Bought a Wells MAF SU145 for my IROC, when I was having MAF troubles and found out I have the wrong maf on my car.

Car is running pretty good now. Got the WELLS sensor today and put it on. Car had a HORRIBLE idle search and died about 5 times. Put my old MAF back on, and works fine again.

IS this just a plug and play thing, or do I have to calibrate something?

Do I have to disconnect the battery to reset the ECM before it will work? What's the deal?! VERY unhappy.

 

Make sure that the wells doesn't have any physical problems. I bought one at autozone one time, and it had a puncture in the housing!!! bastage

Other than that I would return it before you get stuck with it and order a new one. Try and get the bosch, thier sensors are what our cars were programmed with. I'm sure they are all close, but why take the chance.

sorry, can't be much more help.

 

The Wells Maf is a direct repacement and requires only that you disconect the battery to reset the ECM. The Wells is a much better design then the stock Bosch. Make sure the two sensors on the firewall are OK. And are you showing any codes??
Also what do you mean the wrong Maf on your car???

 

maybe you got a defective one.

 

Mine works fine Pauly. You might want to interchange the two relays at the firewall to see if one is defective. I have a new one at my place if you need it.

-Schultzy

 

My main power and burnoff relays are fine. I am throwing no codes.

My car is an '87 originally with a 305... it has a 350 now. The MAF is that of an '85 TPI car, the part number is different between 85 and 86-87.

So I guess I have to reset the ECM to make the wells work?

It doesn't look physically bad, except it looks hokey having the chip stuck to the housing with what looks like hot glue.

 

Depends on which type of wells that you get. There are two different ones witht the same part number. I agree that one of them is better than bosch, the other sucks.

Anyway, back to the point... You have to reset the computer in order for it to work.

 

You were using an '85-type MAF? If it ever worked, it is because you have an '85 ECM. If that's the case, you cannot use the SU-145. The '85 system used a digital (frequency modulated) output, while the later MAF cars used an analog voltage signal. The two types don't mix well.

What is the part number on your ECM? It had better be 1227165 for that SU-145 to have a chance.

 

Dang I'm glad you saw that. I didn't even read that.

 

The 85 MAF will most definately work with a 165 ECM. I've got 2 cars to prove it.

I had always thought that it was because the input buffer on the ECM was set up in such a way that the pulsed output of the 85 MAF just happened to get buffered to a voltage that correlated with the constant output voltage that the ECM was looking for, but somebody on the corvette forum has informed me that the 32 and 32B codes will recognize a pulsed signal on the MAF input. This was news to me, but makes sense. I haven't tried an 85 MAF on a 165 car that's running a 36 bin.

But anyway... when I swapped my 85 to a 165 I continued to use my stock 85 MAF, and my g/s numbers all looked good. That MAF is now on my GTA, and although I haven't put the scanner on it, I get no codes and drivability was uneffected by the swap.

But... the reverse is not true. Before I pulled my stock 85 ECM I tried my SU145 and a stock bosch 86-89 MAF, and as expected, the computer had no idea what was going on.

 

Since I bought a stock 350 Memcal for an '87 5.7 TPI, which would be the $32b... and my 350 seems to run pretty well for the mismatch in it's thinking IE 24lb injectors.... I will assume I have the 165 ECM.

How do I tell which WELLS unit I have?

I will try resetting the ECM.

 

Jim,

I've head that before. Apparently, the 5V P-P FM output will average out to nearly the correct analog voltage when the buffer extracts the RMS value. I've gotta wonoder a little about the accuracy and calibration, but I've heard it works.

The reverse is not true, however, in that later Bosch MAFs only output an analog signal and the '85 ECM cannot "convert" that to a modulated frequency that the ECM can interpret. The Wells SU-145 MAF is also a pure analog device, so it wouldn't work on the '85 ECM. If he has an older ECM (and it seems that he doesn't) it would explaing the problem.

- - - - - - - - - - - - - - - - - - - - - - - -

As for the initial problem, you should be able to find the part number right on the device. It was probably on the packaging, too.

If you have cleared the ECM and it still doesn't work, check you connections, relays, and grounds at the ECM and engine. Beyond that, the Wells MAF should have a lifetime warranty. Mine did . And it worked correctly right out of the box.

 

I tried the Wells MAF on my 85 Setup as well. It ran fine....just once in a blue moon it would set a code 34 ( or 33 ? ) MAF high or something...ONLY happened on initial startup and maybe every 25 starts or so. If you cut it back off, then started it, it would behave.

I went back to the 85 Bosch MAF until I do the 165 swap ( HOPEFULLY soon ) I just had the Wells on hand as a good spare to eliminate some things...



HTH

 

I can't understand why the Wells worked on your 85. Vader did a good job of explaining the differences between the 85 and later MAF signals. As expected, neither my wells nor the stock 86-9 bosch worked on my 85. The service engine light came on at startup (and stayed on), and the car ran no differently than it did with no MAF at all.

 

Couldn't tell ya...

When I first got the IROC, I spent a good deal of time correcting previous owner hacks. After that was a FULL tune up, including replacing a leaky intake gasket.

I was having some weird problems, and I wanted to eliminate the MAF as a suspect with a known good MAF. I came across a brand new Wells SU-145 MAF for cheap, so I bought it. Had no idea at the time it wasn't supposed to work.

In fact I drove the car for a month with that MAF with no issue, EXCEPT for the code 33/34 error I would SOMETIMES get. The engine ran fine with it regardless of the code.


I swapped back to the '85 MAF simply to get rid of the annoying light, the engine did not run any differently between the two ( that I Could tell ).



HTH

 

One thing might be if you ever put in the "updated" prom from GM in. If you had the updated prom already, then I dunno.

I too am running an 85 MAF (bosch) with a 165 ECM and they get along just fine.

 

The point is that while you MAY be able to use an '85 (frequency modulated) MAF on a later ECM, you cannot use an '86 & later (analog voltage) MAF on an '85 ECM.

The later ECM has an input buffer that can derive the RMS value from the 5V P-P square-wave output of the early (FM) MAFs and convert it to a usable analog signal.

However, the earlier ECM has no input A/D converter that will derive a digital FM sugnal from an analog input source, as one would get from a later style (analog) MAF.

 

If you are saying the 85 MAF is a Freq maf, it isn't, it is a DC voltage signal it uses.