Car shuts off when braking or large rpm drop
 

I have a 1997 Honda Prelude (base model), H22, 5spd transmission, 230k miles. The car randomly shuts off when decelerating/braking to a full stop. However, the car starts back up with no problem and idles and drives fine. This does not occur all the time, just randomly.

I do have a couple of CELs:

1) Knock sensor. I have checked the resistance across it. It is bad and needs to be replaced.
2) EGR valve.
3) ABS voltage too high. Possible bad control unit. I have not checked yet.

So, I tried to narrow things down. The problem occurs when decelerating, not braking. If the car is in neutral and braking to a full stop, it will shut off. If the car is in gear while braking, the car will return to idle as expected. In the driveway, if you rev the engine to 5k rpm and let off of the gas, the rpms will drop and the engine will cut off. If you rev the engine to 4k and below, the engine will return to idle as expected.

Other than the car shutting off, everything else operates fine.

So far…
-I have replaced the wires, spark plugs, distributor cap, and rotor button.
-I ran a compression test: 185psig in all cylinders.
-I have checked for vacuum leaks; none found.
-I have cleaned the IAC and EGR valves; no change.
-The problem occurs whether the gas tank is full or empty.
-I have wiggled the key in the ignition easy and rough; no change. The car does not cut off.
-The battery voltage is good.
-The oil level is fine.
-The coolant level is fine.

I know there are a few other things I could do, but I am looking to see if others have ran into the same issues before continuing to troubleshoot.

Re: Car shuts off when braking or large rpm drop
 

wow, i have been reading and re-reading this over and over. first thought was IAC, but if you dont have any fluctuating idle and you pulled it and cleaned it (the IAC should read between 8-15 ohms, i believe those are the right numbers) what is the normal idle speed on a good day? sounds like a carbon build up somewhere. if you have access to a spare, try changing out the EGR. wish i knew more, if i remember anything ill be sure to thro it down. does it stall whether the engine is hot or cold? also check the intake and make sure all the hose clamps are tight up and down. if there is no vacuum lines off, are there any kinked? also get a bottle of brake clean and while the motor running spray around the intake mani and all vacuum lines, the car will bog if there is a leak. just throin out some random stuff.. hope i helped a little bit. Fair winds and following seas

Re: Car shuts off when braking or large rpm drop
 

^ like he said check for vacuum leaks, but start with the knock sensor, and also clean the egr ports

Re: Car shuts off when braking or large rpm drop
 

Sounds crazy but try running your air conditioner while you idle. If that holds up the idle then I'd double check your vaccume lines. It took my like 3 days to locate two staple size holes in one of my lines. Good luck

Re: Car shuts off when braking or large rpm drop
 

A better way to check for vac leaks is use a propane torch, [don't light it :thud:] start the engine, open the valve on the torch move nozzel tip around the vac lines, don.t forget the brake booster, a rise in RPM indicates a leak, it is not messy like brake clean would be, a BIC lighter will also work but harder to move around as you need to hold it "on". 94

Re: Car shuts off when braking or large rpm drop
 

Internal leak in the brake booster.

Re: Car shuts off when braking or large rpm drop
 

This might sound stupid but rev limiter?

Re: Car shuts off when braking or large rpm drop
 

Have u found out what it is? I have this same problem.