AFM Question

[supraguy31]

Ok all, Before I go and buy something that I dont need, Let me throw this out at you and see if anyone can help.

I was running a VPC setup and decided to go back to a Lexus AFM setup for the time being. Now once I got everything switched back over and started up the car, She Idled great and my Average Wideband reading are 14.4 to 15 or so. I drove it for 3 miles and as soon as I get ready to turn down my Street, I press the clutch in and the Engine Idle Dropped to 300rpm and it almost shutoff. I do a Diagnostic check since my CEL came on and Im getting a code 24 and 31. Now the only thing different that I have done with this engine is that my ISC hose isnt routed into the Accordian hose, I have it routed and taped into the Intake pipe between the Valve covers on the back side.

So I pull the AFM off and put the VPC back on so I can drive it for the day, Next day I put the Lexus setup back on the car, Start it up and not touch the gas, She started up a little sluggish but my A/F readings where around 15.0 at Idle, As soon as I Press the gas and release, the idle drops to like 2-300 rpms and is struggling to stay running and my wideband A/F readings are 10.0, I pull the throttle and get it to Idle but the A/F reading dont change.

Does this sound like a ISC routing problem and It needs to be routed to the Accordian hose somewhere. I dont want to buy a AFM sensor if infact it doesnt sound like it might be the Problem, I know how sensitive the ISC can be

Thanks
Robert

 

[jetjock]

Hello Robert. It's not possible for variations in ISCV plumbing to cause either of those codes. You have a bad AFM or wiring. Your symptoms also point to this. That both codes were set leads me to suspect wiring or a connector problem although it's certainly possible both sensors are dead. Unlikely though.

 

[supraguy31]

Mr JJ, I was hoping that you would chime in.

Well for the ISC valve, I can hear the clicking Noise once I shut it off so Im sure that its working. I have noticed and Im not for sure if this is relivant but on a customers mkiii that unless you have the ISC valve routed back into the Accordian hose that It runs like crap when its first started up and atempt to get it to Idle but he did have a small filter on the end of the ISC Valve. Went ahead and Put the Hose back on and routed it back into the Accordian hose and It Idled perfect.

Im going to go out and change the connector and see what it does. The only reason I havent looked at the AFM is I did drove the car for a few miles with on/off acceleration and it ran perfectly fine, Then all of a Sudden within 200 feet from my driveway, it just fell on its face once I pushed the clutch in and A/F went straight to 10.0, Sitting in the Driveway its smoking black.

 

[jetjock]

Your customer's engine idled poorly because he was using pirate air to feed it. It doesn't matter where the idle path source is as long as the air going through it has been metered. For example early 7Ms have an idle bypass passage right in the throttle body that works fine if one chooses to use it instead of the normal path. Regardless, the diagnostic system is not capable of detecting such things.

Your symptoms (and the code 31) are indicative of a faulty load signal which is what the Karman provides. You could try unplugging the connector altogether and force the TCCS to enter Fail Safe Mode. Things should improve but rpm will be limited to about 3000. Note the TPS has to be working right for this to happen.

If the engine behaves in that manner with the connector out it'll be another indication the ECU is not receiving a correct airflow signal with it plugged in. You could also measure it assuming you have a frequency counter or a multimeter capable of frequency measurement.