Schramm

Hey, I'm having trouble with my GF's car. Earlier this month it threw a CEL, when I checked it it was the IACV, nothing else. She was also complaining about jerkiness when on off-throttle, as if it wasn't getting air through the IACV (at least that's what it seemed to me when I drove it). So I took off the IACV, cleaned it, tested it, tested all the circuits (including its port on the ECU) and everything checked out fine. Re-installed the clean IACV, reset the ECU (by disconnecting positive battery) and when we turned it on, it threw the CEL immediately, and has been driving even worse ever since. She had also mentioned that before the attempted "fix", she could shut the car off and restart it to get rid of the problem and jerkiness, now she can not.

Just trying to find out what could be the problem? I looked around here and saw that it could be something like the following:
- PCV Valve
- Ignition/Plugs
- Fuel Pump
- Vacuum Leak
- Sensor issues (TPS, MAP)

Any ideas or experiences? I'm hoping someone can put me on the right track, because I really don't have the time to tear the whole thing apart looking for the culprit, and she needs the car daily. Also, the motor mounts seem to be very worn, causing the jerkiness to be 10 times worse due to the motor having lots of room to shake around.

Any help is appreciated,
Thanks,
Alex

joeshmo

Had a similar problem with my car. It would jerk on and off the throttle as long as it was in gear. I honestly just cleared the code and it hasn't done it again in 1k miles. But since the code is coming from your IACV, I'd do everything possible to rule that out. Do you have a known good IACV you can swap in to try?

Deetz

This car is known as an EX model in the US so others don't get confused

motegicivic

Did you make sure you put the coolant hoses back the proper order?

What shape was the gasket in? Maybe a vacuum leak?

What did you use to clean it?

Sometimes it could be your TPS, or MAP as well.

PardonmyEK9

check for a loose throttle cable. sometimes is the problem

sde780

Check the voltage for your TPS

fleabag

First of all, you can't always reset the ECU by disconnecting the battery, sometimes you need a code reader. If you DO disconnect the battery, I'd imagine you'd have to wait a considerable amount of time before it would fully clear the code. Your issue with the throttle and jerkiness is identical to the problem I had with my civic. To resolve my issue, I cleaned my IACV, took off the throttle body and thoroughly cleaned it, every little passage, removed the idle screw to clean under there as well. The great part about my IACV finally freezing up and resulting in the "bouncing idle" was that after cleaning the IACV, it also resolved my jerkiness issue which I had incorrectly assumed was due to a sticky throttle cable and not because of a partially sticking IACV and dirty throttle body.

Schramm

All I have is whatever was on my D15B7 from my EG8, so probably not the same

Right, forgot about that, sorry. Has the D16.

Pretty sure they're in the right order, seems hard to mix them up (they stay in the same position). The gasket was in good shape. Used break cleaner and a toothbrush.

Is there a way to reset it that doesn't cost >$200?

So here's a list that I figure I have to check then:
- TPS/MAP (I'll have to find out how)
- Throttle Cable
- Clean the TB
- Somehow properly reset the ECU

I'm going to change the plugs and wires anyways, maybe a new cap + rotor depending on the price. Maybe I can find a working IACV to test. I'll get these things done (hopefully) and get back to you guys. Thanks for the help.

- Alex

fleabag

Depending on where you live, you might be able to go to a place like kragen or autozone and they'll check your codes for free. I bought myself a Scangauge because I monitor fuel economy and I can use it on any OBD-II vehicle in order to reset codes, check to see if it's smog ready, check long term and short term fuel trims, oxygen sensor output, rpm, ignition timing, coolant temperature, oxygen sensor closed/open loop, etc. etc. The newest scan gauge has performance features so that you can calculate your 0-60 time, your quarter mile time, your 1000 meter times, etc. etc. I'm going to wait awhile before I send my scangauge in for a free upgrade b/c I don't want to spend $10 on shipping only to have them upgrade it again with other nifty features. At least mine comes with xgauges which allowed me to plug in those extra features like o2 sensor or long term fuel trim output. Long term fuel trim is useful if you want to find out if your car is overall running lean or rich.

Only bad thing about the scangauge is that it's expensive... (Around $150) An alternative would be the Ultra gauge which is less than $100 and while it has nearly every feature the scan gauge has, the issue I have with it is that if I clear a check engine code, the car will not tell me when it's ready to be smogged while the scangauge will. This is critical if you just repaired your car before you take it in for a smog check b/c if all the tests haven't been performed, you get an automatic fail at the smog check.

motegicivic

I looked up the Ultra, have you ever used it, they also have a EM version with more features.

Do you know if the ultra you can read what the code means on the screen, not just the code itself?

Former User

OBD2 Civics have two different IACV-related CEL codes. Post the specific CEL code that was thrown.

sde780

Advance auto has a free code scanner/deleter

fleabag

I have not used the Ultra Gauge but it is pretty highly rated since it's better in a lot of respects compared to the scan gauge. (Bigger screen, more info per screen, etc.) However, the fact the Scan gauge has performance features and can tell me whether the car is smog ready is to me much more valuable. The good news is, I don't think adding such features to the ultra gauge would make it any more expensive. It's a fairly new product while the scan gauge has been on the market for like 5 years. None of the code readers will tell you on the spot what the codes mean. Look up the codes at obd-ii.com and you hopefully should find them. Otherwise google it.

motegicivic

On your other post you mentioned fuel trim, the ultra has like 4 Banks, how do you read that to know if running rich or lean?

fleabag

Well it's generally considered acceptable for a vehicle to have a long term fuel trim of +/- 3. So if I vehicle has a long term fuel trim of 8, it means it's adding 8 'units' (unspecified) of extra fuel while running, because it's detecting through the o2 sensor that the engine is running lean, probably because there is additional unmetered air entering into the combustion chamber so it has to compensate accordingly. Now if it says -8, then that means the computer is compensating by removing fuel since the engine computer via the O2 sensor is detecting it running rich, probably because of a misfire or a leaking compression ring, burning oil, etc... Fuel trims I guess are done because the o2 sensor is telling the computer how well the car is running based upon the contents of the exhaust.

Cars can and do run without o2 sensors by metering air that comes into the engine, then going by pre-programming fuel-load tables, it injects fuel into the cylinders accordingly. All the sensors in these cars do is help tell the computer as much info about what is going on as possible so that it can do the best it can to compensate for that.

motegicivic

So basically if you within - or + 3 you are ok?

fleabag

For your long term fuel trim, yes... Short term fuel trim, that varies depending on how you drive.

Schramm

Checked the code, it was #14, same as before. I looked it up and it said IACV.


Back on track:
Today I unplugged fuse #47 for the ECU, tightened up the throttle cable (it was pretty loose) and cleaned the TB by removing it and spraying it down with brake cleaner. Put everything back together, re-plugged in the ECU fuse, started it up, waited 15 minutes, shut it off, then took it for a drive. The jerkiness was resolved, the CEL did not come back on, but now the idle seems to run very high (~2000rpm) and will hunt very slowly (every now and then it will drop to about 1200rpm and stay until the gas is used again).

joeshmo

You say you tightened the throttle cable? How did you go about doing this?

Former User

A 97 Civic has an OBD2 ECU and throws corresponding OBD2 codes. By jumping the service connector, you retrieve only OBD1 code versions that are often less informative than the OBD2 codes. In particular, there are two separate OBD2 IACV codes that fall under OBD1 code 14. If the CEL turns on again, take your car to an auto parts store that pulls codes with an OBD2 code reader. Post the OBD2 code that is retrieved.

fleabag

What are you talking about? Jumping the service connector on an OBD2 car shouldn't show OBD1 codes since by definition, it's an OBD2 car. The service connector on the 96-00 civics is only intended for changing the ignition timing. Where did you get this information?

Former User

OBD1 and OBD2 92-00 Civics are combined in this forum due to their high degree of similarity. For example, information in the CEL sticky for pulling OBD1-style CEL codes by jumping the service connector pertains to both OBD1 and OBD2 (92-00) Civics. While 96-00 Civics do have an OBD2 system, they are actually an OBD1/OBD2 hybrid system that uses all 92-95 Civic OBD1 codes as well as a unique set of new OBD1 codes that exploit the more advanced OBD2 system.

Relating to the hybrid nature of the 96-00 OBD2 system, you can also pull OBD2 codes with an OBD2 code reader. While the format of OBD1 codes is a single or double digit number, the format of OBD2 codes is P followed by a four digit number. In addition, the OBD2 codes yield more precise troubleshooting information in some cases. For example, there are two different OBD2 codes (P0505 and P1508/P1509) for the IACV circuit, both of which are retrieved as OBD1 code 14 when you jump the service connector.

For later Civics (01-present), the OBD1-style codes were eliminated.

fleabag

I'm going to have to try this!!

jdmcertified909

agreed 110% good information not alot of people know that. since its not in the service book. service book only identifies that plug as the timing plug

Former User

Actually, if you look very carefully, you will find that pulling codes by jumping the service connector is covered briefly on page 11-81 of the 96-00 Civic service manual:




In addition, the OBD1-style codes are also listed parenthetically within the Table of OBD2 codes in the manual. For example: