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Discussion Starter #1
Hello everyone,
About 3 months ago I took my Supra on a long distance road trip and noted an intermittent check engine light which came on at highway speeds for 1-2 seconds. I found a post which described this issue exactly as a lean issue, and it had a link to a post from a guy named ’Wes’ who described how to adjust the AFM 2-3 clicks to allow the engine to run richer. Now, I cannot find this.
Does anyone have this link? OR, can anyone remember exactly which way you are supposed to turn the dial in the AFM to allow for a more rich system? I can probably remember the rest...thanks in advance for your help!

Mike P
‘84 Supra P-type
 

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The Wes you are talking about is SupraWes, Wes Hetrick and he used to have his own site that had performance mods on it.

http://tscperformance.com
This appears to be a dead link now.

I think that trying this on your car is a band aid solution that will not really fix the issue. I think that you are experiencing a plugged gas filter in the tank or plugged injectors.
Doing the mod may work, but it's covering up the cause of the problem. Unless your car has serious breathing mods there should not be any reason to modify the AFM.

https://www.celicasupra.com/forums/showthread.php?112841-Loosing-power-after-4k-rpm-when-warmed-up-Please-help&p=1235817&highlight=#post1235817

This link leads to others that discuss the symptoms you are experiencing and also the AFM mod although there is no link to it directly.

Just my 2 cents worth.

Dale
 

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Mike, for an un moded MK2 the AFM adjustment really doesn't have any benefits...

I would expect based on air temps, type of gas, amount of throttle and age of O2 sensor that the check engine light was due to engine knock aka pinging...


2 solutions based on my experience...replace the O2 sensor and if still experiencing pinging pre-ignition knock etc etc add a octane boost...my '86 was always exhibited these conditions in temps over 92F, hard on the throttle and or going up hill (or under a load) especially with the A/C on...

Pat Bradden in his books document the AFM mod, I run 2 clicks counter clockwise but I do so mods as well...
 

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I would not recommend modifying your AFM unless you are using a wideband data logger to compare before and after to see if you actually did anything useful. BTW, the AFM mod will not help steady state driving, you are in closed loop mode the ecu is mostly looking at the output of the o2 sensor to fuel. The code you are referencing is also common to get if you have an aftermarket header, particularly one like the Pacesetter where the o2 sensor isn't directly in the exhaust stream. If you don't have one, you probably just need a new o2 sensor as was mentioned, and a good tune up would be a good idea as well (check your air filter, plugs, cap and rotor).

Also contrary to popular belief, if there was benefit to be had by modifying your AFM to the mods on your car, you would actually want to tighten the spring to make the ECU put out less fuel, not more. These cars will run richer and richer and richer as you mod them, while you are experiencing a lean condition.
 

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The Wes you are talking about is SupraWes, Wes Hetrick and he used to have his own site that had performance mods on it.

http://tscperformance.com
This appears to be a dead link now.

I think that trying this on your car is a band aid solution that will not really fix the issue. I think that you are experiencing a plugged gas filter in the tank or plugged injectors.
Doing the mod may work, but it's covering up the cause of the problem. Unless your car has serious breathing mods there should not be any reason to modify the AFM.

https://www.celicasupra.com/forums/showthread.php?112841-Loosing-power-after-4k-rpm-when-warmed-up-Please-help&p=1235817&highlight=#post1235817

This link leads to others that discuss the symptoms you are experiencing and also the AFM mod although there is no link to it directly.

Just my 2 cents worth.

Dale

Dale, here is a pseudo link for that dead website.

Ye old Wayback Machine is handy in these cases, I do not promise the whole website is workable, but you may be able to garner some info from the archived version.

https://web.archive.org/web/20060613064922/http://tscperformance.com/
 

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Discussion Starter #6
GREAT info, everyone! I really appreciate the feedback and will look to replace o2 and fuel filter for now. I hear that job is a bear...
 

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It had become very popular once upon a time back in the 90s as these cars were off warranty and had finally depreciated into the hands of wannabe racers who were game to try anything. Then as I started parting out Supras, people were looking for good, used AFMs, but nobody wanted one that had been tampered with or at least wouldn't pay much. I wound up with I think two that had been tampered. I tried plugging them in to see if they'd work, but neither of them did and I think I sent them to the crusher with the last of the carcasses. People may be willing to take a chance and buy a tampered one now that the supply has dwindled, but I recommend don't even cut the darned thing open.
 

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GREAT info, everyone! I really appreciate the feedback and will look to replace o2 and fuel filter for now. I hear that job is a bear...
IT IS!!!!! i suggest removing the 2 engine mount bolts on drivers side and jack up the engine and stuff a 2 X 4 under it. Makes for less blood loss. A 17 MM FLARE crow foot is handy! Do the banjo bolts first,then the bracket.

Lean condition. HMMMM. An 02 sensor that is lazy usually goes RICH,not lean.
Check for vacuum leaks: throttle body,EGR,cruise control actuator and intake pipe and connections. Some times,the coolant temp sensor goes wacky and tells the engine that it is HOT and will lean out the mixture. In closed loop.
http://www.cygnusx1.net/Supra/Library/TSRM/MK2/manual.aspx?Section=FI&P=8

http://www.cygnusx1.net/Supra/Library/TSRM/MK2/manual.aspx?Section=FI&P=72
 
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