EthanJM

98 civic dx here, no egr system on this one from what I read already.

So, I tried to break the title down as much as I could, but this is what is happening.

If I start the car cold, it runs perfectly, you can let the car idle down all the way, and if you want you can floor the throttle and it does what it is suppose to do without bogging or anything, runs perfectly. It will also continue to run perfectly, you can drive it an hour on the highway, get things hot, everything is still fine. If you shut the car off and turn it right back on after being warmed up, it is still fine. But if you shut the car off after being warmed up, then let it cool for 10 minutes or so, then start it back up, that is when this problem occurs. The only way for it to stop is to let the car cool for several hours.

It can get pretty difficult to accelerate to varying degrees, sometimes it feels like it wants to bog down a little, sometimes it wants to bog down a lot, and sometimes it gets so bad it is difficult to get it going without stalling. It idles a little rough when this is happening, and when you accelerate through the low range rpms engine bogs like it is misfiring, get the rpms up to medium and high ranges and it runs as it should. Can't give you exact rpms as my car has no tachometer.
The symptoms could be many things, except for that one, the fact that it does it under the very specific circumstance after being started back up warm after allowing to cool for a short time is what I felt would be a clue that one of you could use to help diagnose the problem for me.
It doesn't seem to be setting off the check engine light, I reset the light because it has been on for thousands of miles, I reset the light and so far it has not come back on. To my understand this car has no cold start valve. Is there a sensor it could be?
Lastly, I just changed the fuel filter, made no difference. Thanks in advance for any help.

ezone

I'm interested in hearing about time.

How long after the warm start does it take before it starts acting up?
How long does it last once it does act up?

Do you go to pull away from your parking spot and the car goes...maybe 15 feet, then just falls on its face and bogs for several seconds (feels like forever, right?), then will drive away just fine like nothing ever happened?
What code(s) did it have?

EthanJM

I'd say a five minute drive is enough to to get it to do this, maybe a little more. A drive to the nearest grocery store can do it on a hot day it seems, but it is fine until you get back out of the store and start it up in the parking lot. That is how I found the connection, I was thinking back and realized it always happens in the parking lots, the drive to the parking lot is fine, even on really long drives, it's when you let the car sit for a short period of time and start it back up that it acts up. If you give it a few hours to cool down enough, it will start back up perfectly and drive perfectly. I'm only going by memory, but I cannot think of a time where it did it after a good start up and while I was driving it after the good startup. Only after warm startups.

The car will bog before setting off at all, you can do it in neutral or in gear, it does it in the low rpms. Feathering the gas as lightly as you can until the rpms are a little higher helps.

Not sure what codes it had, it was kicking on after every fifty to several hundred miles ever since I've had it for some reason, everything seemed perfect so I never investigated. I drove it for thousands of miles like this without issue. I reset it because I was hoping to see if that would trigger some sort of temporary fix by resetting it. I'm sure the codes will come back, they always do.

I think at one point I was able to make it stop by running it a little hard for a few minutes, but that was the exception, normally the only way to get it to stop is to let it cool down. I'm stumped.

ezone

So...once it starts running badly, how long does THAT last before it runs ok again? 5-10 seconds? 5 minutes?

How many miles on the car?


I can guess at a couple items, but I'd rather have more data like a real and valid fault code or the ability to watch live data from the computer.

Disconnect the primary (front/upper) O2 sensor and repeat your drive cycle (warmup, drive, park, wait then restart), see if the problem no longer happens.
CEL would come on of course because a sensor is disconnected, but this is only a test and you will have caused this code.

EthanJM

It seems to just continue to run badly in the low rpms as long as you drive it after it starts doing it, it will only stop after you let it cool down for several hours. I left it idling for a couple hours one day and it didn't stop, the idling won't really sound too bad, but I hit the throttle a little bit and it just stalled completely. Shut it off, let it cool for several hours, and started it back up with no issues.
I'll try disconnecting the o2 sensor today.

ezone

Dang......that's not what I was hoping to hear.

EthanJM

What is it something serious like the pump or something?

Anyway, I disconnected the top o2 sensor, never would have thought a plastic clip could give me that much trouble. Warming the car up now. And yes, it did throw the code.

ezone

No clue as of yet.

EthanJM

It's 10:10 now, I'm going to let it run until 10:25, get it nice and warm, shut if off and let it cool until 10:45 before starting it back up, then I'll have the results of this test. For now it is running perfectly, even with the o2 sensor disconnected, no bogging or hesitation at all.

EthanJM

Alright, just got done driving it around, got back at 10:25, noticed before I shut it off that it is idling funny, but no bogging or hesitation, I imagine that is the o2 sensor being disconnected. Will see how it does at 10:45.

EthanJM

Alright, it is bogging and hesitating again on startup. Does that rule out the o2 sensor?

ezone

Problem persists? Pretty much rules that particular sensor out at this point.

EthanJM

Alright, what about the bottom one? Think I should try disconnecting it then?

EthanJM

I disconnected the lower o2 sensor, made no difference, even after resetting the codes. Now of course it never got the full test, (cold start, warm up, shut off, cool down for 20 minutes, start back up). I will have to let the car cool for several hours for that test, not sure if it is necessary. Seems like the o2 sensors can be ruled out.

Could this be an alternator thing by any chance? I'm just now hearing something, a low pitched whine coming from the alternator area. The alternator is pretty new. Not sure if a faulty alternator could cause this exact symptoms though.

Oh, the car has 175,000 miles.

EthanJM

When the car is off my battery is reading 12.5 volts, when it is on I get 14.5 volts. Doesn't that rule out the alternator?

It's probably going to be a waste of money and time, but I'm going to put some fuel injector cleaner in.

EDIT
I just read about the cold temperature sensor. I'm going to try that first before wasting money on fuel injector cleaner. Going to make some calls and see if anyone near me has one in stock.

ezone

no

doubt it

ECT, coolant temp sensor (the one for the computer, NOT the gauge) was my next step, but I use a good scanner to read the temp as 'seen' by the computer and check that against a real temp reading from a thermometer of infrared temp gun. (There is a lot more live operating data I look at too.)

I can't just fire the parts cannon at a problem and hope something sticks.

/obligatory parts cannon:

EthanJM

Damn, well I bought a new ECT sensor, it wasn't that. It's throwing no codes. It was the actual sensor though, so you think this is computer related? I'm looking it up and there is a bottom sensor, do you mean this one?
Don't know what to do. Fuel injector cleaner would be a waste of money wouldn't it? Besides, fuel injectors would act up regardless of the temperature wouldn't they? Same with vacuum leaks right?
Thanks for racking your brain with me.

EthanJM

Wait a second, so there are two of them? One is located in the front and comes off with a 19mm, and the one in the back comes off with a 24mm. I did the 19mm one located in the front. Was it the 24mm I should have done?

ezone

6th gen has 3 coolant temp sensors.

One for the gauge, one for the computer, one for the radiator fan.

EthanJM

So I either did the radiator fan sensor or the computer sensor. I found a video of the one I did. It's the one located in the front, taken off with a 19mm deep well socket.
EDIT
Looks like I did the correct one. Damn, was actually hoping I got it wrong so I could fix this issue.
http://www.1aauto.com/1998-honda-civ...-c/1998-375-97

ezone

The gauge uses a one wire sensor.
The computer uses a two wire sensor.
Both of these are on the end of the cylinder head.

The fan temp switch is on the thermostat housing.

EthanJM

Right.
Well I did the correct one. I'm stumped. It seems like it would be easier to pinpoint considering it only acts up on warm starts.
When this all started I thought it was water in the tank, I put some heet in and filled it back up, I swear it didn't do it again for a few days. But it could be that the problem was just coming and going at that time, intermittent. It's gotten worse and more predictable now.

EthanJM

Something of a development. I checked the spark plugs, one was dirtier than the others, not gunked up by any means, just had a noticeable more carbon on it than the others. I brushed it off, then hit it with a torch for a couple seconds. I started the car back up, it was still doing the usual bogging and hesitating, I went ahead and revved it a few times, kind of hard but not to where I hit the limiter or anything crazy like that, the bogging seemed a little better, revved it a few more times, and now the bogging seems gone, if it's there it's not very noticeable. I'm going to let the car get nice and warm again, shut it off for 20 minutes, then see if it acts up again after that.

EthanJM

Nope, problem persists.

ezone

Is it losing coolant? Head gasket leakage letting coolant get a spark plug wet?


Check fuel pressure, see what it is while it's running good, AND what is it during a poor running event?


Injector being turned on wide open at times?

EthanJM

Not losing coolant. The dirtiest spark plug didn't appear wet.

I'll have to rent the tool and check fuel pressure sometime later, cannot do it today.

ezone

Could you be dealing with a single-cylinder misfire?

EthanJM

Is there anything that would cause that on warm starts specifically? I tried disconnecting one spark plug wire at a time, I figured if one cylinder was misfiring, the car would run noticeably different on two good and one bad cylinder compared to three good ones, across all four I didn't notice a difference, maybe someone who is better for listening for problems would notice a difference though. But yes, I'd say the bogging and hesitation is a misfire of some kind, not sure if it is one cylinder or all four, not throwing any codes, hopefully it will throw some on the highway today.
I have to do a couple hours driving today, just for the hell of it (because I'm running out of ideas) I put a bottle of techron fuel system cleaner in there, never used it, but I was reading that it does a decent job for the injectors. It's a long shot, probably wasted 10 bucks, but maybe it will do it for me. Some others were commenting that their car was having similar symptoms and this cleaner fixed it for them.
I appreciate all the help so far trying to help diagnose with me. I'll keep in touch.

EthanJM

Don't want to give my hopes up, but I just went to an appointment, and it seems to be doing better. I filled up the tank, would there be any reason a tank that is not full would act up?

ezone

If you disconnected one at a time and each one made a noticeable difference in the way it ran (and all roughly equal) , then all 4 cylinders were (at least) contributing at the the time you did the check.


Techron is one of the better products that can actually be beneficial (not snake oil like so many others), it was a serious help on lots of older European cars that had big problems with carbon buildup on the back of the intake valves that would cause running problems. Regular use in low doses was best for long term benefits on those cars. Read the bottle though, they used to say something about limiting how much of the stuff you could use between oil changes (at least on the big bottles it used to give a limit).
I think all of the Chevron fuels has Techron in it, if you have Chevron gas stations in your area.

These days regular use of Top Tier Gas is probably the best thing you can do without using extra additives. Read all about why and where here: http://www.toptiergas.com/
(Chevron is on the list too)

No-fault-code running problems are so much fun (for me, not for anyone else).