Need ECU tested

Bus, Microbus, Transporter, Station Wagon, Vanagon, Camper, Pick-Up.

Moderators: Sluggo, Amskeptic

flyfisher111
I'm New!
Status: Offline

Re: Need ECU tested

Post by flyfisher111 » Mon Sep 16, 2019 10:30 am

Still would like to find out if the ecu adjusts for load on the engine. And is there anyone who tests these things?

User avatar
asiab3
IAC Addict!
Location: San Diego, CA
Contact:
Status: Offline

Re: Need ECU tested

Post by asiab3 » Mon Sep 16, 2019 10:45 am

“Load” is the ratio of engine output to requested engine output (from the throttle body/pedal.)

Of course the ECU adjusts for load. As you depress the throttle, more air is allowed into the combustion chambers and the AFM flap moves accordingly. The white wire on the coil negative (#1) gives the ECU an engine speed signal, which is the last variable in the load-based fuel calculation.

Until you have a known good timing advance map, with a mechanical advance cap at 28*btdc, you are diagnosing in circles. GumOut spray the inside of your new distributor until it runs out clear, spray some oil down below the points plate, and get your points gap, ignition timing, and idle speed set properly. THEN see how the car runs. A faulty timing map can wreak havoc on even the best FI system.

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

flyfisher111
I'm New!
Status: Offline

Re: Need ECU tested

Post by flyfisher111 » Mon Sep 16, 2019 11:16 am

I dont have a throttle position switch so would the ecu read the airflow meter voltage to coil pulses? I have a used bosch distributor coming. Any one know if you can buy a rebuild kit for these. What 's the best way to test the voltage from the air flow meter to the ecu?

flyfisher111
I'm New!
Status: Offline

Re: Need ECU tested

Post by flyfisher111 » Mon Sep 16, 2019 11:30 am

One other question. I eliminated the oxygen sensor . I don't have to pass emissions. Could this cause problems?

User avatar
asiab3
IAC Addict!
Location: San Diego, CA
Contact:
Status: Offline

Re: Need ECU tested

Post by asiab3 » Mon Sep 16, 2019 6:59 pm

The throttle position switch only comes into play at full throttle. (Some early models have an idle switch too.) No running issues during throttle application could be caused by lack of a switch unless the two switch wires were bridged together.

You unplugged the oxygen sensor? Plug it back in and see what happens. You removed it completely? You will need to ask your engine what it wants.

I am still a little unclear what your ACTUAL issue is. Is it just a non-smooth throttle response issue? What else?

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

flyfisher111
I'm New!
Status: Offline

Re: Need ECU tested

Post by flyfisher111 » Tue Sep 17, 2019 7:26 am

I'm at the point now where i have good acceleration in first and second gear but bogs down in third (automatic), especially on a not so steep hill. This is a new rebuild complete with new heads valves,bushings heads etc and a new 74mm crank with a scat c25 cam scat solid lifters steel push rods. I have about 500miles on the build plus break ins.' Really good combustion on all cylinders.

User avatar
THall
Getting Hooked!
Location: Verona, Wisconsin
Status: Offline

Re: Need ECU tested

Post by THall » Tue Sep 17, 2019 10:04 am

flyfisher111 wrote:
Tue Sep 17, 2019 7:26 am
scat solid lifters steel push rods.
You sure about that?
Solid lifters = Aluminum shaft push rod (steel tip)
Hydro = Steel shaft push rod
'78 Westy 2.0 FI

flyfisher111
I'm New!
Status: Offline

Re: Need ECU tested

Post by flyfisher111 » Tue Sep 17, 2019 11:25 am

Your right I had to check my receipt . I have aluminum rod with the tips. I had to cut them length. My calculated compression ratio is 7.9/1

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: Need ECU tested

Post by Amskeptic » Tue Sep 17, 2019 1:56 pm

Is the transmission shifting appropriately with the scat cam? Any performance cam can wreak havoc with an automatic transmission because the weaker low speed vacuum is interpreted as heavy acceleration.

The car should not bog down on any hill in 3rd. These things downshift smartly when the load goes up. Youy need a correctly adjusted throttle lever for the mechanical kickdown on later buses, and a properly functioning kickdown switch on the earlier transmissions.

Try 37 mph in 3rd gear, mash the gas down, does it downshift NOW?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

flyfisher111
I'm New!
Status: Offline

Re: Need ECU tested

Post by flyfisher111 » Tue Sep 17, 2019 3:34 pm

The kick down works as it should if I floor the pedal. But i feel it bogs down on hills it should make in 3rd gear.

flyfisher111
I'm New!
Status: Offline

Re: Need ECU tested

Post by flyfisher111 » Tue Sep 17, 2019 3:38 pm

From what I read about the scat c25 is that it works well with an automatic transmission

User avatar
asiab3
IAC Addict!
Location: San Diego, CA
Contact:
Status: Offline

Re: Need ECU tested

Post by asiab3 » Tue Sep 17, 2019 5:25 pm

Have a helper slowly floor the accelerator pedal while you watch the throttle body. is the throttle body actually reaching full throttle?

Do not be afraid to kick-down your engine on hills, the performance cam might need the extra RPM to make good power up a hill. I have never seen a VW automatic transmission that will allow kickdown outside of safe engine RPM.

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

flyfisher111
I'm New!
Status: Offline

Re: Need ECU tested

Post by flyfisher111 » Tue Sep 17, 2019 6:30 pm

'I have never seen a VW automatic transmission that will allow kickdown outside of same engine RPM '

I'm not sure what this sentence means / Can you expand a little?

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: Need ECU tested

Post by Amskeptic » Wed Sep 18, 2019 7:43 am

flyfisher111 wrote:
Tue Sep 17, 2019 6:30 pm
'I have never seen a VW automatic transmission that will allow kickdown outside of same engine RPM '

I'm not sure what this sentence means / Can you expand a little?

The kickdown does not allow overrevving by kicking down too early. My comment about smartly downshifting is not about the kickdown however. A properly adjusted transmission will sense throttle position and just downshift smoothly as the load increases. You should expect a 3rd gear to take 2nd gear without any change in accelerator position as the vehicle speed drops below 35-40.
Early transmissions had a vacuum modulator, later ones use the throttle cable/lever to change the hydraulic pressure that determines shift points.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

flyfisher111
I'm New!
Status: Offline

Re: Need ECU tested

Post by flyfisher111 » Wed Sep 18, 2019 1:20 pm

I am starting to worry about the afm i had rebuilt. I think I'll measure voltages while plugged into the system.

Heres what I got
Pin 7(neg) Pin 9(pos) Starts at 7 volts half on the wiper 4 volt wiper all the way 3 volts. incremental movement of 4 volts but the first 3 volt change was in the bottom half of the wiper sweep.


Pin 7(os) Pin 6(neg) Starts at 2 volts Half way wiper travel 5 volts Full travel 5.8 volts incremental movement of 3.8 volts but again first 3 volt change is in the first half of the wiper sweep.

Kind of echos what I feel on the gas pedal. But I don't know what these number are suppose to be. Are they normal?

Post Reply