[Z09B4U]

The easy one first. B-body cars do not have PCM oil temperature sensors. That is a Corvette thing.

As to the MAF you really need to do some diagnostics. If you back probe the MAF signal at the MAF plug you may find voltage which means you have a wiring problem.

You really need a meter with frequency measurement or a oscilloscope to check the MAF sensor output. Parts swapping is expensive if the part was good and the wiring was bad.

You could unplug the PCM and check the wire between the MAF and the PCM.

 

[Z09B4U]

It could be a bad tune.

Did you have drivability problems with the old tune?

Have you flashed the "old tune" back in to check if Eehack shows MAF reading with the old one?

 

[Z09B4U]

It would be worth the back probing of the MAF plug to at least check for voltage.

Rock Auto only does what they call "customer service" by email. I do not buy anything from them I can not afford to loose the full cost on.

Ask the "reputable tunner" for a free stock tune so you can check something. There are also online sites with stock tunes or someone may have one for you.

MAF Readings - CamaroZ28.Com Message Board

LT1 Based Engine Tech - MAF Readings - 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...

www.camaroz28.com

 

[Z09B4U]

I will ask for the stock tune, good idea. Thats a good start for troubleshooting.

No tuner wants to work with a car with preexisting problems.

Get permission before you swap any tune.

The reason you need to do physical measurements is you have to locate the source of the issue.
Could be a MAF, connector, wiring, bad PCM, or a real odd programming problem.

RE: RA Things can get more problematic when they send the wrong part in the right box or a old dead part in a new box because they do not check returned boxes. I like their prices but buy with caution. When a order comes in I check every parts box and bag for the correct part and the little accessory parts bags that come with some parts. I also double check with another vendor to confirm the RA part is the correct part number. Do not get me wrong they can be cheaper than the local "wholesale" account a friend lets me use.

 

[Z09B4U]

Do you know what kind of reading i should get? Frequency, voltage peak.

Read the link in post #7 even if you will not go to the link.

If I were to receive any voltage signal, I would think that would give something better than zero on the laptop reading.

That is why Eehack can not tell you what part of the system has failed.
Think of a sensor for the PCM as a chain. The PCM can not know which link is broken, or if the PCM is damaged.

You could fire the parts cannon and get lucky with a new MAF being the problem, but if the car is new to you and you have not driven it much on the road I would suggest diagnostics not parts.

This is a example of back probing. In this picture the TPS.

Tip of the day: If you select "Full Image" it is much easier for forum members to enlarge the image to read small things.

 

[Z09B4U]

Great that you looked at the MAF sensor circuit. In a pinch I would have been happy to see the slight voltage change on the sensor output, but the frequency check suggests that the PCM should be showing something other than 0g/s.

As a non expert with engine tuning I have suggestions/questions.

g/s is a calculated value. My point is that a bad table in the tune will result in bad or no calculations which would explain what Eehack is showing you.

The FSM suggests that the OBD1 PCM only will output the calculated g/s so the frequency is not available.

If things start pointing towards the PCM being bad take the extra time to double check that the MAF sensor signal at the PCM.

With all PCM connectors unplugged you can verify that the MAF sensor voltage is on the PCM pin with key on.
The definitive check would be to back probe at the PCM and view the waveform on a scope.

I do not want to get into details but under some weird conditions checking "continuity" may give a false result.

The forum can at times save you a lot of time by other's experience pointing to a specific test. Suggestions of swapping parts without testing can be detrimental in some cases.

 

[Z09B4U]

Thanks, I do have a set of FSM manuals. I could not find a similar diagram to what sherloc9c1 posted. I will print that out and keep it in the FSM.

I always try to use copies when working on the car. At worst I take a picture of the FSM then print it.

The diagrams are available in both drivability and emissions and in electrical diagnosis. 94 FSM 6E-A13 or 8A-20-10.

The programmer responded, all is fine with the MAF reading, it has to do with speed density that sherloc9c1 mentioned. And also why no MAF code was coming in.

Maybe I am not understanding you.

Did you make a special request for a tune that ignores the MAF?

If the tune ignores the MAF it works off tables and the PCM will not be able to make fine tuning calculations.

It is my understanding that the MAF is the only way a PCM can know and correct for the different densities of air due to the change of humidity in the air.

 

[Z09B4U]

My current speculation is that with the call for both fans to run because of the MIL code, it creats a high current draw which somehow cuts out the dash.

What MIL code do you think would trigger both radiator fans?

My digital dash also started to cut out on top of it all which added to the confusion.

There were issues with the digital dash from the factory. In the majority of cases the final solution is to fix the solder cracks on the circuit board.

1995 9C1 Intermittent Dash Display Fix

. After 200,000 miles of trusty service, my speedometer and odometer display would intermittently black out. There have been lots written about this, however, I didn’t see many pics of the failure mode for the 94/95 model years. The speedo is an easy part to access; takes about ten minutes to...

www.impalassforum.com

 

[Z09B4U]

As per FSM DTC 43 PCM will default to retarding timing based on current RPM and MAP. Loss of performance.

Does Eehack show a valid temperature for the coolant?

 

[Z09B4U]

A/C can trigger both fans as well.

 

[Z09B4U]

Parts manufacturers that have been reliable in the past are producing duds and leaving it to the end user to "sort it out". This is where a good relationship with a local parts place pays off. They may not be the cheapest but some still take care of their customers. It was the locals that bailed me out the last time RO sent me two different rear calipers.