Idle problem would appreciate some advice

[ughmas]

Hello everyone, long time civic owner first post, would love some help with this issue, driving me nuts!

1998 Civic DX coupe all stock 5 sp

The story/problem:

Was driving fine one day, sitting at a red light in neutral, Car throws a CEL, idle starts going crazy (bouncing like its hitting a limiter (baw baw baw).

Pulled over, turned car off for 10 seconds, started back up, CEL still on but car idling fine now.
Same thing happens again if i let it idle for 20+ seconds starts going crazy again. Have to turn car off to fix it.

other symptoms-
if idling and press the accelerator breifly, when the rpms drop back down the engine skips when it hits bottom
slightly rough shifting due to weird idle

Went and got CEL read, P0505, suspected dirty/faulty IACV, and was told this is most likely the issue.

Took apart IACV, it was pretty dirty, cleaned with carb cleaner and toothbrush, got it looking like new, let air dry, re-installed and cleared codes.

On first startup after doing this car was running good, but soon the same thing happened. figured it went bad.

SO I ordered a new IACV, installed it, cleared codes.
first startup car idling high, it slowly settled down to where it was supposed to be, idling perfectly, let sit for a few minutes still idling good. Drove around for 20 minutes or so car running PERFECTLY, idling good, shifting smooth, smile on my face i think i have it fixed.

Get back to driveway, sit idle for a minute or so, CEL comes on idle goes crazy again baw baw baw s**t.


-Checked for vaccum leaks, none whatsoever, checked for air in coolant, none.

-When the IACV Is UNPLUGGED (before startup or during idle) it does the problem IMMEDIATELY

Im thinking it might be the TPS, am I missing something? I've searched the internet high and low.

Thanks

 

[mymmeryloss]

Check tps and fitv


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[ughmas]

Check tps and fitv


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the symptoms sound like the FITV but the 98's dont have a fitv do they? if so where?

ill get a multimeter tomorrow and see if i can figure out whats going on with the tps

 

[ughmas]

Volt tested the TPS last night, .55 at closed throttle and increases smoothly... looks like the TPS is OK :\ anything else i could check? im stumped

 

[Failsafe88]

Fitv should not be on their unless someone swapped in older setup. I do believe the stopped in 95. Have you rechecked your iacv to see how it looks?

 

[mymmeryloss]

Good catch. Idk what i was thinking lol...


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[ughmas]

Fitv should not be on their unless someone swapped in older setup. I do believe the stopped in 95. Have you rechecked your iacv to see how it looks?

yep as I said in the original post, I cleaned the original IACV and also replaced it after that failed to solve the issue.

Could it be the ECT? is there a way to test it?

 

[1badej8]

I've had the exact same problem just resently, I drove to work and at a stop light my CEL came on Nd my car just started bogging and edging really high but once I shut the car off and restart it everything ran fine so it was weird, so then I tried to clean the iacv too but it only fix the issue for a short period of time, so then I took my car to my friend shop and he checked my timing and it was off so he re-did my timing and now my car sounds and runs a lot better no CEL came back yet been 2 weeks.

So try adjusting your timing hope this help.

 

[Jersey8]

Fitv should not be on their unless someone swapped in older setup. I do believe the stopped in 95. Have you rechecked your iacv to see how it looks?

is this for all engines? or just d series? My JDM B20B has a fitv and its from a 99 CRV