A Mystery Problem... Stalling when stopping or accelerating.

[ryesworld]

Hi all, I have a 5 speed '89 Prelude 2.0 SI with the B20A5 engine, and about 280,000 kms (175,000 miles).

The car runs fine... except for it wants to stall when I come to a stop and will sometimes jerk when accelerating from a stop. Also, when accelerating from a stop, sometimes the RPM's seem to 'stick' at roughly 1500 RPM. When this happens, stepping on & off the gas seems to do nothing and the RPM's slowly drop. The car will either stall when the RPM's get to 0, or the car kicks in after a few seconds and the problem goes away until the next stoplight. If the car stalls, it usually starts up right away, but sometimes you have to wait a couple of minutes. This is very frustrating and potentially dangerous when trying to make left turns through intersection traffic, etc.

I've replaced my fuel pump & filter, cleaned the injectors and throttle body (which needed it), put in new spark plugs, and tried higher octane gas, but the problem is still there. The gas tank isn't dirty and the air filter is clean. We can't find any vacuum leaks and all hoses are on tight. There are no trouble codes stored in the computer and the check engine light doesn't come on when the problem happens (the light checks OK at startup). My mechanic is baffled and I've already spent way too much time & money trying to fix this ongoing problem.

The most unusual part, is the problem seems to start happening when I have about 1/3 of a tank of gas left, and goes away after I fill up. It's not a shortage of gas as the needle works and there is plenty of gas in the tank. It just occurred to me - I wonder if it could be something to do with gas tank ventilation, as the problem goes away after removing the gas cap (when filling up with gas). When I fill up, you can hear the vacuum sucking air into the gas tank as the cap opens. Is it possible that this vacuum could be the cause of the problem. If so, why would the tank not be ventilating properly?

Does anyone have any suggestions or ideas what the problem could be?

Thanks,
Ryan

[BlueTurboteg]

try playing with the keys in the ignition. i know hondas are notorious for bad ignition switches, just a lil wobbling of the key will make the car stall, youll notice if thats the problem..

[Wafler]

$5 bet: its the gas tank ventilation :)