Update. The car has been back to the shop three times for poor surging idle and lack of power on kickdown. We replaced plugs,Opti, water pump, Opti vacuum line, both O2 sensors, repaired vacuum line to the EGR valve, new left Cat, right is ok.

We fixed the lack of power, turns out the wires while they tested good were breaking down under load. Coil wire showed evidence of arcing to the metal protector. The surging idle still remains a mystery. I was sent the GM shop manual for just the LT1 motor and it’s about 1000 pages long. Extremely detailed. Even so we still have not isolated the problem. Ironically after changing wires the left bank was rich now it switched to to the right bank rich. No reason.

So we are going to try to try again Monday. I’m awfull close to putting a nice Holley carb on this car.

My el Camino with a carb sat for 6 months, never looked at it. It spun over a few revs then started and purred like a kitten.
it drives like a new 42 year old car.

If anyone can offer suggestions please please do so.

 

As you are probably aware by this time, an over rich condition on whichever bank will destroy the converter on that bank.
The O2 sensor is supposed to report the exhaust oxygen for their respective bank. Now, if there is a rich condition for the right bank the list of what can cause that needs to be checked out.
Has anybody checked the exhaust for any restrictions? The converter on the other side may need to be replaced now..
Either the shop where you are having the work done is guessing or they just don't know what to check. Maybe they just don't have the equip .
After reading all the posts so far, could you possibly make a list of what was replaced. When you look at the list you might agree with my conclusion about guessing.
If you would , they obviously have connected a scan tool to get the various data readings.Ask for them and post them here and we may be able to put forth another point of view. What do you think?

 

My post right above shows everything that has been replaced. This shop agrees with my philosophy of not just throwing a bunch of parts at it hoping to cure the problem somehow. Each item that we replaced was for a detected failed item with exception of the right side O2 that I felt should be replaced simply because we replaced the left side too. We did the scan the right side before and after and it shows the O2 operating correctly.. my choice of throwing parts.

BTW, all items are to be OEM GM stuff. Absolutely no MSD or auto store brands. I’ve been burned too many times This car is an old people car, as such it should function near perfect everyday even if great grand ma takes it to sewing circle or great grand pa takes it to senior discount breakfast with other octogenarians. I’m not quite that old but dam close. I’m fortunate enough to still be able to roll around on a creeper or bend over a fender.

My 42 year old el Camino runs exactly this way, so it’s son this 25 year old kitten should too.

yes early on we checked the exhaust by simply disconnecting both pipes and addinding a short extension on each side. This is how we found the left Cat was bad. Going forward we found all the plugs black on the left bank. Why? Plug wires looked good, nice and flexible, came off the plugs correctly. Then we found oil around the Opti. And the vacuum line was deteriorated. It’s not exactly a screwdriver and you pop the cap off operation. So we did pull it out along with the water pump. The big oil seal was leaking badly and had soaked the Opti insides. That’s when we replaced the Opti, the oil seal and the water pump. Also installed a new vacuum lin from the Opti. This is the second gen Opti some don’t have this feature. This fixed the rough running and most of the misfire. We also cleaned and inspected all the related wires and connections.

interestingly I’ve been to 5 very popular shops other street rodders frequent. None have good experience with this OBD1 and none had scanners good enough to really read the system. Some shops have not even been around since these LT1 were created. I swear they all are bolt on freaks and when it comes time to create and delve into how these systems work they are lost. I asked about fuel trims as a test. I got ??? WTF is that?? If their equipment can’t even get to the point where these can be seen they really are just guessing. They all told me it’s not possible to scan this deep. You can’t without top notch equipment.

Our last scan scan shows everything operating within range. The richness on the right bank is right at the top of the scale while the left bank is below center of the range. There are no codes showing on the more or less standard code reader. The average shop would blow me off as nothing is wrong. Why hell does this car rock and roll like a pro mod then? My supercharged ****** did not do this., and if any car would it should have.

So electronically it seems ok. We have checked for vacuum leaks and replaced virtually every piece of hose on the motor. The air intake duct hoses are smooth and not cracked, all the hose clamps are tight. We tested by wiggling the air intake stuff as though it were on a rough road and no motor operation changes occurred. We have wiggled about everything movable and nothing is affecting operation.

This issue comes and goes. One day the car is smooth as glass, the next day same road same stop lights same traffic it idles like a junker. It doesn’t matter outside temps have been -20 to + 80 rain shine or blizzard. I’ve tried full tank of gas to near empty, both standard 87 and non oxy premium 91. I usually go to one of three stations, all are very high volume stations so no back road month old gas.

This problem is not unique. There are many LT1 posts in other Camaro and Corvette forums covering the same issues. I’ve yet to see a definitive solution. We’ll fix it I’m sure.

Looking at this from an engineering view...I am one of those geeks, retired, GM was way ahead of the game with this system.....when it works. It’s capable of very close air/fuel management matching engine and road conditions. Many of these have been modified with good results. There are re-programmed computers for these. I’m not about to even consider this until I can see a problem with the existing one. It may already be there, we just have not got that far yet.

Other than the messy idle the car runs great. I’ve averaged around 20 mpg all winter. Highway speeds are ridiculous in the morning rush hour. 75-80 in the left lane. I drive nearly 50 miles each way so it get a good work out.

Monday we’ll be back at it. That monstrous manual is hard to page through on the computer. I wish it was a paper book.

Sorry for the long post, it’s been a long hard winter.

 

Thanks for the reply.

OBD l required the tech to do the detailed testing manually.
OBD ll does it for you. What you need is a retired tech who is looking for a way to not let his/her valuable experience go to pot.
Can you obtain those multiple read outs and post them here?
Things like oxygen cross counts, voltage readings , coolant temp, RPM, Idle Air Control, Fuel trim (if under 128 or over) is required to know as is injector on time .
Grant you all the parts were OEM , but sometimes they were questionable and it required the tech to know how to check the system and what it was supposed to do.
There was no such thing as "Freeze frame" with OBD l and the scan tool had a feature described as "Road" and those results were indicative of what the conditions were at the time the system was malfunctioning., but the tech had to be watching the readings at the time. I hope I might be able to offer some assistance, but we do the best we can.
Since you have the manual, and you like to read, it's April now and maybe in July, or sooner, you will know what you want to check and how.
You know more about this vehicle than the people you are taking it to , so don't be shy asking them questions. Sometimes a question will open another pint of view and hopefully more ideas will help pin down the problem(s).
Can you get them to scope the crank and cam sensor waveforms and watch them later when they /you bring it back off the road test?

 

Thanks for the info.

we got the down shift issue fixed. Plug wires arcing to the protectors. The trans works great.

We have had issues getting the expensive tool supplier scanners to work properly. Without this you are just guessing. There are no codes showing on my car yet it runs terrible. The car only has 115 k on it and no winters except this one.

we have the EEHack software but ran out of time as I needed the car for a couple Doc appointments. I’ll bring it in next week again.

Its too bad that I don’t have a place to work on cars anymore or I’d be more into it myself. I don’t have a laptop anymore but I could get one then I could have running scans.

yeah, I know OEM stuff is not without faults but aftermarket stuff is worse by a long ways.

The switching of sides AFR is puzzling. The only thing that was changed was the O2 sensor. We’ll try and put the old one back in and observe what happens. That was my call....throwing parts at a problem that doesn’t exist. We’ll see.

The nice thing about the EEHack is that you can save a scan and look at it.