My next door neighbor has a 94 Prelude Si. When he starts his car it just revs up and down constantly. I looked at it and couldnt find any vaccum leaks. He said it just started on Christmas eve. When he drives the car it runs fine though. I was thinking it was maybe the idle/air sensor or something that needed to be cleaned. If anyone knows what to do please let me know. I told him I would try to help him out on it.

 

Not much help... I had something similar though.... I have a 96 Prelude S, mine did that last night. I had my car over at a friends house and we were looking at putting in some driving lights. Hood was up for about 2-3 hours... but we didn't touch anything. Mostly just measured and fitted things outside the engine compartment.

When I left it was reving between 1-2k rpms. I let it do that for about 5 times then backed out like normal... and pulled up to the nearest stop sign and stopped. It stopped and didn't idle funny. I attributed it to it being cold. Thats the first time I had it happen. It was rainy and cold last night. Other than that, it never happened.

 

Have you bypassed the throttle body coolant line? my car does that in the winter because I routed the small throttle body coolant line so it doesn't run through the throttle body anymore. I pick up good power from it in the summer cuz it's not heating up my intake air and then I switch it back in the winter so it doesn't rev like that.

 

Like I said, its my neighbors car. I havent done anything to it. He just aksed me about it the other day. I doubt very seriously though that he did that because he is not very mechanically inclined and doenst know much about cars anyway.

 

check coolant level. there is a pallete in the throttle body that uses the warm coolant to control the idle. it the pallete does not warm up from the coolant, it idles irratically. this is commonly caused by low coolant levels caused by a leak in stock cars. if it is low, fill and look for leaks. the reason why is does not do it when the car is warm is because the pallete eventually warms up.

 

I have a 92 Prelude Si...
I had the same EXACT problem...it would do just great driving but once I was at a stop light or whatever it would act like it was about to die...
My problem was the distributor...hope that helps any...

~allie

 

ha, mine does the exact same thing, although it doesnt start until my car has warmed up. I just went from a f22 to a h22a, and was wondering if it might be the fuel pump, or maybe my idle control unit.

 

it's probably your AIC... air idle control valve.. my bf had this problem over the summer(92 Si).. unfortunatly there are no authentic honda parts left in the world.. according to the dealer he got one of the last 3 available... you'd have to look in a junk yard or online... it was $160 installed by Honda.... good luck...

 

I talked to 2 people here in town that had the same problem........one on an Accord and one on a Mustang. They both took the Air idle Control off and cleaned it with carb cleaner. Said all kinds of black carbon came out. They let it dry and put i back on. Took care of the problem.

 

I have the same damn problem in my 92si , make me feel stupid at a stop light . reving up and down like a broken down POS but it still runs fine . i keep an eye on the coolant level cause my stock rad does leak and i need to get a new one so i will try the AIC route. thanx for the help. is there another name for the AIC i just looked in my chilton book and it had no referance to anything by that name.