afm troubles!

[frewmanchu]

Hey everyone,
so so my 79' fuel injected westie will die if i try to start it with the MAF sensor plugged in. When not plugged in it will run and idle, have to feather the gas up though or else if you put the pedal to the floor the engine will cut out. I checked the resistance on the Maf and it is within specs of what it should be, with the ignition on i can physically move the flap inside and hear the fuel pump kick on. Also i tried starting without the AAR unplugged and it made no difference as welll.
so far i have replaced:
fuel pump,double relay, spark plugs/wires, distributor, rotor. I have looked for vacuum leaks and have not found any significant!
If anyone has any idea why she wont run or helpful tips that would be much appreciated!!!!
thanks.

[SlowLane]

if i try to start it with the MAF sensor plugged in.

Wahl, that's yor problem right thar. MAF sensors didn't exist in 1979. What you need is an AFM.
Okay, kidding. I know that's what you meant, but be aware that "MAF" stands for Mass Air Flow sensor, which uses a different technology to measure a different thing than our old-fashioned flappy-air-vane AFM air-flow sensors, though they serve essentially the same function in an FI system.
Whew, now that I've satsified my pedantic tendencies, let's explore your issue.

First of all, has it ever run properly for you? Is this a new issue, or have you just acquired this bus and are trying to figure out why it doesn't run? If it was runnig previously, what has changed between then and now?

Are the basic mechanicals of the engine sound? Got good compression? Valves adjusted correctly? Do you know if you have hydraulic or solid lifters?

Confirm that you have continuity between the AFM connector pins and the ECU connector pins on the wiring harness. Examine the female connections in the AFM connector to make sure that none have come loose and backed out.

Does your AFM flap move freely from fully closed to fully open with no hitches or sticky points in the movement?

I have looked for vacuum leaks and have not found any significant!

What insignificant ones have you found?

[Amskeptic]

Well, I can spend my day working with Rumdum . . . you got this one, SlowLane!
Colin

[frewmanchu]

so this is a bus that i recently acquired that has not been running, the afm flap does move freely compression is good, i haven't checked continuity in the ECU connector which is what i will do next. I will keep you updated on any progression. I was going to check the temp sensors as well to see if they are in good working order. i realized after that i wrote "MAF " instead of "AFM" oops!

[SlowLane]

Okay, since this is an engine of unknown provenance, I suggest you perform a defensive oil/filter change and valve adjustment. Find out if you have hydraulic or solid lifters (1979 had hydraulic lifters from the factory, but many things can change in 33 years). If you determine that you have solid lifters, then you may very well have an aftermarket camshaft that a P.O. installed to get more power, but which may not play very well with the L-Jet F.I. system. Determine this before you go much further. Do you have any history on the vehicle at all?

Do you have a vacuum gauge? Can you get a vacuum reading from the intake manifold when it's idling?

Check the model number of your AFM and ECU and make sure they're the right ones for your engine. Ratwell has an excellent FI component swap article here: http://www.ratwell.com/technical/FISwap.html.

Be sure to check out the informative stickies on this forum. If you can swing a visit from Colin you'll be miles ahead in understanding your bus.

[SlowLane]

Hmm, well, guess he decided he liked the advice from The Samba better: http://www.thesamba.com/vw/forum/viewtopic.php?t=515254

[frewmanchu]

for starters i forgot about this forum. Here is an update if your still interested.... i got the bus running with the AFM connected. Changing out the FI seals seemed to have made that difference, I havent checked the valve adjustment yet, with the AFM plugged in it will run but will not hold an idle i have to keep giving it gas or it will die. I am skeptical about putting a new AFM in because i metered it out and all the resistances match , moving the flap inside cause the fuel pump to kick on as well.
thanks again,

[Amskeptic]

for starters i forgot about this forum. Here is an update if your still interested.... i got the bus running with the AFM connected. Changing out the FI seals seemed to have made that difference, I havent checked the valve adjustment yet, with the AFM plugged in it will run but will not hold an idle i have to keep giving it gas or it will die. I am skeptical about putting a new AFM in because i metered it out and all the resistances match , moving the flap inside cause the fuel pump to kick on as well.
thanks again,

Inability to idle is often an air flow issue, far and away beyond any (unlikely) component failure.

Dumb and hidden things, like your mentioned injector seals, the auxiliary air regulator seals, and especially the boot, intake manifold gaskets, brake booster line (and the wye it goes into along with the decel valve plastic tube), even valve cover gaskets that are not in position can cause idle issues.
Good luck,
ColinInCA

[Gypsie]

At the risk of sounding brusk I say, slow down a bit. You have made some nice changes and thrown some decent money in parts here. You say you have replaced some rather spendy parts though your post indicates that you may not have done some of the basics work yet.

It is worth taking in some of the theories that are at play here. The idle portion of the mix is very sensitive to vacuum leaks.

Just a cursory review of the items you have mentioned suggest that there may have been some things out of whack. Leaky fuel injector seals (how long as that been going on...?), a melted injector tip (What may have caused that?...Burnt intake valve due to an overly lean mix at speed (Less likely) or a valve out of adjustment (more likely)?) ...?, unknown valve adjustment (this is what I call a "foundation setting": ie: timing and advance, valves, point gap, spark gap...).

If there were vac leaks have been going on for a while, perhaps the PO had done some 'enrichment adjusting' to compensate. With corrections and repairs this will have to be uncompensated (or, rather, readjusted to the new conditions.)

Just a few more ideas:
-Have you checked the aar boot? that little bit of rubber can be a sneaky leaker.
-Do check valve adjustment. The valve adjustment procedure may be tricky the first time you do it, but after that first time it will get easier each time you do it.
-Do confirm solid or hydro.
-Do check your timing advance curve (at least set your timing for high rpm) but checking the curve (high mid low) can tell you if everything is working smoothly in the dizzy.
-Do check the TII for a good snug fit, and perhaps that resistance is in spec.
-Do look through Colin's AFM adjustment sticky. There is some good info there.

All the above mentioned items can be done before you spend another dime so you can spend your dimes effectively.

Thars my 2 cents.

[frewmanchu]

alright once i get some time in the next few weeks i am going to take apart all the vacuum lines and check for cracks or any possible broken pipes and seals, and hopefully check valve adjustment and gaskets.

[frewmanchu]

alright so i started looking into the valves and first off one of the gaskets was pushed in on one side and someone had tried to silicone it to fix the hole! , also the thermostat bellow cable is broken off( i assume has been for a while) i havent had a chance to adjust the valves yet as i ran out of time today!
thanks guys!

[drober23]

Now you're getting somewhere!

Be careful, sometimes FI hoses that look good can still leak.

I want to second Gypsie's advice of adjusting your valves. I would add a suggestion to check your timing and point gap/dwell if you're running points. As Slowlane mentioned, you are running an engine of unknown provenance (I loved that line!). You need to get a handle on all of its systems to be able to get it running reliably.

Once you have the engine set up correctly, it will be much easier to maintain.

[frewmanchu]

i changed out the valve covers while doing the adjustment, after putting everything back in place i took it for a quick spin. Now while giving it gas it drives really nice except, it wont hold an idle. I turn it on, revs up, and then stalls out if i dont give it gas. So i am going to go through the vac lines and start replacing them.

[frewmanchu]

Thanks everyone for all the advice! i found a vac leak on one of the intake manifold lines, as soon as i fixed that up it idles and runs great now!!!

[Amskeptic]

Thanks everyone for all the advice! i found a vac leak on one of the intake manifold lines, as soon as i fixed that up it idles and runs great now!!!

Thanks for the update.
Colin