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Discussion Starter · #1 ·
Just changed plugs. drivers side all sooty black no big build-up of anything. Pass. side all reddish brown no build-up of anything. All 8 were dry. This is my 1st plug change. It had Bosch plat's in it. I put AC Delcos. I don't know why one side would be different. Pass side is normal IIRC. So what's up with the drivers side?

PITA job. All from the top, taking my time as I can't stay bent over the fenders like I used too...LOL. 3 hrs. Jacking up the car & taking the wheel off ??? I don't think so. You do have to work more by touch than anything else. Also donate a little blood to the grease Gods, but that's nothing new ..lol.

Any ideas on the plug difference from side to side guy's.?
 

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I'm guessing there exists a difference of some type between the two cylinder banks. Exhaust leak on one side,Oxygen sensor performance,and intake leak are some possibilities. I'm sure there could be others also.
 

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Just changed plugs. drivers side all sooty black no big build-up of anything. Pass. side all reddish brown no build-up of anything. All 8 were dry. This is my 1st plug change. It had Bosch plat's in it. I put AC Delcos. I don't know why one side would be different. Pass side is normal IIRC. So what's up with the drivers side?

PITA job. All from the top, taking my time as I can't stay bent over the fenders like I used too...LOL. 3 hrs. Jacking up the car & taking the wheel off ??? I don't think so. You do have to work more by touch than anything else. Also donate a little blood to the grease Gods, but that's nothing new ..lol.

Any ideas on the plug difference from side to side guy's.?
the driver side has the PCV. replace it and make sure those vac hoses to it are good. also be sure the opti vac lines are good .

check the passenger side also for cracked hoses. a vacuum leak can throw off the PCM fuel mixture control.
 

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Discussion Starter · #4 · (Edited)
Didn't think of the PCV as I thought that would effect both sides , But I did notice that there is a hose off of the evap canister purge solinoid that comes off the bottom, does a 90 degree turn and heads towards the firewall...it just broken off about an inch from the solinoid but there is nothing there for it to go to....?

All intake bolts are tight.
 

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All PCV events occur inside the intake and do not favor either side.
 

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Didn't think of the PCV as I thought that would effect both sides , But I did notice that there is a hose off of the evap canister purge solinoid that comes off the bottom, does a 90 degree turn and heads towards the firewall...it just broken off about an inch from the solinoid but there is nothing there for it to go to....?

All intake bolts are tight.
cannister purge switch, that is a vacuum leak the forum has good pictures showing where this goes. fix all hoses and after you run it a few hundred check a plug on each side to see if it is normal light brown both sides.
 

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An exhaust leak on the driver side is your #1 suspect, which the O2 sensor reads as lean, and the PCM commands more fuel to that bank.
If you're running GM O2 sensors, failure to cause your condition is rare. I've found that 250k mile GM O2 sensors work just fine if your base tune is even close. They don't switch as fast as new ones, but don't consistently read high or low.
 

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An exhaust leak on the driver side is your #1 suspect, which the O2 sensor reads as lean, and the PCM commands more fuel to that bank.
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^^^^^^^^^^^^^^^^^^^^^^^

look at your rear exhaust bolt to see if it is missing, loose or the manifold is cracked in that area. rear exhaust bolt on iron heads have a history of breaking
 

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Discussion Starter · #9 ·
OK, This thread from a few years ago explains the vac line that goes nowhere. That's the way it's suppose to be...

http://www.impalassforum.com/vBulletin/showthread.php?p=2308633

The rear exhaust bolt is broken off, has been since I got the car 7 years ago, no indication that it has been leaking, no black carbon tracks, no ticking hot or cold. Car has been running fine until the other day when I noticed a severe loss of power at low speed take-off, Thats when it looked like some smoke out the back , but it was dark and I was just looking in the rear view at the lights from a car 50-75 yards behind me. Since the plugs were Bosch I'm wondering if the prev. owner also put Bosch O2's in it and that one just quit. I'm still trying to figure out why I can't read codes, so I'm out of luck with a code to point me at. I have 2 new AC Delco O2's that I should probably throw in anyway since the car is down until I get emissions done and the drivers side looks like it should be quick from under the car.
 

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the vacuum lines on my 1996 impala are not routed that way. I am the original owner and person who repairs it.

I know that there are better diagrams with this info which is a OEM routed GM diagram.

the only hose that has no connection is the canister vent hose and that is mounted between the battery and the back of the passenger side headlight.

the reason it is mounted there is so it is not near the engine.. gas vapors !
 

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...The rear exhaust bolt is broken off, has been since I got the car 7 years ago, no indication that it has been leaking, no black carbon tracks, no ticking hot or cold.
Even though you don't see anything visible and this thread doesn't really mention what the issues are, I'm assuming you answered your own question w/ the above. That bolt needs to be replaced.

As for plugs, I run autolite iridiums. Switched to iridium after i saw a couple of platinum tips from delco double plats completely gone upon plug swap. Don't want that stuff banging around in the cylinder and the gap is WAY off once the tip becomes dislodged.
 

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Many things contribute to codes setting and even not setting. There can be current codes that are active but do not set the MIL light since they haven't met enough criteria. Its also possible that the previous owner converted to obd1.

As others have said, the cause of the plug differences is the broken bolt. Fuel trims tell the tale. You can test your o2 sensors on the vehicle with a scanner. Will a scanner get data if it is hooked up? Lets start there.

Chris
 

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Discussion Starter · #14 ·
Scanner keeps getting 'link error'. I have used this scanner for years with no issues so I know it's OBD II. There must be a problem with the data feed port as the scanner will power up when I plug it in. I can get to the bolt as it broke off at the head. I will get on it as soon as it cool's off.
 

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Scanner keeps getting 'link error'. I have used this scanner for years with no issues so I know it's OBD II. There must be a problem with the data feed port as the scanner will power up when I plug it in. I can get to the bolt as it broke off at the head. I will get on it as soon as it cool's off.
if you have a stud to grab I used a small vise grip pliers about 4.5 inches long and I got this stud out. use some penetrating oil to help lube the threads. these are installed with a GM thread compound to hold in place. try to unscrew when it is heated up a little. also work it in and out to remove. the stud is bent from all the manifold expansion.

advance auto has these 3/8-16 x1.5 inches. grade 8.
 

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Discussion Starter · #16 ·
I don't get it. Just plugged the scanner in for the hell of it....it linked up, gave me "O2 Oxygen Sensor Circuit High Voltage (Bank1, Sensor2)" P0138, let me erase the codes, then scanned again & came back with No codes pass. I wonder if I don't have a bad/loose pin on the ALDL. ?
 

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I don't get it. Just plugged the scanner in for the hell of it....it linked up, gave me "O2 Oxygen Sensor Circuit High Voltage (Bank1, Sensor2)" P0138, let me erase the codes, then scanned again & came back with No codes pass. I wonder if I don't have a bad/loose pin on the ALDL. ?

the driver side after cat O2 is most likely bad. or the wiring/connector. O2 DTC will take some time to make a code.
 

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Discussion Starter · #18 ·
Would the after cat O2 going bad cause the rich condition on that side? I thought they didn't do anything as far as engine function. I'm still trying to get the rear manifold bolt out, my little visegrips don't want to hold,,,damn it.
 

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Would the after cat O2 going bad cause the rich condition on that side? I thought they didn't do anything as far as engine function. I'm still trying to get the rear manifold bolt out, my little visegrips don't want to hold,,,damn it.
If the rear is bad (or more likely faulty), this tells the PCM the cat isn't there. Since all they do is basically check for the cat, I'd guess that O2 might be salvageable w/ some cleanup or it may even be a wiring connectivity issue.

You've probably read, but many swap good, used O2's into the rears and save the new ones for up front where they're actually reading and sending O2 values.

I may even have a good, used O2 laying around. PM me and I can send it to you if desired.

For the bolt, use a propane or MAPP torch to heat the bolt and spray w/ penetrating oil.

Have even heard of people using heat to clean carbon off of used O2's, but have never done this. I'm OBD1, so if the sensors go bad, they just get new (which is why I've 1 or 2 used ones laying around).
 

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Would the after cat O2 going bad cause the rich condition on that side? I thought they didn't do anything as far as engine function. I'm still trying to get the rear manifold bolt out, my little visegrips don't want to hold,,,damn it.
on the bolt removal use the penetrating oil not other lubes. allow to work a few days. with the small vice grips work the stud in then out as you do this it will slowly work its way out. the vice grips I used had a jaw for a pipe not straight.

with heat from the engine running it should loosen the stud as well....
 
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