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Basically it idles very rough reving up and down specially when gear is on D and car is parked.
My MAF was missing (its located just before the air filter underneath the engine) during that time I had no such a behavior but it was throwing a code and gauge was on. I installed a new OEM MAF and since then it started acting this way. No error codes though.
If I disconnect the MAF cable it stops surging and of course it throw a code. I can't believe something wrong with the MAF since its a new OEM.
Shall I look at the IAC ?
Thanks
Last edited by Abdulrahman; 02-01-2020 at 11:47 AM.
When you disconnect the MAF sensor, the PCM defaults to the speed-density method (MAP, IAT, RPM, VE tables) of calculating the mass air flow. Apparently that method is more accurate than your MAF sensor. You indicate the sensor is located before the blower.
What "gauge was on"?
Who tuned for the blower, and how did they address adding the extra fuel, and allowing the stock 1 bar MAP sensor to read the pressure correctly?
There's an arrow on the MAF sensor. Is it facing in the correct direction?
Since the MAF sensor is before the air filter, it is exposed to dirt.
What inlet air ducting are you using? Is there any chance there is a leak after the MAF sensor? That can throw off the MAF sensor reading, but not affect the speed-density calculation.
Check for the correct voltage supply at the pink wire in the MAF sensor connector, key on/connector off sensor. Should be 12 volts to engine ground, and to the black/white wire. Check the black/white ground wire in the harness to engine ground. Should be very close to 0 ohms.
Thank you for all the thoughts and I will soon double check them all. For time being let me explain this:
I have a power dyne Supercharger and all tuning was done by Hypertech power programming.
All were fine up until I found that the MAF and filter parts were missing (either falling while driving or stollen I couldn't figure it out).
Check engine gauge was on and a code was thrown.
Originally the MAF was located about 10" from the air filter.
When I discovered the missing item I purchased a new OEM MAF and a filter and I installed them my self. the MAF I got was the latest plastic model (not sure which year came on) not the metal one that came on the 97 Camaro and it is installed in a way the filter is on the screen side.
Edit: Oh and that black plastic MAF came with a wiring adapter to fit to the original clip as it seams this can fit on newer model with different clips.
This is similar to what I got. Got it from GM dealer. He told me they don't do the Metal one anymore https://www.ebay.com/itm/For-Chevy-C...sAAOSwO5JdDB9L
Let me also add that this surge happens only when engine is hot and after a long drive. it doesn't happen as soon as I drive it with cold engine ... and on D at traffic light.
Last edited by Abdulrahman; 02-02-2020 at 03:17 AM.
Seems to be a language barrier. You describe the MAF sensor is “just BEFORE the air filter”. The incoming air should enter the air filter. The MAF sensor should be located AFTER the air filter, and the screen should be on the INLET side of the MAF sensor. The accuracy/calibration of the MAF sensor is affected by the ducting arrangement. Ideally you should have a long, straight section of duct BEFORE the air enters the screen. Obviously that's difficult to do with the S/C setup.
Could you post a photo of the air filter / duct / MAF sensor / duct arrangement?
Yes sorry I meant after the Air filter.
The below photo is for a similar application.
the air filter then a short elbow duct then the MAF then the long duct going to SC and TB.
and I installed the MAF so this side goes to filter
and yes with the SC its too difficult to have a setup where the MAF is on a longer duct unfortunately. At least with this PowerDyne SC.
if the setup is correct? Do you think this black plastic type of new MAF should be ok ? or shall I try the original MAF out of Ebay ?
GM still sells the metal 94-97 MAF sensors as "remanufactured" in their "Pro" line. There was even a picture of it in the band at the top of the eBay ad you linked.
The MAF numbers are typical for idle, but obviously the RPM is all over the place. If the idle is much more stable with the MAF sensor disconnected, putting the PCM into speed-density mode, it would seem to be a problem with the MAF sensor, either the sensor itself or the ducting arrangement, Speed-density only cares about the MAP and IAT readings. MAP is measured in the intake manifold plenum, eliminating any leaks or other problems with the ducting. Where is your IAT sensor located?
I guess a remote possibility is that the the added pressure drop due to the MAF sensor downstream of the S/C is causing the S/C to surge???????
if a problem with the MAF itself shouldn't it throws a code ? I get a MAF multifunction code when disconnected and there is other codes for low input , high input and something about the circuit.
below is the IAT location
Edit : Since it idle alright when I disconnect the MAF is it logic to say that I should NOT look any where else but the MAF for now ? trying another MAF as a first step.
Last edited by Abdulrahman; 02-03-2020 at 05:17 AM.
There are several codes for the MAF sensor. P0100 is for insufficient activity, and should set when you unplug the MAF sensor. You indicate your SES light (which you prefer to call a gauge) is on, and a code was set. And it was an MAF code - was it this one?
P0101 is a rationality check. The PCM compares the MAF measured flow to the speed-density calculated mass air flow. But the difference has to be fairly large to set the code.. Your MAF could disagree with the speed-density calculation, and not set a code if the difference is not very large. The 96 manual (same as 97) does not indicate the difference required to set the code, but in other years I have seen a number like 25% difference, which is fairly large.
P0102 sets when the indicated mass air flow is less than 3.9 grams.sec.... an impossible value if the engine is running,
P0103 sets when the indicated mass air flow is above 300 grams/sec, not possible with a stock engine, but possible with a modified engine.
Whether theses codes set depends on the battery voltage. IF it's less than 10 volts, no codes. What is the battery voltage at idle?
There is no way, reading your descriptions about a vehicle that is what ???, 8,000 miles away from me, significantly modified from stock, in unknown condition, that I can't examine, that I could state with ABSOLUTE certainty that it is the MAF sensor, and you shouldn't look anywhere else. That is not a fair expectation. . I'm giving you my logical analysis of the problem, but I have also suggested that there could be some other cause, like compressor surge from the S/C. I don't know all that much about the specific of your setup, I just know what I learned about compressors as a mechanical engineer. The last thing I want is for someone to say "you told me it was the MAF, I replaced it, and it didn't fix the problem". I'm offering you input, suggestions on what to check, but I assume no responsibility for the results. Can't help you if that is your demand.
I am not a mechanic but I tinker with my stuff cars, bikes and electronics and I enjoy doing that with the help of those wonderful people like you around the world who love to help. I no way would hold anyone responsible for anything. I am sharing my problem and sharing my ideas and learning from professionals like yourself and very thankful for the time you put on this forum to read my problem with my bad English and to suggest solutions.
My question was if it is logic to start looking at the MAF as a first step through diagnosis and may be my English didn't help me sorry about that.
I will leave the MAF disconnected for now as the surge is really annoying and never mind "SES light" at least I know why its on.
Its been 9 months since my last post. I haven't really used the car a lot due to lock down. Problem is still there and yes I got the chance to check the MAF harness voltage and all seams ok as per Post#2 @Injuneer I also borrowed a functioning MAF from a friend and tried it on my car but it didn't solve the problem.
I really fed up of it and I am using the car now with MAF disconnected and everything run smoothly except for the ses light
My 2 questions:
1- When disconnecting MAF does it run in Speed Density Mode by default ? if yes (which I am happy with) is there a way to get rid of the ses light ?
if not, how can I reprogram it (nowadays) to run in Speed density mode disconnect MAF and get rid of ses ? the car is on Hypertech power programmer (I still have the device) and unfortunately no option to change the mode.
2- would it be ok to run in Speed Density mode with my 4.5psi supercharger ? some say might be even better !
You indicate "all tuning was done by Hypertech power programming.". Did you fiddle with settings yourself, or did you get a custom tune cartridge from Hypertech? Even though the S/C is small, the A/F needs to be adjusted for the boost, and the need for a richer A/F ratio under boost. Without knowing what is in the Hypertech tune, I can't know how the tune accomplishes this. Generally, the Hypertech stuff is not very good, and I would even attempt to use one to control a supercharged application.
Is there something like an "FMU" to control the extra fuel required under boost?
You need to find a quality mail order tuner, and have the PCM tuned, rather than using the Hypertech. If the tuner feels he can get better results with speed-density, he can set the PCM to run in that mode, and eliminate the MAF code and the SES light. I seriously doubt the problem is the MAF sensor. The problem is the "tune' or the lack thereof. And, speed-density requires accurate input on MAP in IAT, and correct VE tables, or it won't work right. VE tables could be screwed up in the tune.
Hypertech got basic programming that I did myself to cover things like rev limiter, fan operating range/powerstat, top speed limit correction and tire size, rear axle, shift points and firmness. When I installed the SC I contacted them and they sent me a cartridge to load. I was new to this 20 years ago and Hypertech was easy to install. Now I tend also to believe the issue got something to do with tuning, but confused why the surge is happening now after all of these years.
02-01-2020 | 10:48 AM
