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 1993 L27 MAF sensor Frequency or volts?

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waynehere
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Name : Wayne Oonk
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptySat Dec 26, 2020 12:28 pm

So just bought this awesome 93 Riv with only 60k on it and no rust. I am only getting about 19MPG though. So going through things and found an Actron scanner that seems to read the live data ok, but the MAF readings are from 1700-11000? The scanner says it is gr/sec, but I am thinking that it is Hz? Anyone know if this is supposed to be in Hz? I have the 93 service manual, and it says it should be in grams. I can not seem to find much info, except that if in Hz, it should run about 5000 hz at 3500 rpm? Mime is way over that. It does seem to be pretty smooth increase and decrease when I rev it up and down, and cruising down the highway at 1900 rpm, 65mph, MAF stays around 7500.

Any thoughts would be greatly appreciated....

I also read somewhere that these don't get the typical MPG of 30+? I had an 86 Old's and it was great on fuel.
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LARRY70GS
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LARRY70GS

Name : Larry
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptySun Dec 27, 2020 7:50 am

The MAF measures the mass of air entering the throttle body. It uses that to set up the fuel injection. The signal is in Hertz. According to my 1998 FSM, the reading should vary from 2000 Hz at idle to 10,000 Hz at maximum engine load.

_________________
98 Riviera SC3800  All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54
https://www.youtube.com/watch?v=UHCda-t_Jls
https://www.youtube.com/watch?v=sfT2tEO4XcU
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waynehere
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Name : Wayne Oonk
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptySun Dec 27, 2020 8:00 am

Ah, this is the confirmation that I needed. Thanks Larry.
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LARRY70GS
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LARRY70GS

Name : Larry
Age : 64
Location : Oakland Gardens, NY
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptySun Dec 27, 2020 8:25 am

https://www.aa1car.com/library/maf_sensors.htm

You need to look through your 93 FSM and see what normal readings are. I quoted 1998 figures, apparently, it varies.

_________________
98 Riviera SC3800  All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54
https://www.youtube.com/watch?v=UHCda-t_Jls
https://www.youtube.com/watch?v=sfT2tEO4XcU

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billw22
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptyThu Dec 31, 2020 8:52 am

Quote :
So just bought this awesome 93 Riv with only 60k on it and no rust.  I am only getting about 19MPG though.  So going through things and found an Actron scanner that seems to read the live data ok, but the MAF readings are from 1700-11000?  The scanner says it is gr/sec, but I am thinking that it is Hz?  Anyone know if this is supposed to be in Hz?  Essay writing service at https://homework-writer.com/ you will find I have the 93 service manual, and it says it should be in grams.  I can not seem to find much info, except that if in Hz, it should run about 5000 hz at 3500 rpm?  Mime is way over that.  It does seem to be pretty smooth increase and decrease when I rev it up and down, and cruising down the highway at 1900 rpm, 65mph, MAF stays around 7500.

Any thoughts would be greatly appreciated....

I also read somewhere that these don't get the typical MPG of 30+?  I had an 86 Old's and it was great on fuel.

mine stays around these numbers too
always thought its normal


Last edited by billw22 on Fri Jan 08, 2021 4:18 pm; edited 1 time in total
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LARRY70GS
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LARRY70GS

Name : Larry
Age : 64
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptyThu Dec 31, 2020 8:57 am

One reason the Rivieras are so good on gas is the gearing. 60 MPH is about 1600 RPM, at 2000 RPM, I am very near 80 MPH.

_________________
98 Riviera SC3800  All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54
https://www.youtube.com/watch?v=UHCda-t_Jls
https://www.youtube.com/watch?v=sfT2tEO4XcU
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waynehere
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Name : Wayne Oonk
Location : Cuba, NY
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptyThu Dec 31, 2020 9:25 am

LARRY70GS wrote:
One reason the Rivieras are so good on gas is the gearing.  60 MPH is about 1600 RPM, at 2000 RPM, I am very near 80 MPH.

Really? Now this if one of the 1st comments about the Riv's getting great MPG? And your rpm's/MPH sounds more in line of what I thought I would see too... I wonder if they changed the gearing between the 93 and 98 models? I envy you man.... smile
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LARRY70GS
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LARRY70GS

Name : Larry
Age : 64
Location : Oakland Gardens, NY
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptyThu Dec 31, 2020 10:03 am

waynehere wrote:
LARRY70GS wrote:
One reason the Rivieras are so good on gas is the gearing.  60 MPH is about 1600 RPM, at 2000 RPM, I am very near 80 MPH.

Really?  Now this if one of the 1st comments about the Riv's getting great MPG?  And your rpm's/MPH sounds more in line of what I thought I would see too... I wonder if they changed the gearing between the 93 and 98 models?  I envy you man....  smile

Yes, the gearing was a bit different. According to what I could find on the net, the 93 Riviera had a differential ratio of 3.06, and a .70 overdrive gear for a final drive of 2.14. The 98 Riviera has a 2.93 and a .70 overdrive gear for a final drive of 2.06.

To figure RPM at speed, use the following formula,

336/tire height X gear X MPH = RPM

The stock tire for your 93 is a P205/70R-15. That tire is 26.3" tall

336/26.3 X 2.14 X 65 = 1777 RPM


For my 98, the stock tire is a P225/60R-16. That tire is 26.6" tall.

336/26.6 X 2.06 X 60 = 1561 RPM

336/26.6 X 2.06 X 80 = 2082 RPM.


_________________
98 Riviera SC3800  All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54
https://www.youtube.com/watch?v=UHCda-t_Jls
https://www.youtube.com/watch?v=sfT2tEO4XcU

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albertj
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albertj

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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptyThu Dec 31, 2020 5:21 pm

...at 55 MPH the '98 Riv is not that far off cold idle...

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waynehere
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptyThu Dec 31, 2020 6:49 pm

I was just doing some testing and my LTFT is way high.  Like 148, where 128 is supposed to be "0".  STFT was bouncing above and below 128, which I think is normal.  That was sitting still and revved up to 2500 rpm for 45 seconds.  I also have recorded going down the road and it runs high, like 138 or higher. This is supposed to mean it is running lean? It never does get back down to 128. I took it on a 100 mile trip on the expressway and only got 21 mpg. According to the original sticker on it, supposed to get 27 on highway.

I tested the fuel pressure and it starts out at 43ish and drops down to 38ish when I start it.  All within specs according to the shop manual.  Also have put a new GM O2 sensor, fuel filter, MAF sensor, PCV.  Tested exhaust pressure and less then 1.5#.  So not plugged.  About only thing left is Vac leak or fuel injectors.  I tried starting fluid around the engine, but never noticed any change in rpms...

So looked into getting the fuel injectors cleaned and tested, then found some reman injectors on Rockauto for $21/injector.  Cleaning was going to be about $18 a piece.  This way, not much of a down time swapping them out instead of sending them out and not getting them back for a couple of weeks.  Should get them next week sometime. Also, going to build a smoke machine to see if I have any Vac leaks.  

Interesting fact is there is no EGR valve on this?  Someone told me maybe it was built in Canada, but the VIN shows it was in the USA.  Weird...

Thanks to all of your responses...
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LARRY70GS
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LARRY70GS

Name : Larry
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptyFri Jan 01, 2021 1:24 pm

On my 98, Fuel trim is expressed in a percentage, and it can be positive or negative. Typical values range from -10% to +10%. Negative values indicate the PCM is pulling fuel in response to a rich condition, Positive values indicate the PCM is adding fuel in response to a lean condition. One of the indicators of a bad MAF is large negative fuel trim numbers.

_________________
98 Riviera SC3800  All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54
https://www.youtube.com/watch?v=UHCda-t_Jls
https://www.youtube.com/watch?v=sfT2tEO4XcU
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albertj
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albertj

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Location : Finger Lakes of New York State
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptyFri Jan 01, 2021 3:07 pm

waynehere wrote:
I was just doing some testing and my LTFT is way high.  Like 148, where 128 is supposed to be "0".  STFT was bouncing above and below 128, which I think is normal.  That was sitting still and revved up to 2500 rpm for 45 seconds.  I also have recorded going down the road and it runs high, like 138 or higher.  This is supposed to mean it is running lean?  It never does get back down to 128. I took it on a 100 mile trip on the expressway and only got 21 mpg.  According to the original sticker on it, supposed to get 27 on highway.

I tested the fuel pressure and it starts out at 43ish and drops down to 38ish when I start it.  All within specs according to the shop manual.  Also have put a new GM O2 sensor, fuel filter, MAF sensor, PCV.  Tested exhaust pressure and less then 1.5#.  So not plugged.  About only thing left is Vac leak or fuel injectors.  I tried starting fluid around the engine, but never noticed any change in rpms...

So looked into getting the fuel injectors cleaned and tested, then found some reman injectors on Rockauto for $21/injector.  Cleaning was going to be about $18 a piece.  This way, not much of a down time swapping them out instead of sending them out and not getting them back for a couple of weeks.  Should get them next week sometime.  Also, going to build a smoke machine to see if I have any Vac leaks.  

Interesting fact is there is no EGR valve on this?  Someone told me maybe it was built in Canada, but the VIN shows it was in the USA.  Weird...

Thanks to all of your responses...

Your post jogged my memory as to some chit chat with the service manager at my local GM dealer. We were talking about the low quality of certain aftermarket EGR valves, and he explained about the tuned port version of the 3800 not having EGR valves installed, from MY 1990 thru MY 1992, and that depending on how you looked at it the EGR was not really a need. SO... I did a quick web search and found that GM also deleted the EGR from the 3300 v6 from 1989-1993. Both engines passed emissions without EGR valves, but over time (I imagine, longer than the warranty period and internal testing, shorter than lifetime testing and field experience) GM found burning exhaust valves and cracking exhaust manifolds due to higher combustion temperatures. So, in MY 93 GM put the EGR Valve back on the 3800 Vin L Tuned Port. They did not bother putting it back on the 3300 because they stopped using that engine.

Where I ended up -- the original EGR on my car gave out after several years, and I was venting to the service manager because the replacement (A Standard T-series) quit after 2 years and cost a good buck (at retail, locally). He quipped that an earlier version of the 3800 didn't even have the EGR on, and the electronic version on my car was there (instead of a vacuum operated version) because if you controlled the EGR electrically rather than by vacuum you could get the computer to run it so as to improve performance... or at least, to not be such a drag... With that in mind, I put on a BWD, which itself only lasted about 45,000 miles... SMH... I replaced that BWD with a new Delphi and installed a gasket with screen because I had heard that one think killing the EGRs was soot getting in. How that screen stops anything I have no idea BUT I have not had to mess with the EGR since I did it about 100,000 miles ago, in 11/2014.
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waynehere
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptySat Jan 02, 2021 6:19 pm

Interesting with the adding an EGR valve. Do you remember what all was involved? Did they replace the exhaust manifold with one that has a port on it? Where did they hook into the intake manifold? Is there a kit?

Thanks for all this info.. Never too old to learn things.. smile
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albertj
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1993 L27 MAF sensor Frequency or volts? Empty
PostSubject: Re: 1993 L27 MAF sensor Frequency or volts?   1993 L27 MAF sensor Frequency or volts? EmptySat Jan 02, 2021 11:53 pm

waynehere wrote:
Interesting with the adding an EGR valve.  Do you remember what all was involved?  Did they replace the exhaust manifold with one that has a port on it?  Where did they hook into the intake manifold?  Is there a kit?  

Thanks for all this info..  Never too old to learn things..  smile

Easiest and best thing to do is look at any '94 or later 3800 engine in a junkyard GM car -- Camaro, Firebird, Olds 88, 98, Pontiac Bonneville, Buick LeSabre, some Grand Prix, some Buick Regal, some Buick Century.
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