ea82C drivability has me stumped...

[RenaissanceMan]

OK this is for all the good experienced crowd with the dreaded hitachi carb.

 

Car: 1986 3door coupe ea82 Carbed, california emission, 5sp d/r 4x4. Only significant mods is that I moved the battery to the back, and the flywheel MAY have come from a different year.

 

Condition: Resealed motor, new valve job, new timing belts, new cap/rotor/plugs/wires/waterpump, rebuilt carb, etc etc etc... basically everything is tip top shape and it doesn't leak anything . All this work was done before I ever tried starting it btw...

 

Problem/Symptoms: Poor drivability. smells very RICH at idle(will quickly foul plugs). Idle occasionally changes between 500 up to 1100 rpm, but not rapidly changing. Upon acceleration, it falls on its face and stumbles, but you can force it up to high rpms. Really really gradual acceleration and the stumbling is less pronounced. No power but you can freeway drive it. on WOT acceleration, you can feel it surge.

 

Check Engine Light Codes:

EGR system

Pressure Sensor System (aka "boost" sensor, even though the engine has no "boost")

 

What I have tested:

 

Compression : 140ish on all 4 (my guage usually reads a little low btw)

 

Vacuum: LOW rapidly oscillates around 15 in.hg however if I advance the timing to like 30 deg. BTDC then the vacuum goes to a normal 19 in. and no oscillating

 

EGR Valve

Functions normally, slowly opens when throttle plate slowly opens (though it even does it when its cold, and I though it only started doing that when it warms up) Not clogged, not leaking.

 

Timing Belts:

yes even I doubt myself but I double checked them and they line up accordingly, with the little hole on the sprocket with the top of the timing cover notch with the 3 little marks on the flywheel etc etc etc...

 

Ignition Coil:

Swapped with another coil I had lying around. No change, spark is good. Engine is well grounded btw.

 

Carburetor: Float level is calibrated and float valve is functioning properly. Accelerator pump is functioning properly. Jets are clean and are the correct numbers per application. Choke functions properly. Car seems to run better when the idle mixture screw is closed all the way.

 

Timing:

factory 8 deg. BTDC and it runs like poo (infact barely runs) Advanced to about 16 deg BTDC and it runs OK but still no power. Advanced to 30ish and it has a high idle, but runs a lot better, hesitation almost completely goes away, still not full ea82 power, but better, and I worry about detonation going up hills. (yes I am using the green service connector to set the timing) I checked the timing upon acceleration and the advance mechanism does work as it should.

 

Pressure sensor:

Doesn't create a vacuum leak, so I can rule it out for now, because even with the computer disconnected the car will run mostly "normal"

 

PCV:

I can pinch off the hose that goes to the PCV valve itself and this has NO effect on how the engine behaves. PCV valve wasn't new, but it was cleaned upon reseal of engine. If you removed the hose you can hear it "rattle".

 

Exhaust:

Free flowing, has a flowmaster on it and is Plenty loud to suspect any plugging, plus it reacts different from any experience I have had with plugged exhausts

 

Vacuum lines:

Vacuum diagrams have been rechecked more times than fingers on my hand. (all hoses are new) upon replacing hoses, all the orphices were replaced in their proper locations

 

I think thats all the information I have... My only suspicions I can think of have to do with the tic marks on the flywheel being different if the flywheel perhaps came from a SPFI car?? Never ran into this problem before, but I wont rule it out.

 

Could my fuel return hose be plugged maybe?

 

anyway, this is what I have and any thoughts are MUCH appreciated.

[GeneralDisorder]

OK this is for all the good experienced crowd with the dreaded hitachi carb.

 

Car: 1986 3door coupe ea82 Carbed, california emission, 5sp d/r 4x4. Only significant mods is that I moved the battery to the back, and the flywheel MAY have come from a different year.

 

So do you *need* the feedback system to pass your emissions tests? With the CEL on I would assume you don't.... but I ask anyway.

 

Condition: Resealed motor, new valve job, new timing belts, new cap/rotor/plugs/wires/waterpump, rebuilt carb, etc etc etc... basically everything is tip top shape and it doesn't leak anything . All this work was done before I ever tried starting it btw...

 

When the carb was rebuilt did you remove the throttle shafts? And was there any play in them? I ask because setting the throttle plates in a touchy business and it's best if they are not disturbed.... if you can help it.

 

Problem/Symptoms: Poor drivability. smells very RICH at idle(will quickly foul plugs).

 

The rich idle - is that warm or cold? I'm assuming warm as it would be normal for it to be rich when cold and I suspect you know that. On the feedback carbs there are two ports on the side - low speed and high speed "sensing" ports. The carb receives a metered amount of filtered air into these ports by way of the duty solenoids - they turn on and of at a frequency determined but the ECU. It's a sqaure wave signal and many modern DMM's will actually read duty-cycle so it's not impossible to troubleshoot the system. You may have an issue with a blockage on the low-speed circuit - less air gets you more fuel IIRC although it might be the other way around. At any rate this duty cycle is largely determined by the O2 sensor and the coolant temp sensor.

 

Idle occasionally changes between 500 up to 1100 rpm, but not rapidly changing.

 

That could be related to the low-speed circuit I was talking about above, or it could be worn throttle shafts, sticking linkage, bad throttle cable, etc.

 

Upon acceleration, it falls on its face and stumbles, but you can force it up to high rpms. Really really gradual acceleration and the stumbling is less pronounced. No power but you can freeway drive it. on WOT acceleration, you can feel it surge.

 

Surging is a good indication of a lean condition. Being that you are having a very rich idle and a super lean WOT..... is there a possibility that the electrical connectors for the low speed and high speed duty solenoids were switched at some point? Or the air lines going to/from then were swapped around?

 

Check Engine Light Codes:

EGR system

Pressure Sensor System (aka "boost" sensor, even though the engine has no "boost")

 

The EGR is probably just the solenoid. An easy fix - just replace the solenoid with any 12v solenoid you have around.

 

The manifold pressure sensor ("boost" sensor) is a tough one. I've never actually found one that was *good*. In my experience they have all failed. The cost from the dealer is really astronomical and it probably wouldn't last any better than the original. This little gem was the death nail for my attempts at making the EA82 feedback system function as designed - and the fact that the engine was totally gutless with the feedback hitachi. My only reccomendation is to source an EA81 feedback ECU and wire it in. They didn't use the MAP sensor.

 

Car seems to run better when the idle mixture screw is closed all the way.

 

That would seem to indicate that you might have issues with where the throttle plate is set with the choke pulled off. It should basically die if you cut off the idle circuit fuel supply. But then again it may be getting too much air from the low speed circuit - again I might be backwards on the duty solenoid operatioin. It's either more air or less though (as if you couldn't have figured that out )

 

PCV:

I can pinch off the hose that goes to the PCV valve itself and this has NO effect on how the engine behaves. PCV valve wasn't new, but it was cleaned upon reseal of engine. If you removed the hose you can hear it "rattle".

 

I wouldn't be concerned about it. The PCV won't affect runnability - it will only cause you to foul the oil quicker if it's not functional.

 

Could my fuel return hose be plugged maybe?

 

Wouldn't matter if it was. The EA series fuel pumps only put out about 1.5 to 2 psi - not enough to blow the float needle off the seat. I've run plenty of them with no fuel return line at all - Weber's too. It's not neccesary. In fact it's not even included on 80/81 models where the pump is located in the engine bay. I think it's primary purpose was to insure that the pump would have a good supply of fresh gasoline to cool it under all potential operating conditions.

 

GD

[RenaissanceMan]

So do you *need* the feedback system to pass your emissions tests? With the CEL on I would assume you don't.... but I ask anyway.

 

unfortunately yes, I am trying to get it operating properly so I can pass smog so I can finish the title transfer

 

 

When the carb was rebuilt did you remove the throttle shafts? And was there any play in them? I ask because setting the throttle plates in a touchy business and it's best if they are not disturbed.... if you can help it.

 

Thankfully no.. The throttle shaft play was ok, so I left the whole throttle plate assy alone, other than clean it really well.

 

 

 

The rich idle - is that warm or cold? I'm assuming warm as it would be normal for it to be rich when cold and I suspect you know that. On the feedback carbs there are two ports on the side - low speed and high speed "sensing" ports. The carb receives a metered amount of filtered air into these ports by way of the duty solenoids - they turn on and of at a frequency determined but the ECU. It's a sqaure wave signal and many modern DMM's will actually read duty-cycle so it's not impossible to troubleshoot the system. You may have an issue with a blockage on the low-speed circuit - less air gets you more fuel IIRC although it might be the other way around. At any rate this duty cycle is largely determined by the O2 sensor and the coolant temp sensor.

 

sorry I should have clarified that it is rich all the time, warm or cold, choke open or closed... even when the engine is off idle at persay 2000 to 2500rpm no load, it still smells rather rich

 

I have swapped the duty solenoid connectors with no change btw. Also disconnected them with no change.. Perhaps my little plastic air filter thingy is clogged??

 

 

 

The EGR is probably just the solenoid. An easy fix - just replace the solenoid with any 12v solenoid you have around.

 

I figured as much.. I was wondering however, doesnt the 3 nipple vacuum thermoswitch control what temp the egr functions at?

 

 

My only reccomendation is to source an EA81 feedback ECU and wire it in. They didn't use the MAP sensor.

 

Tempting.. I do have one lying around...

 

 

Thanks for the quick response and speaking my language GD... I'll play around with the duty solenoids some more, see if they are clogged, or the air filter is clogged, or whatever...

[GeneralDisorder]

I have swapped the duty solenoid connectors with no change btw. Also disconnected them with no change.. Perhaps my little plastic air filter thingy is clogged??

 

I would make sure the entire system including the duty solenoids can flow freely. They only work with atmospheric pressure so any blockage or clogged filter can severely restrict their functionality.

 

I figured as much.. I was wondering however, doesnt the 3 nipple vacuum thermoswitch control what temp the egr functions at?

 

I know that's how it works on the non-feedback's, but I think the computer turns the EGR on/off via the aforementioned solenoid on the feedback systems. Thus the code you are getting.

 

Thanks for the quick response and speaking my language GD... I'll play around with the duty solenoids some more, see if they are clogged, or the air filter is clogged, or whatever...

 

No problem - I hate to say it, but it may be cheaper and more reliable to swap out to the SPFI and then register it as an engine swap from an '87 or newer. Being an EA82 already, they wouldn't be able to tell you just swapped the manifold.

 

GD

[RenaissanceMan]

So I investigated the EGR solenoid and discovered it had an open-circuit coil. I gladly took care of that replacing it with another solenoid that I had lying around. It had the extra air filter thing on the back, but I was able to remove that and put a vacuum cap on it, so now everything works like it should as far as the EGR goes.

 

I played around with the duty solenoids... Mini air filter is fine. Hoses flow air etc... I tried removing each of the carb hoses, exposing the air bleeds to atmospheric. If I remove the primary side one, it improves acceleration a TINY bit, but still stumbles. If I remove the secondary side, there seems to be no noticable difference.

 

I'm working on uploading a video to youtube that shows how the engine reacts. I forgot to mention that the gas tank was completely drained and fresh gas was put in it, and the problem was the same both before and after.

[GeneralDisorder]

Actually you don't want to cap that third port on the solenoid - that's the vent port and allows the line from the solenoid to the EGR valve to vent to atmosphere when the solenoid closes - that breaks the vacuum in the line to the EGR and allows it to close if it happened to be open when the solenoid closes.

 

GD

[RenaissanceMan]

Actually you don't want to cap that third port on the solenoid - that's the vent port and allows the line from the solenoid to the EGR valve to vent to atmosphere when the solenoid closes - that breaks the vacuum in the line to the EGR and allows it to close if it happened to be open when the solenoid closes.

 

GD

 

The original OEM one didn't have it vented, thats why I capped it. Looking at the vacuum diagram, it looks like the solenoid doesnt directly control the opening of the EGR, but rather diverts it around an orfice, changing how quickly it opens relative to throttle position. (at least thats what I gathered)

 

HERES A VID OF WHAT MY ENGINE IS DOING..

 

 

I suppose I should note ahead of time that I am not actually out of gas... my sender/guage is wierd... it reads Empty with the light on sometimes, but once you drive it around for a few minutes then all of the sudden it starts working and reads the proper fuel level.

Edited July 27, 2009 by RenaissanceMan

[GeneralDisorder]

Yeah - that sounds like a typical Hitachi stumble

 

Have you sprayed around for vac leaks?

 

Having given it some thought - the feedback system would have nothing to do with an off-idle stumble like that. It's got to be with the carb itself - either there's a vacuum leak and the idle speed/mixture is out of adjustment (it would have to be to run with a vac leak), the accelerator pump isn't strong enough, or the throttle plate isn't sitting on the transition ports correctly.

 

The feedback system is largely for idle and cruise operation - it's not capable of making adjustments fast enough to affect acceleration, and it's not going to be useful for WOT.

 

What does it do when you just *barely* expose the transition port? Just slightly holding the throttle cracked away from the idle stop screw?

 

Will it run with the throttle plate almost completely closed or do you have it "turned up" using the idle speed screw? If so that's indicative of a vacuum leak.

 

GD