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Discussion Starter · #1 ·
Im 100% new the forums, so, hello! Ive recently gotten a 1989 and honestly immediately fell in love. Got the duel carbs you know, quick on its feet starts up and runs fine but every once in a while it goes wonky and when i give it throttle it sputters rapidly. I can key it off and coast for like 20 seconds and turn it back on and its good to go. Im absolutely lost, anybody have ideas? Vapor locking from the heat? Plugged fuel filters or gunked carbed? Im going to give it a tune up tomorrow and see how it goes. Any responses are appreciated.
 

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When was the last time it had a tuneup? If you don't know the service history, it's a good idea to run through the usual service tasks. I'd go through that first.

Typically if the carb is gunked the symptoms include it being hard to start and not idling correctly, since the narrower idle and economy jets are the ones that get clogged. You could get this issue if the carbs are very imbalanced, or are configured to so check them with a synchrometer. If you think it's the fuel pump, do a flow test of the fuel pump to make sure it's working right.
 

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Discussion Starter · #3 ·
When was the last time it had a tuneup? If you don't know the service history, it's a good idea to run through the usual service tasks. I'd go through that first.

Typically if the carb is gunked the symptoms include it being hard to start and not idling correctly, since the narrower idle and economy jets are the ones that get clogged. You could get this issue if the carbs are very imbalanced, or are configured to so check them with a synchrometer. If you think it's the fuel pump, do a flow test of the fuel pump to make sure it's working right.
Thanks for the reply! It starts very easily and runs pretty okay, sputters a little between 1.5-2.5k rpm but when i give it some throttle it and it warms up it clears up. I ran some seafoam through it, change the oil, threw some plugs in it, plugged an exhaust leak, and it still did it. Very peculiar occurrence, almost like something sticks, flips, disconnects perhaps, and it'll start sounding like a 2 step battle until i key it off and back on. The coolant level was a little low so i topped it off just incase because i know these carbed ludes can be finicky with that stuff.

I am again a newb, therefore i have to ask, is the fuel pump electric? And where is it located? I'd figure its a single electric pickup pump in the tank but im not sure.

One more question, are the little electric valves in the carbs supposed to tick in synchrony? When i have someone key it on i hear an initial tick and a very delayed tick. I'd assume as with everything on carbs, those could gum up from ethanol gas too. Thanks.
 

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Seafoam does help, but for cleaning gunk in the carb, you have to take it apart, remove the jets, and clean them, if that turns out to be the problem. For a tuneup you'll also want to check the air filter, distributor cap/rotor, spark plug wires, fuel filter.

As you guessed, the fuel pump is electric and it's inside the tank. There's a filter in the engine bay, and one behind the drivers side rear wheel. Fuel pressure should be about 1 - 2 PSI.

I don't know what is making the tick sound in your carb. Maybe you're hearing the choke? Or some CVCC emissions component.
 

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Discussion Starter · #5 ·
Seafoam does help, but for cleaning gunk in the carb, you have to take it apart, remove the jets, and clean them, if that turns out to be the problem. For a tuneup you'll also want to check the air filter, distributor cap/rotor, spark plug wires, fuel filter.

As you guessed, the fuel pump is electric and it's inside the tank. There's a filter in the engine bay, and one behind the drivers side rear wheel. Fuel pressure should be about 1 - 2 PSI.

I don't know what is making the tick sound in your carb. Maybe you're hearing the choke? Or some CVCC emissions component.
Oh the tick might be some cvcc stuff, good call. Boy i heard taking these carbs off is a paaaain though. The only other thing i can really think of besides either the chokes falling closed or the fuel pump going out is may e theres a chunk of gunk getting sucked into the entrance of a passage/fuel line/jet when the fuel flows.

Im going to check the fuel filters, blow the air filter out, and next time this occurs im going to take the airbox off and spray some carb cleaner into the carbs to tell me for sure whether its going lean or rich. Thank you for your patience, stub!
 

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Discussion Starter · #6 ·
Update: one of the grounds on the negative battery post connector was loose so i retightened it, the pcv hose was loose so i repositioned it and tightened it securely, and got a full tank of no-ethanol gas in it and after driving around 30 miles it never once tried to have a 2 step battle with me. Not sure which of those did it but i am extremely glad its fixed. It now runs pretty good, gunna throw brand new fuel and air filters on it, change the oil to a 10w instead of a 5w again(mostly as a washing procedure, it was on oooooold oil when i got it) and start my "experiments".

Thank you again Stub for your time and ideas.
 

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Discussion Starter · #8 ·
Bad news. The problem has started again. Its less frequent with a full tank, but in high load situations,(shifting above 4k rpm, fifth gear over 70mph, going uphill) it starts. I noticed a fuel leak infront of the rear drivers side wheel and took the fuel filter out and blew it out with carb cleaner. It seems to be leaking where the rubber line from the fuel filter meets the steel line, but i couldnt get it off because i wasnt using a jack stand and didnt want to get squashed by a 350 dollar shitbox.

I noticed since then the leak has subsided at a stand still but i have a feeling what night be happening is that the leak springs when the fuel pressure picks up from high load situations, in which of course im not able to peak my head out the door and look lol.
 

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I could see that happening if the leak is substantial. Obviously replace the bad hose. After driving the car, sniff around the carb because there might be fuel leaks there as well. (I had to replace several cracked fuel lines and vacuum lines on my carb that were leaking fuel.)
 

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Discussion Starter · #10 ·
I could see that happening if the leak is substantial. Obviously replace the bad hose. After driving the car, sniff around the carb because there might be fuel leaks there as well. (I had to replace several cracked fuel lines and vacuum lines on my carb that were leaking fuel.)
Yeah I'll give the carbs a sniff. Where exactly is the front fuel filter? I still havent found it. Thanks.
 

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Discussion Starter · #13 ·
Update. I fixed the fuel leak, cleaned out the front fuel filter, and figured out that the airbox cap would fall loose. I fixed that, still does the weird noise.i have absolutely no clue in hell anymore. Only things i can think to do now are replace the air filter(it is pretty dirty, and the gasket isnt connected anymore) and check fuel pressure. I know the factory fuel pressure spec is quite low, even for carbs, 1-2 psi so there is like no room for error there. Since im going to be running boost im going to need more pressure anyway so i might as well throw a new pump in. Luckily it looks like there are access ports to the fuel pump in the diagram.
 

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Discussion Starter · #14 · (Edited)
Update, i guess. This thread is basically dead, but i pulled the fuel line off and ran the carbs straight from a mtn dew bottle filled with carb cleaner. After i knew i got good full bowls of carb clean i threw the line back on and went for a drive and by golly if it didnt run perfectly. Idled at 900 on all 4, no breaking up at 1-3k like there was before, and i could shift at 6k without the stuttering occurring.

Changed the oil, runs like dog shit now. Misses and sputters horrendously until 3k then it takes off like a rocket until 5k then it starts to do the 2 step battle with itself. This is the most temperamental little car ive ever dealt with. The chokes are really sticky i have noticed so im soaking them with pbblaster and working them. Oh yeah it also takes 5-10 seconds of cranking and hammering the pedal to start now and it dies at idle until its been running for 20 or 30 seconds. However, new air filter, chinese clicky clack pump, boost referenced FPR, and a carb rebuild kit are on their way!
 

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I wonder if something keeps clogging the carb after you clean it. Check the lines after the filter in the engine bay, because if the steel line is rusted or the rubber line is rotted, that would cause crap to get in the carb. You already found one leak, I wouldn't be surprised to find more.
 

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Discussion Starter · #16 ·
I wonder if something keeps clogging the carb after you clean it. Check the lines after the filter in the engine bay, because if the steel line is rusted or the rubber line is rotted, that would cause crap to get in the carb. You already found one leak, I wouldn't be surprised to find more.
I'll rip em off and see, there cpuld very well be goo sitting down right where the lines connect to the carb. Weirdly though both the front and rear fuel filter were basically perfectly clean, and there are no(noticable) fuel leaks in the engine bay. After i take the lines off the carbs i'll run the carbs on pure carb cleaner again but this time im going to take the front filter off and run that line into another bottle and see if a bunch of gunk gets pumped out.

Thanks again, stub!
 

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Discussion Starter · #17 ·
Also, what is that smaller open orifice between the 2 carbs? Its fairly large and i dont know if it draws a vacuum or not. Ive heard people say its basically just a third mini carburetor? The online manual doesnt tell me anything about it.
 

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If you take a picture maybe I could tell you, but it's likely something that carries fuel vapor for better emissions/fuel economy. Have you gotten around to tuning and balancing the carbs?
 

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Discussion Starter · #19 ·
If you take a picture maybe I could tell you, but it's likely something that carries fuel vapor for better emissions/fuel economy. Have you gotten around to tuning and balancing the carbs?
If you take a picture maybe I could tell you, but it's likely something that carries fuel vapor for better emissions/fuel economy. Have you gotten around to tuning and balancing the carbs?
I dont know what you mean by "balancing" the carbs, but no i havent gotten around to tuning them. I havent done anything to require tuning them and im trying to put off removing them as long as i can because it looks like a royal pain in the dick.
 

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It's not hard but you'll need a synchrometer and a NDIR CO meter to do it properly. To balance the carbs, run engine to operating temperature, remove the air cleaner and the mesh funnels, measure the air flow with the synchrometer, then turn the adjusting screw until air flow is the same for both carbs. I use the STE Synchrometer type SK.

29525


To properly adjust the mixture screws, you need a NDIR CO meter, but those are expensive so you could fudge it by doing what this fine chap demonstrates in this video:
 
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