Engine shutdown on deceleration
 

anybody ever heard of this? I was driving on the freeway and I let off the gas and the tach dropped straight to 0 RPM. This happened 3 more times. When I got home I removed the Air Pump and noticed that it actually runs pretty smooth now. I havent taken it on the freeway yet, cause i dont wanna be stuck on the freeway.

Could the ACV be the culprit for this deceleration bog?

Thanks

-Jon

mine did that when it wouldnt idle. if i didnt give the car gas it would shut off. when i would get off the highway i had to hold the clutch in, hold the brakes and try and give the car gas at the same time. once i fixed the idle it stopped

hmm...weird stuff, thanks for the reply i'll have to play around with the idle and A/F ratio a bit more then.

oh ya thanks for the electric mirror switch, it works quite nicely t-66.

You mean to say your diriving down the hwy and let off the pedal and the engine dies?????????????? Really. With the transmission still in gear?????????????

Or are you talking going down the hwy, pulling the shifter to neutral with the foot off the pedal??????????

On the whole the airpump has zip to do with engine operation. On the whole it passes fresh air to the exaust ports/split air pipe and not much more except the anti afterburn feature.

My old engine use to do this as well. Also the other symptoms were

Hard warm starts
Rough idle

The problem was my fuel pressure was spiking when it shouldn't. The FPR is connected to an electronic solenoid that the ECU controls and the ECU wouldn't turn the solenoid on to allow vacuum to the FPR. So I just connected the FPR directly to the intake manifold and my problems went away.

This was on an n/a

Ignition switch?

mine would only do it when getting off the highway or whenever i was sitting at idle. if i didnt give it gas, the car would shut off

BAC valve, vacuum leaks...

Mine did that for no reason for a couple days. I'd be driving, and let off the gas, then instantly car died. Don't know what fixed it, but it worked after it dying a few times.

thats what fixed mine...fixed a vac leak and adjusted then bac valve

Yes it was crazy, I was in 5th gear and I let off the gas and when the RPM's started to dropped and the needle just flew down to 0 RPM and the motor just shutdown. I did this repeatedly for 3 or 4 times regardless if it was in gear or not, it was just more prone to doing so under load in gear.

Yes I'm beginning to think it is the BAC valve because there was a random ticking noise from that area on the Dynamic Chamber so I will test it and see whats up with it.

Come to think of it I did find that hose that ran from the boost sensor (N/A) to the LIM or UIM which ever it is was quite loose so i replaced that. Other than that I didn't any other leaks and the car now idles at a solid 750RPM.

I will test the BAC Valve and post results right now.

Thanks for the replies,

-Jon

OK I tested the BAC Valve and found it read out 13.9 Ohms, which from what I remember is in spec. I also supplied 12volts to it and you could see the Valve open every time you applied 12 volts.

I did notice a squel or grind upon cold start, but it went away once it started to warm up. I know this motor burns quite a bit of oil so does anybody think there is any relation? Maybe internal motor parts wearing out?

-Jon

Compression test is done and it is

Front Rotor: 100psi
Rear Rotor: 90psi

The only thing i noticed that was wierd was that when I pulled the plugs out, there was quite a bit of carbon build up on the flat part of the plug.

Could my motor be showing early symptoms of Carbon Lock Up?

What do you guys think?

Thanks

-Jon

5th gear implies a manual.

With the clutch engaged (foot off the pedal), in 5th gear, there is no way the engine can stop turning if the car's moving. The ONLY way for this to happen is if the clutch is slipping, or the transmission is broken. So I'm confused as to if the tach dropped to zero (electrical problems), or if the engine actually stopped turning in gear (indicating the car was stopped, or your clutch is really, really fried, at which point you probably wouldn't even get to highway speed).

Those numbers are pretty low. It might be worth considering a rebuild before it blows completely, destroying a rotor and housing in the process.

Also, carbon buildup on the plugs (especially the trailing plug) isn't terribly abnormal. The trailing plug fires into a chamber with a small hole leading into the actual combustion chamber, so it doesn't get cleaned very well.

-=Russ=-

ALSO if you used a compression tester for piston engine those numbers only give you the highest compression of 1 of the three apex seals, other 2 may be less because it only shows max compression total rather than all three seals per revolution make any sense?

Spray carb cleaner into the valve and then cycle it a bunch of times with 12V. Rinse and repeat several times. This will clean the valve and passages.

No, it's not carbon lock. Carbon lock will lock an engine solid.

If your in fifth gear and just let off the pedal and the engine dies, It's not BAC related in any way.

You've go the car in gear and the mass of the car is going to keep the engine turning over til it comes to a dead stop which in turn means the ignition should not have died (tack went to zero immediatley).

Sounds like the power wiring to the ECU has come undone during deceleration.

Yes, i tested the BAC and found it was fine.

Ya i could hear the motor still winding down once the tach dropped to 0, and so it must be something odd with the wiring that was making the ECU shutdown.

One thing I do recognize leading up to this event is that, sometimes when I'm cruising in 5th gear on the Freeway and was starting to let off the gas ever so slightly, the car would get that feeling that it was running out of gas very slightly.

I'm goin down to Autotech Motorsports (local Rx-7 shop) tomorrow, I dont know if anybody is familiar with them, but I will see what they have to say.

Thanks

-Jon

Could a funky ignition switch also make the car shut down randomly?

Those numbers are not low. 90 and 100 are pretty damn good numbers.

If you needle drops to zero while the engine is still turning you deff have an electrical problem. Like Hailers said.

It could if its bad.

OK i found the problem, and it turned out to be a vacuum hose that goes from the boost sensor to the Intake Manifold. You could not tell that the hose was the problem by just looking at it because it appeared to be that the hose was soak in oil therefore cause the silicone to expand (while still on the nipple) and leak quite a bit.

Thanks for everybody help

-Jon