Airflow Meter: The struggle (1 Viewer)

[extremesitting]

I made a post a while ago regarding tuning the AFM on a basket-case 80 series. I followed the wisdom of the kindhearted responders and sent off one of my meters to Bavarian Restoration to work their magic. It took a little over a month and a half to get the meter back. I was immediately floored by how thorough the restoration was; at least visually. However, all my hopes and dreams were squashed after installing it in my truck. It runs exactly as bad as it did before I tuned the other one I have.

I am at an unbelievable loss. I have been working on this truck for literal years at this point. I've found so many "small" problems and fixed potential future problems. Not to mention all the large problems that would clearly contribute to poor idle and lack of power. After all the effort, reading, research, testing, and wrench turning, I'm still in the place I was in when I first obtained the truck.

As of today it will not maintain an idle even long enough to move myself from the driver's door to the throttle body. I have been advised to check the vacuum at idle. Maybe it's just not producing enough to open the AFM flapper. Once again I'm looking to you folks for your wisdom. My ideal future is one where I, at least, understand what's happening and I can decide whether or not to even keep the truck. Right now I just want it off my property and out of my life. The original dream is dead.

I apologize for the complaints. They come from my feelings of desperation. Thank you all for anything you can contribute and all you do for these amazing vehicles.

 

[devo]

With all you put into this I’m sure you removed and benched checked the IACV? It is responsible for a lot of idle control issues.

 

[extremesitting]

With all you put into this I’m sure you removed and benched checked the IACV? It is responsible for a lot of idle control issues.

Thanks for the reply. Yeah. That was a journey on its own. I actually purchased and tested 3 before finally getting one that wasn't DOA on the 4th try. Each one would appear to test fine, but the the resistance wasn't right at full stroke. So I ended up ordering one from a dealership and showed up with my notes, book, and multi-meter to test it on the parts counter before leaving with it.

 

[smritte]

I'm sorry your having to literally throw money at it. What your dealing with, I spent 40 years doing professionally. When it gets that bad its either something real dumb you keep overlooking or something is making the computer unhappy. The shop manual diagnostics barely cover what it takes to diagnose issues like yours and the technology wasn't that good to begin with. At this point in time, I would be pulling out the lab scope and pin checking everything. You also should be aware that your harness's and connectors are breaking down from age. As well as mechanical items.
One last thought for you, checking resistance isn't really the way to properly test most things. Once power is flowing, everything changes. Too bad the shop manuals didn't have you do that until very recently and even then its not common.

The stories I could tell about back feeding, interference from things that shouldn't, cheap replacement parts causing issues they shouldn't be capable of and lets not go down the aftermarket add on things. Then add in vehicle age.

I wish you the best of luck on it and yes, I have felt your pain.

 

[extremesitting]

I'm sorry your having to literally throw money at it. What your dealing with, I spent 40 years doing professionally. When it gets that bad its either something real dumb you keep overlooking or something is making the computer unhappy. The shop manual diagnostics barely cover what it takes to diagnose issues like yours and the technology wasn't that good to begin with. At this point in time, I would be pulling out the lab scope and pin checking everything. You also should be aware that your harness's and connectors are breaking down from age. As well as mechanical items.
One last thought for you, checking resistance isn't really the way to properly test most things. Once power is flowing, everything changes. Too bad the shop manuals didn't have you do that until very recently and even then its not common.

The stories I could tell about back feeding, interference from things that shouldn't, cheap replacement parts causing issues they shouldn't be capable of and lets not go down the aftermarket add on things. Then add in vehicle age.

I wish you the best of luck on it and yes, I have felt your pain.

Thank you so much for your support. I think scoping everything is a lot more effort than this truck is worth unfortunately. Not to mention the fact that I don't have the tools for such an endeavor. I have replaced so many connectors with new OEM connectors. All the injector connectors (along with rebuilt injectors), IAC, TPS, VAF. I even have 2 ECMs that have been tested by a company that specializes in that sort of thing. With all of that each step has resulted in negligible improvement and very little additional diagnostic information. Everything I've touched so far just falls in to the "it's an old truck" category of things that tend to degrade and require attention. With the big exception being the O2 sensors. They were completely shot and replacing them improved things drastically.

I absolutely agree that it has to be something dumb. 1994 is a terrible year for diagnostics.

 

[effjay80]

Did you contact the Bavarian guys? They are very supportive and if it is the VAF I suspect they'll make it right. They did 2 VAFs for my 94 and both work perfectly in and out for 2 years now.

 

[extremesitting]

Did you contact the Bavarian guys? They are very supportive and if it is the VAF I suspect they'll make it right. They did 2 VAFs for my 94 and both work perfectly in and out for 2 years now.

I haven't, but will if you think they'd be receptive. Every report I've ever heard of their service has been overwhelmingly positive. For what it's worth, the other VAF has been taken opened up and "tuned" to get the truck to at least idle. In fact, it runs pretty well other than being generally cold tempered. I talked about the process in my previous post. I just don't think what I did should be necessary. I took a lot of pressure off of the flapper.

 

[smritte]

80's through the early/mid 90's was bad enough but, now you have that and age.

 

[FMC80]

I haven't, but will if you think they'd be receptive. Every report I've ever heard of their service has been overwhelmingly positive. For what it's worth, the other VAF has been taken opened up and "tuned" to get the truck to at least idle. In fact, it runs pretty well other than being generally cold tempered. I talked about the process in my previous post. I just don't think what I did should be necessary. I took a lot of pressure off of the flapper.

Like I said in your other thread, I used BavRest. I had an issue even after they tuned it and they simply sent me a shipping label and they fixed it without any drama.

I’m sorry you’re facing such trials with this truck. Other people would have given up long before now; myself included!

How does your harness look? Have you inspected the “problem” areas, under the EGR and behind the glovebox.

Have you swapped ECMs with a “known good one”?

 

[Kkxrw]

I have so many problems with my 94 it laughable. Here are some things that I found out the hardway.

Every off brand part I bought failed or my truck did not like. AC delco, Bosch, etc.

Bosch O2 sensors didn't work for me. NTK were much better

Buy new don't buy used engine parts

I bought a smoke machine off of Amazon for $65 to help me find vacuum and exhaust leaks. This was a help and confirmed some things I didn't know.

I replaced all my vacuum hoses, had to reseal the top of my vaf, and replace replace the gasket between the vaf and air cleaner.

Make sure your throttle body and EGR setup is clean, small ports, etc

Every time a changed a part I needed to pull the fuse to rest the computer and drive it a few times

It take small steps

 

[Kkxrw]

Make sure fuel pump is working correctly. I ended up replacing mine 2x

 

[White Stripe]

Basically it takes a thorough understanding of the obd1 system to diagnose and repair it. In my opinion, you can make a obd1 truck run as good or better than a obd 2 truck once you have a grasp of it due to obd1 has some adjustability that obd2 does not. Diagnosing correctly is most important. To do that you need actual values/data of everything currently vs good values.