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1998 Honda Civic Hatchback DX 5MT
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Discussion Starter · #1 ·
I am currently dealing with a P0505 code issue.

Car Details:
1998 Civic DX - D16y7 - all original 140k miles

I read through the below post about troubleshooting the P0505, but am stuck.

Before finding this forum I did the following because I had the P0505:

Replaced IACV - from RockAuto, then the car tossed a P1508 and P0505. I replaced the gas cap, all spark plugs (one was totally fouled), all new spark plug wires, ignition, and cap and rotor. P1508 is now gone, but still have the P0505 issue.

I went to do a smoke test, but when hooking up the smoke machine (Mac Tools Leak Attack) and the smoke came right up out of throttle body (had taken off the intake box). What am I missing? Is there a way to plug the throttle body opening? I was doing the smoke test with the car off, should it be on?

Any help would be insanely appreciated, really want to fix this and continue on with the project!

Just adding what my scan tool stated today when the code was showing; not too sure how to read this all.
Freeze Frame:
DTCFRZF - P0505
FUELSYS1 - CL
FUELSYS2 - N/A
LOAD_PCT (%) - 25.9
ETC (degrees F) - 194
SHRTFT1 (%) - 7.8
LONGFT1 (%) - 3.1
MAP (inHg) - 7.7
RPM (/min)- 1512
VSS (mPh) - 0
IAT (degrees F) - 122
TP (%) - 9.4
 

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If you want to fix it, quit throwing moeny at it.

P0505 means idle performance is not as intended, to simplify it.

At any point did you remove the idle adjustment screw, clean it AND the passage, make sure the Oring was good, and re-install?

At any point did you simply bridge the service connector and do an idle relearn and setting?

Did you verify you have zero vacuum leaks?
 

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1998 Honda Civic Hatchback DX 5MT
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8 Posts
Discussion Starter · #4 ·
Hey @mattliston, 100% agree, right after I found this forum, just stop trying random things.

I have never adjusted the idle screw in any way - not sure if prior owner had though.

I have not done the bridge, what is an idle relearn??

Started to, but needed to cap off the throttle body as smoke just coming right out of the top, so wasn't able to cleanly check for leaks. Now I have a rubber/silicon hose to fit onto the top and cap to I can cleanly check for leaks via smoke test. Will be doing this at the end of the month.
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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1,549 Posts
Start with removing the brass idle screw, clean it, the passage it screws into, and the throttle body good with carb cleaner and a clean rag. Reinstall the screw (after verifying the oring is good) and seat it gently, then back it out 2.5 turns, start the car and warm it until the fans come on, shut it down and jump the check connector on the passenger side above the kick panel. Restart the car and check idle and timing, adjust timing first, then idle, then recheck timing. Shut it down and remove jumper from check connector, road test. If it maintains good idle speeds but the light comes back on remove the negative battery cable for 5 minutes, let it cool completely then restart and let it idle until at normal temp.
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Should be a blue 2 pin connector under the glovebox right above the carpet, a paperclip works perfect to jump the 2 pins together, or any small GA. Wire stripped back and twisted.
 

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1998 Honda Civic Hatchback DX 5MT
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Discussion Starter · #8 ·
OK So, I installed a new battery which helped immensely, no more trouble turning over or any issues with rpm fluctuations. For about 30 - 40 miles no light and the car ran great, then the light came back on. I did a smoke test last weekend and found a 0.15 leak, which seems to be coming from the throttle body gasket and a slight cracked hose to IM. Problem is after doing the smoke test the following codes showed up - P1509, P0108 and still the P0505.

I also installed an EX gauge cluster so now I can get a read on the RPMs, seems to bounce between 1200 and 1500 when light is on and car is warm.

Since I did find a leak my plan is to replace the throttle body gasket, the 3 hoses on the IM, IM gasket, IACV, TPS and MAP sensors. While TB is off ill check the idle screw @Oldcivicjoe was talking about and the o-ring for it.

Thoughts?
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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I'd just start with the tb gasket and the idle screw oring along with a thorough cleaning of the tb, unless you really want to scrub everything down good, maybe send injectors for cleaning, ect.
 

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If repalcing the gasket does not fix it, if you have one of those old school squirter oil cans, you can have the intake tubing off the throttlebody, and squirt a little oil on the throttle blade's shaft inside, and if it lowers the idle, the actual throttle's shaft is leaking.

Solution is a different throttlebody. I have run into this exactly twice in 20 years. But it is indeed possible.
 
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