful trips it ran for 10-15 miles, with several stops and didn?t hesitate or lose power. There was a slight misfiring, but not enough to affect the speed.
By ?cutting out? I mean that I can increase the RPM gradually up to 1500-1900 RPM by slowly pressing on the accelerator. If I let the clutch out slowly, I can make it back home at 5-10 MPH. Pressing on the accelerator more than a small amount causes the motor to die. If I let go of the throttle before it dies, the motor recovers to idle and will idle indefinitely no problem.
I have had the air cleaner off innumerable times, several since this last problem. While stranded a couple days ago, I took off the air cleaner and checked the vacuum tubing and found a big piece missing out of one of the three labeled A, B and C that are attached to what appears to be a big solenoid valve on the passenger side. I think it was the A hose that was broken. I replaced it but it didn?t help. There were a couple of others that were looking worn so I fixed them, to no avail. I also tried disconnecting the other vacuum hoses in succession to see if the car would accelerate past 2000 RPM with individual ones disconnected. The fuel filter was replaced. After messing around with the carburetor, hoses, etc for over an hour I gave up and started slowly driving home. About ? mile along, the motor started working normally.
There is a myriad of vacuum hoses on this model. The other family car is a ?88 Honda and I have done a lot of carburetor and related troubleshooting on both cars. One of the problems on the ?88 that I thought might also be on the ?86 is a vacuum valve that opens one of the bypasses that dumps air into the intake, effectively causing a huge vacuum leak, killing the motor. It?s permanently disconnected on the ?88 now because I don?t know how or don?t have the know how to fix what is causing it to open. So I tried disconnecting them on the ?86, but it didn?t help. I plugged the three open vacuum lines all the while I was working with the air cleaner off.
The downloadable manual for the 86-89 Accords has been helpful in troubleshooting past problems, but I don?t understand how the carburetor controls on this car are integrated, in spite of having read the shop manual many, many times and making repairs and adjustments. The Honda repair shop at the dealer was unable to help. It?s been so long since they serviced a carburetor they only know to replace it. When I took the ?88 there the manager recommended replacing the carburetor, which cost more than the total. Just about any repair is more than the book value. As it turned out, replacing the carburetor myself didn?t solve the problem. A faulty ground in the control unit located under the driver?s seat was not allowing the idle solenoid valve to open. A jumper to the floor pan fixed it. So I could use the good carburetor off that car to repair the ?86.

Your point about a non-functioning secondary is well taken, but I don?t think the secondary gets involved until a greater throttle level. At least I don?t see the butterfly opening on that side until much deeper in the throttle travel. And why would the problem be intermittent, if it was a plugged port?
I?ve eliminated the fuel filter and fuel pump because I can see and manually adjust the fuel level in the sight glass window on the side of the carburetor and was able to move the level up and down with the adjusting screw on that same day I got stuck.
Thanks for taking the time to share your know how. My original efforts were to get better gas mileage after an emissions test derated my miles per gallon. Never did recover the old 40+ mpg, though I do get 40 at elevation on trips west.