High idle on D16y8 replacment motor, hours of toruble shooting, no fix yet
 

Im not new at cars, I've been messing with motor for years, also I'm and A&P mechanic


anyway, I bought my brother 99 Civic EX with a blown D16y8. I found good deal on a D16y8 from a 96 EX (just the longblock).


Swapped the motor in and i now have a high idle problem about 1500rpm although if you give it a minute it will go down to 1100. threw a CEL for "high idle"
There a very loud "rushing air" sound sounded originally to come from the fuel rail, but using a tube, it appears to come from the area below the valve cover where the intake and motor meet.
I replaced the intake gasket with a felpro ms91553. Did not fix

I've checked every vacuum line and none are leaking. I took the IAC apart and cleaned it, bench tested it to verify the motor was working. didn't help.


I did some searched here and on other civic forums, and found a couple vague posts saying there are two different d16y8 intakes any time i search for one though, there always listed as a 96-00.
Felpro shows two different part number for gaskets... 91553 for a '99 and 91485 for a '96
majestic honda web site says a '99 civic intake manifold PN: is 19564 and the '96 is 19563

So this appears to maybe be the problem.



So how do i fix it? do i have to get a new intake for a '96 civic? can they be adapted or the leak plugged?
Any help is appreciated.
Ken

Re: High idle on D16y8 replacment motor, hours of toruble shooting, no fix yet
 

The 96-98 IMs are different than the 99-00IMs. The 99-00 IMs have air injection holes in that should be plugged when used with a 96-98 head. Usually JB Weld does the trick but personally I'd go out and get a 96-98 IM for $40 or so and not deal with the patchwork. If you need pix and stuff LMK and I'll expand on this issue.

Re: High idle on D16y8 replacment motor, hours of toruble shooting, no fix yet
 

Yah, thats what i did the other day... jb weld the holes... runs great now,

thanks

Re: High idle on D16y8 replacment motor, hours of toruble shooting, no fix yet
 

Sorry to bring back an old thread, but I'm having the same problem. Where are the air injection holes on the intake manifold? Thanks!

Re: High idle on D16y8 replacment motor, hours of toruble shooting, no fix yet
 

The holes are circled in yellow. Plug them with JB Weld.

Attachment 102140