VW Vortex - Volkswagen Forum banner

Digi 1 16v N/A Lean "Burp" Under Acceleration

6K views 22 replies 8 participants last post by  9aba16vt 
#1 ·
Ok I've had this system installed for a few years now and it's been running awesome until just recently when started to run funky. It's chipped for 16v N/A and I have Vac, WB, and FP gauges installed for monitoring....no ISV.

Closed loop acceleration is where it gets wierd. I can be cruising at any speed and run about 14-15afr BUT as soon as I dip into the throttle slow or fast I get this lean spot 16-18afr for about 1sec. After that it settles anywhere from 12 if WOT to 14 under continued acceleration.

Yesterday, in an effort to remedy the issue I did some maintenance.

Here's what I found/did.

1. Checked ECU grounds
- Found that larger gauge ground to the head was cracked in a couple spots. I spliced into the existing wire near the ECU and connected back to the head with a new terminal.

2. Checked CO Pot
- It was totally fried and not giving any resistance value! Luckily I had a spare so I installed that one and dialed it to 450ohm.

3. Checked Vac Lines
- All my lines are 3yrs old and they still look brand new. Pulling 20 in the vac gauge at idle...

4. Checked fuel pressure and fuel system for leaks.
- FP is 50psi and I did not find any sign of leakage


So any advice or tips??

Pic for clicks -

 
See less See more
1
#4 · (Edited)
It is very possible that changing the CO pot amplified the affect. What Chip are you running?

It is possible that w/o the CO Pot, Digi stays in OL where you would not see any Lag. Was just the CO Pot thermistor giving you a 0 reading on the old one? What about the IAT terminals on the CO POT? Just curious.

Anyway, 450 ohm (COLD) is usually a pretty good spot, but you may want to lower it and see if it has any effect. ..and possibly raise it to see if Digi is over compensating in Closed Loop just before it ticks over to OL.

Here is a fairly good thread in case you have not come across it: http://forums.vwvortex.com/showthread.php?1860918
 
#5 ·
It is very possible that changing the CO pot amplified the affect. What Chip are you running?

It is possible that w/o the CO Pot, Digi stays in OL where you would not see any Lag. Was just the CO Pot thermistor giving you a 0 reading on the old one? What about the IAT terminals on the CO POT? Just curious.

Anyway, 450 ohm (COLD) (outer terminals) is usually a pretty good spot, but you may want to lower it and see if it has any effect. ..and possibly raise it to see if Digi is over compensating in Closed Loop just before it ticks over to OL.

Here is a fairly good thread in case you have not come across it: http://forums.vwvortex.com/showthread.php?1860918
I'm running a chip that I bought from a user on here. I believe it is an SNS copy. The thing ran sweet for years before this lean issue popped up.

I was getting a zero reading on the outer terms of the old CO Pot.
 
#8 ·
Change your O2?
Check for bad ground on O2
IS TP sensor working properly and showing vary in resistance during range .
Vacume leak?
Vacume leak to FPR?
Just a thought.
I have had fuel pumps show good pressure while idleing but lean while driving . That would explain a lot lean during exceleration .

I'm hoping to do this swap and I need your help on getting a DIGI1 on my 87 scirocco 16v . Hopefully I can get it all figured out on the harness and parts needed for a NA swap!!!
 
#9 ·
off subject...

dont have your intake tube put pressure on your trans cable like that..
its pulling the cable, like youre pressing the clutch slightly, making the clutch surface not fully engage, furthermore causing slippage...
 
#11 ·
Been busy getting married this summer and haven't had the chance to eff around with this much.

Back at it now tho;)

I've replaced the O2 sensor with new...No change
Checked fuel filter...Squeaky clean
Have not checked tfer pump.
WOT switch is good.

I can drive the car with the WOT switch tripped. It will hold about 12 on the afr no matter what.

Im thinking my issue may stem from timing because I remember on the days leading up to when this BS started the car was backfiring slightly on decel.

So tonight I'm triple checking my mechanical timing.
 
#13 ·
Bumping this up again. Still haven't solved the issue and frankly, I haven't really touched the car in quite awhile. This week I plan on checking mechanical timing tho.

I should note that the car will spike lean and almost stall just after it runs for 15sec or so. It cannot be run unless the WOT switch is tripped. :mad:
 
#14 · (Edited)
I should note that the car will spike lean and almost stall just after it runs for 15sec or so. It cannot be run unless the WOT switch is tripped. :mad:
By holding the WOT switch, you are sending the ECU into open loop and ignoring the 02 feedback. It looks like Digi-Lag in form, but does look waaay exacerbated. Check 02 wiring and ground there. Also, make sure the 02 heater circuit is op. You may want to configure the output from your Innovate to simulate the NB signal to Digi. This way, you know what you are seeing the gauge is what is being told to the ECU.

Have you made sure that the ECU line it proper diameter, length (And More Importantly) on the correct port on the TB? Wrong port is a very common mistake that will wreak havok on accel.
 
#16 ·
Bumping this because I'm still having this problem although its worse now. I haven't driven the car in like a year because of it.

As soon as I start the car it slowly creeps lean until the engine stalls from lack of fuel (or combustion).

Just to recap, I've wired in a brand new bosch O2 sensor with a fresh ground to the tranny ground and saw no change. Confirmed my tbody switches are functioning. Changed my ecu vac line to a hard line that is the same inner diameter as the tbody nipple. Verified that fuel flow is not being blocked and the pump is giving proper pressure.

What I did find is that my cts and distributor plugs have exposed wire from the insulation cracking over the years. If anyone has good pigtails for these feel free to sell them to me asap :thumbup:

I don't think its an ignition issue because the engine seems to run smoothly and

Next steps:
Triple check mechanical and ignition timing again
Wire in good pigtails for the distributor and cts
Check and replace any suspected faulty ignition components
Possibly use wideband O2 output signal for ecu O2 input
Might change out the injector harness
 
#17 ·
Just a thought have you checked the fuel flow/ pressure? My caddy does this same thing, I have a custom fuel cell (alloy) and even thro I've drained it and cleaned it a hand full of times I still get a few shaving. ( we had to modify it after the sending unit after it was built). Every time it does it I pull the filter clean and off I go.
 
#19 ·
Whats really funny is, I am going through the saaame exact thing! I am just to lazy to post it.
I have tried new o2 sensors, ecm, bought and havent installed WB, checked grounds for o2, everything... Haven't checked filter my filter yet. I set my ignition timing back to 6 btdc but the car runs like crap... I have to set it to like 10 atdc ti get it to run ok... Im am T though.. I unhooked it to solve the issues before I detonate again like years ago. I have noticed that when letting it sit at idle and after normal operating temp, the car will start bucking and idle hunting like it starts loading up with fuel.. (loads of rich smoke)
Ive even put a new alternator because of the fuel enrichment due to low voltage, different gel cell batteries.. too many changes to list..

Wtf is wrong with digi!?

The last thing I think it could be is the distributor.. when it gets hot, it acts a fool...?
IDK

Sent from my SM-N900T using Tapatalk
 
#23 ·
I think my culprit finally showed its face.. it was the ground on the battery.. when hot, I would guess the load from the fan would cause the connection to vanish causing the ecm to dump to prevent detonation.. havent solved it yet but I will confirm in a day or two. .

Sent from my SM-N900T using Tapatalk
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top