1990 PA Engine bucks at full throttle prior to downshift

timoch

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1990 Buick Park Avenue
Anyway... it seems, to me, you are dealing with an issue I already described to check or the service data I showed has an answer. If you are dealing with random stalling, lets go back to tier 1. Fuel pressure, fuel filter, fuel lines, fuel pump.

Here new idea i just found: grab the TV cable and pull. Some resistance but slack? OK
start car, pull it. Should not have slack. If so, your car has an issue with throttle valve.

Those wires are the Gear switch sensors things that the ECM uses to monitor shifting(Monitor is key word) and also the TCC electrical. There is an o ring on the TCC solenoid apparently that if missing or not sealing can cause shift complaints. how is your TCC working

5db1b0b00bdfb09081a7446d8ce422b5.png

Gyazo
By grounding that terminal (F) You can engage the TCC manually. Do you have a tach by chance? If DIC or tach is present, use that to watch. drive a constant, and then ground it. Use alligator clips with a toggle if you want to be safe about it.

Thank you for responding and the pics. Your pics look like my car parts. Pic 4 and your comments helped me to learn that the feature in pic 4 is a feed through for the connector to the TCC. I don't think the TCC is the problem because the trans easily shifts in and out of OD, indicated by feel and a drop in RPM on the tac, when I move the selector in and out of D and OD.

I think the low standing start and lower speed issue has been alleviated, probably by a week of the tv cable (thanks). The 1-2, 2-3 shifts or now occur at lower shift points and firmly, not harshly. I can down shift 2-1 and 3-2 easily with medium pedal application. At high speeds above 50; however, when I floor it, the engine bucks. If I press the accelerator half way, the car speeds up to 75 easily with no hesitation. When I approached a 5% grade, and pressed the accelerator farther down, the engine started bucking. This condition seems worse when the selector is when the the selector is in OD than D, but still occurs in both.

After the problem started, I checked the pressure at the fuel rail and it is in spec. About 25 k miles ago, I replaced the plugs, plug wires and fuel filter with new parts. I checked the resistance on the coil pac and it was normal, and ran a dedicated ground wire to its base. (My buddy says that I should replace the coil pack anyway, but I replaced plenty of good parts already and want to be sure first). The tv cable has good spring tension with engine stopped and running. The vacuum modulator seems to be doing its job because the shifts are not harsh and tested out on the bench.

Thank you for the training video. Here's a trouble shooting guide for transmissions that I found: THM 440-T4 (4T60) – ATSG (Automatic Transmission Service Group) – PDF Download Have a happy turkey day.
 

HotZ28

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Thank you for responding and the pics. Your pics look like my car parts. Pic 4 and your comments helped me to learn that the feature in pic 4 is a feed through for the connector to the TCC. I don't think the TCC is the problem because the trans easily shifts in and out of OD, indicated by feel and a drop in RPM on the tac, when I move the selector in and out of D and OD.

I think the low standing start and lower speed issue has been alleviated, probably by a week of the tv cable (thanks). The 1-2, 2-3 shifts or now occur at lower shift points and firmly, not harshly. I can down shift 2-1 and 3-2 easily with medium pedal application. At high speeds above 50; however, when I floor it, the engine bucks. If I press the accelerator half way, the car speeds up to 75 easily with no hesitation. When I approached a 5% grade, and pressed the accelerator farther down, the engine started bucking. This condition seems worse when the selector is when the the selector is in OD than D, but still occurs in both.

After the problem started, I checked the pressure at the fuel rail and it is in spec. About 25 k miles ago, I replaced the plugs, plug wires and fuel filter with new parts. I checked the resistance on the coil pac and it was normal, and ran a dedicated ground wire to its base. (My buddy says that I should replace the coil pack anyway, but I replaced plenty of good parts already and want to be sure first). The tv cable has good spring tension with engine stopped and running. The vacuum modulator seems to be doing its job because the shifts are not harsh and tested out on the bench.

Thank you for the training video. Here's a trouble shooting guide for transmissions that I found: THM 440-T4 (4T60) – ATSG (Automatic Transmission Service Group) – PDF Download Have a happy turkey day.
What brand of coils & wires were installed?
 

BuickGirlFromMars

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1999 Buick Park Avenue Ultra (Supercharged) , 1977 Buick Electra Limited (350 SBB)
What brand of coils & wires were installed?
He said coil pack. Hes using a magnavox coil. EGADS!

@timoch my bad I should have realized this sooner, you need a series 2 kind of 3 coil setup. I have 3 used coils but no ICM you could have for a low price, but they are affordable enough to be honestly best buying new and high quality ones. But The reason about the TCC feed was to see if loading or unloading the car during these events triggers or eliminates it while maintainign the same speed and all other conditions.
 

BuickGirlFromMars

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1999 Buick Park Avenue Ultra (Supercharged) , 1977 Buick Electra Limited (350 SBB)
Thank you for responding and the pics. Your pics look like my car parts. Pic 4 and your comments helped me to learn that the feature in pic 4 is a feed through for the connector to the TCC. I don't think the TCC is the problem because the trans easily shifts in and out of OD, indicated by feel and a drop in RPM on the tac, when I move the selector in and out of D and OD.

I think the low standing start and lower speed issue has been alleviated, probably by a week of the tv cable (thanks). The 1-2, 2-3 shifts or now occur at lower shift points and firmly, not harshly. I can down shift 2-1 and 3-2 easily with medium pedal application. At high speeds above 50; however, when I floor it, the engine bucks. If I press the accelerator half way, the car speeds up to 75 easily with no hesitation. When I approached a 5% grade, and pressed the accelerator farther down, the engine started bucking. This condition seems worse when the selector is when the the selector is in OD than D, but still occurs in both.

After the problem started, I checked the pressure at the fuel rail and it is in spec. About 25 k miles ago, I replaced the plugs, plug wires and fuel filter with new parts. I checked the resistance on the coil pac and it was normal, and ran a dedicated ground wire to its base. (My buddy says that I should replace the coil pack anyway, but I replaced plenty of good parts already and want to be sure first). The tv cable has good spring tension with engine stopped and running. The vacuum modulator seems to be doing its job because the shifts are not harsh and tested out on the bench.

Thank you for the training video. Here's a trouble shooting guide for transmissions that I found: THM 440-T4 (4T60) – ATSG (Automatic Transmission Service Group) – PDF Download Have a happy turkey day.
Your TV cable should NOT have good tension while stopped and while running, it needs slack stopped and tension/resistance while running. Your TV cable is out of adjustment!!
______________________________
 

timoch

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5
8
Utah, USA
Buick Ownership
1990 Buick Park Avenue
What brand of coils & wires were installed?
The wires are Autolite Proline silicone. I checked the resistance on several of them, and they were in spec. I also sprayed water mist in the dark and didn't see anything
I didn't replace the coils. I don't think the problem is misfire, it misfired at high speed before I changed the wires. It seems to be more of the pulsing that occurs when the max rev controller kicks in. Of course I could be wrong. I plan to take it up some steep hills in the next few days, maybe that will give me some more insight.
 

timoch

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5
8
Utah, USA
Buick Ownership
1990 Buick Park Avenue
I
Your TV cable should NOT have good tension while stopped and while running, it needs slack stopped and tension/resistance while running. Your TV cable is out of adjustment!!
Regarding the tv cable: I think I misunderstood you. Yes, there is about 1/4 movement before the throttle action before the reaches the ferule at the end of the cable. What I was describing is when pull on the cable on the transmission side, there is spring tension.
About the coils: they are the ones Mr Buick put on at the factory. I've elsewhere in one of these forums that the Maggotbox coils are troublesome, but that it mainly is a grounding issue. Per advice, I removed the coils and installed a grounding wire which I connected to the alternator frame. That seemed to have helped some issues I had. I'm not adverse to replacing the coils if that is really the problem. Are you recommending the three coil arrangement that are on the newer cars? I considered these, but the part recommender at the parts store sites says "these will not fit your car". Will they?
 

HotZ28

Full Member Since 2005
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Are you recommending the three coil arrangement that are on the newer cars? I considered these, but the part recommender at the parts store sites says "these will not fit your car". Will they?
Yes they will!
 
Last edited:

BuickGirlFromMars

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1999 Buick Park Avenue Ultra (Supercharged) , 1977 Buick Electra Limited (350 SBB)
I

Regarding the tv cable: I think I misunderstood you. Yes, there is about 1/4 movement before the throttle action before the reaches the ferule at the end of the cable. What I was describing is when pull on the cable on the transmission side, there is spring tension.
About the coils: they are the ones Mr Buick put on at the factory. I've elsewhere in one of these forums that the Maggotbox coils are troublesome, but that it mainly is a grounding issue. Per advice, I removed the coils and installed a grounding wire which I connected to the alternator frame. That seemed to have helped some issues I had. I'm not adverse to replacing the coils if that is really the problem. Are you recommending the three coil arrangement that are on the newer cars? I considered these, but the part recommender at the parts store sites says "these will not fit your car". Will they?
Magnavox coils had 2 versions, 1990/1991 cars got a revision part number based on production cutoffs that was better for reliability than the previous but you dont know which you have. also magnavox coils had a failure rate attributed to 1) water intrusion 2) vibration breaking the insulation materials 3) heat killing them too, and also, 4) High end cutting out for power when they would start to fail but not outright fail, as happened to some.

My magnavox coil, original, died from vibration. It was actually rather instant but not everyone had that
Yours is due :)
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BuickGirlFromMars

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1999 Buick Park Avenue Ultra (Supercharged) , 1977 Buick Electra Limited (350 SBB)
Thanks, I'll look into it. Any recommendations, I'm just a geezer who only puts 3k miles/yr on the car, so I don't need a racing unit.
if you have access to a junk yard, any lower mileage GM car with a 3.8 from 1993+ should have An ICM and OEM coils identified by white numbers indicating the cylinders conected to them. If its low mileage and still has original, they are probably going ot last you a LONG time :)

just remember, your car has a different firing order than those ones so you cant follow the white numbers to put the wires on
 

timoch

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5
8
Utah, USA
Buick Ownership
1990 Buick Park Avenue
if you have access to a junk yard, any lower mileage GM car with a 3.8 from 1993+ should have An ICM and OEM coils identified by white numbers indicating the cylinders conected to them. If its low mileage and still has original, they are probably going ot last you a LONG time :)

just remember, your car has a different firing order than those ones so you cant follow the white numbers to put the wires on
I can get the 3- coil set for 30-40 bucks at Amazon and the ad says they're compatible with my car. It isn't clear; however, if they will fit on my ICM. I can go to a wrecking yard, but the chances of finding the parts on a car from the '90's with less than 150k mi is very slim to nil, which means that I would get an ICM but also need new coils. I'm in a big city and the yards don't have a lot of room for old domestic cars, but I will call around Monday. Thanks for the advice.
 

BuickGirlFromMars

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1999 Buick Park Avenue Ultra (Supercharged) , 1977 Buick Electra Limited (350 SBB)
I can get the 3- coil set for 30-40 bucks at Amazon and the ad says they're compatible with my car. It isn't clear; however, if they will fit on my ICM. I can go to a wrecking yard, but the chances of finding the parts on a car from the '90's with less than 150k mi is very slim to nil, which means that I would get an ICM but also need new coils. I'm in a big city and the yards don't have a lot of room for old domestic cars, but I will call around Monday. Thanks for the advice.
I am unsure

looks like you need the pad and the mounting hardware but they should plug in (?) this guide seems complete and he has an LN3 as well!
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BuickGirlFromMars

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1999 Buick Park Avenue Ultra (Supercharged) , 1977 Buick Electra Limited (350 SBB)
Also, if you get the coils from a L67 you will have better coils that will last longer overall. Since your car isnt needing the extra oomf from them, its like having an overbuilt alternator and that isnt a bad thing.

May not cost too much more for them either.
 
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timoch

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Utah, USA
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1990 Buick Park Avenue
Also, if you get the coils from a L67 you will have better coils that will last longer overall. Since your car isnt needing the extra oomf from them, its like having an overbuilt alternator and that isnt a bad thing.

May not cost too much more for them either.
I found the assembly from a 1988 regal for around $40. Will it fit my car? In the article you linked it said to use a 92-93 module, but that was an old article. Another guy had a 92 regal who wanted $16 for the module and $11 for each coil. If I opted for that, I might look for new coils which I can get for the same price on amazon.
 

BuickGirlFromMars

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1999 Buick Park Avenue Ultra (Supercharged) , 1977 Buick Electra Limited (350 SBB)
T
I found the assembly from a 1988 regal for around $40. Will it fit my car? In the article you linked it said to use a 92-93 module, but that was an old article. Another guy had a 92 regal who wanted $16 for the module and $11 for each coil. If I opted for that, I might look for new coils which I can get for the same price on amazon.
The only reason I say go for the used OEM module and coils is because the aftermarket ones can be a bummer and the OEM ones are available new but they are expensive. You know you at least need some junkyard hard ware, so that is why i recommend getting it from one car, maybe pending the coils. The small stuff provided on the forum i linked is to make the new stuff stick to your aluminum mounting pad

the reason why is this cannot bolt to your engine as is:
image0.jpg 20210226_112053.jpg

The bolt hole you see there that is by the intake gasket that is the only hold down beside using those studs to center on the head, but the engine you have has a different head, a different deck height, different etc. but the conversion thread is to get a bracket your car Can bolt directly onto the pad you have. That flat with 3 holes. literally flat I think.
 

timoch

Full Member
51
5
8
Utah, USA
Buick Ownership
1990 Buick Park Avenue
T

The only reason I say go for the used OEM module and coils is because the aftermarket ones can be a bummer and the OEM ones are available new but they are expensive. You know you at least need some junkyard hard ware, so that is why i recommend getting it from one car, maybe pending the coils. The small stuff provided on the forum i linked is to make the new stuff stick to your aluminum mounting pad

the reason why is this cannot bolt to your engine as is:
View attachment 34471 View attachment 34472

The bolt hole you see there that is by the intake gasket that is the only hold down beside using those studs to center on the head, but the engine you have has a different head, a different deck height, different etc. but the conversion thread is to get a bracket your car Can bolt directly onto the pad you have. That flat with 3 holes. literally flat I think.
Thanks for the info. I'll look at the 92 unit then. It's at a pic-n-pull so I can look it over before I buy. I don't want to jury-rig a later one, that sounds like work. I figured that the pad must be different.
______________________________
 

timoch

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51
5
8
Utah, USA
Buick Ownership
1990 Buick Park Avenue
Thanks for the info. I'll look at the 92 unit then. It's at a pic-n-pull so I can look it over before I buy. I don't want to jury-rig a later one, that sounds like work. I figured that the pad must be different.
I have a new wrinkle now. I drove over the grocery store today. When I finished and tried to start the engine, it wouldn't start. I checked to see if I was getting any spark, there was none. I called my son to come tow me home, but when he arrived, the car started. He said that was likely a thermal problem in the coil pack or icm and that he has a friend who had a similar problem in his Ford Victoria. When I got home and turned off the ignition, it would not start again. Looks like I'll be hitting the salvage yard sooner than later.
 

BuickGirlFromMars

Well-known member
2,451
616
113
Buick Ownership
1999 Buick Park Avenue Ultra (Supercharged) , 1977 Buick Electra Limited (350 SBB)
I have a new wrinkle now. I drove over the grocery store today. When I finished and tried to start the engine, it wouldn't start. I checked to see if I was getting any spark, there was none. I called my son to come tow me home, but when he arrived, the car started. He said that was likely a thermal problem in the coil pack or icm and that he has a friend who had a similar problem in his Ford Victoria. When I got home and turned off the ignition, it would not start again. Looks like I'll be hitting the salvage yard sooner than later.
if you want to confirm without upgrading You coudl go get a new coil and ICM.. pricey... but if you upgrade you can keep the aftermarkets on a shelf ffor backup? Or sell? basically if you want to confirm, it will work. honestly your ICM may be fine, you could try a new Coil alone and that may just do it lol
 

timoch

Full Member
51
5
8
Utah, USA
Buick Ownership
1990 Buick Park Avenue
if you want to confirm without upgrading You coudl go get a new coil and ICM.. pricey... but if you upgrade you can keep the aftermarkets on a shelf ffor backup? Or sell? basically if you want to confirm, it will work. honestly your ICM may be fine, you could try a new Coil alone and that may just do it lol
I took a close look at the coils and icm and noticed a bead of slightly pliable substance on the seam between the two. It seemed to be more abundant on the right (downhill) side. I then removed the hold down screws and tried to pull the coils off, but it was held fast. I pushed a screwdriver between them and tried to pry them apart and and saw a lot of the sticky stuff between them. At first, I thought it might be some sealant applied. I found a video
where the guy replaced an icm like mine and his had no sealant under the coil. I some of the following comments to the video, someone mentioned "the green goo of death". I assume that in my case, my coil is leaking and that the icm is alright. When I checked for codes, there were none and if the icm or crank sensor were bad they would show a code. I can get a Standard coil pack fairly reasonably from Rock or Amazon. That might be the way to go. What do you think?
 

MelsRegal

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Regal GS 2017
I took a close look at the coils and icm and noticed a bead of slightly pliable substance on the seam between the two. It seemed to be more abundant on the right (downhill) side. I then removed the hold down screws and tried to pull the coils off, but it was held fast. I pushed a screwdriver between them and tried to pry them apart and and saw a lot of the sticky stuff between them. At first, I thought it might be some sealant applied. I found a video
where the guy replaced an icm like mine and his had no sealant under the coil. I some of the following comments to the video, someone mentioned "the green goo of death". I assume that in my case, my coil is leaking and that the icm is alright. When I checked for codes, there were none and if the icm or crank sensor were bad they would show a code. I can get a Standard coil pack fairly reasonably from Rock or Amazon. That might be the way to go. What do you think?
I think it is the better way rather than start modifying things.
 
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