stokdd

I have searched and found a decent thread with a lot of useful info. It also contained a lot of off-topic crap. Instead of having to sort through 5 pages of random stuff from a two-year old thread, I figured it wouldn't hurt to make a new one that's a little more user-friendly.

Problem:
My '95 SC400 has a hesitation issue.

Syptoms:
1. A split second after accelerating (at any rate) from a dead stop, the vehicle hesitates significantly. It almost feels like the car is a manual transmission and the driver doesn't know how to drive a stick.
2. Under very light throttle (maintaining speed) the vehicle hesitates/bucks. Most prominent just above 40mph.
3. Occasionally under full throttle the vehicle will hesitatly sharply at 4,000rpm.

Failed fixes:
1. Replaced spark plugs with OEM Lexus
2. Replaced spark plug wires with OEM Lexus
3. Checked intake tract for leaks (none)
4. Thoroughly cleaned MAF (VAF) with electrical cleaner (completely disassembled to clean)
5. Reset ECU following these guidlines

Temporary fix:
Using this information I unplugged my MAF (VAF) and the vehicle runs stellar, with the exception of the inability to idle (due to MAF being unplugged) and a CEL.

I do not know what the ECU does when the MAF is disconnected, but it works. After finding out the the car runs perfect with the MAF disconned I thoroughly cleaned the MAF and reset the ECU, but to no avail - the hesitation issue remains.

Contrary to what many people suggested in other thread, I don't think the issue has anything to do with a clogged fuel system/injectors. Replacing the plugs/wires made no difference, so I also doubt it lies in the ignition system.

I know many people have (or had) this problem. Feel free to share any information you may have!

Drocay

This happned to me on saterday, out of no were which really pissed me off hopefully mine can be fixed with just a MAF cleaning we'll see. But from everything i read replacing the TC didnt do any good either.

Tammy

Your mileage, please ?

dinhNER

iTrader: (5)

interesting i wanna know more

stokdd

123,XXX miles

jibbby

I would go for the fix in this order until solved...

Clean out the throttle body.....
change the air filter...
Check the Throttle position sensor...
Change the spark plugs, wires, caps and rotors...
Change the main battery ground cable
Lastly all electrical...or go get a diagnostic check to see if something is a miss...


Good luck..


I always got and get hesitation from a dirty throttle body...that is probably the kulprit..

stokdd

But why would the vehicle run absolutely perfect when the MAF is unplugged? Did you actually read my post all the way through?

DIYsquirre

Any updates? My Sc300 is acting the exact same way.

Regardless, Bump for this thread.

over40driv

The best result to clear a hesitation after all standard diy, like fuel filter, is to have the injectors cleaned at a diesel injection shop out of the car.

Och

iTrader: (3)

Any solution yet? I'm having the same issue with my 94 LS400, which has the same engine. So far I cleaned the throttle body, replaced spark plugs, wires, distributor caps and rotors, cleaned maf, all at no avail.

over40driv

Sounds like it could be a bad maf.

stokdd

^ That's what I'm thinking. Nothing has helped....

Happen to have the testing procedure for the VAF?

sc400CTI

Check the main coil. Since the car has 2 coils the secondary will make up for the main , leaving you with hesitation. Number two check the cam position wire of the distributor housing (behind the ignition covers) the wire sometimes rubs the timing belt (cuts the wires). Hope it helps.

2JZ_SC

I could be wrong, From what I have seen, One coil runs one side of the motor and the other side runs the other. On TIS (Toyota/lexus Tech site) there is nothing about a main and a sub coil. Only Right and Left. From the EWD It looks like that the only common point for the coils is the ingition switch. The 1UZ not only has 2 coils (one for each side of the motor) but 2 Igniters as well.

2JZ_SC

Will this work????


SFI (1UZ–FE) – MASS AIR FLOW (MAF) METER

FI6961
Ohmmeter
E2 THA
SF0SE–03

INSPECTION

1. INSPECT MAF METER RESISTANCE
Using an ohmmeter, measure the resistance between terminals
THA and E2.

Temperature Resistance
–20°C (–4°F) 10 – 20 kW
0°C (32°F) 4 – 7 kW
20°C (68°F) 2 – 3 kW
40°C (104°F) 0.9 – 1.3 kW
60°C (140°F) 0.4 – 0.7 kW

If the resistance is not as specified, replace the MAF meter.

2. INSPECT MAF METER OPERATION
(b) Connect the MAF meter connector.
(c) Connect the negative (–) terminal cable to the battery.
(d) Using a voltmeter, connect the positive (+) tester probe to
terminal VG, and negative (–) tester probe to terminal
EVG.
(e) Turn the ignition switch ON.
(f) Blow air into the MAF meter, and check that the voltage
fluctuates.
If operation is not as specified, replace the MAF meter.

(g) Turn the ignition switch OFF.
(h) Disconnect the negative (–) terminal cable from the battery.
(i) Disconnect the MAF meter connector.
1996 LEXUS SC400/SC300 (RM438U)