I have an intermittent performance problem with my 93sc400 running good most of the time
but occasionally very poorly .... no power, max 3000 RPM pedal to floor. Car dies and
then normal again on restart. May go several weeks before recurrence of problem.

I suspect an unstable ignition coil. My questions are:

1) I have read that the drivers side coil is usually the one that goes vs the other coil due to being
exposed to higher temperatures (closer to engine block). Is this a valid point??

2) Can I disconnect this coil and start the car to see if the car runs similar to the poor performance
when in the problem mode. Would this disconnect hurt the car or would the car even start??

Plugs look good and MAF is sparkling clean. Throttle plate and housing thoroughly cleaned.

OBD checks show nothing. Car has 90K miles and in excellent condition.

 

if you disconnect the coil and nothing changes, you know you have a bad coil. If you disconnect it and its much harder to start or starts and runs worse than before, than that coil was working before you unplugged it. you only have 2 coils to test, and yes it seems to be more common for the drivers side to go but either one can go bad really.

 

Yes, the drivers side coil would be the culprit in this case. Make sure to report in the "coils" thread and let us know how it goes.

 

Thx Ali SC3 for your reply.

I plan to unplug drivers side ignition coil and start car. If it starts and runs, I will see if the same symptoms occur... no power and can't get rpm's above 3000. This should tell me that this coil is the root problem. Does this make sense?

I guess what I am asking is, even with only 4 cylinders operating, can you get car to rev above
3000 rpm. If so, then my problem is most likely not the coil.

 

Slide...thx for reply. I will let all know how I progress thru this as I know it is a common problem but
each case seems to be different.

As a side note, my wife is constantly on my a** to sell this car and get a new one but before I do
that, the divorce papers would be activated..been married to her for 47 yrs. I also am the
original owner of a 1965 Mustang 289 coupe (pony interior) and I get the same story, Why can't
the other half let us have our fun.

 

I've had the same problem on a 4-cylinder, the engine amounted to no more than 3000 rpm !

 

Believe it or not it will go above 3000 rpm's with 1 coil but it wont be like normal or with much power. another issue that is related to not being able to go past a certain rpm from experience is the tps out of adjustment/bad, or a cam/crank sensor issue. If it was the tps though it would have issues shifting as well, as in it may not shift into the next gear at all the right times, so I am thinking its prob not that. cam/crank it would run badly possibly throw the light. on the front of the motor there are a couple wires by the accessory (serpentine) belt for the cam sensors and stuff, make sure the belt is not eating through any wires really, but especially the 2 by the coil sitting on the engine.

Lol, Yeah that will tend to happen some of us do spend a good amount of time with the cars, maybe even too much time, but it is funny though that is how I got my 1985 Toyota 4x4, I bought it from a older gentleman who bought it in 1985 brand new off the lot, drove it for 25 years, and his wife told him after all those years he had to get rid of it and I was in the right spot at the right time to get it. DMV workers were shocked when I slapped an original 1985 title on the counter they almost didn't know what to do with it, I should have framed that thing.

 

I noticed that recurrence of my poor performance usually happens when car has sat in sun or
in hot garage. This morning the car started and ran normally. I removed the MAF sensor and
heated the sensor element with a hair dryer, replaced and immediately started car. Guess what....
the erratic performance showed up just as before. I let car sit for an hour and the car started
up normally. Repeated the hair dryer treatment and bad performance again. I am convinced
the unit is faulty as suggested by the retrieved error codes 24 and 31. I also read that if the
sensor connector has 5 pins, the the unit is both MAF and IAT combined which clears up
the 2 error code readout.

I hate beating this dead horse but MAF's are very expensive new. I can't find a used one on
this forum as suggested by another member. I found a new one for around $150 at the web site
below and the sensor is supposed to be compatible with my 93sc400. The body of the unit
looks exactly like mine but the sensor element looks different. No silver wire or little bulb on the
bottom of mine. Anyone have any comments re the test I ran or as to the unit listed below working
as a replacement sensor?? Laying out $450 or more for a new OEM unit and later finding out that
the diagnosis was wrong would be very depressing.

PS ... I put my 65 mustang in garage if you wish to see the other car that p****s my wife off.
Today is our 47th annv...maybe if I take her out she may lay off for a while



New Mass Air Flow Sensor Meter MAF for Lexus sc400 Toyota Supra 2220442011 | eBay
New Mass Air Flow Sensor Meter MAF for Lexus sc400 Toyota Supra 2220442011 | eBay

Last edited by SC93; Today at 12:44 PM..

 

Don't need to lay out 450 for an MAF, (AFM in your case). http://www.ebay.com/itm/90-94-LEXUS-SC-400-SC-300-GS-300-LS-400-MASS-AIR-FLOW-SENSOR-OEM-22204-42010-/231024737149?pt=Motors_Car_Truck_Parts_Accessories&hash=item35ca25bb7d&vxp=mtr

 

all the toyota maf's have an integrated temp sensor and they all share the same grounds so you do usually get those codes together alot of the time. It does sound like a bad maf then, and those maf's are the picky frequency type that are tough to clean properly. The one on ebay looks like is generally the same part but you are right the base looks different, the toyota one is more covered but it is most likely aesthetic as non oem parts sometimes do look a little different but if everything else is the same and they say it fits it could be worth a try.

 

Thx for the lead slide. My part number is slightly different 2204-42011 vs 2204-42010 but
I am sure it is a duplicate and will put in a bid and also consider the one on ebay for $160 now that
Ali pointed out the aesthetic issue re non oem parts.

 

it is wierd though on the non oem one that they list it for the 300 and the 400. I guess the main difference is just the size of the housing and not the sensor itself. If thats the case you could use one from a 300 and well and just put it in the larger 400 housing, but I am not positive on that one maybe a last resort?

 

Tired of chasing this issue. Bought the $160 unit on Ebay and will report results next week
when unit arrives.

Thx guys for your imput...... hopefully this will end my woes and I can contribute to the data base
to help others with similar problems.

 

Got new MAF sensor and after installation the only difference in my " come and go" good/bad
performance is only error code 31 shows up rather than both 24 and 31 codes. This may
be due to the new sensor being exposed metal wire type as opposed to the one it replaced which
was a karmen vortex unit.

I guess my next move will be to check out the ICS located on the air duct where the throttle
plate is located and remove for inspection and cleaning. I also read that the 31 code could be
due to a ground/short problem but all the visible wires appear look in good shape and the
connector to the MAF sensor looks normal.

Any comments would be appreciated.

SC93

 

If I were you, I'd would have replaced the SC AFM with what came out. If you replaced the Karmen vortex AFM with a 95+, IDK if it will work the same way. I'm pretty sure you'll have problems. Ali will know.

The ICS, (IACV), probably should be cleaned if it hasn't yet. There are a couple of DIY's here on CL of doing that.

Sorry if I missed it, but whatever happened to the coil replacement? That would make the most sense if it were that.