my car is stalling after i drive it on the highway or beat on it it doesnt do it all the time some times itll catch itself. anyone have any idea? thanks jerry

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1990 300zx 2+2 n/a
lowered
exhaust
nismo racing seats
k&n filter

It's injected, right?

Some of the later 240 cars had serious vapor lock problems (with the flat-top carbs) and experienced afterboil as well. The injector system was supposed to correct that.

1. When you beat on it, does the engine temperature change much?

2. After a full-throttle burst, does you rpm decline slowly, or "crash" back to idle speed?

3. Auto or manual?

4. There should be a vacuum-assisted dashpot somewhere in your linkage, which slows throttle closing after "bursts" ~ is it in good shape?

5. Does your car have power steering, and can you associate the stall with a turn (like the rpm being too low to handle the load of the P/S at low speeds?)

*(RDZ ~ Help! )
Frank

its injected and its a manual the temp does not change when i beat on it the only code on the ecu is the 02 sensor and i changed that out today and its when i press in the clutch and you can watch the rpms drop trys to catch it but then just dies
thanks

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1990 300zx 2+2 n/a
lowered
exhaust
nismo racing seats
k&n filter

Well, that's really odd. I'm trying to picture how pressing IN on the clutch would put any additional load on the engine.

Might you be pressing the brake at the same time? If the brake booster has a small tear in the diaphragm, that could dump your manifold vacuum when you pressed the brake pedal. But I'm guessing wild, not 'diagnostically'. Let me think awhile. (It's never happened to me that way ~ my engine has died PLENTY of times when I let the clutch OUT! )

Running hard on the highway raises internal engine heat, of course. With all the wind coming thru the radiator at speed, it's not hard to maintain normal temperature. But if you come hard off the highway without a "cool down" lap, it's harder for the fan to keep things cool. CARBURATORS often have heat-related problems at that time (afterboil, perculation, leaning out), but I don't think injectors should suffer from that.

Think about what ELSE is also happening when this occurs. We might be focusing on the wrong event, which is coincidentally happening, but is diverting our attention from the actual cause.

Trying to sound like a real mechanic ~ Frank

Another thought ~ when you de-clutch, the moving car stops "driving" the engine. If the engine has any low-throttle problems, it will then be unable to sustain itself and will die.

I want to wash my hands of any "injector wisdom", because a little bit of knowledge is a dangerous thing. What I do know is that unless your sparkplugs are in good shape and the proper heat range, the engine will not be happy to changes in combustion conditions (running hard at speed, then slow at idle).

Another *GUESS* would be a clogged cat. At speed a small restriction might not be enough to kill the engine. But at idle (when it's only making a fraction of its full horsepower), the engine might gag against the buildup of exhaust trying to escape thru the restricted catalytic converter. De-clutching at that point would cause the moving car to stop helping the engine turn, and it could choke out.

Somebody else get in here with some ideas, please

Frank

Have you changed the injectors and wire harness yet?

Is your problem still happening?
I was thinking, your car stalls when you press IN on the clutch, this happens because you are taking load off the engine. I have something similar in my Maxima right now. But all I have to do is tap the gas a little to save it.
To temporarily band aid the problem have you increased your idle RPM?

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CART Activites Director
2007 Nismo 350z

Sounds to me like the IAC (Idle air control) valve could be bad. It's an extra valve just downstream of the throttle plate, that lets different amounts of air bypass the throttle plate to keep the idle steady as different alternator and AC loads are put on the motor. They can be controlled by a vacuum line and solenoid or electronically (by the ECU) with a stepper motor, not sure which your car has.

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71 on a rotisserie, two more in pieces in my shed...and a 69 1600 waiting for me to get to it

Also check the voltage at the TPS . Replace vacuum lines as a leak will sometimes send you in the wrong direction.

Could be a number of issues. first do you have an aftermarket air intake?

If so, stalling is a problem because direct air hitting the MAS unit confuses the ECU. Common problem, shield the air filter using ABS plastic pot (email me direct I send you info).

If stock air box or shield is put in place and problem persists, then it could be any number of things some of which are mentioned above.

Because of the age and the number of different systems on these cars it is difficult to diagnosis over the net.
I can only offer to put you on my list of waiting customers and have you bring it in at that time.