I would have liked to put a better description of what is happening in the title. No room

My ‘94 Buick RoadMaster wagon has 110k on it and never seen a winter. It has the trailer package with the 2.92 gear and posi. I don’t think it ever pulled a trailer as there is no hitch nor evidence there ever was one. I had to install a fuel pump earlier this year. I also installed new belts, air cleaner (not Fram), changed oil and filter, also new OptiSpark plug wires and plugs and water pump, then we put a driver side catalytic convert on as it was plugged or inoperative. I thought it would be ready for enjoyable cruising. Actually it is but now the issue:

first when its thoroughly warmed up when stopped at a stop light it wil idle up. About 3-400 rpm. The 94 does not have a tach but that’s what we found in the shop. There are no codes. OBD 1. It acts like the AC is cycling but it is not always when the AC cycles. This situation makes parking in my underground apt garage a bit shakey. I nearly backed into a car a couple nights ago. It jerks pretty hard. We did put the car on a high end scanner and we were able to see the various sensors working p. The driver side bank is going up and down but in the range it is supposed to be in. The passenger side is steady but towards the low end of the range. You could see the rpm pick up and go down but nothing seemed to be matching it. So I made an appointment to leave the car and he said he would spent the day if necessary on it. He called and said the scanner was down again and not reading GM cars so I’ve been out for 2 weeks.

problem 2. When cruising at 50-60 give or take and began going up a hill, if I step on it to maintain speed the trans seems to unlock the converter the try’s to drop out of OD. This is messy with some what feels like misfire but actually motor and trans related. The shop says the trans (4L60e) is perfect. The pressures are correct and the fluid is clean and not burned. Once in 3rd or direct the motor picks up ok. Once I’m up to 70-75 it will shift to OD then if I can ease up a little you can barely feel it lock the converter. So simply put at 50-60 the forced down shift is just plain messy. I can manually down shift and all is well. Also if I tap the brake first it will down shift ok. I thought the converter was bad but he claims it’s perfect. Not sure how he tests this.

Otherwise the car runs great. 20+ mpg and everything works perfect on it. It really does have some low end power easily out running my 77 el Camino SS with its 300 hp crate motor, t 350 and 3.42 gears. It’s over 500 pounds lighter than the Buick too.

thanks

What brand is the Opti? In the past year, by reviewing data logs, I found three cases of an MSD Opti causing an erratic, surging idle. The Opti was producing a brief, spurious (false) high RPM signal, as high as 7,000 RPM. The PCM saw this brief false data, and responded by raising the idle air control (IAC) counts in response, jacking up the idle to over 3,000 RPM in some cases. After providing the data logs to MSD, they figured out the problem, and were replacing the faulty units with upgraded caps and optical sensors. Unfortunately, not all the replacements were successful. The faulty MSD units appeared to have been manufactured starting (this is a crude estimate) in late 2015 or early 2016.

With regard to the sensors, you referred to checking “various sensors”, But the comments in the sentence following that appear to be related to the O2 sensors, and how one side was cycling normally up and down and the other side was not. Is that a correct assumption?

There is a free download of scanning software available, for both OBD-1 and OBD-2 LT1’s. This can be a valuable tool in sorting out these kinds of problems.

As far as the trans, with that 2.92 rear, it's not going to be happy accelerating a heavy car at low RPM, and I would expect it to unlock the converter and drop out of O/D under the circumstances you describe. Your concern seems to be that your trans’ response is “messy”, but it isn’t clear what this means.

Thanks for the comments. I’ll clarify a little. I no longer have a nice garage or shop to service my fleet so I have to “take them in”. The guy that is helping me is an identify the problem then “fix the problem” guy not just a parts replacer that throws a bunch of parts at a problem and hopes it goes away.

The Opti is a vacuum ported OEM. I was already aware of the aftermarket stuff and the MSD issues. I’ve had my issues with MSD on my other cars so it was out of the question.
Since this is typically called an “old people” car and I qualify for that even though I deal with the hotrods, I insisted on OEM parts, no rebuilt stuff. Even though I had to pay a premium price, I felt there was enough labor in the Opti and water pump R&R to warrant not having to do it again soon.

Checking various sensors. I’m pretty new to this electronic EFI. My diesel truck has an Early EFI so that is about my depth of dealing with these. His scanner is top of the line...I guess, unfortunately he has had trouble with it not reading GM. He said he is really fed up with it. He tried on several other later model GM and had problems so he sent it in.
Anyway it took a bunch of effort but it finally worked for a few minutes so we just got to see the display but did not get to really delve into it. He suspected the O2 or the cats so he disconnected the exhaust and that’s where he found the left side cat bad. The car ran pretty well with the “test pipes” on it. I drove it about 500 miles like this as I needed the car.

Backing up a bit, when he replaced the spark plugs the left bank were all fouled while the right bank were clean. Then going to the Opti it was full of oil from a failed seal behind it. The vacuum line was rotted and oily too so all this has been cleaned and replaced.

This idle up issue doesn’t start until the motor is fully warmed up. About 15 minutes of driving. When we tested it I had just come in off the highway from a good hour drive so it was well warmed up.

We were able to observe the sensors on his display. You can select individuals or a group apparently too. We just didn’t get that far. Essentially everything is within the “range” they are supposed to be in, even when it idles up. That’s about as far as we got then the scanner pooped out or disconnected and would not reconnect.

The left side shows a “ wiggly line” but with in range. The right side showed a n almost straight line but toward the lower side. On idle up there is little change on the right side but left side gets much more saw tooth. Then when the idle drops it go back. That’s about the best I can describe. We only got a couple minutes at best before his scanner went down. So I’m stuck for now. I can drive the car and it really does run nice except the idle situation.

i did see the software you noted and it appears to be real answer to this issue. I sent a link to the guy so he is aware of it also.

Now for the shifting issue. By messy I mean the downshift is very rough. It feels like it downshifts then goes back up then downshifts again a couple times. All of my 3 spd autos and T-Bird Super Coupe 4 spd auto downshifted very clean and distinctly. This one is terrible when forced to drop out of converter lockup OD to unlocked but OD then to direct. Going to 2nd from here is fine. It’s this 50-60 mph area that it really gets rough (messy). I’m rather disappointed as I feel the 4L60e is really a good trans. All other shifting is perfect, it never seems to be in the wrong gear except here.

This is supposed to be a top of the line car built for non car people in its day and it really is a nice car. I shouldn’t have to tap the brake leading into hills then manually down shift then go back to drive. If I wanted to row the shifter I’d have got a manual trans car. I’ve already driven my truck over 400k and I’m tired of rowing gears.

I’m well aware of the 2.92 gear but it’s the performance ratio available in this car. It comes only with the trailer package. Imagine what the issues with the 2.56 or worse gears some of these had. Im sure there are aftermarket ratios available that would make this car really run but I really don’t need that. Many thousand of these cars were built and operated very smoothly so one way or another this one will too. It’s had an easy life, maybe too easy. I drive it daily and I intend to continue even though it’s a semi classic car. I drive my cars. No garage queens.

I hope this helps.

Byron

OK.... guess my input wasn’t very helpful. Maybe someone else can jump in and sort it out.

I hope I didn’t offend you. I appreciate all comments.

I gotta admit Im a rank newby with modern EFI. But I am trying to learn. If it’s one thing I learned with carbs it’s that you need to understand exactly what the motor needs and tune accordingly.

i took this car to five respected trans shops because I thought it had a converter problem. All wanted to do an expensive rebuild. I asked “ what exactly is happening or wrong? “. None could give me a definitive answer. So my comment was “ you are going to do this rebuild and hope it fixes the issue.....what if it doesn’t ? Then I’ve paid for an expensive rebuild I didn’t need. Sorry, it’s not going to happen that way.” I finally found the gentleman that’s been working on the car. He went step by step approaching the problem. His main line is trans but he also does general repair.

He first tested the trans and found it is working fine. He said there was a motor issue so let’s look at the plugs. One whole bank was bad. Then while he had the air cleaner off he noticed the Opti vacuum line was in poor shape. Once he found it full of oil he said we had to get into the Opti. At that point we agreed that it probably would need replacing so he ordered a new GM one. A local dealer had one in stock so he got it with the ability to return it if we didn’t need it. Also a set of plug wires and the water pump. Because the whole bank was not running well he suspected the cat and or the O2 was bad and that was proven. With these changes the car ran pretty good. Driving a bit harder up hills again brought out the downshift issue.

So now it’s back to further motor issues as the motor is not pulling hard enough, quick enough to complete the shifts properly because something is preventing it from speeding up as it is supposed to. A carb with a too lean secondary can do a similar issue. The same with a plugged exhaust system. You just don’t see it this way because it’s not real common to have a 4L60e behind a carb motor. Yeah it’s done but usually you have a well done carb too. Give it 100k miles and you might.

Its an issue that most old people would never see as they don't push cars as hard and are more gentle on the throttle. I can drive this car easy enough so it doesn’t need to go from 4th with the converter locked to 3rd and unlocked in a second or even ask it to drop down to 2nd. A lot has to happen perfectly for this to work seamlessly.

I’m hard to please I guess. I like this LT 1 and the 4L60e. I think it a wonderful combination......when it works properly. A friend has a ‘95 Z28 that runs beautifully. We did a test on the same stretch of road with me driving and his downshifts perfectly so I know it’s possible. We even talked about comparing scans since his runs perfectly. I like to see this. His is OBD 2 but I think the information will be similar.

any comments are welcome

Byron

That’s really slick. I’m going to order this Wed. There are not many times when a video is of the exact car in question.

Then I have to find a laptop to use it on. Maybe I can talk the guy in the shop into trying this out. His scanner does essentially the same thing.....when it works.

thanks for the video.

Byron

You won’t believe the incredible response/support I received from my request.

I sent an email Wed. And received a nice personal response on the next day,Thurs. why can’t more businesses do this? Not even my family doctor is this good.

thank you,
Byron