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View Full Version : No high idle after carb swap (still)



sona1111
09-17-2017, 07:39 PM
Hello again. Let me know if this should be moved to carb tech only or if its fine being in this forum.

Went in for another project this weekend which basically ended up the same as it started. Backstory: Bought 89 accord LX auto for cheap with bad engine (low compression) About a year ago I swapped a new engine in it from an 88 model, which fixed the compression issues. I was not as familiar with the car back then so I was not exactly sure what I was looking at in terms of components sometimes. I will explain this because it might be relevant. On the new engine, (which came with the carb and all the metal plumbing and crap in the middle) the TV cable piece on the carb was missing (it only has the one slot for the throttle cable), so I ground off the mount for it from the old carb/engine and fit it to the new carb. Also, after matching all the vacuum lines up, everything fits except there was one extra line coming from a small box near the black box on the passenger side labeled '20' which there was no receiver for on the new engine. I guess this function was missing from the 88 model ; This line was just plugged. This has been running questionably for the past year or so. By this I mean that I don't think almost any of the vacuum controlled devices work (most vacuum lines were replaces, but the devices themselves look fairly rusty) - there was never a high idle, car had to be revved manually when cold to stay alive ; there was no increase in idle when put in gear, to neutral idle had to be set excessively high ; I doubt that the secondary worked at all, etc.

To take a first stab at this I decided to buy I reman carb online. It was for the A/T model and matched up completely to mine, minus the rust. I just got around to swapping it out today. It does not seem like much has changed, except there seems to be a smoother idle in general. The cold idle is low but it no longer dies if you do not rev it. Using the idle stop screw or the idle speed adjust screw I can not seem to lower the idle past the 1.2k or so mark. I have three goals that I would like to accomplish on this car: get fast idle to work, and get the idle to raise while in gear, and stop it from dieseling.

-For fast idle, I am baffled so far. I just recently tested with everything together and this is what happens: pump gas to floor twice and turn the key. Car starts pretty easily and sits at about 1.3k RPM. It does this speed pretty much forever. pressing the gas has no effect (idle just raises and lowers to the same spot). I tried the procedure in the shop manual for testing fast idle. It says to get the car to operating temp, then disconnect and plug the 'inner' (which I assumed to be the one closer to the center of the carb) vacuum line from the fast idle unloader. Next it says to hold the choke closed and fully open the throttle, then start the car. When I did this, yes indeed, I get fast idle in the nice 2.7k range. Now while the car was still running, I took out the vac plug and reconnected the hose to the unloader. Idle did not drop. Tried blipping gas pedal, still did not drop. Turned off car and it dieseled some, fully pressed in gas once and restarted, and now idle is back to low speed. I can not figure out what is supposed to trigger it or turn it off or what, but definitely neither the engaging or disengaging of fast idle is really working right, and the cam and unloader are now 'new' so I hesitate to blame it on them...

-For the in gear idle raise, it looks like it is supposed to work off of the 'AC idle boost' diaphram. This is on the driver side next to the carb, with two vacuum lines going to it. One from the AC solenoid and one from presumably wherever the thing is which tells it the transmission is in gear. The new carb unfortunately did not come with this diaphram. All I know is that I have it disconnected from the arm on the carb now (both vacuum lines still connected) and when I put the transmission in gear, the stick does not move at all. I am not sure if it is this diaphram itself or whatever is on the other end of the vacuum line for the transmission. The diaphram does look to be in fairly bad shape from the outside though. How can I test if it is getting the correct vacuum? How can I get a new or rebuilt one, or a rebuilt kit for it? If it is not getting the right vacuum to operate, where does the vacuum source originate? Is it electrical or somehow directly connected to the transmission itself?

-For dieseling, I am not sure how to go about fixing it. Not every time, but most of the time when turned off the engine will continue to clunk around for a while. It can be killed more quickly with a loud bang if put into gear....

Yeah, this is just kind of a plea for help post I guess, maybe I went off track slightly, but I was a little tired writing it. Maybe I can edit it a bit tomorrow, sorry for any confusion!

slithica
05-05-2018, 01:39 AM
I know this is old but whatever.
Sorry, I don't have a solution, just adding my experience with this.

Dieseling is probably that your car is running hot. Because once you turn the key off there should be no spark. Check your cooling system?

As for the idle speed mine is stock carb that seems to work properly and the idle rpm is about the same as yours. I've driven the car for a few years and when I bought it the carb would go down lower, but now it stays around 1100 or so rpm all the time.

It's an odd condition, mine doesn't diesel or have any other issues. Just a slightly high rpm. All my hoses and everything are good and it's generally in good shape. I think it may be something to do with the idle screw, or the air intake. I never really checked into it to be honest because it isn't really an issue for me.

gcovarrubias412
05-05-2018, 07:34 AM
I know this is old but whatever.
Sorry, I don't have a solution, just adding my experience with this.

Dieseling is probably that your car is running hot. Because once you turn the key off there should be no spark. Check your cooling system?

As for the idle speed mine is stock carb that seems to work properly and the idle rpm is about the same as yours. I've driven the car for a few years and when I bought it the carb would go down lower, but now it stays around 1100 or so rpm all the time.

It's an odd condition, mine doesn't diesel or have any other issues. Just a slightly high rpm. All my hoses and everything are good and it's generally in good shape. I think it may be something to do with the idle screw, or the air intake. I never really checked into it to be honest because it isn't really an issue for me.

Mine diesels a bit too but not often. Maybe its running a bit rich and slightly hotter than usual. Or maybe the ignition timing is off.

You should try fixing your high-ish idle. It’ll improve your mpgs alot once its taken care of.

Dr_Snooz
05-05-2018, 07:21 PM
Dieseling is almost always caused by two things:

1.) An idle speed turned up too high
2.) I forgot. Sorry. There is a solenoid on these carbs specifically designed to prevent dieseling. It's called the fuel cutoff solenoid, I think. Check that it's working properly.

gcovarrubias412
05-05-2018, 09:32 PM
Dieseling is almost always caused by two things:

1.) An idle speed turned up too high
2.) I forgot. Sorry. There is a solenoid on these carbs specifically designed to prevent dieseling. It's called the fuel cutoff solenoid, I think. Check that it's working properly.

I got a weber, so no solenoid on mine

slithica
05-06-2018, 10:05 AM
Maybe its running a bit rich and slightly hotter than usual. Or maybe the ignition timing is off.

You should try fixing your high-ish idle. It’ll improve your mpgs alot once its taken care of.

I know mine isn't running rich or hot, I've checked. My ignition timing is advanced so that's likely the cause of mine. I'll see how it performs if I back it off a little. It's not pinging or anything so it's not dangerous. However I drive highway often and having my idle at 1100 instead of 800 isn't having any real effect on my mpg. I rarely idle at all.

In the big city it made a 2 mpg difference from me sitting in traffic.

gcovarrubias412
05-07-2018, 08:03 AM
I know mine isn't running rich or hot, I've checked. My ignition timing is advanced so that's likely the cause of mine. I'll see how it performs if I back it off a little. It's not pinging or anything so it's not dangerous. However I drive highway often and having my idle at 1100 instead of 800 isn't having any real effect on my mpg. I rarely idle at all.

In the big city it made a 2 mpg difference from me sitting in traffic.

Yea i think if you retard your timing a bit it’ll go back down to 800. I was thinking of advancing mine a bit, but i dont see a point if its running fine