Thanks for reading my post! Before posting this I read through all the post and found nothing on the site related to this problem:

I have an 89 CRX HF 1.5, stock, that has a "miss" regardless of RPM's until the A/C is activated. When electrical load is applied the miss gets better but does not go away like when the A/C is activated. I've checked the ignition system, timing, compression and sensors and all appears OK. No CEL and no codes.

The "miss" is also accompanied by a distinct "pop" from the tailpipe that also goes away on A/C start. The exhaust smells kinda eggy with the miss.

The "miss" is throughout the RPM range and always ceases when the A/C is activated. Turn on the A/C and the engine runs smooth and quiet with no popping from the exhaust.

On cold startup the idle speed is low, but after about 20 seconds and a little feathering of the throttle it goes to fast idle. The "miss" is still present when engine temp is cold but not as bad as when engine temp is hot. Fuel mileage is low for an HF, about 41mpg or so. Engine bay seems a little warm at op-temp but coolong fan operates properly and engine temp is appropriate.

The EACV has been checked. It's clean but missing the filter screen.

My inclination is to think the EACV is defective?

I was hoping someone has an idea or maybe even seen this before? It's sure got me stumped! I'd appreciate any help you folks may be willing to give.

With appreciation,
Steve

 

I think you might have more than one problem. The eggy exhaust smell is from a bad cat.

did you check all your vacuum hoses?

 

Vacuum lines are good. Eggy smell is slight and I'm thinking the smell is more due to improper mixture into the CAT from this problem?

Thanks for the reply!

 

So this morning I try disconnecting the EACV while the car is running. The miss is still present throughout the RPM range until the A/C is activated. Once the A/C is turned off the miss returns.

The mystery deepens! I've never seen anything like this. Hoping someone has a suggestion? I'm at a loss!

 

Do yourself a favor and just disconnect the downpipe from the catalytic converter and look at it to make sure it's not partially melted/broken.

 

An improper mix most certainly may be causing your egg smell. Over a period of time, the improper mix takes it's toll on the CAT and the CAT starts deteriorating and you get the eggy smell.
If you do the test like "N3va3vaSatisfi3d" suggested and your miss goes away, then you have a bad CAT, -but- you should take a serious look at everything on your engine to make sure that it's running properly. If you do not, and you replace the CAT, then you may run into the same exact problem sooner than you expect as an improper mix will eat up the new CAT.

... or just knock the cat through with a broomstick or something and call it a day until you need to smog the car.

 

have you done a basic tune-up?? filters, plugs, wires, cap, rotor? checked the timing?

 

I know they melt down and thought about putting my eyeballs on it, but a vacuum test seems to indicate it's clear. I just looked at it externally and I see no heat discoloration (under the shield). Exhaust flow seems appropriate. I'd think that since it smooths out with the A/C on if the CAT were bad it would still miss.

The basics have been checked and they're all good.

I know there may be some disagreement about this but I'm starting to wonder if there is a ground problem somewhere. Just seems odd that the problem gets better when an electrical load is applied and goes away as soon as the A/C is switched on. The very moment the switch is turned on the miss disappears and stays away, no matter the RPM's.

This said does anyone have an electrical schematic for the computer control system? I used to have one....until someone broke in to my shop and stole my old Honda FSM's....and a bunch of other stuff. It's a 1989 Honda CRX HF 5-speed 49 state emissions model.

 

The only connection I know of that is associated between your A/C and ECU is one wire to bump idle.

The grounds that would be associated with 'missing' are at the thermostat ground point and then your main grounds from chassis to battery. I would figure that your problem would increase if you added more electrical demands. Sort of like adding another light bulb to an already dim circuit - the bulbs will just get dimmer.

 

Do you know the pin location at the ECU for the idle bump wire?

I figured the miss would increase with load as well, this is why I'm thinking a circuit is "bleeding over". Perhaps internally in the ECU? I will go ahead and re-check the grounds anyways and see.

Do you concur on my suspicions of bleedover? Thanks for your help!

 

Since they came out with fuel injection cars I have never personally seen or heard of an ECU failing like that... not that it's impossible, just highly unlikely.

B2 - Fast Idle Air Control Valve (not the IACV)
B3 - A/C Clutch Relay
B8 - A/C Switch
B19 - ELD

Those are the only ones I am aware of that would have anything to do with the A/C...

 

THANKS for the info been out there checkin looks like the miss returns when the A/C compressor is unhooked, switch "on". Unhook the pressure switch and the miss returns (obviously). It appears the A/C switch turned on (compressor unhooked) has no effect on the miss.

I absolutely agree.....in the past 20 years I've never seen an ECU fail this way either. If this is a first I'm gonna be wiping skid marks outta my shorts!

I'm curious if you may know whether or not the ELD and A/C clutch signal are somehow tied together in the ECU?

Also o2 voltage is 8.5 volts +/- .2 at idle with or without the miss. Momentary WOT and the o2 drops to .48 - .55 or so at its lowest. The condenser fan is inoperative (cooling fan is). All grounds to thermostat hsg., engine and chassis underhood have been cleaned. Exhaust smells rich (burns my nasal passages) with or without the miss.

I was unaware the HF 1.5 had a fast idle air control valve. There is no second hole in the throttle body, lead me to believe mine is not equipped? If mine has one, and it is stuck it would sure explain at least some of what I am seeing here (vac leak = longer injector pulsewidth = ECU adjusting fuel to a little rich and spark plugs slightly carbony...cleaned 'em before diagnosing the ECU). If I am wrong do you know where it is?

I sure miss my old FSM's!

 

Bizzump

 

I am not familiar with the HF to know if it had the fast idle or not... It's the only model I don't know extremely well... The pin outs I gave are across "all" platforms, but your platform may not have that option... I am curious though - you say 8.5 volts, did you mean .85v?

 

Yeah I meant .85

 

I am not sure where else to go with this... I can check my ECU invetory I may have a HF I can sell you for decently cheap... the only other thing maybe would be to check the ignition module, ignition wires, spark plugs, cap/rotor... ect... I hate to say start throwing parts at it, but I am limited sitting here behind this computer screen.

 

Yeah I hear you it's hard to fit a wrench through the modem. I'm going to do some more diagnosing tomorrow and I'll let you know if I need any of them parts. Most parts I have are 90-93 Accord stuffs, no CRX stuffs in the house here.

Thanks for hanging in there and for your help/suggestions. I appreciate it!

 

I tried a coolant temp sensor today still not better. *bizzump*

 

Also tried the injector resistor pack and verified the connections at the ECU are ok.

Thought I'd give this thread one last *bizzump* and see if anyone came up with a brainstorm. Any help appreciated. Thanks.

 

Looks like a solution to this is close, will post it up if diagnosis accurate! If it's what I think it is you all won't believe it!

 

So I thought a solution was close. WRONG! Found a carbon trail in the coil tower and places where burned thru. Replaced coil, distributor cap and rotor and it still misses.

Went to check ignition timing. Ground the service check connector and timing does not go in to bypass.

Come on folks......someone has seen this before. Help me out here I'm getting incredibly frustrated and now lost without any further hope of resolving this issue, and I need to resolve it.....right away. Help me out here people, please!

 

Ck ur icm

 

Sorry, I was vacationing.... Have you tested your Inition Control Module (igniter) like I already asked and the poster above me mentioned?

 

Have not tested it yet. That's in the works 4 tomorrow.

 

Would a bad ICM caus3 th3 tach to jump around? Also r3ad on3 thr3ad in h3r3that th3 3ACV can caus3 th3 tach to jump as w3ll? Would you agr33 with any of this? Thanks for jumping back in and h3lping m3 out! *props*