Why would, during idle, my car suddenly drop maybe 50rpm, go up about 100rpm, and then go back to down to normal? This happens maybe every five or ten minutes, sometimes less often.

This is a D16Y8 running on a chipped P28 with D16Y8 map (minus CKF, KS, and SHO2S). No CEL. Runs rich. Seems to have a loss of power.

 

If you let your car sit in neutral/park, does it do it? If you drive with as little electrical load as possible, does it do it? If you drive with maximum electrical load, does it do it more frequently?

 

Misfire maybe slight missfire

 

Sit at idle, it does it. This is only a problem that shows during idle. It does it while up to temp only. Getting car to temp to test under most and least load.

Car is getting terrible gas mileage too. 17-21mpg when rated at 36 or so.

MAP, PHO2S, and TPS all test good currently. Cylinder 1 (iirc... might be 4, have to check records) plug slightly chalky.

Be forewarned this is in an '88 CRX, which is why it has some sensors cancelled.

 

If it doesn't do it, or does it less often, at idle with absolutely no unneeded power draw, I'd be inclined to blame the alternator or ELD. I doubt the gas mileage thing is related to the surging - that probably has something to do with the rich running problem you're having. For that part, have you checked spark, ignition timing, and fuel pressure?

 

No other changes in anything electrical when this happens btw.

 

Timing is dead on. Fuel pressure tester I rented did not have a small enough adapter for my car.

 

Have you tried running it with the O2 sensor unplugged? Kinda sounds like an O2 sensor that's not quite bad enough to throw a code yet.

 

I've had this problem before. Blown ELD and O2 at the same time smh

 

If I unplug the O2 sensor I get a CEL. Going to test resistance om injectors in a few (hopefully before work) so I'll get back to you.

 

There are no other electrical issues with the car. No flashing lights or anything. It's an '88 CRX and so far they don't seem to have the ELD issues as often as the 6G Civics seem to.

 

Injector resistance (left to right, driver to passenger): 1.7, 1.7, 1.8, 1.8.

Running with O2 sensor unplugged now. So far running smooth. Not to temp yet. Throwing code 41 with 4 wire PHO2S unplugged. CEL came on within a minute of starting.

It's 23° out and this sucks.

 

Finally got out and checked the ECT sensor. At temp I got 0.2.

 

Dry compression test results: 165-160-160-165. Vacuum steady at 21psi at idle.

 

My civic does this during summer every time the fan kicks on the rpm drops at idle. do you hear the fans kick on when it happens?

 

How did it run after it warmed up?

 

I have had a similar prob on my gsr. ever since I did a fuel treatment, vaccu flush and sprayed throttle body cleaner on my throttle body I have a lumpy idle ever since. once the car warms up it slows down and the eventually stops I just ont get it, and ever since the fuel treatment etc ive had worse mpg then ive ever had. changed out my plugs wires and rotor and that never changed anything, 1 spark plug was covered in crap but still when I put new ones in it never changed anything. iacv is fine

I need help figuring this out its annoying!!!!

 

Bad O2 sensor maybe?

 

I actually want to jump the wiring for the fan because I can't remember the last time I hear or saw it come on. It is cold here, but I wouldn't think that cold.
Fine. I got a consistent hunting idle once I got to my destination. Fine otherwise.

I did a compression test and a Honda Master Tech recommended I check my valve adjustment. He thinks I have a tight valve.
I definitely do not have a lumpy idle. The idle is smooth other than every few minutes I get this very slight movement. I've seen a bad IACV idle before and mine isn't comparitable. I do not have a hunting idle if everything is plugged in (except briefly twice after swapping the MAP - haven't seen it since).