How to clean MAF

[Ariamius]

I have an 88 Turbo 7mgte it has the KVAFM sensor. Bought CRC MAF cleaner. Lucky for me, I read the bottle...if u can't use the cleaner, how do I clean it properly?

[Ariamius]

Also, any help in how to clean the idle air control valve and the TPS would be greatly appreciated.

[cre]

Don't try to clean the AFM. You don't have a MAF, by the way... very different types of device. You can use compressed air to blow debris out of the honeycomb but There's not really anything I'd recommend beyond that.

The TPS isn't something which needs to be cleaned... it's mounted on the exterior of the throttle body and just interfaces with the throttle plate's shaft.

The ISCV may be sprayed with carb cleaner but I don't recommend it for GTE's as there is a rubber diaphragm behind it... in that case just take it off and spray it out thoroughly. Don't open the stepper motor side of the unit.

[professorbob]

In an effort to correct a problem with the engine being unable to move out of limp home mode. (see thread elsewher) I have removed the Idle Speed Control Valve ISCV and the Throttle Position Sensor TPS to eheck. The position sensor checks OK with the meter. The Idle Speed Control Valve was covered with bypass blow by. I use carb/brake cleaner and sprayed down the recirculation tube while keeping the stepper motor upright so it would the valve closure cone. I then used compressed air to blow out the port and cone. It is somewhat clean, but have a .... QUESTION: Is the passage suppose to be air tight. I am still able to blow by the valve cone. Also, are there any resources other than the dealer for shaped hoses, as the 1/2 inch broke off when I removed it.

[cre]

It really doesn't matter if it stays open a TINY bit while at rest as any air coming through has been metered. As far as I know, the computer simply adjusts it as needed until the airflow is within spec, it does not have a "closed" position to which it returns to when the car is turned off that I've ever noticed. The GTE has a diaphragm following the ISCV which should not allow air to flow back into the ISCV from the intake plenum... The inclusion of this alone leads me to believe that Toyota knew it was going to be open to some degree in all situations.

[professorbob]

Thanks, I'll run the power own stepper motor test and reinstall once I locate the replacement hoses. Really appreciate your help. Prof

[professorbob]

Well, I'm back after considerable delay. Had to purchase new vacuum hoses for the Idle Speed Control Valve ( ISCV ) I cleaned the plunger with solvent to remove the carbon etc. I checked the values and they checked OK.

I also checked the values on the Throttle Position Sensor ( TPS ) off the vehicle and they checked OK. I double index marked the TPS before removal and reinstalled to the same exact location as original.
The Battery had been disconnected since the parts were remove for cleaning and check.
The Check Engine Light flashed and I ran a code check and received a 41. Probable need to run an additional check on the automatic overdrive light as well.
I removed the jumper and after some hesitation and several crank attempts the engine finally started. Now the engine RPM fluctuates from idle up to 1400 and back over and over.

Also. The gasket at the exhaust manifold and header is now leaking. Could this cause enough upset in the system to create the problem I have been unable to resolve?

Any suggestions are appreciated.
Prof

[cre]

I recommend you calibrate the TPS properly, it takes less than a millimeter for it to end up out of alignment. The fact that there's not code 51 present id a fair sign but it doesn't mean that it's not adjusted too far the other way causing the IDL switch to remain closed while the throttle is open. A code 41 will occur if wiring or TPS are bad... or the ECU, but they're pretty robust and seldom the problem. A code 41 will be stored if the ignition is turned on while the TPS is disconnected too, so try clearing it and see if it is recurring. TPS are wear components too, while they may test well with a basic meter they may still be in bad shape... but they are just a trim sensor; You can drive without one but your idle and throttle response will suffer.

Have you tested the cold start time switch, the ECU coolant temp sensor? Have you inspected your vacuum hoses recently? Have you checked the ignition timing?

A mild exhaust leak isn't going to affect your idle at all... boost will suffer terribly and you'll be pouring a lost of uncalled for heat into the engine bay. There's also the risk of it entering the cabin.