19 replies to this topic

[ae7f]

Immediately upon starting the engine:
It starts easily and RPMs go up to 2500 where it sits on high idle to warm
up the engine. After several minutes of warm up, high idle turns off and
the RPMS drop. They should then drop down to the specified idle speed and
hold, but instead, when high idle turns off, the engine drops down to 1k
and then below that and the engine dies. It will not hold idle no matter
how many times it's restarted and dies when you let off the gas.

After starting/starting again, but engine still cold:
Good throttle response above 1k. But let off the gas to bring the car
down to idle and the engine kills.

After driving and engine thoroughly warmed up:
Engine will drop down to 1k and hold sometimes. Other times it drops
lower than that, nearly dies, then revs back over 1k and back down to 1k
and struggles to hold idle. Still other times, after driving, the idle
would not drop below 2.5k - like a hanging idle that eventually drops
closer to where it should.

Other odd behavior noticed after driving:
I've experienced some kind of problem that can be described as after a
certain point of steady driving with the accelerator set to hold freeway
speed, the engine starts to miss/sputter. If you keep driving it, it gets
worse. You have to give it more pedal to make the sputtering go away.
But it only goes away for a bit and returns, and you have to press the gas
even more. This repeats until you are full throttle just to hold the same
speed. Let off the gas and the engine immediately dies and will not start
without cranking with the gas pedal fully pressed. Then the car seems to
run fine for a period of time and it will repeat.

More odd behavior after driving:
The way I have been able to drive the car like this is when all of the
sputtering happens during highway driving, I clutch into neutral and coast
while turning off the engine. The engine does not always immediately
stop. In fact, with the key off, coasting down the road, sometimes the
engine will try to run by itself, as if from a lean preignition condition
or something. Sometimes this will happen for a duration of 5 or 10
seconds before the engine stops turning.

I believe all of these problems are related to one or more component
faults. If I find one problem, I start to solve them all.

The manual indicates vacuum leakage for idle problems, engine stalling
problems, rough idle, etc. It specifically mentions in troubleshooting
each one to check the carb gaskets.

I think if there is a gasket leak at the carb base, it will suck in air
behind the metering circuits. This will cause a lean condition. The lean
condition when the engine is cold prevents the car from idling at all for
anything below fast idle. When the engine is warm, idle is rough or still
nonexistant, hit or miss.

When driving at highway speeds in 5th gear the RPMs are at or below 3k and
the gas pedal isn't even pushed that much. The carb circuit in use would
then include the overlapping idle circuit. If the lean condition exists
even at highway speeds, the engine increases temperatures and may sputter
as it needs more power during the lean condition. When trying to stop the
engine it continues to run for a few or more seconds. After it stops,
pressing the gas all the way to the floor and cranking seems to fix the
problem for awhile, possibly because with the gas pedal all the way down,
the carb is filled with rich gas and mixture?

What I have done to try and fix the problem:
Tested the fuel pump
Replaced cap and rotor
Changed air filters - problem happens with K&N or stock
Tested with airbox off and on

This problem has been occuring since probably 2002. It seems to be worse
in cold weather, wet weather, cold and wet weather, and/or when the
vehicle is not fully warmed up prior to driving the vehicle.

Fuel economy right now is 42mpg on a 271k mile engine and engine operating
temp is just a hair over half way on the gauge.

To me, the clues seem to point to fuel issues that are in turn caused by
vacuum leakage, which causes a lean condition, which causes idle problems,
hanging idle, increased engine temp, and engine running for seconds after
the key is turned off.

??

Ben

[xfurb]

Hello all,
Yes- I’m new to board and it’s my first post.
...and I hope this makes sense.

So here goes.
Assuming this is a ’84 DX with pretty much all stock engine. Your cold idle issue is probably caused by Vacuum Thermo Switches- Those pesky things on the intake manifold and crammed next to the firewall. One of them has three hoses attached the others have two. Recently- My ’87 DX with 250,000 wouldn’t Fast idle over 1200 rpm no big deal until it quit cold starting all together. I ended up replacing two of the four, Vacuum Thermo switches. With that replacement I fixed the Vacuum advance- fast idle unloader and feedback system. Felt kind of dumb ‘cause all this stuff was bad and it really didn’t affect drivability to much. Later on I replaced the one of the other Switches and that fixed the Vacuum secondary delay circuit – apparently it delays the secondary during cold engine operation.

Your high speed drivability. Had that exact problem- mine became really apparent on left hand turns at high speed. Never on right turns. Intermittent at high speeds just under 3000 to just under 4000...above 4000 no problems at all. Just weird. I sat down on the garage floor with the air cleaner box off and the top of the carburetor off to expose the fuel bowls. I was drinking a beer, cause I had been plagued with this problem for about 3 to 4 weeks and worked on everyday after work. Tried everything! Fuel pump pressure/volume fuel filters; coil, distributor, rotor, cap, all vacuum lines, In CA model that’s more hose than.... Well that’s a lot of hose. In fact I need psychiatric now... So I turned to Dr. Microbrewery. But I digress... While I was sitting there distraught - I placed my finger on the secondary main jet? (that part that is across the throttle opening) and then moved it to the primary side. One of them moved! I mean it was loose! So loose in fact pulled it out of the carb! And I found a little itty bitty o-ring rock hard stuck to it! Replaced the o-ring with a little bit over sized one; I didn’t even tighten the set screw to the hold the thing in place, and took it for a test drive. Problem GONE like a new car... considering I replaced and cleaned nearly everything- it better! The other reason I didn’t and haven’t as of yet tightened the set screw is because; well you have to remove the whole carb and the choke assembly... I needed a brake.

The carburetor base leak is really apparent during cold starts. The engines starts normally runs for 2-3 seconds dies and restarts sometime hard. But once it warms up no noticeable issues. At least with mine... and the problem was fixed some ten years ago. I don’t really remember the details.

The run-on with thoughts of pre-ignition? You have 270,000+ on the little DX motor- Pretty sure there is a lot of “junk” (technical term) in the combustion camber. I have heard of trickling water into the carburetor at half throttle with the engine hot. I think, the thought is, it will steam the “Junk” off? But I think that will be a moot point if the above fixes work. But I think there is a idle cut relay on the back of the Carb, the name implies what its for!

I thought a long response was in order for a long post.

I hope this helps.
~dan

[Daveed]

Great info Dan!
Was there anything special about the little o-ring you used (e.g. oil resistant)?

[Daveed]

ae7f, Sounds like you are on the right track. Keep us informed as you go along with diagnosing this issue. I have a similar issue but on a much much smaller scale.
PS Did you check your timing? Advanced timing can yield "run on" or dieseling after shutting off the motor.

[xfurb]

Buna-n
Any part store should carry them I think. The hard part was it was so small. I put a little grease on it to hold in place. I'll most likely upgrade to a viton o-ring when I go back in to tighten it up permanently.

~dan

[badpenny]

Could you post a pic of where you found this O-ring that needed replacing and where it came from?

[xfurb]

[quote=badpenny,Dec 21 2005, 05:33 PM]
Could you post a pic of where you found this O-ring that needed replacing and where it came from?

<{POST_SNAPBACK}>

[/quote
Sure- it might be a bit- like this weekend for the pics?

The name of the part is- booster venturi. not main jet -oops.

[DarkHand]

Great first post there, xfurb, welcome aboard.

There's a little o-ring between the throat of the carb and each booster venturi. I don't have one in front of me, but I believe that you can't usually get to them without breaking down the carb unless it's as loose as xfurbs was.

[xfurb]

The ease of removal was a tad bit scary. A set screw holds the Booster Venturi against the o-ring. Keihin apparently thought a little yellow paint stripe would keep the set screw from backing out.

[ae7f]

Yes, nice first post. Thank you all for the help. Hopefully this weekend I will be able to check through the list of things.

I would bet you guys are right on track. I really want to eliminate these problems....

Ben

[ae7f]

Still have not found the problem yet, but still haven't had enough time to look...

Plugs are not rich. They also do not look lean to me. Brownish? I have not yanked them when the car starts to run crappy - will do that.

The engine seems to run a little better with the airbox top removed.

Will update again...

Ben

[ae7f]

  Assuming this is a ’84 DX with pretty much all stock engine.  Your cold idle issue is probably caused by Vacuum Thermo Switches- Those pesky things on the intake manifold and crammed next to the firewall. One of them has three hoses attached the others have two.  Recently-  My ’87 DX with 250,000 wouldn’t Fast idle over 1200 rpm no big deal until it quit cold starting all together.  I ended up replacing two of the four, Vacuum Thermo switches.  With that replacement I fixed the Vacuum advance- fast idle unloader and feedback system.  Felt kind of dumb ‘cause all this stuff was bad and it really didn’t affect drivability to much.  Later on I replaced the one of the other Switches and that fixed the Vacuum secondary delay circuit – apparently it delays the secondary during cold engine operation.
....

I had a bit more time to fiddle this weekend despite the crappy weather.

When the engine started to sputter I pulled a plug and is definitely not rich.

I yanked the air intake pan to inspect underneath. I messed with the idle speed screw to force the engine to run, then I carefully sprayed aerosol around in various locations. I was not able to determine any speed increase by doing so.

On my 84 1.3 carb model, while standing in front of the car with the hood up facing the engine, there is a covered black box forward and to the left. Lots of hoses run to it. I carefully inspected it with the cover off but it all looks good, too. By the way, can someone tell me what the components are that are located in this box?

Second, I checked the covered black box near the driver side fender. It looked brand new inside as well. Can someone tell me what components are inside of this box?

There are hoses feeding the airbox. Two go to separate switches inside the air cleaner housing. The other goes to the valve that opens or closes the intake temperature door.

I don't know anything about the two little airbox switches, how to test them, or if they could be part of the problem. Are these the vacuum thermo switches? I really don't think there is any vacuum on either of those three tubes.

I bought a vacuum pump for testing but am not sure exactly what components I should test.

My manual is very generic on these components. The parts stores look at me funny when I ask for thermo switches and stuff like that.

I would like to understand the flowchart from when the engine is cold started to after it is warm. Example, engine start, automatic choke richens the mixture because it receives a signal from sensor x located at y in the engine compartment. When the engine gets warm enough to idle, sensor xx sends a message to component yy to drop fast idle. From that point, part zz controls warm idle.

Etc.

I just don't think I'm understanding all the details yet.

Thanks,
Ben

[ae7f]

And it is tempting to rebuild or replace the carb, but what good would that do if it is sensors or other components that are bad?

[xfurb]

I don’t really know all the part names. But I opened both boxes before. The one on the firewall controls: EGR functionality ( the larger alloy thing ) The Power valve control solenoid is in there, Cold start relays. The other box on the fender in feed back system related.

Defiantly need pictures. After work I'll head to the garage and snap some pics of the thermo valves and the guts of the black boxes. I'll try to name what I know. My dx is a California Model and a ’87- so they will look a bit different.

When I was dinking in the black boxes I started with one solenoid, attach my vacuum pump to one side draw vacuum with 12volts and without 12 volts. If it did something different I assumed it worked- moved on to the next so on and so fourth. The firewall box has two vacuum switches at the bottom of the box -the vacuum present opens or closes the switch, electrically check the switch- I had a bad one- I replaced the switch for 2 bucks ‘cause Honda wanted 124 for the whole thing!

Frankly I still don’t really know how all the stuff works... It’s a FM to me.

As for the carb. If I remember right a woodland creature tried to commit crx-suicide? You might have a plugged jet/ air passage because of the deceleration trauma thanks to Bambi. Maybe a can of carb cleaner- I wouldn’t buy a rebuild kit unless you have to. If you’re real gentle you can pull the top of the carb and spray out the jets and reuse the top paper/cardboard gasket.

~dan

[Fennec]

Has this problem been solved yet? Sorry to bring up a dead post, but my 83 has been doing the highway sputter thing for a month now...