Tranz Zam

Hi,

I made a post a few weeks back about installing a VSS. I ended up going with the Dakota Digital setup and getting a mail order tune from Frost. The car ran great for about a week cruising about 80 miles. The VSS did make a pretty big difference.

Now...

The car was running great the other day, but it all went south. I gave it about 45% throttle and it started sputtering and running really rich. Its so bad that it almost sounds like a rev limiter that cuts out spark when you're first trying to get the car moving. Its pig rich, almost completely on the driver side.

I ran the scanner on it and got P0500 and P0131.

P0500- Speed sensor faulty, not reading correct, possible short circuit.
P0131- Faulty front o2 sensor. Low voltage.

The speed sensor is about 2 weeks old. Worked perfectly. I tested the sensor by jacking the car up, running it in gear and putting my volt meter on it to see if its providing a signal. It is creating a signal.

The o2 sensors are about a month old. Both bought brand new and installed at the same time.

I snaked out all the wires for the driver side o2 and checked for burnt wires. I also tested the wiring with a test light to see if there was power going to the sensor and there is.

There are no other codes at this time.

Any ideas? It was perfectly fine while driving then all of the sudden it went south.

Specs:
02 LQ4,TH350,DBC.

Tranz Zam

I should also mention I pulled some plugs. The driver side plugs are completely black while the passenger side look fine. I'll post up a pic when photobucket is back up and running.

jcvett56

Did you but a pigtail or VSS with Pins for PCM terminals already on it or did you conjure up something your self? Not utilizing the proper crimpers could result in intermittent problems if you don't get a good crimp and keep the pin true. Try wiggling at the ECM, idk which computer you have, and try your test or you use a signal generator if you can at the VSS and look to see if the gauge is operating while you wiggle like a Gigolo over the added VSS plugs, near PCM/ECM, or at the plug itself.

I believe the PCM needs to be flashed for a manual as well. Not 100% of functionality issues if it is or isn't.

Tranz Zam

I had leftover wire from another harness rewire I did. I took a long piece of wire with the factory pin and pinned it into the computer, connected that wire to the VSS and had the computer reflashed to read the new VSS. It was running fine but now it went haywire.

I pulled all 8 plugs and the driver side plugs are jet black while the passenger side look fine. That would make me think its something in the harness that went wrong?

Tranz Zam

Update: So I decided to pull the driver side o2 and it was pitch black like the plugs. I replaced it with the old GM o2 sensor and another set of used plugs I had and the car runs better, but I'm still experiencing a severe stumble at around 2-3k rpm. The car isn't throwing any codes now. I cleaned the MAF and check all connections to other sensors.

Any ideas?


Here's a pic of the plugs:

jcvett56

I would say since it's acting up at a certain RPM it's tune related. Maybe Post up the tune for some of the smarter tune guys and see if they can spot any irregularities. Not saying it is but that's a good place to start.

Tranz Zam

I sat around thinking about it and I ended up switching the Corvette regulator with another one I had. The car seems to run fine now. Pulls hard, no bogging, no codes. I guess the filter/regulator went bad?

How often does that usually happen? It was about 3 years old.

ls1nova71

iTrader: (4)

What brand was it? I've seen cheap ones bad right out of the box.

JetMech442

iTrader: (1)

yeah, I've had two of the filter regulators so far. One was the kit from speedway, the other from amazon. Amazon one gave me issues right out of the box, which I didn't expect and spent a long time trouble shooting other parts. The speedway one (Wix???..not sure), will be rocksolid 58 psi with engine off, once idling it jumps erratically between ~42-60.
I think I'm just going to get a dedicated adjustable FPR and be done with all this.

Tranz Zam

I cant remember what brand it was, and there's no markings on the outside of it. I ordered another one off ebay, I hope it doesn't give me any issues.

Tranz Zam

Well the issue is back. Stupidly enough I forgot to plug the MAF back in after I cleaned it, that's why it was running better. So it wasn't the regulator.

I'm still getting a code for the VSS, but I checked it and its creating a signal that increases and decreases with speed.

The car runs like total caca. I don't know why its throwing codes like crazy now. I really need to get this fixed, its getting frustrating.

I tried hitting up Frost but he never Emails back.

33willys

iTrader: (1)

One bank of plugs are fouled and the other bank good which indicates to me that one bank is running rich. What would cause that? The only thing I can think of that is bank related is the O2 sensor. If the O2 sensor thinks it's cold then it enriches the mixture FOR THAT SIDE, which will foul the plugs. Good way to check is to swap the O2 sensor plugs and see if the fouling goes to the other side. If the plugs foul on the pass. side then it's the O2 sensor wire but if fouling stays on the driver side then look at the O2 sensor. Each time you do a test clean the plugs first.

Tranz Zam

Hmmm good idea. I'll try this tomorrow.

I did replace the new Bosch o2 sensor on the driver side with my old one because I assumed the Bosch took a dump and that's why the car was acting up. But I'm getting the same reaction with the old o2.

superdave84

This is probably not the case, but are you sure you have the O2 sensor plugged into the right part of the harness? Your harness should have 4 pigtails total for O2 sensors. Presumably you have turned off the rear sensors in the tune, but if you accidentally have the sensor plugged into one of the pigtails that has been turned off, then you would continue to get this problem no matter how many sensors you throw at it.

A longshot maybe, but not impossible.

Monte4ever

iTrader: (2)

Did you figure this out???

Tranz Zam

Its a stand alone harness, so theres only two o2's and only 2 places to hook them up.

Yeah. I think it was the driver side o2. I think the new Bosch I had on the driver side took a massive **** and caused all sorts of problems. When I replaced it with an old o2 I had the codes went away but nothing really changed. I ended up getting a Denso o2, replaced all the plugs and cleaned the MAF real good. The car runs great now!

Oddly enough, I still get a VSS code. The car runs perfect, and it definitely feels like the speed sensor is working with the computer. I check the output signal on the VSS and its fine. I just clear the code every now and then.