pete53

Hello. New to this forum.Have a 1995 Z28 LT1. Had a question with my MAF sensor. I checked voltages on wires/connector OK. When I get to checking the MAF (Signal voltage) it is 4.47 volts (at idle)..When I increase the throttle the voltage DROPS...Is this normal??? I do not have access to the recommended frequency reader.Also, I have the K&N filter. Will this hurt the MAF? I have only had the car a couple of weeks.

Thanks, Pete53

Injuneer

You have to use a frequency meter. They are included in some relatively low $$ multi-meters. I've been helping people with scanner readings and data logs for 15 years, and I've never checked the carrier voltage. The factory manual indicates the voltage on PCM pin B19 is 4.3V and varies.

A K&N filter will not "hurt" the MAF sensor, but coating the filter with too much oil can cause the oil to deposit on the sensor wires and screw up the readings. The oil can be removed with electronics parts cleaner and a Q-tip.

Why are you concerned about the MAF sensor readings? Do you have a trouble code?

GaryDoug

When measured on a DC volts range, the meter will show the average reading. The maximum voltage of the MAF output is 5 vdc. It is pulsed to ground for a constant amount of time with a varying frequency. The higher the RPM, the higher the frequency. You can see in these scope screens that the average voltage will drop as the frequency/RPM increases. But that is not the best way to measure the signal.

Injuneer

Best thing to do is run a data log, and evaluate the air flow as expressed in grams/second. Easiest way to do this is to use GaryDoug's Scan9495 data logging software, free download:

https://www.camaroz28.com/forums/com...95-lt1-874306/

If you want the stock calibration table for frequency (hz) to mass air flow (g/s) we can provide it. If your PCM has been programmed, the tuner may have altered the stock calibration table.

pete53

Thanks for the replies...GaryDoug seemed to reassure me more. Only had my 1995 Camaro for 2 weeks. It was a "one owner" with 115k miles. What got all this started was a high idle (1000 rpm) and sluggish response. I took off air box and components and checked sensors. I did find a bad TPS (erratic voltage readings) and ordered another one. I also sprayed sensor connections with electronic cleaner spray. I also cleaned the K&N filter and "lightly" oiled it.Also cleaned out throttle body (had some sut) best I could without taking it off. I did look at the MAF and it looked clean.I did notice that the car ran better after I threw everything back together.Any more suggestions appreciated.

Pete53

Injuneer

What trans do you have? That determines the PCM idle speed programming. Idle speed is elevated on cold start, with engine temp as measured by the coolant temp sensor. Stock idle for the M6 manual trans is 800 RPM with the engine fully warmed up. The stock tach typically reads 100 - 200 RPM higher than actual engine RPM. You have to use a scanner to read the accurate RPM from the PCM. Stock warm engine idle for the auto A4 trans is 550 RPM in gear and 650 RPM in neutral.

Cold idle can elevate to 1,000 - 1,200 RPM.

pete53

I have the auto A4 transmission. The numbers you stated sound about what it is doing (roughly) at those values...That's why I am hoping the new TPS will straighten things out further. The TPS definitely checked bad.

Injuneer

What was the TPS voltage at closed throttle? As long as it is below 0.90V, it will not affect idle. If it is above 1.0V, it could. As the throttle opens and RPM increases, the PCM starts to open up the idle air control valve to prevent the engine from stalling if the throttle suddenly closes.

maybe2fast

Is the rubber intake duct torn?