hondastrtracr

I have a mildly modified 99 Civic EX Sedan. Engine: D16Y8 For several months I have had an idle issue, it has just gotten worse over time. It was not throwing any codes but went ahead and replaced the IACV started it up and same thing! The idle still bounced all over. it bounces from 1000 to 2000 rpm. I took it to Honda and they will not touch it due to my mods. Now once the car is warmed up it seems to idle ok... Still a little high but smooth atleast.

I checked the O2 sensors they seem fine.

I checked the TPS all voltage checks out.

Timing is dead on.

IACV is BRAND NEW 300 dollars for nothing!

I am running out of ideas.

I tried to adjust the base idle by unplugging the IACV and all the car does is bounce the idle even faster. But the screw seems to be all the way in.

I unplugged the map sensor and the car died, but today i unplugged it and the car almost died but didnt die completely, basically it recovered.

checked all vacuum lines

Checked FPR

The ECT sensors dont seem to be the problem either cuz I simply unplugged them got a CEL but it still bounced the idle the same.

I am lost and Honda wont help because of cam gear fuel rail and fpr and pulleys.... I told the tech it keeps throwing the P0505 code, he said IACV, I said BS its brand new and the old one does the same thing!

I finally said screw it and am now contacting the people who know the most!! And thats all of you true honda owners and people who are willing to help a honda brother out. If any suggestions you have fix it ill buy you dinner!

Thanks,

Matt

pearlcfcivic97

I have no clue if you have a intake temp sensor but if you do I would try and replace that since it gets better when it gets warmer out, my accord used to do that and it was the fitv fast idle thermal valve there was a white plastic screw that unscrewed and all I did way tighten it and it was fixed good luck

sicones

automatic or manual?? make sure the IACV plug is making good contact, check the wires, put some dielectric grease on the plug

hondastrtracr

It is an automatic, also when it is warmed up it will idle around 1500 RPM's in Park and Nuetral and While in drive ocassionally ill get a bouncy idle when I bareley have my foot on the pedal. I checked the transmission and changed the transmission fluid and it shifts awesome and I know its not the transmission. Could it be te MAP sensor? I dont have another one to try but if anyone thinks its that I can definately look around for one.

All around it seems like it just gets worse and it has only to do with the idle, which has to be something so simple yet I can not firgure it out.

I also thought maybe it was the ECU??? Could it be???

NathanielH

it could be the ecu, but i would do more investigating into the wiring before i would think about dealing with that. do you have a multimeter? if so check for voltage at the terminals and make sure you are getting power, wiggle the wires also while you check and make sure there is continous continuity also. i hop eyou get it figured out, if you need any specs for what voltages should be at various sensors/rpm's let me know and ill check my alldata program at work

hondastrtracr

I have tried testing voltage also. I mean I have literally spent hours under the hood. Everything is getting power ok. I read the earlier reply about the IAT sensor I will try that I think, but I also heard the EVAP purge could cause it too.... I shoudl try that too. I wish I lived in a bigger city with more access to more resources. Any other ideas? What does the IAC System consist of? I was looking for a tree diagram that might connect everything together how it works with that particular system.

sicones

you said you changed your cam gear to an adjustable one, I bet alot of money thats the problem, check you timing

hondastrtracr

Checked the timing, it is at factory setting. Another question is could timing really affect it in such a way that it is only doing it while its "warming up"?