98 Civic fluctuating idle problem
 

Civic info:
1998 Honda Civic Ex Coupe 2 door
D16Y8 engine, 1.6L SOHC Vtec 4 Cylinder Automatic

The idle fluctuates a little bit after start, idling as high as 2.5k rpms and as low as it will go, try to die, then rise back up fast by it's self. It will do it 4 times at least, and starts to settle down at a medium where it rests just at or a little below 1k rpms.

Sometimes it will do the same thing, but instead of starting fluidly, it will hesitate it's self in start, jolting/rumbling, sounding just like it does when it idles real low in it's fluctuating idle, then it rises to 2.5k rpms, and about 10 seconds later it will do the fluctuating idle.

It will also power down or "Bog" for a few blocks unless I slam on the gas, which I don't. It used to only do this bogging twice and only 100 feet after driving, then abruptly ending and would not show it's self again. The bogging is a given that will happen no matter what the car does at start.

Sometimes the gears will switch oddly, and all I can relate the sound to is using clutch on manual, revving down a little, like it's not engaging right onto the next gear up like an automatic transmission is supposed to, or at least what I am used to. I am sure the torque converter is fine. I am sure the torque converter solenoids are fine. Why? Because it does not happen when I reset the ecu. It happens after I have turned off the car and started to drive again, just like the other problems were and still are.


Parts replaced so far (within 2 weeks) from first to last:

:violin:

Fuel filter
Battery
Cap and rotor
Fuel pressure regulator
Starter (Duralast)
Alternator (New, Not reman, NAPA)
Power and ground wires (4 gauge, copper, copper connectors, solid connections)
TPS (Throttle position sensor)
Spark plugs (double platinum, laser something)
Spark plug wires (NGK)
IACV (Idle air control valve, from honda)

Others 1 month before:

Head gasket (MLS Gates and resurfaced head)
Radiator, hoses, 172 degree oem thermostat, heat sensor and relay
70/30 coolant mixture. Fan turns on.

Oil is level and new, 10w30. Transmission fluid is level.

Re: 98 Civic fluctuating idle problem
 

i would say its got to do with your egr. try taking it off and cleaning it.

could also be the main relay or ignition coil

Re: 98 Civic fluctuating idle problem
 

There is no EGR on this civic. I hear that EGR's do not come on the D series engines.

I still haven't figured out the problem. It still starts up with a rough idle. It still drives down the road a few blocks with powering down. Hitting the gas seems to make it worse. I see myself only having 2 alternatives: Slam on the gas, or give it a little.

Re: 98 Civic fluctuating idle problem
 

oh yeah. california emmisions d series do though.

well i can tell you if you've already replaced the tps it sounds electrical. ive heard if the main relay is going bad it can do some weird things to the car. its about a $25 part fairly easy to install.

Re: 98 Civic fluctuating idle problem
 

My car is also overheating from it

Re: 98 Civic fluctuating idle problem
 

ah ha.

check your coolant for oil and pull your spark plugs see what they look like.

is there any smoke coming from the engine? exhaust? black or white? give it some gas and see what color the smoke is.

also im pretty damn sure (my 2000 ex and my 99 dx both) u should be using 5w30 not 10w30 oil. also ONLY honda ATF. manual transmissions can use 10w30 but not auto.

Re: 98 Civic fluctuating idle problem
 

The spark plugs are brand new. They look like ordinarily sparking plugs, all of them. Just a gray dusting on them. There is no smoke coming out at all.

Yesterday I replaced the Map sensor, reset ecu (left positive cable off battery over night) and test drove. Today I drove it 3 times. The first 2 times I didn't see any weird down the road bogging. I felt relieved. Twice in a row meaning I took a spin for about 2 miles, came back and had it sit for an hour or so. The third time it showed it's self, but what is good is that it didn't do it for the long length of time that I am used to, doing it from 100 feet after I start driving, to 2 blocks away then being fine. It only did it 1 time, 1 powering down for a few seconds. That is a bummer, but also a relief, but still, it is doing it.

There are no more sensors to replace on the throttle body. The only other sensor left to replace is the Mass air flow sensor (MAF), located in the middle of the air flow delivery hose.

I am starting to suspect that, and I am also starting to suspect that the Starter is also the problem.

But, I see a reason why it WOULDN'T be the starter, but I also do see a reason why it would be the starter.

Reason why I think it might not be the starter: because when I try to start, it will rumble at very low rpm's, then go up to 2k rpms and drop to 1k with a good idle. If I turn it off immediately and then turn it back on, there is no low rpm rumbling. It starts normally then.

Reason why I think it might be the starter: I got the starter from Auto Zone. I got the cheapest one that I could buy, a Duralast. The last time I bought something from them was the Alternator, and that was a problem before I replaced the current Alternator. The Alternator I got from them was a REMAN. It was the reason my car's battery light was flashing intermittently for a month and a half. Replacing spark plugs, power and ground wires and the battery did not fix the issue. Replacing the alternator with a NEW non-reman Alternator from Napa DID fix the problem. There is no more flashing.

And so long story short, might be the starter, because it's cheap. But, It is still very conflicting.

Why would a car have problems with the first start, then the rest of the time it's fine, then it sits for a while and then it has a problematic first start again?

Re: 98 Civic fluctuating idle problem
 

i doubt its your starter. the starter has a little gear on it that contacts the flywheel (in a manual) when you turn the ignition over. when you crank it the gear is touching the flywheel. after you let off the ignition the gear sinks back into the starter. sorry thats the best i can describe it. here look in this video.

[autostream]http://autostream.com/ibcivicforums/?page_type=firebirdplayerthumbnail&framepage=1284& transactionid=1345092564-7623535151&posted_by=pwnsauce_www.civicforums.com& youtube_video_id=8Q5Y28dujyc[/autostream]

you could try pulling the starter and making sure the little gear can move freely and its not binding up.

actually if at all possible you should record what your car does while driving and post the video here. thats gonna get the most accurate diagnosis. other than actually taking it to get diagnosed lol.

Re: 98 Civic fluctuating idle problem
 

Just had a similar problem with my 98 Civic DX (manual trans). First noticed a couple days ago that when I would put car in neutral at a stop, that the engine rpms would go up to 2000, and then down to 3-400 (and sometimes stalling). Next morning the check engine light went on (and stayed on).
OBD-II code reads P1106 which indicates that the Barometric Pressure (BARO) sensor inside the Engine Control Module (ECM).
Does this mean I have to replace the ECM?

Re: 98 Civic fluctuating idle problem
 

Many honda use Valve overlapping instead of the EGR valve.