No idle and missfire when cold - carb setup

[chrisellis211]

Hi people

Bought a new project now which has a few problems, most of which i can fix but one i have no idea about.

It's my first car with carbs other than an EN1, it's a d15b duel carb setup on a d15b in an ef2 anyway, i've spent 3 days going through the search with no luck to my particular problem.

Basically when cold first thing in the morning it will not idle at all so you have to hold it on the throttle, if you hold the revs upto around 2000rpm it will sound like it's miss firing slightly as well, my first thought is that it's running to rich. If i take it for a run and carry on for a few mins and let it warm up then it will idle perfect and not cause a problem for the rest of the day.

I've heard of choke plates being mentioned in a few topics i have read through but i have no idea where or what there are, but still i can't see why it would run so bad if a setting on the carbs had untuned themselves slightly so i'm guessing there is a component failure along the line.

I have checked all my vaccum hoses and they appear to all be in good condition so is there anything else i can check? Could it be caused by a vacuum unit or something or is there anyway i can check any of the componets which may be causing the problem?

Sorry for the long post and thankyou in advance to anyone who can help!

added a pic if anyone wants to give referance to any sensors etc

[NAspirated]

whats the exhaust emissions look like when you start it up cold...


you need a Tune. Honds Kei-Hin's are Shit.

Because they run an Auto Choke, the solenoid could be sticking, or it could be "Out" (of alignment)

your Needle Valve could be jammed open (bent Float), causing the carbs to flood, which means if you turned it off as it was idling it would be hard to start again, or it would backfire through the carbs.

remove your air filter, check its condition. start the car without it if its shit. check/replace the fuel filter, remove and clean the float bowls. Carbs dont like dirt/grit/water in the fuel just the same as injected cars.

shouldnt be a Vac problem, 99% of carb Vac issues will cause a High Idle, or a lumpy idle.

If its misfiring, check your engine timing first. make sure your plugs are firing when the should be, then look at the fuel delivery.

[chrisellis211]

Hey what an awsome reply so thanks for that!

Firstly Where abouts is the solenoid located??

When cold it's backfiring quite badly through the carbs for sure, i'm 99% sure it's a to much fuel problem, it's feels underpowered when cold under acceleration and you can hear it back firing in the carbs

i have removed the airfilter as ye it was horrible, i'm gonna check out what you said with the float bowls now and take them apart, i'll post pictures up in a bit

[AccordB20A]

all carb issues i have had in hondas mostly come down to a soleniod not having power.

[chrisellis211]

Is this down to the solenoid itself or a faulty wire normally?? Got the float bowls out as we speak and they have carbon build up on one side so gonna post some pics up soonas give them all a clean

[chrisellis211]

update - float bowls are out and have been cleaned, few pics of them once i removed them :









All look normal on these?

Cheers poeple for the help so far!

[chrisellis211]

Just taken it for a run, still seemed a bit off when I first started it but hard to tell now until i start it tommrrow morning, can anyone direct me in the right direction of the solenoid? Is there anyways to test it for resistance/voltage etc?

Is it the unit on top of the manifold with the 2 hoses going in and out and the white plug with a blue, and blue and yellow wire?

[Ped Rac3r]

It will most likely be a choke problem, open the choke on start up a little to see whether it is or not.

The choke is not controlled by a solenoid, but by water (from the engine) flowing through the automatic choke mechanism, and as the water gets hotter the more the choke opens. The choke mechanism is on the right of the carbs looking down on them. If you can get a pic of it, I can point it out. I cant find a good picture of it on the net.

The pics you posted are not the float bowls, but the secondary valves. They open at a certain RPM (3500) and allow the engine to rev out further. The float bowls are underneath the carb.

[b18c1]

hehe i know a few half decent mods for thoes carbs,

[chrisellis211]

Ok cheers, my knowledge on carbs is limited so it's a good learning curve for sure!

I've found plenty of mods so far but i want to get them running right and then go from there. Whats the device with white plug and 2 hoses? Is it worth changing this with a spare?

I had a look at the choke mechanism at the weekend and couldn't see anything wrong, everything seemed to be moving but i may be looking at the wrong bits or may be looking for the wrong issue entirely, anyone fancy earning some beer money at the weekend?? :p

I'll try get some pics tommrrow then of that area and post some pics up, can't remember if i said or not but it's miss firing on number four at first when cold as well, still haven't got my tools from the UK so gonna borrow a multimeter tommrrow and check the resistance in the HT leads.

Cheers guys

[Ped Rac3r]

It might just be that one of the adjusting screws have slowly vibrated itself out of spec over time. Mine used to idling like a rotary and puff out black smoke on cold start up for the first 30secs, then I opened up the choke plates a little and it stopped.


Theres a huge thread on D-series.org, under engine building about D-series carbs, lots of little mods you can do. Its a good read, you should check it out.

Heres my dual carb SOHC ZC,



I ditched the airbox and added some filters on the end of each carb, helped quite a bit and sounds pretty cool too (You'll see my post about it in the D-series carb thread).

[chrisellis211]

haha ye had a long read through the carb thread the other night, i've got massive build up threads on there from when i did my mini-me, i read about the choke plates but couldn't find a thread on adjusting and setting them up.

You sympton sounds the same as mine for sure! How do you adjust the choke plates though? would it be those 2 little white screws on top of the carb?

Chris

[AccordB20A]

thats one thing honda got right, if they are going to use a carb, go sidedraught. those useless 1980's downdraught carbs are fucking useless

[chrisellis211]

Ok solved for those interested!

Turned out to be 3 problems in one..

1st - crack in distributor cap causing missfire when cold with the moisture in the cap
2nd - Partially blocked cat, causing it hard to sustain revs when cruising and low rpm
3rd - choke operation failure where the 2 water lines go through, the piston that pushes down on the throttle linkage had seized causing the no idle at all issue when cold

Thankyou to everyone who pm'd and messaged back in the topic, just need to adjust it all now for rpm.