rTc417

I looked around a little bit, but couldn't find any definite answer. I have a 92 Civic with a 97 B18c1 GSR swap that's had this low idle problem for the past a couple months. The low idle only occurs when the car has been warmed up for about 10 minutes, when cold the car runs brilliant.

What happens after the car gets warmed up, is that it idles at around 800 normally, then drops to about 300-400rpm and repeats idling from 800 to 300 for several minutes. It seems like after those several minutes are up, it fixes itself and stays at 800 the rest of the time. Also when this all happens I can feel the car lose power as a whole, kind of boggy when accelerating, and having a slightly jerky or hesitation feeling when cruising around holding the exact same throttle percentage.

I've replaced the IACV which didn't fix anything, I've looked and tested both the TPS and MAP sensors which they came out looking fine. The plugs, wires, cap and rotor all seem to be in good condition but were thinking about replacing them just to see if it did anything, but haven't yet. It doesn't have a FITV and there's no check engine light nor can I get any codes (the CEL does work correctly)... After hours of recording everything on Hondata, everything looks to be perfect. To me I've always thought it was a bad TPS seeing the symptoms I have, but all tests come back looking great. Now I'm to the point where I have no clue of what to do other than throw parts at it. Thank you any answers.

And for general knowledge, the car has been together with the swap for at least 5 years.. So the problem has only been recently. Also, the ecu is a P72 with Hondata, setup by King Motorsports.

harms_is_back

**** it saves gas lol

chanek

Low idle as long as not dying why bother. Probably that's the way the ecu is set up if not put on more advance or adjust your idle more if you need idle to be higher...

rTc417

The car doesn't die every time that this problem happens, but it has died several times from dropping so low during idle, plus it runs like **** when this happens. The ecu is not set up that way since this problem has only been recently and I've had the same ecu and motor for over 5 years.

I'm beginning to tie it to when I put a new exhaust on it several months ago. During the process I replaced the cat with a test pipe though I still don't know what the problem would be. During one of my Hondata tests I noticed the o2 sensor way out of whack but I know the o2 sensor is good. However, I'm not sure what would throw it out of place.

rTc417

I'm not sure if I'm allowed to post pictures or not, but this is what I was talking about with the o2 sensor. It's off the charts.

Also, at the very end of the recording (18 minute recording) is when the idle thing happens and stalls.

amaq

same problem !!!

Fox14120

Same problems with my 97 civic have a D16Y8 in it the problem just formed last week.

rTc417

Well, the o2 sensor wasn't the problem. I'll keep you updated if I find a fix, but I still have no idea what it is.

Former User

Seems to be a misfire not an idle problem. Therefore, replacing the plugs, wires, cap, and rotor is a good idea. Testing the coil, ICM, and FPR would also be worthwhile.

Duane_in_Japan

O2 sensor off the charts, is this just a regular O2 sensor or HO2S, heated sensor or is it an Air Fuel Ratio sensor.

If you were 6 foot tall, relating to an O2 sensor cycling from say 0.2 volts to 0.8 volts. If you stood on top of a milk crate, how tall would you be, YOU would still be 6 foot tall but you were elevated 2 feet by the milk crate. A bad ground (voltage drop) will elevate the O2 sensor in the same way.

Verify what type of sensor you have also. Did someone put a wideband in there??

rTc417

It's pretty damn weird about the whole O2 sensor thing... Some tests show that it's completely fine, other show like what I posted.

The O2 sensor is a HO2S heated sensor and no wideband.

And yeah, I still thinking about replacing the plugs, wires, cap and rotor but I don't know.


The knock sensor being thrown off might be because of the test pipe being a little off, I'm going to try and fix that asap but I doubt that's the whole problem.

Former User

If you suspect the O2 sensor, then just unplug it to see whether it eliminates the problem.

In general, ignition problems are the main cause of performance problems like yours. If this is ruled out, check the fuel system, such as the FPR.

rTc417

I know for a fact it's not the O2 anymore. For the performance issues I'll be installing the wires, rotor ect today to see what happens there.

For the idle I'm hoping that by relaxing this test pipe will do the trick seeing how that might be throwing off the knock sensor, which I should be doing tomorrow.

rTc417

*Update*

I replaced the wires, plugs, cap and rotor... I relaxed the test pipe since it was 'twisted' a little bolted to the exhaust, which is now fixed. And also replaced the O2... Even though I have yet to see the idle problem happen (I haven't driven it a lot yet), the car still runs like **** with the knock sensor still spiking every time I give it throttle after it's warmed up (as it shows in the picture). I uh, I don't know hah. The CEL hasn't lit up this whole time either.