Hey H-t.
Car: 94 Honda Civic ex coupe.
Motor: 98 b18b1 Gsr tranny
syptoms: Low Idle(300-500 rpm), very lumpy idle(muscle car like), Very Low Gas mileage( use to get 32+ miles per gallon now I'm around 15-20 mpg.

No CEL's

I ran the codes anyway and got a code 8. So I replaced the dizzy cap, dizzy rotor ,spark plugs,wires,timing belt,water pump,battery. All brand new.

Tested the ohms at the tdc wires on the dizzy and got 470 ohms.
Also bought another ECU. And got my valves adjusted. Still no luck.

The CEL's gone now but Cars the same. I'm running out of ideas. And don't wanna just buy things I don't need. Any helpful suggestions would be great.

 

Any smoke out of the exhaust?

How old is the engine?

Also, check for vacuum leaks.

 

Is the car running fairly rich?
Soot accumulating on rear bumper near exhaust pipe?
Lack of takeoff power, but seems normal once car is moving?
If car dies trying to take off is it extremely hard to start back?

If yes to any or all of these, replace the ECT sensor. Should cler right up.
Oh, BTW, it won't throw a CEL for it unless it is just not reading, if its is reading waaaay too cold will richen mixture to compensate for air density.

 

Thanks For The Fast responses.


I have checked for vacuum leaks by ear but i dont hear anything(Will look more Into It) But no smoke out of the exhaust thats really noticeable...I get a little black build up on the tip of my exhaust after about a week of driving. back bumpers black so i dont really notice soot on there if it is. but it does lack power lower rpms. especially from a take off. car hasnt ever died on me though. But The Rpms have dropped to like 100 rpm. after im moving powers there, just not like it used to be.

Engine has 140k. pretty healthy til this point.


Koney: Do You knnow how i can check to make sure its that sensor? I dont want to replace something i dont need to..

 

You'll need a manual to check the resistance on it. I'm not sure how to tell what it's reading without hooking to a scanner, and obd1 isn't all that intuitive. It's like an $8 sensor at part store, or free trial from another car. It is the only two wire plug that is in the head directly beneath the dizzy.

 

could be o2 sensors going poop. cheap fixes that might help include BG 44k fuel additive. its like seafoam only you get better results. its like $15 give or take

 

Okay. My local parts store has ect sensors for $20, so I'll be replcaing mines tomorrow when I get off work. Hopefully that's it.

I was thinking it could be my o2 or a clogged cat?
And I tried Lucas fuel system cleaner recently with no luck. I'll have to see if somebody around me carries 44k.

Again thanx for the suggestions, I'll be back with results.

 

Report back after you do it, I have a similar problem.

I know the other poster said a bad ECT might not trigger a CEL, but I know if it is going bad you will have hard time starting the car.

To properly check for vacuum leaks let the car run, spray some brake cleaner or carb, around the top near hoses, intake etc if you hear a change in idle or it bogs then there is your problem, do not spray too much could be a fire hazard.

 

Funny you say that.it seems like when my car has a hard start(4-5 cranks) it runs worse then when it starts normal(1-2 cranks).

And I'll probably buy some brake cleaner when I buy the ect sensor. But I'll for sure let you know what happens.

 

Well I changed my ECT(engine coolant temperature sensor) a couple mins ago. No luck. Still idles low.

Didn't bother test driving it. Just let it idle while I sprayed car cleaner on all the hoses. Didn't hear any change in the idle so I'm pretty sure there's no leaks.

I also disconnected my 02 sensor. Didn't change anything just got a CEL.

Disconnected my IACV. Idle dropped to around 100rpm but car stayed on so that's not it.

I'm running out of ideas. I don't think the motors done cause it runs great after I take off and the compression numbers are all around 190-200.

 

Just to make sure the ECT is the plug that has 2 terminals (when you look inside the sensor) right under the dizzy, not the single wire sensor.

When you changed it did a lot of coolant come out of the block?

 

I would have the pressure tested on the exhaust. Sounds like your cat converter may be the culprit. If you know of a place that you can trust to get the pressure tested without them trying to sell you a new one whether or not you need one, that would be something to do. If you want to just bite the bullet and try it, online is the cheapest, you can find it for about $100.

I believe they go bad from burning too rich (excessive heat and un-burned gas). That can be from a number of things (O2 sensors, ECT, bad computer, bad injectors, or something else). You may have fixed the rich issue with replacing the ECT, but that CAT may still be bad. I know when they go bad, sometimes they operate really hot, maybe you can check it with an IR thermometer (Don't touch it!!), but I don't know the normal operating temp. I've heard of someone driving at night, then looking under the car and seeing the CAT just red hot, but that may not be your case.

 

Man if it got red hot seems it wasn't traveling thru at all. lol which would be real bad on your motor and gaskets..

 

Yea I know for a fact I changed the ect. And yes coolant poured out til I plugged it with the new sensor.

I'm thinking it's my cat also. It's almost the only thing left & it's the one that came with my car years ago. That'll be my next mod if no other good suggestions come up.

Thanx again guys.

 

Bump.

 

any update on this im curious. have a similar problem

 

Update: I changed out my catalytic converter the other day with one a friend had laying around. Car feels wayyy better. No lumpy idle but it's still around 600-700rpm. Motor feels Very responsive and has power now but I'm gonna get a brand new OEM cat & fuel filter in a week or so to see if that cures the low idle...