I have had 2 different diagnosis from 2 different mechanics for issues of black smoke and high idling with my Honda Civic 93, DB15 engine with twin carby, manual, AC.

I have lost my faith in mechanics and I would like to know opinions on what I should do. Should I fix it myself??? I have already replaced the fan switch, O2 sensor and have had a major service done.

The car blows black smoke, even after a major service. Once warmed up, it would idle at 1800-2100 and the black smoke usually disappears. The black smoke is due to a fuel and air mixture issue which results in my car only getting 300-340klms per full tank, than before where it use to get 480-550klms per full tank. I presume this is due to the high idle and fuel mixture/black smoke issue.

It struggles to stay idle at less than 1600rpm, so when I first start the car in the morning, I would have to drive it around till it gets warmed up otherwise it dies or otherwise, I have to rev the car when at a stop at about 1800rpm for it to remain running.

1st Mechanic diagnosis-
sticky choke
valves need adjusting to fix black smoke

2nd Mechanic
Carby requires overhauling
Choke/Wax pellet not working
Power vale fault(I presume its a mistype and should say valve)
Vacuum leak from carby intake rubbers

I tend to believe the 2nd mechanic since they were recommended by a close friend who has been going to the same mechanic for over 10 years.

Are the faults listed from the 2nd mechanic DIY'able? Would I be better off buying a used twin carby or engine? What are my possible options because I have spent almost 4K on this car on repairs alone and I have only had it for a few years!! Now I have to spend more!!! I could have spent for a later model car at the start if I had known this car would have had so much issues!

Any help, opinions or advice appreciated.

 

Congrats on starting yet another thread about the same problem. If it were my car, I'd look into a MPFI conversion so the car is modern like the rest of the world has. The US '92 to '95 with a D15B7 and MPFI was arguably one of the best economy cars ever made. This will require considerable work, but not much cost if you can find a parts car to strip the intake, ECU, etc. from. It seems that your engine itself is sound; the problem is in the carb system. If you look at the choke shaft (nearest the air cleaner) you can see if the chokes are opening. Force it open if it is not, and see if the black smoke quits. There is usually an actuator on the end that is activated by electricity warming up a thermal coil to open the chokes a short time after a cold start.

 

The engine number sais D15B42.... so I do not think it is a D15B7??

In regards to the choke, the issue is that it remains open causing the idle to remain high or as a mechanic sais, it has a sticky choke?

Is it easy to replace a twin carburator with a used one?

I did notice this though last night, whenever it is cold, like raining, my car remains running on first starts and do not require warming up. Though it still idles high though.

Thanks for your reply.