damian517

New to the forum and only have basic auto knowledge. Purchased a 1986 Honda Civic with JDM replacement engine (carbed, 5 spd manual). Don't know much else about the engine or where the #would be. Purchased from 1 owner who had engine replaced but it would die after warming so owner parked it...sat for 4 years. Bought it and my mechanic got it running with new ignition module and alternator (surging). Now it runs but 2 problems exist.
1. Starts fine and initially idles just under 2k rpm (on tach). As soon as I move or pump the accelerator it goes to 3k and sometimes surpasses 4k. Sometimes norms after 20min of driving. Mechanic thought it may be auto choke. Some forums list paper gasket that deforms and restricts it but a few say no way the choke will cause that high of rpm...thoughts?
2. Drives OK on flats / downhill but jerks badly when going uphill (primarily in 3,4, or 5th). I have to really baby the throttle to keep it going but pushing in the clutch and letting the rpms calm a bit seems to help briefly. I replaced the fuel filter at the tank and a bottle of sea foam in the gas (yes, i replaced the 4 yr old fuel) but no help. I think there's another fuel filter in front of the firewall which I was planning on replacing next and inspecting fuel line for obstructions.
Any thought appreciated.

letank

Welcome to the asylum,

You could have a vacuum leak, meaning that one of numerous hoses that are connected to the intake manifold -the metal chunk on which the carb is installed- is loose, rotten of simply disconnected.

The hard part is to keep the engine running while spraying some WD40 around the base of the carb and watch for idle speed change, when it changes you have found the source of the leak, or an area that has some issues.

The carb base was known to have some issues...

The brake booster could be leaking, that big hose that goes from the brake booster or power brake unit to the engine part of the intake manifold.

One more important thing.... those engine are a bit fussy, make sure that you have the exact spark plug brand and ref for your engine.... Many years ago, I put the cross referenced spark plug recommend by the local parts store and it ran like... you described... having issue while going uphill.... the 3000 rpm is more likely a vacuum leak.

Good luck

damian517

letank,

Thanks for the great ideas. I will follow-up once I've tried a couple of them to let you know how it went. The spark plug idea is one I've come across before but am unsure how you match up the right spark plug (and gap) when it's a JDM engine? Do I just try to find the engine number somewhere?

It may be a week or so due to my work schedule though. Thanks again.

letank

Try to find out which spark plugs are recommended by JDM for this specific engine.... I remember that some motorbikes were very specific on which brand and type of spark plugs made the engine run better.... being young we did not believe it... but after a few trials.... it worked.