When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey guys
I have a 97 sc400, just wondering what was the proper idle and drive rpm levels for my car.
I am trying to attach a pic of the dials because Im unsure what the two bottom hash marks stand for. From 0-1000rpm, we have 3 hash marks in between, I know the one nearest the 1 is for 750, just wondering what the other 2 stand for. My car in park usually idles at 750, or just below that hash mark.
Now, once it warms up for the life of the car at a stop light or in traffic the car idles at the 2nd from the bottom hash mark.
Just seeing if this is normal for my sc400 and what those hash marks mean (rpm #)
Have had an issue with car turning off and turning back on immediately a few times in the morning every few months but recently had the car turn off while driving and then when restarted would surge up and then stutteer down, when put into drive or neutral would stall out. Fixed serpentine and havent had an issue since.
Just wondering if my car runs at a normal rpm or if I should adjust the idle higher. I like it idling low as its super quiet when driving but if itll prevent a stall out in the future or its at an improper level I would make the change no problem.
why are you at 20mph though with the car at 0 rpm's and the door open. something wrong with the speedo?
the first mark is like 250 and the second at 500. maybe the first mark is a little less?
where is your sitting at idle again?
I would say your idle sounds mostly normal. maybe a little on the low side. try resetting the ecu and letting it relearn.
how long ago did you do o2 sensors? might play a very small part in it.
I should say that the pic is not of my car, just one I found off google to show what the sc400 tach looks like.
My car when started cold will idle at around the first white notch above 1000rpm, then as it wartms it will settle around the third notch above 0, first notch below 1000. Then, once warm, itll find its way down to the second notch above zero and sit there queitly without issue. Ive had the car since 2010, has idled like this since then, never an issue except for a few mornings where id start the car, would rev up then stall out, would start back up one or two more times, then it'd be fine for months.
Now recently, I was driving and the car stalled on me. When trying to start back up, the engine would rev, then sputter down, down, until it stalled out, never allowing me to get going and forcing me to be towed to lexus, where I had the serpentine belt changed. No issues since
Its really bothering me because the one thing I loved above all else about my car was its relentless reliability even in the colder weather of PA.
Just want clarification that that second notch above 0 is 500rpms, and that that is normal or should I adjust idel higher? gas mileage is not an issue.
Also, any ideas on the issue that left me stranded for the first time.
that second line is 500 and it is a little low to be at 500 (should be about 650), but its not that far off.
you may want to do the o2 sensors, that could be causing the little bit to be off since you do have a code for them they are probably both very old.
there is no right way to raise the idle, its controlled by the ecu. if you do raise it via the throttle body mechanically then it can cause other issues so I would say leave that alone and fix the known problems first.
sometimes these cars stall out when the fuel pump ecu is going bad. there is a 12v fuel mod quick fix for getting around that but its not the best to leave it permanently.
nope I don't know and the number of wires and type of sensor vary so you have to look yours up or what I do is go take a look at it and count the wires and see if its screw in or bolt on and then order the correct denso universal one and splice it in.
when the fuel pump ecu gets bad enough the car won't want to start anymore. that is the main symptom.
if the o2 is feeding garbage to the ecu though it wont be running at the right air fuel and can affect the idle.
I wouldn't try and fix an idle problem when there are codes like that, cause there is a decent chance its a result of the o2 sensor code.
Kinda hard to idle at the exact right rpm if you don;t know what the air fuel ratio is on one bank, and then whats even worse is that its not throwing the code for the other bank and unless someone just replaced 1 o2 sensor (rarely happens), then likely the other one is old and bad also, just not bad enough to throw the code. this is worse cause its likely slow but the ecu still thinks it can read it. If you have not done both front o2 sensors ever, or don't know if they have been done in the last 100k miles, just go ahead and do them since you have a code. that would be my suggestion. will it fix the idle problem, hopefully, but there is no guarantee that is the only issue, but its hard to figure out what else is wrong when you are looking at something thats already wrong unless you fix it and then go forward.
The stalling could just have something to do with the alternator also and not the o2 sensor. I do think the o2 sensor comes into play but how much is the question, might not be bad enough to stall on its own. but if the alternator is getting soaked it could be having a tough time keeping up at that low of an rpm. was the old serpentine belt bad or something, just changing the belt should not have fixed it unless its something that went away from cleaning the alternator or something else they did.
I am not sure how the o2 sensors on the sc400 vary over the years, if it was a 300 I could give you more info but the denso is the right brand just need to figure out the right model number.
there will be 2 types, screw in and bolt on. the screw in type have threads on the end like in the picture on that link, and the bolt on type will have an extra flange at the end and 2 holes to bolt it on.
I would say if you can get a flashlight and spot one of them you can see what kind and how many wires they are. some are 1 wires, some are 4, like all california models are 4 wire. once you figure all that out you order the right denso sensor and it will be easy. like in that link its a 4 wire screw in type.
the sc300 uses more of the bolt on types until you go turbo downpipe and then you need screw in.
The v8 I am not sure but if you get screw in type and its bolt on, well thats not going to fit without an adapter.
you can also look up the part number in a catalog for your car based on vin number or year etc..
once you get the right one its a matter of removing and fitting the new one, and then matching the wires up which can be a little tricky the first time but not too bad.
also good advice for removing o2 sensor is to drive the car around till the exhaust is heated up to normal temp, then shut it off and crack the o2 sensor loose with the special o2 sensor socket before the exhaust cools down. I usually wear gloves and long sleeves as to not burn myself when the exhaust is hot, but if you do it like this with the right o2 socket it will break free easily every time. If you do it cold it usually requires a much longer breaker bar and a bunch of PB blaster and hopes and wishes that you don't pull the threads out of the manifold cause its so seized up over the years. The heat lets the exhaust expand some and makes it much easier to crack it free.
I will usually wait till the exhaust cools down though to finish the rest of the work, I just break them free when its hot.
11-30-14, 06:44 AM
Need Some Help With RPMs
