My car was stalling at stops about once a week. I didn't think anything as it always started back up right away. One day it did it twice while driving and then stalled while on the highway. Since I was rolling on the highway I kicked the clutch and it restarted however I couldn't really accelerate much and it would not go into boost. It stalled again in a quarter mile and this time it did not want to start. I managed to get it onto the off ramp and tried to restart it.

It was difficult to start and when it did it sounded like it was on one rotor. It would only start and run with the accelerator pinned to the floor. Sometimes while stumbling it would catch and rev all the way up to redline like it was fine but go back to stumbling/stalling once the accelerator was released. I ended up having to tow it home.

There was spark and fuel, TPS signal was within spec, and the CAS signal seemed good since I had a tach signal. I didn't do a compression test but by listening all pulses seemed even on both rotors. I cleaned the spark plugs and replaced them and it still didn't start. I ran across a thread that mentioned similar stalling/start issues with the coolant temp sensor so I inspected mine. Sure enough mine had crumbled into dust so I replaced it thinking it was the culprit - but it still didn't start.

With nothing left to do and not wanting to chase crispy wires and plugs under the UIM I decided to just swap the plugs for new ones as a last attempt and it started right up! All that troubleshooting and all I had to do was put in new plugs (which I had laying around the whole time!).

 

Good PSA.
Never had the stalling but starting has always clued me in. If you didn’t know the car you’d think my car starts up “normally”. But with time it will start taking just a half-second more cranking, and maybe a half-second of lumpy idle before it fires and settles down. That’s always been my ‘tell’ that the plugs are due.

 

Sgtblue, that is exactly how my car was behaving for the last few months. I had assumed it was a weak battery due to age. Now it fires right up and even idles the best it ever has.

The old ones seemed fine as I pulled them and visually confirmed sparking at the electrode when cranking which is why I disregarded them as being the issues. I can understanding starting issues but it is baffling as to why they would just quit mid drive.

 

Visual spark plug inspection can miss the cause of misfires, since it's often hard to see the conductive deposits on the center electrode insulator that bleed off voltage and make the plug not fire.

There are several conditions that make these misfires more likely:
o Low RPM that gives the voltage more time to bleed away, and
o High charge pressure that makes it harder for the spark to jump to the ground
o More than normal gap and/or rounded/worn electrodes that need more voltage to fire

Back a long time ago when plugs were routinely oil fouled, there were plugs made with an internal gap to force voltage to increase (w/o bleeding off) to a point where a fouled plug would fire.

 

My cars up for the winter. But the PSA caused me to add a set of plugs to the coming-out for spring list next year.

 

I’ve had the same issue, replaced my fuel pump, checked tps etc and still chokes like it’s not getting fuel and stalling while driving or idling when already warm. Starts up fine though.
Going to give this a shot, praying this is the issue, been chasing this for months.

 

Good luck Tom Smith, that sounds exactly like what I had going on. If it doesn't work don't forget to check the coolant temperature sensor too as I was 100% confident it was going to be the culprit after reading up on it.

I've always known these things were bad with spark plugs. I've heard of people religiously replacing them every other oil change too. I was just never a victim until now and I'll admit these are the same new plugs that the rebuild was restarted on but I thought I'd get more than 10,000 miles on them.

 

NGK Platinum plugs are only good for 5-10k miles. Generally more if it's a stock or near-stock car, less if it's modified and/or using some sort of aftermarket ignition (IGN-1A, HKS Twinpower, upgraded ignition amp)

When in doubt,, change them out. Cleaning 9 times out of 10 doesn't help.

Dale

 

mine have maybe 2k miles on them, but, had a whole new engine installed, so the break in and leaking turbo may have fouled my plugs prematurely. I’ll let you know how it goes.