[jst1dab]

I'm having a issue and no one can seem to find the problem. My check engine light keeps coming on and says it's the mass air flow sensor. However, after replacing it for the fourth time I can't imagine it is the problem. I have a new engine, new EGR, new fuel pump, new oxygen sensor, and have checked all of my fuses and still nothing seems to fix my problem. I've now got more than $17k into this thing that I can't use. Had several shops that keep trying to figure it out, and still nothing. I'm just about to the point of adding explosives to my truck and blowing it up. Does anyone have these issues and or advice on anything that might help me?

 

[sdspeed]

What drive train? Any symptoms besides the CEL and have you checked for a OBD1 code.
Did you replace parts that needed replacing? What brand and where to you get parts?
Your gonna need to give a little more background.

 

[DCM]

To add to that, have to you checked the wiring for continuity? If you have wiring breaks, no amount of MAF changes will fix it.

 

[Handyman85383]

Another thing to look at is the wire insulation itself. On those older trucks the insulation on many of the wires near the connectors gets brittle and flakes off leaving exposed wires that can touch together and short out signals. That becomes especially apparent on fuel injectors, throttle position sensors, distributors and cold start injectors that are right on the engine. I had to reinsulate many of those wires near the connectors with liquid electrical tape. If the engine was recently replaced along with many parts all of those connectors were disconnected and the wire bundles moved around. If the problem started after the engine swap that is a good place to start. Time consuming but it doesn't cost much. Good luck!

 

[Techsus]

I concur-- please post if all parts you installed were genuine OEM Toyota (incl. Aisin, Denso) or cheap Chinesium knockoffs.

 

[retiredat444]

I have a friend who has a Volvo and had a similar issue (but it was stalling, fuel starvation cause the computer to think it was something else.) and when I saw it run, i thought it was actually the fuel pump, or fuel pressure, which did turn out to be a valve on the fuel line at the fuel tank. when the maf was disconnected the issue went away. Is there a fuel pressure regulator in the line? it is just saying the mixture is incorrect. So, it is either the air or fuel.

 

[MIflyer]

Several months after a major wreck my 4X4 1988 pickup started misbehaving one day and the trouble code said it was the mass airflow sensor. I went to the local dealer and they told me they did not have one in stock but it would cost $680. So I pried the plastic top off of mine, noted that basically it was a potentiometer, attached an analog type volt ohm meter and could see how sweeping the mass airflow sensor back and forth revealed the resistance reading went from smooth, to "scratchy" to back to smooth again. This is similar to what occurs when you have a scratchy volume control on a radio. I kewn what to do to fix that. I poured a little LPS-1 into the wiper area of the device, observed how the resistance reading got much smoother, and glued the top back on. I had no more trouble with that component, drove the truck for 3 more years, then gave it to my brother, who drove it for years and then sold it. The guy who bought it had no problems with the truck until he pulled into a gas station one day, forgot to set the parking brake, and it rolled down the hill into a ditch and was totaled.

So, first, test the airflow mass sensor with an ohmmeter, and if it looks "scratchy" then, open the top, pour a teaspoon of LPS-1, and see how that works. It's easy to do and costs just about nothing.

And put some LPS-1 into the electrical connectors, too.

 

[93celicaconv]

I'm having a issue and no one can seem to find the problem. My check engine light keeps coming on and says it's the mass air flow sensor. However, after replacing it for the fourth time I can't imagine it is the problem. I have a new engine, new EGR, new fuel pump, new oxygen sensor, and have checked all of my fuses and still nothing seems to fix my problem. I've now got more than $17k into this thing that I can't use. Had several shops that keep trying to figure it out, and still nothing. I'm just about to the point of adding explosives to my truck and blowing it up. Does anyone have these issues and or advice on anything that might help me?

Some feedback. Your 1989 4x4 truck does not have a mass air flow (MAF) sensor. It has an air flow meter (AFM). They are very different from each other. Also, there is no DTC that say's any particular device is the source of the problem. The DTC will say, for an AFM for example, that there is a problem with the volume air flow meter signal. This statement means the ECU determined there was an open or short detected in one of two circuits the ECU needs to get feedback on in order to control fuel volume correctly. The source of the problem could be an open or short in the wiring circuit between the ECU and the AFM, an AFM fault, or an ECU fault. Given you tried so many different AFM's (I don't know where you found that many - given they are discontinued by Toyota, they are rare and hard to find) and that did not change anything, it is unlikely that all those AFM's have the same fault. The problem could be the wiring circuit, or it could be your ECU.

ECU's of that era, given they are 30+ years old now, have problems with capacitors failing. You also said you had a new engine installed at some point, so that would distrub the wiring, which could now be a contributing factor. The best bet is to determine wiring continuity between the AFM and the ECU to see if that discloses any open circuits. If you discover an open circuit, that is most likely your issue. You also need to check if there is a short in the wiring between the AFM and the ECU - this is done by checking circuit resistance at the wiring harness connector at the ECU that involves the AFM, and also checking each circuit's resistance to ground. If all that checks out, then I would try to find another ECU for your specific truck, check that ECU for visual problems on the circuit board (sometimes a failed capacitor will be obvious from a visual inspection of the ECU circuit board, but sometimes there is no visual evidence present), and swap it in place of our old ECU, then see if there was any positive effect of that swap.

It's not that hard on these older vehicles to diagnose the root cause of a problem - it just takes time & patience.

 

[Jeff83]

You have to do some diagnosis to find the problem. Firing the parts canon at the problem rarely fixes anything. Check engine code flashes in your case or OBD2 scanners tell you WHERE the problem is not WHAT the problem is.