if you do a search, there are many posts with symptoms of wandering idle and engine stalling while the car is sitting at the light. Perhaps even while cruising with the foot off the gas pedal. Well, after living with this "seasonal" problem for over a year, I finally had enough. I say "seasonal" because the problem is intermittent and mostly apparent under hot/humid conditions - definitely not there when it is cold.
On to the fix. Well, I have an Apexi S-AFC which reports on revs, throttle position, and airflow. This helped a great deal when troubleshooting. Every time I experienced the phenomena, I noticed that the throttle position was wondering off of 0%. This is when I had the foot off the gas pedal! Sometimes it would wander all the way up to 25% before stalling the engine.
Through the help of Todd M at TM Engineering, we deduced it was the TPS (throttle position sensor). I replaced it w/ a new one for $75, and the car now runs great!
Thanx again Todd!

 

I have a 1992 SC400 which has recently began not starting on occasion. The car is turning over just fine and I have replaced the battery and the starter in the last year and the fuel pump the year before, so I don't think that is the problem. Both time it has not started it has been much colder than normal. It happened yesterday and I tried several hours later and it started fine. This problem does not occur unless the car has sat for several hours without running.

I was suspecting the fuel filter, but I wanted to bounce this off of some of the gurus here first. Any suggestions?

Thanks,
Chad

 

In these kinds of cases, it's always best to start with a tuneup. If you don't know the last time the fuel filter was changed, go ahead and change it. Put in a fresh set of spark plugs as well, maybe even a cap and rotor.

Can you just NOT start it, even with cranking on it a while?

Dale

 

I should have mentioned this as well, but I did a tune-up last year and replaced all the spark plugs, and I keep it maintanined regularly.

What do you mean can I not start it? I don't know if this answers your question, but it will turn over fine, but it will not start. I can let it turn over for over a minute and it will not start, however if I leave it for a while it will start eventually. I have not replaced the fuel filter EVER, so that is another reason I suspect that. I have replaced pretty much everything else within the last 1-2 years.

Thanks for your help,
Chad

 

i remember reading a post about cleaning the ignitor contacts, maybe give that a shot.

 

Check out the cold-start injector for proper function.

Good luck,

DJL

 

i have the exact same prob with my 92 sc400. it has been tuned up with new oil, plugs, fuel filter. ... when you start your car, check to see if a small cloud of smoke emits from the exhausts for a brief moment upon startup. if so, i would suggest you have atleast one leaking injector. good luck!

 

I tried to perform a test yesterday that a mechanic suggested (spraying auto starter fluid into the intake with a hose off), but the car started up just like normal before I had a chance to test it. I am going to replace the fuel filter today and see if that fixes the problem since that is a relatively cheap fix and it needs it anyway.

Thanks,
Chad

 

I recently purchased my 94 sc400. Most everything seems ok - I have had the dealer do a tuneup and clean the injectors (pressure cleaning?). They missed the coolant leak around the resourvoir hose at the radiator, even though they supposedly did a pressure test, and the low power steering fluid.

My problem is that if the car sits 3 to 5 days without being used, when I start it it runs very rough, like its on 4 cylinders, and puffs a grey/blue cloud out the exhaust. It will run rough for 30 secs to 1 minute then it clears up and runs fine. No problem if I start it every day or every other day. I quess it could be faulty valve guides/seals, but it only has 38,400 miles on it. Is there another possibilty - a cheap one by any chance?

Thanks
Jim

 

MAF could be getting moisture in it.

Where in TN are you?

 

i am in West Knoxville.

Thanks for your suggestion. Is there any way to check for moisture?

Jim

 

Another possibility is leaky injectors - letting the car sit for a bit, the gas depressurizes into the combustion chamber, flooding the engine.

Don't know if it would be as drastic as you've seen, though.

Have you changed the fuel filter? Good plugs/wires/rotor/cap?

Dale

 

Man! i have the same exact issue....didnt start happening until winter hit here in sacramento I think a tune up is in order though...i have had the car for like 2 years and the only stuff that i have done is just oil change/oil filter religiously every 3k.

 

It is cold over here in Minnesota. Every morning when I started my SC400, it running rough and shaking like the engine misses fired. This problem only happened if is about 20F or below. After the car is running for about 5 minutes, the problems go away. Any suggestion would be appreciate.

 

I have the same problem in my 93 SC4. I've changed the maf sensor and the fuel filter. Still does it. I've been having too many problems with it so I'm selling it. I never thought I'd say that, though.