I'm not sure what the Chevy dealer put in when both O2 were replaced in the past, but perhaps they installed an AC Delco unit, and maybe that is why the readouts are so different from each other even still? (with the new Bosch on the right) - - I will take a look when I get a chance, but do you think I should locate an AC Delco O2 and replace the right side with that? - - Again - I have read other posts that say to stay away from Bosch or that they used Bosch and it was good few a few weeks then craps out.... switching to AC Delco seems to have been their fix.... Perhaps I am just experiencing the same problem with these Bosch units... I might expect the Chevy dealer to have used AC Delco... and perhaps it was the smashed up/partially clogged right side cat that fried that unit.... What are you guys using?


Also - I just paid for my e-tuning service from PCMforless... If they aren't operating again until Monday I suppose I can't expect to receive it until then... I will let you know if that fixes anything........ Will a new tune from PCMforless be like tuning the factory programming? I'd like to know if anything that might have been fiddled with is completely negated... either way I can't wait to see how it runs after the tune... Bryan has stated in the past that his tune would render 15-20RWHP (from a stock car) - that sounds like a lot - I'd be happy with half that. What should I really expect?

 

I had a problem with a Bosch O2 but others have not so just be aware of it.I believe you will have to send the PCM to Bryan to be tuned or swaped out I don't think they send a file to load up but they might be able to do it that way your just going to have to talk with them.Bryan has a lot of good media reports and I am sure you will be satisfied but it make take a couple of tries to get it exactly right with some feedback from datamaster.

If you send the PCM in I am sure he can tell if it has been touched.Your making a good choice going with them I did PM Alvin to come to this post and look at your files I posted and he usually does and may have some feedback.

There are some parts that OEM is better and to me they are Opti (except for Dynaspark),O2s ICUsand WPs but if it can be replaced easily and has a good return policy it is possible to get aftermarket that will work.Hope you get this all worked out you have been at it for too long and deserve a break

If you looked at my file I bet you can see why I was freaked if it looked like yours did to me.Good Luck and keep us posted on your tune.

 

For some reason I can't access the site at the moment - but I am certain that I do not have to send my PCM in for the tune. I have purchased the $75 over the internet deal for 1994-95 Vettes.

EDIT: Today I drove the car again, but this time in hot/warm weather. It drives fine still, but I did get a certain backfire once on decelleration...

 

I'm betting that is bacause of the hollowed out cat.

 

As long as the poping is out the exhaust side that is somewhat normal.

 

I was not sure as I have an ECM but as long as you can use tuner cat is should be doable.I have not used it but if you can save a copy of what you have Bryan should be able to look at it and see if it has been touched.I am sure you will get your moneys worth from them.

 

Hmm... I've had this sort of backfiring before I gutted the cats... But if you think this adds to the occurence.... Would it be less likely to do this when sometime in the future I add LTs and straight pipe the cats...? Either way... I've always seemed to have some kind of backfiring problem (though I rarely have any problems when it is cold out).

 

Do you still have the AIR pump hooked up and working?

 

I haven't touched it... From the scans it seems to be working (isn't it the EGR readout?)... But again - there have been many other owners - so I don't know what all might have been fiddled with, but I doubt it was removed...

EDIT: would it cause this sort of thing if it were still there? - Or if it were removed? - since I'll probably be removing that as well whenever I get around to purchasing and installing LTs..

 

The AIR pump has a "dump" function that is supposed to port the air to atmosphere on decel to prevent backfiring in the cat converters. If it were removed, disabled or just not working, this could be another source for the noise you are hearing.

 

Ok. Where is the AIR pump on my car? - - How cn I tell if it is not working? If it is not working should I just remove it? Is there any performance gain in that?

EDIT: Also - is this something that would cause the backfiring mostly in hotter weather?

 

The AIR pump is a belt driven accessory, so to remove it you'd ned an AIR deleat pulley kit. It has a large rubber hose going from it to a PEDEs valve which handles the porting of the air. Not sure how you'd test the dump function of the valve though.

 

I believe if your car is like mine it is in the area under the drivers headlight and is not belt driven but electrical.It is used to heat the cats up at start up but I don't know if can be disconnected with out codes appearing.It won't cause any backfiring.

Backfiring where?Exhaust or intake?If it is exhaust and doing it after letting off the gas it is somwhat normal because without cats there is still some fuel going into the exhaust and since there is less backpressure with non stock exhaust it detonates in the exhaust.

 

I didn't read all of the responses but the datalog didn't look TOO terribly bad.

The o2 did seem to be a touch lazy compared to the left o2 but nothing bad bad. I would go back and look for

1. Exhaust leaks on the passenger side
2. Wiring to that O2 either oily or burnt on the passenger side
3. Misfiring on your passenger side.


If all that checks out I would try swapping the left o2 with the right and see if the problem follows over.

Typically backfiring on decel is because hte car is a touch lean.

What driveablity problems are you seeing? Any soft feeling? How do the plugs look on the left and right side? Have the 02's ever been changed?

 

I believe the 85 & 86 were still belt driven, maybe even later than that. I know all of the LT1's were electric pumps and pretty much everyone removes them. In fact a friend of mine has a 95 Impalla SS and his pump went bad, he said he found a TSB from GM that said to just remove the pumps and plug the holes, because of their high failure rate and they wern't needed to pass emissions.

 

Which file did you look at? The first one he posted (remote site) was pretty messed up and was throwing a code for the RH O2, this has gone away since he replaced the O2 sensor.

 

Hey Alvin thanks for checking in.History is he punched his cats out because the Pass side was polluted and he has gone through several O2s on that side and just recently replaced another.If you look at the zip I posted it has 2 files try3 was before the replacement and the other after.He is going to get a tune from you guys.

 

Gotcha,

Just downloaded the zip attachement and looked at the latest file.

The car looks A-OK to me now. I mean unless he has any big driveablity complaints that would warrent a more closer look. The 02's fly up and down nicely, no excessive or unusual spark retard, all the sensors look reasonable, and the BLM's averaged nicely.
Averaged being a key word as the purpose of them is to keep the car in trim all the time.. They will fluctuate constantly but as long as they are sitting on average close to 128 your good to go.

 

Well the cats were punched out because the car became completely undriveable and had tons of black smoke coming out the right side (before the x-pipe). Turned out they were both smashed to pieces and the right side was polluted and partially clogged... - - - -

Alvin - thanks for taking a look. This computerized stuff is all new to me. And since the O2 swap I don't seem to have any driveability problems at all (just drove a little over 2 hours on the highway with it - pulls good even in 5th). I'm glad to see that your interpretation of the last file checks out fine. I was wanting to have my problem sorted out before I received the tune (I have already purchased the over-net deal with Bryan - can't wait to see what that will do). - - Anyway - I couldn't see great when I did the swap - I was working with a flashlight and not having my fathers shop - I was stuck with a mini-jack at the one corner... But there was a little bit of oil present and the connectors were resting on the cat... I didn't look for heat damage, but now that you have mentioned it..that is always possible too... - - - at any rate - I cleaned up the connector with contact cleaner and made sure it was dry in and out before connecting the new O2.... - now the connector is off of the cat as well (and appears to be out of the way of whatever oil is still leaking - whatever it is must be very minor - I have yet to see any oil in the driveway).... Of course, with the feedback I have heard on the Bosch units... I figure it could be anything mentioned that caused the O2 to fail (or a combination).

Either way - it is driving good now. Thanks to Morley and RedEasySport for all your input. I will look into checking the vacuum if I get a chance while I am down here this week... I have yet to think I've gotten all the little bugs worked out... I've fixed a lot, but this car has had a lot of owners.. I can't remember how many but it was more than 10.... I was the 3rd owner of the 20 years older Ferrari (75)... When I got the Vette it was full of creaks and knocks - now it is dead silent on the road... And it seems like the performance issues are about zeroed in on. - - The shattered cats were definitely a shock ( the Ferrari didn't have them from the factory - so I felt as if they shouldn't be there anyway).

I will keep you guys posted on the tune. I don't know if the Datamaster files will show much, but you can let me know if you would like to see any of them after tuning. Perhaps I could e-mail RedEasySport to post them if they are interesting.

Thanks again! - sorry for writing so much... And hopefully I can get my car painted this week and I will have some pics for everyone (these C4s look like they were meant to be two-tone ).

 

$50 a piece for Bosch ones from Autozone

Autozone O2