Idle Problem

I recently bought a 1990 Accord but soon ran into problems with the engine (leaking and buning oil). i ended up having the entire engine rebuilt and thought my problems were solved, however sometimes when i come to a stop, the engine will almost stall , the idle will dip down to 200 or 300 rpm and eventually come back up. i have taken it back to the shop but they have been unable to duplicate this problem. i also have a problem with my tachometer, some times at around 3500 rpm the needle will "jump" to 5000 rpm. the two poblems don't seem to coincide with one anther, but i would like to be able to fix them. thank you in advance for any replies.

P.S. the car is MT with the original clutch (140,000 mi)

ok bout the idle problem it may be ur o2 sensor.... if its bad it'll make ur engine idle wrong like when u stop it'll be at 1 for a second then drop to 5 all of a sudden then up to 1,2 and then come back to 8 and keep goin.... if thats it it could be ur o2 sensor and the rpm needle problem... the guy b4 u could have messed with the needles installing gauge faces for the car.... its common for people to do that a dumb friend of mine actually took the needle off to put the gauge face on and then put the needle back on and as u accelerate it tends to stop and all of a sudden jump to where ur real rpm is at

thanks but i don't think that's the problem. from what you say bad o2 censors make the engine rev high, but my engine is doing the opposite, it's idling at the egde of stalling.

Any new information on this? Mines doing almost the exact same thing.

Let me know

~Chris

I am not sure what is causing the tachometer problem. I would take a guess at a momentary ground in the tachometer circuit?

Your rough idle problem may be caused by a dirty idle air control (IAC) valve. Here is a link on how to clean the valve. I have not had this happen on my Honda, but this appears to be a fairly common problem on older Hondas.

http://www.g2ic.com/forums/showthread.php?threadid=35534

the idle problem is now temp. related. when the engine is warming up it idles a little odd (dips and goes high) but the point where is almost stalls is when the engine reaches it's operating temp. when it just reaches the temp, the problem occurs but goes away after driving for a while. the shop i go to says they need to check the fast idle valve, is this something i can do myself?