94 Buick RoadMaster Estate Wagon LT 1 issues

[Bentwings]

I’m sure I posted some time ago but I couldn’t find it. Also did a search but couldn’t find that either.
So just to recap
94 Buick RoadMaster Estate Wagon LT 1
this Car only has 110k on it and is like a brand new car. A granny had it since new and it was like a daughter to her.

anyway the car has never seen a winter. No rust just minor weather stains.

So I get it and it runs fine for about 5k miles then it developed a miss across the board. Since I no longer have a place to work on cars I’m forced to “take it to the shop”. Well the shop tells me the trans is not shifting properly and needs rebuilding. I’m not buying this and go to 4 more shops all saying the same thing.
finally I run into a guy who is old school that “fixes” things rather than throw parts at it hoping to hit the one that works. He says the trans is fine.

Long story shorter.
new belts, air cleaner, oil change with Wix filter, fluids topped off. Suddenly the car stops running altogether. So new fuel pump and Wix fuel filter. Car runs but still has Miss. new Cats both sides, new O2 sensors (one was definitely bad)
checking the motor for leaks and we find the Opti Spark is saturated with oil. Seal behind it is bad. New Opti Spark and vacuum line, new water pump. New plug wires and plugs. EGR is not functioning. New EGR.
More scans. Motor is running very rich on left bank. O2 out if range so it is replaced again.

Now it runs rich on the right bank. But all sensors are in range and almost dead center of range.
Very thorough inspection of intake hoses. They all are nice and flexible, none oil soaked or brittle. All clamps centered and tightened....not excessively.

Now I might add that I specified to use all GM OEM parts. No MSD, no aftermarket hard parts. Mostly because of my experiences and others of my cruise groups. Even the OPTI was new old stock.

car still has a miss. Mpg has gone from 21-22 to 12-13. Also have run several tanks of non oxy premium through it. It still is solidly rich on the right bank.

i went and got the EEHACK and a brand new laptop just to run scans on this car. Even got a cool memory stick for USB port and connection to download to Apple IPad Air lol. Unfortunately misplaced during recent move.

however my scans show exactly the same as high dollar tool man scanner.

one thing that seems unusual in that I can’t reset the BLM while others say I should be able to do.

Last week my guy got a very expensive smoke tester. It showed no,leaks. I suggested he compression test the whole motor which means I get charged for plug R &R again.

I told him at this point I don’t care, just fix the car, what ever it takes, I need the car as my el Camino will be headed for winter storage shortly and the Buick will be my driver. It’s only been 6 months of messing around. He is getting tired of having the car around and I’m very frustrated.

i didn’t call him last week as I didn’t want to be a pest but he called me and said he had new OEM injectors coming Friday and would install them as soon as he could. He’s been very fair with charges and so I can’t complain there. Nobody else around will even look at the car now. They see me coming and they put the closed sign in the window.

Im looking for any help I can get. It may be a bad computer but the general feeling I get is that these hold up pretty well. There are at least 6 Other LT 1 in the cruise groups I hang out with and all are virtually trouble free. All have a log more miles on them.

byron

[steveo]

if one bank is rich it’s probably an injector or two. usually i would swap the lefts and rights to see if it follows.. but also the fuel pressure regulator could be leaking through its vac line? its hard to make an engine run rich. show us your eehack log maybe we’ll spot something

[Bentwings]

Thanks for the quick reply. My “guy” and I talked about this. Were I working on the car myself I’d certainly have tried swapping side for side. However since I’m paying him to do the work it’s more cost effective to just replace the injectors. The disadvantage is that if it works we won’t know which one or if all were faulty. He has rounded up new OEM injectors that he has either installed or will shortly. I’m going to stop by his shop later today and see how it’s going.

I’ve got four scans somewhere in this iPad but I’ll have to search them out. My memory stick got stuck in a box somewhere in the move and I haven’t found it yet.

I’ll post results later
Thanks

[Bentwings]

New injectors responded the same. Or no change which ever way you look at it. The compression test looked very good. Three cyl are running max rich one is only very rich. No motor problems as far as pistons rods and crank.

The interesting thing is that the left bank was originally rich. New O2 and Cat and it switched to the right bank. New O2 and Cat there made no difference. Been that way ever since.

I’m simply lost in the daylight over this car and it’s systems.

[Bentwings]

Update. We installed new injectors and new plugs again. Got. “0” change. The right bank is still dead rich. Tried new O2 wire pigtail. Nothing changed.

Finally we have decided to go with a new computer. It was supposed to be done Fri but I didn’t hear anything somhave to wait until Mon. If this doesn’t fix it I’m completely baffled.

I’m not sure just how the injectors work. Normally open or normally closed. Is it possible that the injector wires for the right bank are open or closed all the time, in other words an open or closed circuit That is supposed to open and close by the computer command?

[steveo]

there's constant power to the injectors. the power comes from two independant circuits from the fuse block (one for left and one for right). the ECM closes the ground to each injector to fire it. yours is a sequential injection system so they all fire individually depending on engine rotation.

i sincerely doubt replacing the ECM is going to do anything

to be completely frank with you, if you're replacing ECMs and injectors for a rich condition, your mechanic can't diagnose worth a crap. it barely takes any time to determine if the injectors are the cause of a fueling imbalance. you're just throwing money away at this point

how do you know it's running rich on that bank, anyway? and how do you know it's the entire bank?

still need to see that log...

[1project2many]

I feel there is more to this story. If no one wants to work on the car it's generally not the car's fault. From perfect to undiagnosably messed up in a short time is atypical. Good mechanic "actually fixes things" can't fix car??? Also uncommon. Belt and basic maintenance items repair bad trans? Huh??

I have 38 years' car experince and they way this is presented just doesn't work. I can't help but wonder about the good mechanic first. Sorry, but as a mechanic I've worked with too many guys that make convincing arguments that their incorrect diagnosis is right. When they don't fix the problem they are highly skilled at covering the fact with "getting closer" or "made a difference" or "that part was hiding the symptoms from the other broken part." And if good mechanic is actually good then I wonder about "like brand new" status of car.

Why is it rich? What are the symptoms of rich operation? Are you sure the symptom you're seeing is actually causing rich operation? How can O2 sensor be reporting okee-dokee if three injectors are "max rich?" And really, what is "max rich?" In my mind that indicates the injector is at 100% duty cycle... "always on." That's an easily diagnosable problem. The way the problems are reported requires interpretation, which makes an accurate diagnosis tough.

Oscilliscopes were once rare in the auto repair field but a shop without one today is not fully capable of diagnosing problems. The injector on and off time can be measured with an external tool to confirm that ECM is reporting correctly. Time for each injector can be recorded and compared. If all injectors are at similar times then injectors get checked for leaking or improper delivery rate. If injectors are open for same time, and are all delivering same amount of fuel, then it's not injector or fuel delivery problem. Stop chasing injectors and look for other issues. Good mechanic knows when to trust facts.

Spark plugs black? Wet? Dry? Oscilloscope on coil wire will show secondary pattern to determine whether or not plugs are being fired correctly, if voltage is going where it should, if cylinders are rich or lean. Good scope reader can tell if plug gaps are correct, if EGR is active, if cylinder compression is not correct. Good scope reader can see crossfire, failing wires, bridges in coil insulation. Good scope reader can do many amazing things.

How can O2 be "perfect" and engine be "max rich?" Oscilloscope on O2 sensor will show O2 voltage and signal pattern. Does voltage match ecm reported value? Does disconnecting injectors change reading on scope? How about reading from ECM? Good mechanic will be confirming data with trusted tool, not just accepting what's on computer screen.

Is the cam good? Is the vacuum signal strong and steady? A weak cam can produce good compression readings while failing to fill a cylinder fully. Vacuum gauge is one way to see this. Oscilliscope on MAP sensor signal can be even better. Oscilliscope on MAP can be read to see intake valve opening and closing, pressure waves "bounce" as valves are closed, throttle angle changes appear imediately, restricted exhaust shows up quickly. This Oscilliscope thing sounds more versatile all the time.

Why are we not suspecting an ecm? Because someone else's isn't broken? But you want this fixed so how can you rule anything out? ECM response to rich or lean O2 is critical part of feedback loop. High O2 signal voltage from rich engine should result in less fuel delivered. But O2 sensor value is fine: "all sensors are in range and almost dead center of range." So what is telling you engine is rich? BLM high = ecm adding fuel to correct lean problem. BLM low = ecm removing fuel. My feeble mind follows training from 1980's EFI classes. Misfire = fuel not reacting = excess O2 = lean O2 reading = ECM tries to add fuel. Engine is not rich! Engine is misfiring and ecm is responding as programmed. Did Good Mechanic discuss this with you?

I'm not invested in diagnosing this. The questions are for you, not for me. The way this is presented I do not believe there's much chance of successful diagnosis in an internet forum. There are too many subjective descriptions and there's too little actual data to work with. "I changed the injectors but they're still rich" is not the same as looking at a recording of injector on-time over time. "The O2 readings are perfect" does not present an opportunity to evaluate the O2 readings. It tells the reader "Don't bother looking here because you won't find anything."

Hopefully you and your "guy" will find an answer to this obviously frustrating problem.

[steveo]

injector pulsewidth (the output that your mechanic is questioning) is easily checked by comparing the duty cycles of all the injectors. if you suspect a bad output (in this case injectors) that output needs to be measured, then you verify if your inputs are sane, if they're sane, then and only then can the ECM is suspect. it would be really odd for an ecm to be in a failure state that erroneously delivers MORE pulses.

you don't need a scope to check that your injector outputs are good, a dwell meter will do too, does your mechanic have one of those?

a mechanic that has neither a scope and knows how to use it (new-school) or a dwell meter and knows how to use it (old-school) isn't really from any school, and probably needs to go back to school pronto.

the entire thing sounds like a waste of money

you could likely go buy a perfectly running LT1 car and swap the entire engine and wiring over with less time and money that have been put into this issue

but as a tuner and LT1 guy on a forum for tuners and dataloggers, again, i'd be willing to look at a driving log to see if all your inputs and outputs are sane, and give you theories based on that just as a brain exercise

[kur4o]

I really feel sorry for this guy. His mechanic is best at swapping good parts but not that good with diagnostics.

SInce there is a missing cylinder[ or random missing opti], that might be the reason it runs pig rich. Missing cylinder means unburnt oxygen in the exhaust, which leads the pcm to think there is lean condition and dumps fuel till the blms are maxed out.

The simple test to see what`s wrong is to force open loop and see how it drives and monitor 02s reading [Make sure the blm and int is showing 128]. DIsconnect the battery, at least for an 1/2 an hour, prior to tests to clear any out of range blms.


Post the eehack log to get more insights.


With eehack and the built in real time controls you can pinpoint any electrical and mechanical issues in less than hour, you`d better start diagnosing yourself if you want the car to get fixed.

[daveosx]

I love these Engines

A couple of really simple things to check.
1. One bank rich in 94-95 the EGR gas flow was pulled off from a port on the exhaust manifold these crack and leek Air into the exhaust manifold causing O2 to read lean and BLM to go up.
If the little tube is cracked it will make that side rich.
If you have the cast iron manifolds you may also have a crack there.
Any exhaust leak from the head down to the sensor will make it rich on that side.
2. Correct PCV valve for old engines I use a 774 standard it works and does not lean out on old rings.
3. The 94 throttle body had a tendency to clog where the PCV goes into the top of the throttle plate right under the badge plate on the throttle body without PCV you will foul the O2 sensors.
4. Oil fouling often people think that low miles old cars mean that they are in better shape, this can be problematic if the owner actually let the car sit for extended periods or worse the car was only driven 3 miles a day.
These engines are designed to run with the oil in the block at or above 220 F if the oil does not get to 183 F then it will be soaked with ethanol from the gas letting the car sit the low tension rings get damaged.
If you get oil on the plugs then the sensors will foul and it will go full rich. I had valve guide seals go bad after an overheat that did this to one of mine. I used a spark plug extension drilled out to move the O2 sensors out of the exhaust flow to allow normal driving until I overhauled it.
Heres a link to some one else describing how to use them.
https://www.evolutionm.net/forums/ev...cel-light.html
5. Persistent miss, I have used a lot of these coils and modules for all kinds of builds a couple of common things on the coil that will cause a miss is that the epoxy fails look for white powdery residue around the coil body and bracket. If found replace the coil and coil wire. Another area that the OPTI had issues with is the short wire harness between the Opti and the engine harness on the passenger side behind the water pump.
6. To localize the miss pull one injector lead off at a time and find the missing cylinder. If none change then look at the ignition closely the wires that are clipped to the block behind the exhaust manifolds may be sorting out.Take off the serp belt and use a test light to puncture each plug wire and watch for miss. If no miss found pull the valve covers off and look at the rockers as you rotate the crank the early roller lifters where common to fail and wipe the lobe of the cam.




One of my project builds is another LT1 engine
I am going to use a set of CompE Speedmaster heads on one I have the heads already On these the oil return passage can be plugged to open the reverse cooling port to fit Gen1 heads on the GenII block.
I love really old school tech fusion so the plan is to use the LT1 lower end with TRW1157 flat tops and 3.75 stroker crank after market main caps and a girdle.
With the new build looking for monster torque.

I have one of these motors that had a LT4 cam and wildly ported heads 280cc intake runners with Orange springs and a lifter REV kit It turned 9000 Rpm.
Stock coil won't even pull 6K The OPTI pickup works great all the way high as you want to go MSD cap and rotor held up pretty good. I used my own Ignition controller and CATS tuner to tune the ECM OBDI.
The old screamer will be getting new springs pistons and a overhaul looking to put 4 small turbos on it.

FYI the stock injectors are like 26lbs so if you are tuning it you could have bought a really cheap set of 44lbs EV1 style micro drilled injectors for less than 80USD.

[Terminal_Crazy]

Stock coil won't even pull 6K The OPTI pickup works great all the way high as you want to go MSD cap and rotor held up pretty good.

What would you advise to use for a coil upgrade that won’t melt the opti ?

Thanks
Mitch

[Bentwings]

Vilefly, I’ll try and follow your suggestions.

Since I got the car I have used it to go to work. It’s about 45 miles depending on route each way. 95% highway cruising. Traffic often goes 75-80 for about 20 miles. Then about 55-60 the rest of the way. There are a couple miles at the start and end of city driving so. There is a long grade about 6-7 miles. I don’t know the elevation but traffic still goes 75+ up it. The car could do this easy and I was a left lane cruiser everyday. So it got lots of fast lane use for the first 6k miles. Then the issues started. It never over heated the gage stayed dead center, it never burn or lost oil, never used coolant. Basically a perfect highway cruiser. I was very happy with it.
Then it developed a miss, slight but it caused a lack of power and the converter and trans acted up. Dropping out of lock up then out of OD. I thought the trans was the issue. I went to 5 well known shops and all wanted expensive trans repairs. However I was suspicious since I was driving the car everyday and had begun knowing it. So I asked if this would definitely fix the issue. They all said the trans was the issue but said the motor was fine. I wasn’t buying this besides there was no guarantee they problem would be fixed.

So I looked for good shops with OBD 1 scanners. Few had them. Some wanted to charge me to upgrade their stuff. Forget it. I finally found the shop I’m at. He also does trans. He had it for a day and really flogged it. He said the trans was perfect but there were issues with the motor.
Long story short, step by step issues were addressed before a really complete scan of the motor operating was done. The Opti Spark was full of oil and caused ignition issues. Bad oil seal. It was replaced with new old stock unit. Along with wires and plugs.
And so on, everything was done with discussion of why this or that needed fixing. Bottom line is today there is nothing showing on his scans and mine using EEHACK except for low manifold vac.

There is no real anti freeze smell, no oil smoke, just a random puttering in the right exhaust. Scans show the front cyl and the back two on the right bank dead rich. BLM maxed out. The plugs on the right bank are all fluffy black but not packed. We have replaced them three times already.

So we spent an hour discussing where to go. I have to give him credit for being patient with me and not over charging me. I know he needs to make a living so his time is of value. I have no choice but have someone do my work as I simply do not have a place to work on cars.

I’m at a loss now so depending on others who really know this system. I’m trying to learn too. In some cases tests simply need to not be done and just fix a suspected problem. Certainly not the best way but economics enter too. I hate this but it’s less Expensive to just do it and look at the cause afterward. Certainly a poor way of doing things.

If you scan this thing with a parts store scanner it will show nothing wrong. It takes something that scans deeper so enter the SnapOn or Matco or EEHACK. And now we see an issue. Every attempt has failed to fix this. Certainly some were unnecessary. I know this and have to accept this.

We now are at perhaps what should have been done earlier position. Were it a carb the manifold gaskets would have been replaced early on....I think. I would have done this myself based on carb experience.

So maybe by late tomorrow I’ll know what happens. Even this I still have misgivings. I can’t imagine real hard parts failing this way. The switching side for side of the problem keeps coming up. But now with the intake issue “fixed” it may point some other direction.

I don’t like making long post but I like to present the issue as complete as possible.

I did try to post my scans but I simply can’t from my iPad and down here on the boat our WIFI is very unstable. I’ll take my laptop up to my sons this weekend and see if I can work something out.

I know y’all are trying to help out so thanks again. I’m listening ...reading.

Byron







[vilefly]

I would like to state for the record that I said test the manifold, and not replace anything yet. The small block chevy, prior to the CPI vortec motors, seldom had intake manifold gasket failures when the OEM gaskets were used. When they eliminated the center bolts for the manifold, things began to fail. There is a slight possibility that the gasket rotted out from underneath the metal edges of the ports, but it doesn't happen often. Just make sure the rest of the manifold ports and gaskets are sealing, too.

Hopefully, there is not a constant hissing sound from the brake booster when you hold down the brake. A leaking brake booster can skew things, too.

[Bentwings]

I have not checked the brake booster but I’ll do that. The brakes are very good on this big car. Very light pedal.
The motor doesn’t make much noise even with the hood open. I have heard no “hissy” sounds at all. I’ll have to ask as I don’t remember. Early on the EGR was looked at and serviced if not replaced. There was a problem with the vacuum line or something. I’ll ask him.

I missed calling him Fri so I called today....no done, finish tomorrow. He is really busy I know that so I’m trying to be patient. The weather is turning early I think this year. Miserably cold and driving cold rain and wind today. Got soaked then had to go back out and snap down the rear canvas on the boat.

I still have an uneasy feeling thatbthis gasket job isn’t going to fix it. I’ll be totally lost. I asked him to take a look at the valve action, possibly a flat cam. Also look down the ports of use the bore scope at the intake valves and see if they may be really carboned up. I’ve seen some really bad ones that only caused a little loss of power.

So more later.

Byron

[daveosx]

What would you advise to use for a coil upgrade that won’t melt the opti ?

Thanks
Mitch

I just noticed this post like a year later
Coil voltage tapers off as the coil become saturated at Hi RPM so some guys opt for high voltage that tends to cause the cross arcing at lower rpm.
If my memory is correct I think that I use < 6.6mH primary with a 60KV peek above 6500 RPM and a regular Speedmaster below that..
https://www.jegs.com/i/NGK-Spark-Plu...U1117/10002/-1 hi rpm
https://www.jegs.com/i/Speedmaster/7....1007/10002/-1 Lo RPM

Nology Hotwires also work well with the NGK coil many people do not believe that they do anything but in normal driving they provide a store of energy in the inline capacitor on the wire lead. So as each low rpm firing pushes enough energy VA into the sparkgap it charges the cap so at higher RPM the cap discharges along with the lower coil output. Looking on a scope the area under the spark is increased using nology.
Many turbo and rice burner guys gap their plugs to .035 to get longer spark durations.
A lower resistance secondary coil with higher voltage increases the duration as well.
I found on the LT1 the gap is good all the way out to 0.10 with the Speedmaster coil and .065 with the NGK
Because caprice headers are tight I set the gap at 0.050 with the iridium AC delco plugs.
The Speedmaster coil gives you 1.5-1.7ms duration at that gap the NGK is about 2ms.
I have run the NGK coil in a waist spark setup with a crank trigger out to 7400RPM so the coil is about 60K times a minute.
On a non waist spark like the Opti the coil is only sparking 30K per minute.
Somewhere there is a calculator I think at Megmanual for mili henries vs Spark duration.
You have to adjust the Dwell of the EST to optimise.
The stock LT-4 corvette ignition module is like a ford TFI in that it measures the peak coil primary amperage and keeps it at 5.5Amp.
Later truck coil modules can be used to get higher current as well.
A 1996 GMC 7.4L HEI module connected to the ECM and coil works to raise current and adjust the dwell.
You do not have to use the reference signal you bring the EST bypass to ground and the EST and coil wires hook up the same as the LT-1 coil.