starting/stalling problem

[westernb4]

My 93 NSX (I have owned it for 12 years) has developed a problem with
hard starting.
Engine turns over just fine, but won't start unless I press the accelerator while I turn the key. Even then, it stalls several times a few seconds after starting. I can tell by watching the tach whether it's going to stall---the revs
drop to zero, often several seconds before it actually stalls, even though the engine is clearly spinning when this happens.
When it does finally start, it runs just fine, especially if the engine is warmed up just a bit.
I replaced the main relay, because it's a simple repair, but the problem did not improve.
Any ideas about the cause of this problem?

 

[A.S. Motorsport]

A few causes,

IAC valve (idle air control)
Fuel pressure (FPR or filter)
Sparkplugs

 

[NSXCessive]

My 93 NSX (I have owned it for 12 years) has developed a problem with
hard starting.
Engine turns over just fine, but won't start unless I press the accelerator while I turn the key. Even then, it stalls several times a few seconds after starting. I can tell by watching the tach whether it's going to stall---the revs
drop to zero, often several seconds before it actually stalls, even though the engine is clearly spinning when this happens.
When it does finally start, it runs just fine, especially if the engine is warmed up just a bit.
I replaced the main relay, because it's a simple repair, but the problem did not improve.
Any ideas about the cause of this problem?

If you already changed the main relay you might have a bad Ignition Switch or Fuel Pump Resistor these are 2 other common problems seen on most cars.

To check the ignition switch check if the dash lights go out when the car dies, and sometimes if you wiggle the key in the ignition see if the dash lights flicker? Part # is 35130-SL0-003 probably run you around ~$35 from most dealers.

Fuel Pump Resister you can test it by jumping it out using a piece of wire or even a paper clip will work. If the car starts and runs replace it. Fuel Pump Resistor 1991-96 Part # is 16717-PR7-A01 around ~$48 from most dealers.

If none of these are the issue you could have dirty throttle body and vacuum lines that need cleaning which is also a common issue. If cleaning doesn't resolve you could also have a bad idle control valve.

 

[cmthomson]

I had a very similar issue. It would crank and fire, but stall right after releasing the key to the on position.

As you can guess from the above (20-20 hindsight) description, the problem was the ignition switch. It was intermittent for a while, then failed completely and had to be towed.

 

[westernb4]

Followup:

Finally got around to replacing the ignition switch and it solved the problem! Car is starting and running perfectly again.


Thoughts:

1. a bit surprised that a part like this would wear out with relatively few miles--79000 in my case.

2. I pried off the old part's plastic housing, and the electrical contacts were dirtier and more worn than I would have
expected. Based on the appearance of my part, it looked like just cleaning the contacts would have only been a
temporary solution. Based on my experience, I would definitely just get the new replacement part.

3. The repair really was simple, and if the part was in a more accessible place in the car, might have take 5 minutes to complete.
As it was, the job took me somewhere between 30 and 45 minutes to complete. To get to the repair site, you're upside down with
your head in a space much tighter than an MRI scan tube. Not a job to attempt if you're claustophobic.

4. When I was first under the dash to look around the area, I got a little confused because the ignition switch wires were carefully and tightly
taped to another bundle of wires next to it, making it look at first like the other wires, that led to other unrelated things, were part of the
ignition switch module. Removed the tape and things clarified.

5. It was not necessary to have the key in the ignition to remove the part.

Thank you to those that offered suggestions and comments.