MAF sensor data?

[geniushanbiao]

1999 AEG, engine DTC shows multiple misfire and cylinder #1,2,3 misfire. Also hard start. Today I regapped the spark plugs from .035 to .039 inch and the hard start problem seems to be better however after running like 30miles the check engine light comes on again reporting the multiple misfire and cylinder #1,2,3 misfire. I suspect the MAF sensor is bad although the previous owner told me he replaced with a new one. I backprobed the MAF sensor's signal wire and got the result:

When idling at around 800rpm, it gives out around 1.52V signal;
When at around 1800rpm, it gives out around 1.74V signal;
When at 3000rpm, it gives out around 2.03V signal.

Are these signals normal or the MAF sensor is bad?

By the way, I have an Actron CP9575 which can read the Live data. It worked with my vehicle when I bought this scan tool but now everytime I connect it stucks on the "communicating with vehicle" and seems never want to work. Is it not compatible with this car or there is something wrong?

[jcthelight]

Originally Posted by geniushanbiao

1999 AEG, engine DTC shows multiple misfire and cylinder #1,2,3 misfire. Also hard start. Today I regapped the spark plugs from .035 to .039 inch and the hard start problem seems to be better however after running like 30miles the check engine light comes on again reporting the multiple misfire and cylinder #1,2,3 misfire. I suspect the MAF sensor is bad although the previous owner told me he replaced with a new one. I backprobed the MAF sensor's signal wire and got the result:

When idling at around 800rpm, it gives out around 1.52V signal;
When at around 1800rpm, it gives out around 1.74V signal;
When at 3000rpm, it gives out around 2.03V signal.

Are these signals normal or the MAF sensor is bad?

By the way, I have an Actron CP9575 which can read the Live data. It worked with my vehicle when I bought this scan tool but now everytime I connect it stucks on the "communicating with vehicle" and seems never want to work. Is it not compatible with this car or there is something wrong?

What i'd do is unplug the maf sensor and see if it still misfires. And some how get your scanner to work or find someone with a vagcom and look at the gps for the maf should be around 2.75 - 3.5 gps.

[geniushanbiao]

I unplugged the MAF sensor and cleared the trouble code yesterday. Today I drove it like 30miles and now it shows no misfire on the DTC except for the MAF sensor codes. However the hard start problem is still there. I'll drive more miles tomorrow to make sure about this.

[geniushanbiao]

Drove another 25 miles today and still the MAF sensor and IAT sensor codes. What I concern is that before I unplug the MAF sensor, besides the misfire codes the computer also gives out Catalyst converter code which hasn't shown up till now. Will MAF sensor also cause catalyst converter code?

[maxs]

Just because he replace the maf dont mean it good ,i put 3 maf on with in 6 week befor i got a good one,all of them was new

[geniushanbiao]

I replaced the MAF sensor yesterday and drove another 25 miles today. Now the computer throws out 16806(catalyst) and 16556(=P0172, Fuel Trim too rich). Any ideas? Hopefully this is not another bad MAF(if it's bad I can exchange it it's still under warranty but what a bad luck of me...)

[geniushanbiao]

By the way, the hard starting problem is still there....

[jcthelight]

Originally Posted by geniushanbiao

I replaced the MAF sensor yesterday and drove another 25 miles today. Now the computer throws out 16806(catalyst) and 16556(=P0172, Fuel Trim too rich). Any ideas? Hopefully this is not another bad MAF(if it's bad I can exchange it it's still under warranty but what a bad luck of me...)

What I think happened is with the MAF being bad and causing misfires it may have damaged the cat because of running rich.

[Smileybug]

The catalyst code points more to the O2 sensor than the cat. A failed cat typically throws a P0420 code. If you have access to VAG-COM, I'd take a look at your O2 sensors and see if they are performing correctly.

Here is a good site to help with your codes: Ross-Tech Wiki

[geniushanbiao]

today my wife drove the car for about 50 miles and it's now throwing out misfires again......

I've placed an order of VAG-COM cable and probably going to receive it in a few days.

Therefore, after replacing this MAF sensor it's throwing out all the codes it threw with the old MAF, together with the fuel trim rich code. This makes me to believe that the MAF sensor might not be the cause of the problem. I'll monitor the O2 sensor data and see whether the O2 sensor is bad or not. By the way I replaced the upstream O2 sensor when I got the car....

Any one knows how the computer monitors misfire? Which sensors are involved in misfire monitor?

[geniushanbiao]

I replaced the fuel pressure regulator yesterday and now it seems not throwing any misfire codes out. My wife drove the car for nearly 100 miles today and I only read the fuel trim rich code and this only code doesn't lit the check engine light... but the hard start problem is still there. I'll probably do some further work after the VAG-COM cable arrive rather than randomly changing parts. However I'm trying to do some guesses.

Since replacing the fuel pressure regulator seems fixed the misfire problem, I guess there's some problem in the fuel system. Also the car starts good each time within 10 minutes after shutting off the engine and after that it becomes very hard to start. This makes me believe that the fuel system might be something wrong because after 10 minutes after shut down the only thing changed is the fuel pressure. There don't seem to have any leakage and the fuel filter is new, I'd suspect there might be one or more injector(s) leaking. However is injector(s) leaking related to the hard start problem? I think if injector(s) leaking the car won't run good but it runs very good...

Also there is another sympton that I can't clear the ABS code. It throws out 01276 which is the ABS pump code and I can't even erase it....I'm using the U280 VW/Audi code scanner. But there appeared some time that I can use this guy to erase the ABS code. This makes me to suspect that there might be something wrong with the computer. However anyone knows where the ABS codes are stored? Are they stored in ABS control module or the ECU/ECM?

[toledotom]

Yes, I do throw ABS code, it is the ABS hydraulic pump code. You probably have a BAD Fuse link in the Battery Compartment Tray. Their are 3 fuses in a row normally Green in color and check the main silver fuse links. A hair line crack will give you this fault and Yes sometimes it will clear the ABS light on its own on start-up. Other wise you need a Vag-Com program to read and reset!Check your wheel sensors also if they are not completely gummed up with rust and crap. My NB was also throwing Mis fire codes, changed the coil pak and wires, got same code but in the mean time I cleaned the MAP sensor off with CRC cleaner and new air filter. THOSE pesky MAP sensors will cause great problems along with the Air Pump on cold start ups. Check air pump, make sure it is working and pumping, other wise MAP will set engine Rich or lean out.