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Hello, I have a 1994 Honda Prelude Si with about 50k miles on it. Last week I swapped out my 211k mile engine and automatic transmission due to a cracked block with a used JDM engine and automatic transmission with about 50k, which run great btw, anyways, my problem was I have a high idle only in gear, which would be Drive or Reverse, in Park or Neutral the idle would be normal, sitting around the 850 mark, when I get into gear on a cold start the intake would make a loud sucking noise and the idle will climb from 850 to about 1300 and stay there, at operating temperature when doing the switch to park to gear the idle would go down like it’s supposed too, but as soon as i touch the gas pedal the idle will climb to 1300 and stay there until I switch back to park or neutral, on my old engine the car use to surge in gear sometimes at a stop, that was annoying, hasn’t done it with the new engine and tranny yet, though. Another thing is when I barely touch the throttle the idle will climb on it’s own to like 1300 and then I can hear a “pop” coming from the intake, then the idle will go back to normal, also at operating temperature going low speeds lets say in a parking lot I’ll be stepping on the gas a lil then I hear that pop from the intake and the rpm’s will slowly go back to like 1k, I can describe it like the transmission shifting but it really isn’t, when going accelerating and the rpm’s are climbing and if I let go off the gas the rpm’s will dip to like 1k and quickly come back to like 1800 or so. It all started last year when i took my old engine to get serviced for a timing belt and water pump, when i got it back it ran worse than before and the throttle had to be kept open to prevent the car from stalling, changed the intake gaskets and the throttle can now be closed fully, he also told me to change the throttle body and IACV, got used OEM ones and put them on and still nothing, I noticed he messed with the throttle screw, I tried another used throttle body that had a still sealed throttle screw, I tried another IACV, adjusted the FITV, bled coolant, sprayed carb cleaner on vacuum lines and still nothing, it’s still doing it even with the new engine and transmission in the car, I did use my old intake, cause the new one was different, any ideas? I can’t get it smogged until I fix this problem, thanks in advance.
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list of things i checked when i had my prelude idle issues
o2 sensor
throttle cable
throttle position sensor
egr valve clean the shit out of it and the runners for it
i replaced all my vacuum lines
trust me even with carb cleaner they can hide
pcv valve , grommet, and connection to the manifold
and if you went with the h22 i believe the idle is suppose to be a hair lower than you stated 650 maybe i haven’t read it in a long time but I’m pretty sure
the butterfly for the throttle body
thats all i can think of for the moment
oh your gonna need the service manualhttp://www.superhonda.com/forum/f146/prelude-service-manual-online-303151/
free to dl thereIf you didn’t install the same engine in the vehicle, this could be the issue. The ECU may still be trying to run the old engine. If that’s the case, no amount of parts swapping is going to solve the problem. You’ll likely need to get an ECU that works with the new engine to solve the problem. Also there is the possibility that something didn’t get hooked up correctly during the engine swap. For that I would recommend going back over all your work to make sure everything was hooked back up correctly. More info here.
http://www.ericthecarguy.com/faq/solving-automotive-idle-problems
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Good luck and keep us posted.
[quote=”EricTheCarGuy” post=137349]If you didn’t install the same engine in the vehicle, this could be the issue. The ECU may still be trying to run the old engine. If that’s the case, no amount of parts swapping is going to solve the problem. You’ll likely need to get an ECU that works with the new engine to solve the problem. Also there is the possibility that something didn’t get hooked up correctly during the engine swap. For that I would recommend going back over all your work to make sure everything was hooked back up correctly. More info here.
http://www.ericthecarguy.com/faq/solving-automotive-idle-problems
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Good luck and keep us posted.[/quote]
Thanks for your reply, I actually had this problem with the old engine as well, It is the same engine and I used all new intake gaskets and marked every hose and I put everything where they came off of, I tried another ECU and nothing. When this problem first appeared was when I took my old engine (H23A1) to get serviced for a timing belt, when I got it back the engine wasn’t even idling correctly, he told me to replace the throttle body and IACV, throttle was also being kept open, some time later the engine had a head gasket done and I used all new intake gaskets, the throttle can be kept closed but that high idle is still there only when put into gear, that mechanic did something because this didn’t happen before I took the car to him, I thought mechanical timing at first, but I checked it and it was off when I did the head gasket, put it back correctly and still same problem. I used the injectors that came with the new engine just rule that out possibly. I have no CEL so I’m staying away from the MAP, O2, and Coolant temperature sensors. Here’s a video if it, this was with the old engine but the new one is doing the same thing, I was moving the steering wheel because sometimes as I turned it the idle would surge, also surge when A/C was on full blast, It doesn’t do it as much with the new engine, but still does it then it sorts itself out, but see how the idle climbs when I put it into gear, I need to get this fixed so I can get it smogged, thanks in advance. https://www.youtube.com/watch?v=V8PjhYym374
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