Black smoke out passenger side tail pipe.

[girvin]

My 1994 Coupe has recently started to run very rough, especially at idle. I noticed black smoke (fuel) coming from the passenger side tail pipe only. I checked the plugs and found that again, only the passenger side plugs were fouled (completely black), while the driver's side plugs were still in great shape. I thought maybe it was the O2 sensor on the passenger side that had gone bad. I went to the local auto parts store and had them attempt to run a diagnostics test. Their tester was "unable to establish link" with my computer. Also, the guy at the store didn't seem to think it was a sensor. I'm about to take the car to a dealership and undoubtably pay an arm and a leg. Before I do, I'd appreciate any imput as to what you guys think the problem may be.

Thanks,

Greg

 

[taegdh]

Could you have something in your fuel rail? Is there something which is causing your injectors to remain hung open? (Dirt, carbon buildup etc..)


Too rich on the one side, yeah, I might suspect the O2 sensor, but first check the connections to it. But that is probably a very good place to start. I'd also see about having the injectors cleaned. BUT there is something which tells the right bank of cylinders to run rich and the O2 would do that.

I don't like the idea of not being able to access the computer. You ought to be able to "pull codes" and cross check from those. I often wonder if some of the young fellows at parts places know how to work on Corvettes. Lately when I've been to Auto-Zone, or Pep Boys they seem to be overloaded when I mention Corvette, but if I mention Honda or Toyota 4 cylinder they seem to have a grasp on what's going on, and that's just the parts guys looking up numbers.

 

[jiangtao]

while on the subject of O2 sensors does anyone happen to know how many are on an '86?? i have replaced one and it was truly shot, but up until now i have always thought there was only one??

 

[Moonunit 451]

while on the subject of O2 sensors does anyone happen to know how many are on an '86?? i have replaced one and it was truly shot, but up until now i have always thought there was only one??

Just the one

 

[vetteboy86]

I would think if you had a rich problem like that, the car would throw a code. I cant believe that one bank could foul that bad. However were the plugs gas fouled or oil fouled. There is a difference. I also thought those injectors were on a spring like mechanism that would shut them off in case of a malfunction. I dont really know though.


Craig

 

[stu]

I have seen a 2.8 v6 have a single injector go bad and take out all the injectors because of the way the power bus is setup. Have you tried testing the injectors with an ohm meter?

 

[vetteboy86]

Yes but why would it only foul the one side?


Craig

 

[Vettefan87]

I have seen a 2.8 v6 have a single injector go bad and take out all the injectors because of the way the power bus is setup. Have you tried testing the injectors with an ohm meter?

I might be wrong, but one injector wont make the other 7 crap out. If you just have one bad injector you can just change that injector right?


Justin

 

[Florida Guy]

Do the injectors on the right bank have a common grounding point? Could be corroded. Just a stab at it.

 

[stu]

I might be wrong, but one injector wont make the other 7 crap out. If you just have one bad injector you can just change that injector right?


Justin

It would depend on how the things are wired up. An 87 Grand Prix is setup with all the injectors in parallel on a single power bus. When one goes bad and grounds out, all the current will go to that one. The result is not having enough to make the others work.

I don't have a wiring diagram for the L98 but I would guess that it has left and right banks for the injectors.

 

[Magmotor]

My '89 has a fuse in the fuse box for each bank of injectors. Check the voltage at the good side and compare to the bad. Could be a place to start. Another is Pin D15 & D16. This is where the pluse width comes from to control each bank. If a pin is correded or loose it won't send the correct information to the injectors. Hope this might help a little.

 

[girvin]

The local Chevrolet dealership said it would be AT LEAST $300 just to diagnose the problem. I called around and got the same response everywhere - "Those older Corvettes are a bear to work on" - which I take to mean "this guy owns a Corvette, we can charge him an arm and a leg and he won't know he's getting bent over."

Wednesday, I dropped the car off at a shop that sounded more reasonable - 1-3 hours work to diagnose the problem at $70/hr. I got a call Thursday that sent my blood pressure through the roof. Sir, we found the problem, you've got a bad 02 sensor! I told the guy not to replace it - that I would pay for the diagostics, but do the repair myself (he wanted an additional $429 to replace both 02 sensors!). The mechanic's response was, "this car is 10 years old, good luck getting the old one out" - which ticked me off, considering a have worked on cars since I was a kid and have replaced several 02 sensors in my life. Needless to say, when I picked up the car, I was charged for the full 3 hours. So I paid $210 to confirm what I originally thought was wrong with the car.

I feel like going back to Murrey's and choking the guy that talked me out of buying the 02 sensor.

Thanks for your input guys.

 

[Aurora40]

How much is the o2 sensor on the car? They used to be like $25 things on all the '80s cars I owned. But the post-cat (post-cat! Not even one the engine needs to run) o2 sensor crapped out on my beater '95 Nissan, and the thing is $177 from the dealer for just the part! In that case, just swapping one on a hunch would be a big gamble...

 

[girvin]

They are $54 a piece at the autoparts store by me. The mechanic was going to charge me $83 a piece.

 

[froggy47]

Sorry I got to this post late, I would have suggested replacing any 02 sensor with more than 50k miles on it as money well spent. Even though it's "guessing" at the problem I think it's a rip off what these "diagnostic" charges are.


My kid's 89 Bronco II failed smog & I was faced with the same deal. The smog guy (a friend) said don't just throw parts at it. Well I threw an o2 sensor in & it passed with flying colors - original had about 75k miles on it. With the cost of "diagnosis" you can do plugs, dist cap & rotor wires & o2 sensors and probably fix 99 out of 100 problems. Also check all the vac lines - free

Only then would I start shelling out for a diagnosis. OPti is another one but certainly not an "easy" replacement

Well at least you got it running good again

I do tend to get the best replacement parts I can - I like bosch for o2's.