This is the new(er) VX engine/trans we just put in my car about a month ago. Supposedly came out of another car with 30-40,000 miles on it. I replaced it because the old engine had over 230,000 miles on it, and the trans was going out on it.

It ran OK with the traditional PCV valve in it. However, I couldn't get the idle set below 1000RPM, no matter what.

I do have the correct VX PCV valve coming in, hopefully tomorrow. I'm going to try that next and see if it helps. Apparently it has a small orfice to restrict air flow, which may fix my problem.

The surging or bouncing is about 2 seconds apart...may have to do with the fuel injector timing.

Guys,

I've been following this thread because my VX had this same idle bounce problem, and my current '95 DX has a little bounce once in awhile as well. Here's what I read on a honda-tech.com thread aboutthis problem:

"It's unlikely its the Idle Air....that's the f*ckin annoying H-T answer to all idle problems that is rarely the actual issue. What is FAR more commonly the issue is the thermo valve below the throttle body. The valve seat inside screws it's way out and the valve never seats when the motor reaches operating temp allowing constant blow by air...essentially a vacuum leak.
Pull off your intake tube and idle the motor to operating temp. On the inside of the bore of the throttle body there are two holes in the side. With the motor at operating temp put your finger over the lower hole. If it's sucking vacuum at operating temp, that's a problem. You need to take the assembly apart beneath the throttle body, screw the plastic valve seat all the way in, then back it out 2.5 turns. You don't want the valve seated when cold, but as the coolant warms the thermo valve you want it to seat and shut off the bypass air.

That's likely your issue. Check that first, then if that isn't it check the idle air. The Idle Air gets blamed on this site constantly for bad idle just simply because the work "idle" is part of its name I swear. I've done this for years and I've fixed the bouncing idle syndrome more times than I can remember and out of all the times the IAC was bad twice, maybe three times. When they are bad the rubber boot inside is usually cracked or broken down. The IAC's are pretty straightforward to check. Get a two pin plug as a test plug and run some extension wires. Hit the IAC with 12v....if it clicks it's good. It's a simple solenoid...that's why they rarely go bad."

https://honda-tech.com/zerothread?id=...ostid=30429468

Thanks for the info...will check it out tomorrow AM.

D15Z1 motors (VX Motors) don't have FITV (Fast Idle Thermal Valves).


Check to make sure that your coolant system is bled properly and that the coolant level is where it is supposed to be. If an air bubble gets up into the lines for the IACV (Idle Air Control Valve) or the coolant temp. sensor, then it causes some issues as well.

OK..still hoping the correct PCV valve shows up today.

OK, received the new PCV valve, NAPA part #2-9379 (Echlin box) today. Upon inspecting the same, discovered it had a plunger (but no spring). Rattles when you shake it, not like the one I "modified"...it had a spring that kept the plunger shut. Find below blurry, poor quality photo of the PCV valves...black one is what my mechanic had installed, white one is what I installed today.

Installed in my VX, runs great. Going to try and adjust the idle again tomorrow morning...

Damn. I'm sure glad my VX is idling well. I would suspect a vacuum leak if all these things you have tried don't work. I know my engine idles perfect w/the OEM PCV and I cleaned out the IACV lately.

Good luck.

Yeah, going to take another swing at it this morning after running errands. Alternator is making a lot of noise (I think it's days are numbered), so I couldn't hear a vacuum leak if I had to. May try a little carb cleaner, see if I can find a leak that way. Still not convinced the vacuum system is right...I may have to invest some $ and take it to a Honda dealer to see what's missing.

Well! Unplugged the IACV, set the idle to around 400 RPM per the Haynes manual, plugged the IACV back in, shut off the car. Unplugged the "reset" fuse in the engine fuse block for about 20 seconds. Restarted, and it's idling right around 600 RPM!:)

I think a lot of the problem was I wasn't unplugging the "reset" fuse, to reset the ECU after dinking with the idle/IACV. I am gradually learning the ways of the Honda....a lot different than the Detroit iron I'm used to.

Yeah, ECU controlled cars are a whole different story.

You'll hate it at first, but once you get the hang of the obd1 Hondas, you'll never want anything else. Self diagnosing and how they tell you what is wrong is just so convenient.

Glad to hear you got your idle fixed.