drone6

Last week, my 93 LS broken down so ended up taking it to the Lexus dealer, the car wouldn't go when giving gas more than 5mph. They said that the Mass Airflow Sensor needs to be replace - $1800 to replace it.

I said no thanks and decided to do this myself. So, after looking closer at the issue, I can see that the MAF assembly looks fine, so I thought I'd just replace the sensor. Bought one from ebay and replaced it yesterday. However, still have the same issue.

I saw on another thread that some people have unplugged the MAF and the car still works, so I did the same. Sure enough, everything seems to work - plug it back in and it doesn't work. By "it doesn't work", I mean that the car does turn on, seems to idle fine, no lights are on (Trac, engine) but when I give gas (in Park or D), the engine hesitates and gives out after about 1500rpm.

If I unplug the MAF sensor, it works fine, but I get the Trac light.

The next thing I'm thinking of trying is to replace the MAF assembly with one from ebay (used).

Anyone have any suggestions?

Legender

hmmmm, interesting...
You don't say what happens if the MAF is unplugged and you try to drive, or increase the RPMs. With the MAF unplugged does the car behave the same at 1500 RPMs as it does with the MAF plugged in.... that would help to isolate the problem.

somewhere on this site should be the test readings for the MAF to see if it's good or not...
check this thread...
https://www.clublexus.com/forums/mai...elerating.html

Not to steal form LScowboy... but could be leaking ECU capacitors.... check the above thread... very similar symptoms...

drone6

Thanks for the response. If I unplug the sensor, the car does not have any issues. I wasn't too sure about running the car too long with it disconnected, but I got up to 25mph and even the rpms were in the 4k range. It was like there was no issue.

Going to read that thread you linked, hopefully can figure this out.

LScowboyLS

often this kind of issue is caused a large air leak (essentially a vacuum leak) somewhere past the MAF

I would thoroughly inspect the intake tube, starting at the MAF and going towards the engine for leakage or some hose that has come lose or just an open hole where a hose was previously attached

be sure to NOT use solvent in cleaning a MAF that is pre-95, only low pressure compressed air and/or a new chamois

drone6

If there is a leak, why would unplugging the MAF sensor make the engine work? Wouldn't the leak still be an issue? I will check though.

After reading a bunch more threads, I think I'm going to try replacing the MAF assembly, replace my air filter, check for leaks, reset the ecu and then give it a go.

Is there anything wrong with driving the car without the sensor plugged in? Will it cause damage to the engine?

deanshark

It's actually an AFM (Air Flow Meter) not a MAF. They are very sensitive for cleaning, be VERY gentle. There's a certain spray to use but cant think of it right now. The problem could be the IAT sensor. (Intake Air Temp) which is inside the AFM and cant be changed by itself, the whole AFM needs to be changed. Have you checked for codes? http://www.lexls.com/tutorials/intro/codereading.html The IAT is code 24 and the AFM is 31.
By having it unplugged the ECU just goes to factory settings and the car will run great. But....I dont recommend you do that for too long. It kills the O2 sensors, and I get really bad MPG, only about 15 highway-12 city. I've had mine unplugged for over three years now. I think it also screws the ECU somehow b/c I can't even get any codes out of mine anymore. Try to find one (if they're not all taken) at the junkyard, it's cheaper then most anywhere else.

LScowboyLS

I know, but if you don't say MAF, people get lost - lol


because almost all sprays will ruin an AFM, better to not recommend any spraying!


correct


this would not cause your ECU not to generate codes, but not getting any codes out is a classic symptom for failing ECU caps!

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usoff89

iTrader: (2)

I've been driving for about a year with my maf/afm unplugged. I'm having the same issue but not as bad. I can get mine up to speed but very very sluggish. In park or neutral mine will idel and rev as if there are no issues. Only does it when in gear and driving. I still havn't had time to check for any leaks, work is killing me.

I'm going to look into the IAT sensor also. Although I don't recall seeing any type of sensor on the AFM housing?

drone6

So it's possible that maybe just cleaning the front of the housing where the honeycomb metal is might fix the issue? Is that where the IAT is? If so, how is it connected to the sensor?

deanshark

I knew you would say that.

drone6; I don't know exactly where the IAT is, just inside the AFM and it CANT be changed. I read somewhere about it a few times. I'm sure if you search you can find some info on it.
But I would suggest that you DONT clean the AFM. I was very gentle with mine, then 2 days later is when I started having the trouble.

usoff89

iTrader: (2)

Someone correct me if I'm wrong. But the IAT if inside the AFM would have to be attached to the AFM sensor somehow. The only plug the goes into the whole unit is the AFM plug??? And you can take the AFM out of its housing with three screws.....

usoff89

iTrader: (2)

Just after I typed the previous post, I remembered seeing a little prong sticking out of the AFM. Here's a picture. Is this the IAT?

drone6

I just purchased a used MAF/AFM assembly, hope it works without an issue:

http://www.ebay.com/itm/LEXUS-LS400-SC300-400-GS300-TOYOTA-SUPRA-MASS-AIRFLOW-METER-MAF-OEM-/221256599683?_trksid=p2047675.l2557&ssPageName=STRK%3AMEWNX%3AIT&nma=true&si=2DHtUPNDZKdv3ZFv%252FYunapxpjcw%253D&orig_cvip=true&rt=nc

deanshark

Not a bad price for it. But, it says it's been cleaned. Hopefully it works good for you.

LScowboyLS

yeah, I would want uncleaned & virginal!