Yet another EFI help thread :/

[Zed Head]

Not sure about the resistance jumping.  The ECU can only react so fast so a nanosecond blip might not register on a millisecond ECU rate.

Your comments about injectors did make me remember how far off mine were on my car right after I bought it.  I drove it around like this and, who knows, might have even "wasted" money on a new AFM, assuming that the injectors were all good.  The new AFM "worked" for me but I still discovered that some of my injectors were clogged, later.

Short - maybe you have one or two clogged injectors.  They'll still click, they just own't squirt much.  I ran these for quite a while.  They're not urine samples.

[dakinez]

I dunno man, looks like you drink too much coke to me

So over a period of time, injector #1 shot nearly double injector #3?

[Patcon]

On the loud injectors, if an injector was dry would it be louder? It seems like it would be...

Maybe partially dry?

[Captain Obvious]

Checking the AFM with resistance like that doesn't really work. The black saw tooth shaped thing on the AFM circuit board is a resistor. And it's resistance follows a similar saw tooth shape. That's what you were seeing on your meter.

You need to check it hooked up to a voltage, and check voltage not resistance. I think @Dave WM posted a video showing that method? And if not, I'm sure he'd be happy to put one together?

[rcb280z]

See if this works for you. This is the video CO is talking about.

Edited March 20, 2018 by rcb280z

[Dave WM]

BTW, I finally got around to installing the AFM shown in the video (wanted to test it in the car) actually works a bit better in the idle circuit, no diff in the normal driving (flap) circuit than the one that was in the car. Going to leave it in for now. So if your test like this one, then you can rule out the AFM as the issue. Still need to make sure all the contacts and wiring to the ECU is good. In case I am not clear on the video, the pins to hook up to are 6 and 8 for the batter and 6 and 7 for the meter. I know the FSM show 6 and 9, that just adds a fixed resistor in the mix.

Edited March 20, 2018 by Dave WM

[rcb280z]

I see where you mentioned about the popping thru the intake. Pretty sure thats what I'm hearing in post #13 video as you try raising the rpms a few times. That would indicate a lean condition. Be careful as this can do damage to the AFM. You could judge how bad of a vacuum leak you have by removing your oil fill cap while the engine is running, warmed up, and or checking with a vacuum gauge. Pulling the cap will cause the engine to damn near stall or completely stall if you have NO vacuum leaks. Looks like you have a reading of 15 at idle. That is a little low in my book. Mine is 19. I'd start at the afm boot between the afm and throttle body and go from there. This is how my 77 acted several years ago when it developed a vacuum leak at that afm boot I just mentioned. I did have another one but don't recall where it was. I have CRS right now. Maybe when I remember it I will post it.  

 

[Dave WM]

oh and yea the resistance check of the AFM is typical, jumps like crazy. The voltage test will be a nice smooth increase in voltage. You may even see 0 volts flash by, as long as it just flashes to 0 and you are unable to maintain it then don't worry about it. I don't know why the digital meter does this, I don't know if its really zero or just some digital logic freaking out as you make changes. Analog has its place and checks like this is one of them. You can use the digital I just prefer analog.

[Dave WM]

make sure you measure vacuum after allowing the engine to warm up as well.

[dakinez]

This is good stuff, thanks guys. I'll do the voltage test on the AFM tonight. I have an analog meter but it's pretty crappy and didn't do a good job in this case. I may invest in a better one just for resistance testing.

You are right, post #13 has the front firing, popping through the intake.

My plan tonight is to do the voltage test on the AFM and post the results of that, then take a vacuum reading and try disconnecting vacuum lines etc to see if I can increase vacuum anywhere. 

Thanks!

[Dave WM]

things besides leaks that can lead to low vacuum, timing/A/F mix, cold engine. Vacuum is a good indicator of optimum running conditions, hot rod mods excluded.

I seriously doubt the AFM is going to be a problem unless someone has opened up and messed with it. Your resistance reading show the board is working, I can only see one failure mode, that would be an open circuit. Still the voltage check will give you a better look at it, and you can compare now to a working model (the video) since I have confirmed that one as good in the car.

Edited March 20, 2018 by Dave WM

[dakinez]

I ran the AFM voltage test, it was all dead on. Turns out I have another AFM that came in a box of parts I picked up; I tested that too and it was almost the same (range on the original was 2.58v to 11.56v when the battery was 12.52v; on the spare AFM it was 3.00v to 12.15v). Both were smooth sweeps.

I also disconnected ALL the vacuum lines except the throttle body to distributor. I capped everything, and it made no difference whatsoever. I even took off the crank case hose that feeds the PCV valve and capped the PCV (but let the crank case hose breathe), still low vacuum. Based on my elevation I should be getting 17.5, I'm actually getting 15.5.

When I pulled off the PCV cap it was full of fuel, I guess it is the lowest point so I'm not too concerned but I did change out the cold start injector (I had a spare from another manifold), no changes there either.

I do have a misfire, and its the strangest thing. At idle if I pull off each injector plug one by one, all cause the misfire to worsen (so I don't think its a complete misfire, just partial). If I pull off the spark plug caps one by one, each causes the misfire to worsen except cylinder 5 - no change to the engine speed/smoothness when I pull that one. That does not tally with pulling the injector plug. Whats even stranger though, is if I hold the plug cap near the end of the plug so it arcs, the misfire goes away. How can that be? If I put the cap back on the plug, the misfire returns. It's very repeatable. The vacuum also comes up when it is arcing and the misfire clears.

I've tried different plugs and different wires, same thing with any combination. The plugs are coming out very black and oily.Here is a video demonstrating

 

 

Edited March 23, 2018 by dakinez