Super rich after letting off the throttle

[homebatch]

Hi guys,

I'm new to this forum and have tried doing a ton of searching and researching, but haven't been able to find any answers. Hopefully this should be posted here and not in the tuning forum...

First off, I have a '96 Galant 4G64 w/14b turbo, 450cc injectors, rewired fuel pump, 2G SMIC, and 1G BOV. I'm using the stock ECU (set for 275cc injectors I believe), and an S-AFC II, pocketlogger, boost and EGT gauges for tuning.

I've managed to get my fuel trims around 0 across the board with the throttle open, but whenever I let off the throttle at any RPM, I start to run super rich (up to -25 even) and of course the car stutters and/or wants to stall once I come to a stop.

Before you ask... I have the BOV vented back to the intake.

Any thoughts? Thanks in advance.

 

[Coldandafraid]

you venting your bov?

 

[InferiorWang]

you venting your bov?

first thing that came to my mind too.

make sure you recirculate your bov between the airflow sensor and the turbo

 

[Coldandafraid]

Oops. Heh.

 

[homebatch]

Reset your ECU.

Tried that a few days ago... it actually helped in resetting my LTFT, but had no effect otherwise.

Does the length of the BOV tube back to the intake matter?

Peep this:

http://memimage.cardomain.net/member_images/3/web/411000-411999/411887_30_full.jpg

I would assume that so long as the air is recirculating, it wouldn't matter how long the tube is... am I wrong?

 

[steve]

Is your Idle position switch working?

Steve

 

[homebatch]

The "snorkel" is actually pool hose... pretty funny looking I know. haha

Idle position switch? Do I have one on the 4G64? I'm using the stock 4G64 TB and IAC.

 

[steve]

Idle position switch? Do I have one on the 4G64? I'm using the stock 4G64 TB and IAC.

I'm sure you do, most likely built into the TPS like it is on the 4G64 spyder. How do you adjust/set your TPS?

Steve

 

[homebatch]

I believe the TPS is in the same place as the Spyder...

I set it using the pocketlogger. It reads 0 at closed throttle, 97% at WOT.

 

[steve]

I set it using the pocketlogger. It reads 0 at closed throttle, 97% at WOT.

I believe on all the cars that use a IPS buit into the TPS, the correct and critical adjustment is setting where the IPS opens. The actual TPS voltage at the point is non-critical as long as it's inside something like 0.4v to 1.0v it's OK. The only place where you set the TPS by voltage is on 1G 4G63's where the IPS isn't built into the TPS.

BTW with a pocketlogger you would see something between 8 and 20%. Zero is way to low to be set right. SAFC's will read zero regardless of what it's set to since they auto range themselves to what ever voltages they have seen.

On the spyder the correct procedure is to connect a ohmmeter between pins 3 and 4 on the TPS measuring for continuity. Insert a 0.0177in (0.45mm) feeler guage between the fixed SAS and the throttle lever (the SAS is the screw in the TB over the throttle pulley). Losten the TPS and turn the TPS fully counter clockwise checking to make sure you have continuity between 3 and 4. The rotate the TPS clockwise until the point where IPS just opens (you loose continuity) and lock it down. Remove the and make sure you have continuity with the throttle fully closed.

Steve

 

[homebatch]

BTW with a pocketlogger you would see something between 8 and 20%. Zero is way to low to be set right. SAFC's will read zero regardless of what it's set to since they auto range themselves to what ever voltages they have seen.

Here's where you lost me... so the pocketlogger should be showing a TPS reading of between 8 and 20% at closed throttle??

I witnessed the SAFC adjust the throttle reading to zero on it's own, but I was under the impression the TPS should read zero at closed throttle, and 100 at WOT (tested with ignition on, car off).

I may have access to a multi-meter so I'll try and do the test you mentioned and go from there. Is your assumption that my TPS/IPS is not where it should be?

Thanks for all your help!

 

[steve]

Here's where you lost me... so the pocketlogger should be showing a TPS reading of between 8 and 20% at closed throttle??

I'm double checking since there is a wealth of misinformation on exactly what an OBD II ECU reports.
Digital Tuning seems to back up my understanding that the ECU still reports the measured voltage expressed as percentage of the full 5v range. http://pocketlogger.com/index.php?pid=params&param=tps&type=obdii
The 2G service manual seems to imply that you should see an non zero value at idle based on the test parameters given. I don't have a manual for a '96 Galant so I can't be 100% sure.

That's what it does on OBD I ECUs and how I came up with those numbers.

I was under the impression the TPS should read zero at closed throttle, and 100 at WOT (tested with ignition on, car off).

There are a lot of postings here to that conclusion but none that I would take as conclusive.

I am sure that the correct and critical adjustment of the TPS is by where the IPS opens not by any TPS voltage.

I may have access to a multi-meter so I'll try and do the test you mentioned and go from there. Is your assumption that my TPS/IPS is not where it should be?

That's what I'm thinking. If the IPS never closes the ECU doesn't know your decellerating and to cut fuel. It pretty easy to check that's what I tossed the idea out.

I would think if it was set wrong you would throw a CEL but stranger things have happened but then with a turbo conversion you might always have a CEL and not mention it.

Steve

 

[homebatch]

Well I have no internet access over the weekend but I'll check back in Monday with any updates.

Thanks for the tips and I'll have to see what I can come up with.