evilluc

Hello all. I took my car into the dealership on Monday and just got a call back stating that they didn't fix anything on my car. These are the things I took it in for:

1) I have some kind of driveline clunk when I slow down and then give it gas. This happens a lot when I slow down for a stop light that then turns green before I fully stop. The clunk can be felt through the whole car and is gibing me false knock like no other. The service guy kept talking about "backlash" so that the rear wouldn't snap and that this was normal.... or not?

2) My passenger side window motor makes a CLUNK when you roll it all the way down and then back up. You can see the door panel buckle when it does this. Apparently the motor checked out fine... or not?

3) Fianlly, my gas mileage has been horrible (14 mpg.) I've done all kinds of stuff to correct it but thats another story. I was told to manually test code P0420 (I think that was it) with my Predator. The test failed. It had something to do with one of the cats so I'm guessing I have at least one bad cat and o2sensor. The thing is I have no SES light. I didn't tell them about this because I don't want them to know I have a programmer. They said there were no faults in the computer. or not?

I appeciate any help you can give me. I had heard that this was a good dealership but now I'm thinking otherwise (this is my first time there.) Thanks in advance for the help.

dand35th

gm products have always had tons of driveline slack.. but seems that they could have checked backlash for sure. and u-joints etc. did they state they checked anything. or just "nope, found nothing"

evilluc

Apparently they heard the noise and determined it was normal just from that...

CAT3

iTrader: (9)

The clunk sounds like a loose U-Joint, or it could be the crush-sleeve that supports the pinion gear inside the housing...thats what it was on my car, too many launches. The piece is made to be more of a sacrificial piece.

Window, it probably needs the track lubed. Mine also needed this. Sounds a little like the plastic gears are clinging on the way up & down. Dealer can do it under warranty and should have, but you can also. Remove door panel and use generous amount of lube on plastic guide.

As for the mileage-difficult one there. 14 would be cool fo rme in town. I leave lights a little aggressive since modding. BUT, if you have the Predator you can check the codes yourself. Plug in, turn ign on, go to diagnostics, DTC etc...If there are none there, then the computer is not storing any. Of course, the Predator may not read everycode, not sure, but it does read O2's. You can also do live data monitoring and physically watch the mv output of the O2's as you idle, drive, also look at the LTFT's and see what they read, you might be running really rich.could be a vacuum leak or something.

Good-luck and post back any findings please.

Charlie

evilluc

Thanks for the response. I'm going to call them back and tell them to check the rear and window motor. As for the codes and such, its not storing the code but when I manually ran that test with the Pred, it failed. I was told that it has to fail multiple times in a row before storing a code? Might be hard to get this one fixed... it sucks though because I used to get over 20 mpg on the same driving conditions!

evilluc

Ah ha! I called the service guy back and he admitted that they did not check anything on the drive line. They may have not even actually heard the noise... he didn't really say and I didn't think to ask. They're also going to take a look at the window again. Any suggestions on the cat/o2 sensor thing? I'd looooooove to get it all fixed in one visit!

dand35th

probably a bad o2 sensor?? slow reacting, but not 100% bad

evilluc

I was thinking the same thing. I had a thread going on ls1.com about that. I was assuming it was a dying cat/o2 sensor.
http://www.ls1.com/forums/showthread...hreadid=328675

CAT3

iTrader: (9)

If the rear is leaking at the pinion input seal, then most likely it is the crush collar that is the culprit. Thats how I noticed mine. Ordered a solid sleeve from Thunder (made by Raytech, Raetech sp?) and it is not leaking anymore. Theres still some slack, but normal.

As for the O2's, you can ask them to monitor the O2 activity. Tell them a friend scanned it and was showing a lazy O2, that it was not switching sufficiently, then they may hook it up and watch how it is doing, of course unless you are there, you may never know if they hook it up.

Did you do the live data part, or just look at the DTC set?

evilluc

CAT3 - Thanks for the response. The rear is definately not leaking, although I wish it was since dealerships only seem capable of fixing obvious problems sometimes

I'm going to have them do that with their scan tool tomorrow when I go for a test drive for the driveline clunk. I looked at the DTCs and none were set but when I manually checked P0420, it had failed the last time it was run. That was the only code I ran but I'm willing to bet that others would not pass either. I've been told that the dealership can view the history of these failed tests with their tool. Keep em coming guys

EDIT spelling

gwj

I'll only comment on the gas mileage...If you only do slow city driving, that could be right. I do a combo of city/highway (mostly highway) and I get 26 mpg still after 70K + miles.

Inspector12

iTrader: (29)

I have no clue about any of your other problems but the window (Having replaced a few.) I acn tell you that the fiberglass door shells flex a lot you may just not have notice it before it started making noise. All the ones I've installed flexed the dor a little when the get to the bottom and the top. No big deal as long as the door is not comming apart (Seen a Few 4-5) in the fast 2-3 years. Hope that helps you.

glitch77

On the glass clunking:

Most likely, it was been shut by the glass a time or two (maybe not) and the upper hook isnt grabbing. When in the 100% up position, there is a hook on the glass, that catches on another hook on the door. If it bangs into the hook first, then goes into it under pressure, it will do that.

30thWS6

What is all this talk about the P0420? Is your assumption that the cat is plugged and that is why your mileage is suffering? A P0420 DTC should only set a code if the cat is not doing its job, or there is a problem with the post cat oxygen sensor. On most engine management systems the post cat oxygen sensor is nothing more than a monitor for catalyst efficiency. With that said though, a few systems do use the rear oxygen sensor for fine tuning fuel trim to a very small extent. However, not enough to noticeably affect gas mileage.

An easy way to check an oxygen sensor is to monitor its voltage at WOT and then slam the throttle shut and monitor it again. At WOT the voltage should be high and remain high. When the throttle is slammed shut, fuel cut-off or some other strategy for deceleration enleanment should cause the oxygen sensor to read little to no voltage for at least a few seconds. Monitor both B1S1 and B2S1 and see whether they follow a similar pattern.