WadeLovell

iTrader: (5)

My 1993 SC300 automatic is not coming back to life the way I had hoped. After replacing the head gasket, I have run into a series of issues.

The engine sounded great when I started it the first time (after the head gasket and some sensor work related to brittle wires and a little carelessness). I decided to go out on a main road and when I started after the light changed everything was blissful until about 3000 rpm when the engine died like I had turned off the ignition. It kicked back in around 1000 rpm and the CEL came on. It also stalled on a downhill and then at several stops on the way home. If I jump on it, it runs up to higher rpms. In normal driving, however, it croaks.

I recall taking the slop out of one of the cables but did not change much else. It was running beautifully before I started messing around under the hood.

Any suggestions? Anyone with similar problems? I searched the Forum but did not find similar issues.

Kind regards,
Wade

scviolence

iTrader: (17)

what code is it giving you?? did you set the timing right with a timing light?? did u replace plug & wires also with head change??

WadeLovell

iTrader: (5)

Thanks, the DTC is 31, Air Flow Meter Signal.
I set the timing with a timing light.
I replaced the plugs but not the wires this time (24k on them).

I ran it a bit in a more protected environment this evening. On flats it clearly shifts into second and runs through the low speed streets with speed bumps at under 3000 rpm. If I hit 3100 rpm power falls off completely down to around 2100 rpm. If I jump on it, I can run up to 7000 rpm and that is me limiting it, not the ECM.

I cleaned the MAF when I did the head gasket. I used MAF specific cleaner. I will reinspect the wires and connectors at the MAF next.

Kind regards,
Wade

sc-driver

iTrader: (7)

You shouldn't have used the MAF cleaner. Those cleaners are usually intended for hot-wire style MAF sensors. They don't work on your Karmen-vortex MAF sensor. The lexus SC had hot-wire 96-00, and karmen-vortex from 92-95.

Look at the cleaning can and read it carefully, it will say hotwire only. To clean the karmen-vortex sensor you need either a can of compressed air or some sort of electronics cleaner.

WadeLovell

iTrader: (5)

ARRRRRG! You are absolutely right! Plastic Safe in red. #1 Use on any MAF #2 Improves performance ...#10 (YES #10, don't use on Karman-vortex MAF sesors such as on Toyota...)

I removed the MAF and cleaned it with another CRC product, electrical contact cleaner. This time I also replaced the two O-rings. Reset the codes and calling it a day. I suppose I am probably in the market for another MAF but I will wait to see what tomorrow brings.

BTW, before it throws the DTC 31 it runs like a scalded cat. It runs better with the MAF disconnected than it does after the DTC 31 appears (but the shift points are much higher).

Thanks SC-Driver!

WadeLovell

iTrader: (5)

I ordered a replacement MAF with 90k miles on it from a Forum member last night.

I will test the car after last night's MAF cleaning but I am not sanguine about it coming back to life.

WadeLovell

iTrader: (5)

The front of the can is rather deceiving. #10 on the back of the can says, essentially, DO NOT USE THIS PRODUCT ON LEXUS CARS.

sc-driver

iTrader: (7)

I've seen these kinds of threads countless times, but I'm glad I can help. At least you won't be spending hundreds of dollars trying to diagnose the problem.

My SC is a 1996 and has a hotwire MAF sensor. I use that exact cleaner on it and have no problems at all. Even made the drive-ability a little better.

I know my brother's Audi A4 had a karmen-vortex sensor and so not suitable for that cleaner. It just depends on the type of MAF sensor. Hotwire is the only OK one to use that cleaner with.

WadeLovell

iTrader: (5)

Mine is a 1993 and it has the karmen-vortex MAF. That is a term I admit to not having heard until yesterday. I hope this thread has the right tags so others do not repeat my mistake.

WadeLovell

iTrader: (5)

Thought I had it! CRUMBS!

WadeLovell

iTrader: (5)

Just took it out for another ride. Waited all day because I did not really think cleaning the MAF with contact cleaner after messing it up with MAF Cleaner would work. It didn't! I made it about three miles further this time before it spit out the DTC 31. I unplugged the MAF to get home (otherwise it goes 22 mph at about 3100 rpm - push it harder and it shuts down). With the MAF unplugged the idle is really rough and the shift points are really high but it runs full speed.

WadeLovell

iTrader: (5)

Just communicated with the Forum member about the replacement MAF. It should be on its way Tuesday.

WadeLovell

iTrader: (5)

MAF resolved the problem. (Unfortunately, I bought two and installed the first to arrive.)