Archeantus

I bought a used 88 a few weeks ago. It works great, except for every time i break to stop at a light or stopsign, or whatever, the RPM's drop significantly. It keeps going down until it hits 1 notch above 0 (200rpm?) then shudders. It stalls about 75% of the time. This is getting really annoying. I was thinking about turning up the idle speed, but does anyone have any better suggestions? This is a family car and needs a cheap solution ASAP!

Thanks,

BTW this site is GREAT!

teenlude09

might have a vaccum leak somewhere. also you should check out preludepower.com lots of 3rd genners on there

Colfax

Is your car auto or manual? Does it do this when the engine is cold, warm, or all the time no matter what temp the engine is at? Have you done a complete tune-up and changed the fluids/filters on the car? Those should be done whenever you buy a used car, especially if it's a private party sale.

__________________
89 Prelude 2.0Si 4WS
91 Prelude Si - SOLD

Archeantus

When I purchased the car I had an oil change done, and they topped off all the fluids. It doesnt stall (i just found out) when it has a full tank. It gets pretty close to the stall point on the tachometer, but it doesn't shudder at all.

Also, you mentioned the vaccum leak, how would I go about checking/fixing that?

teenlude09

open the hood while its running and listen for any hissing or what someone told me is to remove the intake hose and cover the throttle body to block air going in. car should immediately stall if it doesnt you have a leak. someone also said spraying starter fluid around the hoses to and if the cars idle changes theres your leak

Colfax

There are other fluids that need changing, transmission fluid, coolant, brake fluid. When I said "Those should be done whenever you buy a used car, especially if it's a private party sale." I meant that they should be done by the buyer so that you know first-hand that they were done. Never trust a seller to be honest about what they've done to the car and how often maintenance was performed unless they have receipts to prove it.

You didn't answer my question about whether it does this only when the engine is cold, only when hot, or all the time. This can help us to point you in the right direction. Also, the first thing you should do is check for trouble codes. Here is a link for you if you don't know how to check the codes...

ECU Error Codes

Unless the vacuum leak is huge, you probably won't hear it. But your other two methods are good. If there is a vacuum leak, fixing it is as simple as replacing a vacuum hose or can me much more involved if it's a bad intake manifold gasket.

But I'm suspecting it's not a vacuum leak because those usually cause the idle to go up, not down. Do a tune-up, then check the codes and post back what you find.

__________________
89 Prelude 2.0Si 4WS
91 Prelude Si - SOLD

Archeantus

I havent checked the codes, but driving around yesterday I noticed that it ONLY stalls when I brake on a down slope. The steeper the slope, the faster it stalls. It's also aggrivated by the amount of gas I have left. ( less gas = more stalls).

Colfax

I wonder if the previous owner did a carb to fuel injection conversion and kept the original gas tank. What you are describing may indicate that you may have a problem with the baffling in your tank. There are baffles in the gas tank that keep gas near the fuel pump pickup so that you don't lose fuel pressure when the gas level is getting lower and starts to slosh around the tank. You will need a new gas tank if that's what the problem is. Be aware that S (carb) and Si (fuel injection) gas tanks have different baffling, and you want to use the right tank for your fuel system.

Try keeping the tank topped off (no lower than 3/4 full) and see if you are still experiencing problems.

__________________
89 Prelude 2.0Si 4WS
91 Prelude Si - SOLD

Scotty3500

I just found this site and was astounded by the problem...I too, have a 1988 prelude (si) and am experiencing the same problem. I have no stalling when the gas tank is full and the same problems you are having when the tank is half full...hard downhill stops on a half of a tank..it stalls out. My mechanic said he thought it may be the baffles but was not sure. What did you eventually do to solve the problem?

Colfax

I doubt he solved the problem yet since his last post was Friday. But if it's baffles, the easiest fix would be to replace the gas tank. Maybe you can find someone who will fix the baffles in your tank, but it may cost more than a replacement gas tank because of the labor involved.

__________________
89 Prelude 2.0Si 4WS
91 Prelude Si - SOLD

acedude450

check your brake booster line going to your intake manifold its the biggest vacuum line going from the manifold to the drivers side fire wall and hooks up near the brake fluid reservoir

__________________

89turbolude

i was having the same exact problem and it progressively got worse. Now my car wont rev past 1000rpm's but once it gets past that point it runs ok, but while im accelerating it shutters like the power is there periodically. checked all the vacuum lines all fine. i replaced fuel pump, fuel filter, air filter, spark plugs, and wires. the car acts like its not getting enough fuel cuz i can have it floored and it not do anything. but it idles fine at 1000rpms but only so often it will get above that but if i let it get below 2000rpms when im driving it takes a while for it to get back up in the rpm range. if unplug the map sensor it will rev up only to about 3000 rpms but it will go in and out cuz thats not hooked up then i hook the mas sensor back up it dies. and help would be great.