Got a strange issue, that started yesterday. 1990 Civic Hatch, converted to MPFI about 6 months ago. About 1 month ago, was having a strange issue with my idle dropping ~400 rpms, while I brake when the car was warmed up, but going back to normal immediately ~ 800 rpms. I thought that it could be my throttle body, so I took it off, cleaned it off with throttle body cleaner and put on a new gasket. it ran better, but the idle was higher, ~1,200 rpms at idle. I first tried to reset the ECU by taking out the fuse and also removing the battery terminals. I left it like that for an hour then came back and put it all together. It stayed the same. I then checked the throttle cable and it was not too tight. I decided to then adjust the idle screw, and disconnected the IACV, put the jumper into the connecter in the passenger side, made sure the car was warmed up, then adjusted the screw until the idle was at 800 rpms. I then turned it off, then connected everything and pulled out the jumper. Then I reset the ECU again and waited about 10 minutes. When I started the car, the idle was at 200, then went to 800, then dropped again, then went back to 800. I drove it around the block and the check engine light came on and the idle went to about 600. I parked the car and when I started it again, the car was at 200 rpms, it jumped to 400, then it went back to 200 and died on me. I started it back up and it died again. In my frustration, I did not look at the ECU code, I should have, but will do that when I get back home from work tonight.

Any ideas what this could be? After I installed the new gasket and put the throttle body back together, I did hear some sharp pinging noises from what I thought was the engine, but my neighbor said that it sounded like it was coming from the exhaust. Could any left over residue from cleaning out the throttle body mistakenly been sucked into the engine and caused problems? Getting the old gasket off was tough and I think I got all the old gasket off, but perhaps I left a little piece of gasket by a screw, which may cause a leak in the throttle body?

Any help would be appreciated.

 

Checked last night and it looks like I have a code 14 flashing. I turned the car on and the CEL does not turn on anymore. I had to give it gas for about 20 seconds after I turned the car on to avoid it from shutting off on me. After that, it stayed on and it was ok. I sat for awhile to let it warm up, then I drove around the block and the idle did stumble once, but was ok. I parked the car and turned it off to see if the CEL would come on or if the car would turn off. It did turn on, but the car did not turn off. The idle was low, around 500, and the car vibrated a lot, but as I sat and waited, it went back to around 800 rpms. As soon as I stepped on the throttle, the idle would settle at 500 and shake a lot, but slowly rise to 800 again. A funny thing is that when I shut off the headlights, the idle would rise again.

I checked the ECU and it was blinking, giving me a code of 14. Perhaps I need to just drive it more to let the ECU relearn the idle after adjusting the idle screw. As soon as the rains let up, I will drive it a couple of miles on the freeway.

 

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Update:

Car is driving fine, idle is constantly at around 750-800. I took the alternator out and it was fine, so I figured it was the battery. Had battery tested and it was bad. Got it replaced for free since it was still under warranty. The only problem that I have is when warm, as I come to a stop, the idle will dip to around 400 rpms and then rise to around 800. I've been reading around the web and cannot figure this out. The grounds are all nice and tight, checked vacuum lines for leaks, alternator is fine, EACV is brand new, distributor is brand new, spark plugs and wires are fairly new...