Suggestions or should I look for an anti-Witchcraft

[Terremotico]

I know some of you may have had the same trouble. I have used the search feature and I found different possible solutions. However I thought that if I explain the symptoms somebody may direct me to the most probable cause of the problem.

Here it is.

Honda Accord 87 Hatchback Dx, carbureted, 170.000 miles, Auto. Two years ago (at 150 K miles) a valve blew. I opened the whole thing, changed valves, valve seats, adjusted valves and put new head gasket, and intake gasket.
After that, new distributor, wires and plugs were changed. Car ran ok, but only when warm. It idle very rough or would die in cold temperatures.

I never touched anything else and learned to live with the problem. Plus it was ok in summer, only problems in winter while the car warmed up. Last summer the car started to idle high and high and higher when warm. It was so high that sometimes when I turned off it would run for a while (dieseling).

Still did not touch the engine or adjusted anything. The car ran amazingly in the highway still… It would consume less than a ¼ gallon in between oil changes, give me 30 mpg consistently plus did not require any other liquid to be added constantly.

Two weeks ago one cold night I went to buy a couple of things and went I turned of the car it keep running for about 10-15 seconds (dieseling). Because it had done that in the past I did not care much. However that same day later I noticed that the car is now idling less than before but it developed a very rough idle almost like there is no spark plug in one cylinder.

The history does not end there. At the same time car seems to be running smoothly at high rpms. To the point that you can hear the tires when before you could not. It hauls hard… merging in highway traffic is not a problem and the higher the rpms the best seems to run. Heck at 70 I have to take the foot of the pedal.

Now the funny thing is when it is cold now, it idles better than 3 weeks ago (before the dieseling event). There is no rough idle when cold. When it warms up… the idle is very rough, again like a spark plug not present and if I take the foot form the gas pedal it will die. But it runs smooth above 2000 rpms and anything above that it runs like a deer.

I changed the PCV valve yesterday and made a nice improvement in the quieting of the engine. At 2000 rpm in neutral you would swear the engine is off… that quiet!! No joking!!! But take the foot of the gas and it will rough idle for 20 sec and then die.

I am completely confused why the idle would have increased in summer, why would the cold idle be bad for a long time… and now cold idle is good but warm idle very rough. Again without touching or adjusting a single thing.


Open to suggestions or ideas


Thanks in advance.

Fred.

[keruhas184]

Sounds like it's time for a carb rebuild. If you're not in an emission-controlling state, I would remove the smog junk as well. Meanwhile, try putting some Seafoam down the carb, and check if you have any vac leaks..

[A20A1]

The vacuum leak... now possibly fixed from replacing the PCV valve or may still be there from another leak elsewhere... was causing your idle diaphragm to loose vacuum and raise the idle out of control.

The other possibility is the fast idle.

If idle adjustment is made when there is a vacuum leak... then you will always have problems even after fixing the leak.

You could have a choke problem also.

There are many places vacuum can leak from.
- Gaskets; intake manifold and carburetor
- Diaphragms
- O-Rings
- Vacuum lines
- Malfunctionng Thermovalves, or thermovalves that fail to recieve coolant because of a low coolant level or something wrong with the water pump or thermostat.

You might want to check your fuel filters and clean out the carb.

Here are a few important threads to look at
https://www.3geez.com/forum/showthread.php?t=46572
https://www.3geez.com/forum/showthread.php?t=5350

[Terremotico]

Keruhas184 and A20A1,

I will do a carb cleaning first. After that I will try the other suggestions.
Thanks for your Input.

Fred.