cormel

I am having a problem with my 91 22re 4runner. The truck will start up and work fine when cold, then after the temp builds up I get check engine light and the truck hardly idles and looses alot of power. I checked the code and I get code 2 which points to the MAF. I had a spare MAF from another 4runner so I tried that, still does the same thing. I reconnected the wire harness etc, still same thing. One thing I wanted to know, my fuel pump is connected directly to the key switch as the previous owner had issues with it working when using the stock wires. Will this cause and issue if it is just directly wired to the key switch and potentially cause this to happen? Is there some test I can do to bypass the MAF to see if the truck runs better? Looking for any and all help, thanks

thook

There's no way to bypass the airflow meter, but you should test the AFM at the ECU connector and make sure proper signal is getting there. It could be the wiring harness. Sometimes the terminals at the connector can back out of there seat and not get a good connection. I'd had that problem with the brown ground wire on my '92 V6 a long time ago.

FSM at ECU testing......
http://personal.utulsa.edu/~nathan-b...ne/44engin.pdf

Also, there's no problem wiring directly to the fuel pump from the key switch. Atleast, not the problem you're having. I'd basically done the same thing for long time until I put in a new circuit opening relay switch.

Lastly, did you try clearing the code after you'd put the "new" AFM in? Clearing the code wouldn't make it run any better/fix the problem, but it would tell you if it's still the same reason for the problem.

cormel

Thanks for the reply. I will use the info you gave me to test the ECU. I did not clear the code but it does do the same thing, runs perfect until it gets warm, then it seems to loose power and seems to be starving for fuel. I will clear the code and run the diag on it again to ensure it is the same code 2 AFM. More to come and if anyone else has any suggestions keep them coming.

thook

Cormel, I found the other thread you started and posted there.

The info is not for testing the ECU. Rather, it is for testing AFM operation at the ECU. You're testing the connector at the wiring harness to make sure signlas from the AFM are getting to the ECU.

Is this wiring harness the same one used by the PO = the original harness? Can you tell how the PO had modified the wiring/rerouted the voltage supply and describe it a bit? I know you said he wired to the ignition switch, but how?

thook

As far as bypassing the AFM, and after having rethunk your situation, you can bypass the AFM's fuel pump power supply circuit. In the grey diagnostic port, you should have a terminal labled FP and one labled B+. FP = fuel pump, and B+ = 12v battery positive. You can jump the two terminals with a paper clip and see how this affects engine operation. What you've done is bypassed the AFM and COR circuits, and in this way will help pinpoint if your temp related issue is atleast somehow related to the bypassed circuits. I don't see how it would be, but running the expirament won't hurt anything.

Bako88

So you experience power loss while driving?

cormel

I have yet to do the test mentioned by Thook but will try both this weekend(test the connections at the ECU for the AFM) and bypass the AFM to see how it idles and runs when hot. Also I believe the harness is the original one used by the truck. I do have alot of spare parts for this truck luckily so swapping out parts will not be a problem. I have another wiring harness and motor(with most parts attached to it like hoses, wiring, etc. While looking at the wiring harness the other day I did notice 2 connectors that were not connected into anything and I could not find what they potentially would connect into. I will take a picture of the wires to see if anyone knows what they are for. They are close to the injector plugs. I know for sure that the injectors are all plugged in so not one for those. Overall this truck is pretty good I think, The motor and Clutch were just redone when I bought it and I got it for under $400 with all the extra parts I mentioned. Guy had it setting in his yard, it needed alot of body work and he just did not have the time to work on it so sold it to me.

Also to answer your question BAko88, yes I do lose power when it warms up and starts to give me problems. Any others thoughts are appreciated and I will try these on the weekend.

cormel

OK I did some testing today, not too much though too cold here!!!!(-35 C, yikes). I unplugged the wires at the ECU and replugged them in and still throwing the ecu code. I did not get the truck warm enough that it actually had the same problem with loss of power and hardly idling, etc, but I am pretty sure it may still do the same thing (just going by when the check engine came on, it has to be heated up for it to come on and eventually when the truck gets really warm the problem happens). Also I did take some pictures of the 'loose wires' I talked about in my previous post. If anyone knows what they are for it would be really appreciated, I cannot find connectors anywhere for these. Third picture is a new one I found, it is next to the fuse box (round connector)

Oh yes I almost forgot, after I had the truck started for awhile today, I noticed the idle moving up and down, pulsing. I wanted to make sure i did not have any vacuum leaks so i used a can of carb cleaner and sprayed around the hoses, did not seem to be a difference. I am not sure it the pulsing of the idle is somehow related to the AFM issues? When I first started the truck as well today (as I noted earlier it was really cold) after 15-20 mins of running to warm it up somewhat the truck took off fine for about 5 mins then started to act up - like not getting gas and hardly idling - loss of power. Then the check engine light came on and it worked better, idle was better, etc. After that the truck was working fine. Just thought I would throw this into this post as well.

cormel

One more item to add, today I am getting code 5 as well as code 2. 5 points to a bad circuit t the 02 sensor. I am wondering if this could cause the issues I am seeing?

Flash319

Just unplug the O2. It will force a code but the engine should run okay because the ECU will run with a default fuel map. That will eliminate that as a problem.

Bako88

I think the connectors changed between '88 to '91. I tried looking at mine to compare to your pictures, but the don't look the same.

Anyway, I am having a similar problem, but no code or power loss. Mine just idles really bad and to me it smells like it's running rich but there is no black smoke.

abecedarian

What ever became of this?
There is no code "2" for a 91. ... '2' and '5' would be 84-87 codes.

Did anyone figure that out?

... sorry...

apparently not else I wouldn't be asking.

cormel

Are you sure there is no code 2 for a 91? I checked it again and it blink twice, then a good pause then it blink 5 times.

abecedarian

i'm 99.9% positive.
...unless someone swapped ecu's... which kind of makes sense considering the fuel pump wiring and the performance issues.