7mgte AFM issues, please help!

[BoostedRunner87]

hey i just joined recently to buy a used AFM for my 7mgte. I have a 1987 4runner with a 7mgte swap. I got the vehicle with the swap already complete. It has been running kind of rough since i got it and it seems to have some slight fuel cut issues during steady-low boost. I started looking into just doing a general tune -up to start with. i took the air filter off (which was extrememly dirty) then i took the AFM off because it was also very clogged with dirt and oil. I proceeded to clean it with brake parts cleaner which was a huge mistake because i am pretty sure i fried the sensor. after i put it back on it would barely run and it was throwing codes 31 and 32. So i bought another sensor from a guy on this forum. He said it was a known good sensor. i installed it tonight and still having the same issues. Is there something i am missing? could it be something else related to the AFM causing it to throw these codes, or did i just get stuck with another bad AFM?
sny help and info would be greatly appreciated

 

[BoostedRunner87]

yeah i had the batt unhooked for a while and i also pulled the ecu fuse. after i put the ecu fuse back in and turned the key to the "on" position it only came up with code 32. I did not start it again after that. i will mess with it more tomorrow. i am going to leave the batt disconnected and the ecu fuse out over night.

 

[CRE]

You do not need to disconnect the battery to reset the diagnostic codes... well, not if everything is wired up as was planned by Toyota (not a given in any swap situation).

Code 32 is not an AFM related code in the GTE... as the manual says. The HAC sensor is inside the ECU on 89 and newer ECUs (they have grey harness plugs) and on pre89 ECUs (they have yellow harness plugs) it is an external sensor. If your components are from a pre89 I wouldn't be surprised at all if they forgot to install the HAC sensor. In a stock MKIII it's mounted below the glove box and has a three pin harness which connects to it. If they did plug it in I don't think the stock harness would allow for it to be ore than 3' from the ECU.

 

[BoostedRunner87]

yeah i saw that 32 is for the HAC sensor. I'm assuming it probly always has that code stored because i dont think they hooked that up, but i can look around on the rig to see if i can find it. what exactly would it look like? also will the engine run ok without it? I do know that i have a pre 89 ECU because it has yellow plugs so the HAC will be external.

 

[CRE]

I don't remember how the ECU responds to that error... best not to have any errors if possible. I recommend buying and installing the sensor... Ask around in the classifieds section for a used one; You should be able to get one inexpensively.

 

[jetjock]

^ Default value is 29.92 in/hg...

 

[CRE]

^ Default value is 29.92 in/hg...

No additional fueling or timing adjustments? It just assumes a static value and goes with it? Thanks.

 

[jetjock]

Yep, it subs that value until the signal becomes valid again. It's listed in the manual as 760 mm/hg. Call it 29.92 in/hg, 1013 mb, 760 torr, 14.7 psi, 33 ft/h20, ect...take your pick. If he's at or reasonably near sea level no problem. As he climbs the mixture will deviate towards rich though...

 

[CRE]

Ah, ok... I know 14.7psi is sealevel, I'll try to remember 29.92hg/in is the same.

If he doesn't mind going rich he could always satisfy the ECU with a couple resistors, but I really recommend just getting the proper part for the job.

 

[shaeff]

Grab a HAC sensor from someone on the forums here. Don't pay more than $10 for it. Always best to have zero codes to start with.

 

[BoostedRunner87]

Grab a HAC sensor from someone on the forums here. Don't pay more than $10 for it. Always best to have zero codes to start with.

ok i will look around for one. Where i live i am at 3500ft. Their is a air/fuel gauge hooked up and its reading right in the stoich range so i think my mixture is pretty good. I also forgot to mention that i replaced all the spark plugs while doing this tune up. I got bosch plugs from napa. thats what they said was recommended for that engine. are those plugs ok? I wouldnt think that the wrong spark plugs would cause it to run this bad.

What i have noticed when i have it running is that it will idle well, then when i push the gas it falls right on its face and just sputters horribly and sometimes i can hear a small backfire or "popping" sound through the intake. It usually does this when i very slowly and steadily push the gas pedal. Looking at the boost gauge it seems like it starts to run bad as soon as vaccum starts to go down and get close to boost. IDK if this is directly related to the AFM in any way. just trying to give you guys all the info i can.

 

[jetjock]

The HAC is a trim sensor and even if it was shifted wouldn't cause those symptoms. In your case not having one is actually a blessing from a troubleshooting standpoint.

Unplug the AFM and see if there's improvement. Contrary to popular belief as long as you're easy on the pedal and don't go over 3000 rpm the engine will start and run near normal assuming everything else is working right. Which is, of course, the entire point of the test.

Without knowing the plug number you put in we can't tell if they'll work or not...

 

[89supracrazy]

I found a print in my book on the hac for 1987 and 1988. I believe you said they were yellow plugs so it has to be pre 89. If you can find the plug for the hac which should be under the glove box it goes like this. It is a 3 prong plug according to my book. It has 2 terminals vertical and 1 horizontal. The plug is facing you with the 2 vertical on top. The one on the left is e2 and the one on the right is vc. The one that is horizontal which is below the 2 vertical with the plug facing you is P. This is the chart in my book. The chart shows vc-p 700-860ohms, vc-e2 2.2-3.3kohms, and p-e2 2.9-4.2kohms. This is how to check the hac itself. I have a 89+ so mine is built in to the ecu. You might not have the plug for the hac it might come with the hac itself but if you do here is something to go by if you want to get you some resistors for troubleshooting.

 

[BoostedRunner87]

thanks for the info but i probly wont have those wires dangling down from behind the glovebox because this engine is in an 87 4runner, not a supra. I did trace out the wires on the AFM and it looks like they wired in a connector for a different AFM. about 18" from the AFM the wires are butt connected to the wiring harness going over the valve cover. The wires all change color after the butt connectors so idk what they did there.

I will try running it with the AFM disconnected. i didnt know that was possible

 

[BoostedRunner87]

also do you guys know if an AFM off an N/A 2jz will work for my 7mgte?

 

[89supracrazy]

I unpluged my afm before and I believe it would idle but soon as I gave it gas it would try to die. You might wont to watch other afm on other vehicles because I bought a lexus afm aluminum housing and it had the black box on it. It looked the same and actually plug up to my factory harness. What you run into is that some afm sends different signals to the ecu. The lexus sends voltage signal and the supra afm sends a different type of signal. If they changed the afm it might be sending the wrong signal to the ecu.

 

[BoostedRunner87]

I unpluged my afm before and I believe it would idle but soon as I gave it gas it would try to die. You might wont to watch other afm on other vehicles because I bought a lexus afm aluminum housing and it had the black box on it. It looked the same and actually plug up to my factory harness. What you run into is that some afm sends different signals to the ecu. The lexus sends voltage signal and the supra afm sends a different type of signal. If they changed the afm it might be sending the wrong signal to the ecu.

yeah i see how it may be sending the wrong signal, but the vehicle was running just fine before i cleaned the AFM. then i put it back on and it immediately threw codes 31 and 32. so i figured i must have fried the AFM by cleaning it. So i got another one that is exactly the same as the one that was originally on it and i still have the same problem. I tested both AFM's with an ohmmeter and they test exactly the same. I believe they are both good. Could a vaccum or boost leak cause a AFM engine code?

 

[89supracrazy]

I believe you need to stick with the code 32 that the computer gave you. If it keeps throwing the same code it is telling what is wrong. When I first got my supra it had some check engine codes and I looked them up and did some troubleshooting on the sensor and it was what the computer exactly said. I know your vehicle is not a supra but the main thing is it is a 7m-gte and it has a tccs computer for the 7m-gte installed somewhere. Since you know that code 32 is the hac you need to find the computer and look to see if the hac wire is going in to the computer. You need to get rid of all the codes and if it still runs rough, then try something else. I edited my post on page 2 because I told you wrong. The post I edited shows how to check the hac. The website below looks like the hac has one wire going into the ecu. Follow this wire and see if the wire dont lead to a 3 prong plug. If you are good with resistors I would bet money you would get that check engine light off. Make sure that the afm that your bought has the same part number as your orginal because like I said alot of the afm will plug up but will not work.




http://www.turboninjas.com/gallery/James/Cars/Mk3Supra/pre89ecu.gif.html

 

[CRE]

The Lexus KVAFM electronics are compatible and send the same type of signal.

Runner, test the voltage at VC. Both the AFM and the HAC circuit receive power from there (in pre89 systems); If the HAC sensor is present, this may be the common link. AFAIK, a boost leak should not cause a code 31 or 32.

EDIT: I should add that I think VC isn't too likely as it is used for a number of sensors, but it is a possibility, so is E2 (they both use that as a ground) and given that the whole setup is a swap and you mention the harness has been modified it is worth checking.

 

[89supracrazy]

The Lexus KVAFM electronics are compatible and send the same type of signal

I bought a ls400 aluminum housing which came with black electronics. The ls400 electronic was one number difference in the part number. It plugged up to my factory harness and I ran it for about two days and it started acting up. It died on me before I got home. I had read somewhere they send different signals. Luckly I had my stock in the trunk. The ls400 is for v8. Maybe some of the sc300 or gs300 might work because they are six cylinder engines. I dont know.