1987 Buick T-Type

Michael Mobile Technician Utah Posted   Latest  
Updated
Driveability
1987 Buick Regal Grand National 3.8L (7 LC2) 4-spd (THM200-4R)
Flat At Wot

I have been fighting this Buick for 9 months now. I go over do some tests. make adjustments and they don't alter the problem. The vehicle goes too rich at WOT, but reaching the same counts accelerating moderately or more aggressive acceleration working fine. The latest shop has put an engine in it. Now I own it (metaphorically) Every time I get a call from the owner, I cringe. Another wasted afternoon.

Would like to find some PICO captures for in-cylinder and Crank / Cam signatures. Wondering if it is an electrical or breathing issue.

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Matt Diagnostician
Minnesota
Matt
 

Any mods, or completely stock?

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Chris Owner/Technician
Ohio
Chris
 

I would check the cam sensor sync. The spec is 25 degrees ATDC. Take a piece of making tape mark it 1.5" long. Line up one end on the TDC mark on the balancer and place it to the left or retarded side from the mark.

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Michael Mobile Technician
Utah
Michael
 

Chris, So 25 degrees After Top Dead Center? The tech that assembled the engine did not do that for sure. That is a great place to look for issues.

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Chris Owner/Technician
Ohio
Chris
 

Yep, that's correct. Usually, an out of sync cam sensor causes a rolling idle, but since the engine was out this should be checked. They are very common to be out. INSTALL 1. Install the Cam Sensor drive assembly with the rotating vane slot facing the power steering pump (toward the drivers side of engine) when installed in the engine with #1 cylinder T.D.C. on the compression stroke. 2…

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Michael Mobile Technician
Utah
Michael
 

Yes, there are mods. Intake piping and exhaust. 90mm MAF, aftermarket adjustable CAM sensor. I had them add a wideband O2 to monitor exhaust gases. I have been using Tunercat to recurve the MAF. Whatever I do it flip flops the problem.

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Steven Mechanic
Washington
Steven
 

What air/fuel ratio is the wide band sensor reporting when it's too rich and also when it's too lean?

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Craig Diagnostician
Illinois
Craig
 

Michael I have no idea where to find the information at this point but could this be a MEMCAL pack issue?

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Chris Owner/Technician
Ohio
Chris
 

Does it have a stock MAF? Take a picture under the hood and post it. What are the MAF counts at wot? I should be able to help you. I own two of these and work on many. I have scope captures I'll share.

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Michael Mobile Technician
Utah
Michael
 

Hi Chris, Because the vehicle had a 4" intake already, I removed the stock MAF and installed a 90mm MAF. I used the MAF translator but now I wonder if it was really needed since I have Tunercat. I have a Mastertech with Tech 1 abilities. I still need to figure out how to connect it to laptop to log the counts. If you don't mind contacting me, I would appreciate the help. ….

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Michael Mobile Technician
Utah
Michael
   

The Calpack is stock. Had a Hypertech chip. I did the Moates Mod with new EEPROM and have been tuning thinking it was the aftermarket intake. I not a master tuner but have done a few successful tunes before. This one has me stumped.

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Michael Owner/Technician
Wisconsin
Michael
 

Do you have access to service info for this? It is important that you understand how the system works. Going rich? How do you know?

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Michael Mobile Technician
Utah
Michael
 

Michael, Sorry for not writing my entire diatribe. It is a long story but their is a wideband O2 sensor installed. This makes it clear when the vehicle goes full rich. Not just 11:5 or 12:1 but down to 7 which is the limit of the sensor. I have searched for decent information on this vehicle. It is hard to find. (at least from the aftermarket) I suppose I could pay for a sub to AC Delco and…

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Michael Owner/Technician
Wisconsin
Michael
 

These cars are nightmares. I'v had some experience with that system. You can manually test each sensor at the ecu with a scope rather quickly to look for any weird inputs. Some of these old sensors fail in strange ways. It is an immediate change or is it progressive with load and/ or throttle? I like to check the pulse with on the injectors also, just to see what the ecu is doing. Like several…

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Grant Technician
Illinois
Grant
 

What mods does it have? Some mods I recall hearing about when I owned an 85 GN: aftermarket tune(chip), adjustable fuel pressure regulator, high flow fuel pump, high flow injectors. Here's some fuel system related info from gnttype​.​org gnttype​.​org/techarea/fuels…

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Michael Mobile Technician
Utah
Michael
 

Yes, lots of mods and aftermarket parts. That is why they called me to try and tune the vehicle to work with them all.

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Michael Owner/Technician
Wisconsin
Michael
 

Sometimes you are better off scraping the antique controllers and updating to a modern ecu and harness.

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Steven Mechanic
Washington
Steven
 

Is this carbureted or fuel injected? If fuel injected, at WOT, with this vintage of vehicle, I would think that fuel enrichment is all preprogrammed, with rpm and MAP being the only main inputs under that condition. Didn't those old ECM's have chips that could be swapped out? Could have the wrong chip in it.

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Michael Mobile Technician
Utah
Michael
 

Steven, It is fuel injected with waste spark system. There is adjustment for Dashpot /Fuel Enrichment in Tunercat. I took it down to zero and it did not help.

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Timothy Owner/Technician
Wisconsin
Timothy
 

How do you know it's too rich on WOT? Are there other symptoms associated with it? Remember, that these totally dumped fuel at WOT, as soon as the ECM saw the TPS cranked wide open. No fuel control at WOT, just ‘give me all you got’ commands to the injectors. Emissions control was not required at WOT back then. Unlikely to be a cam/crank correlation issue, as the cams sensor and the crank are…

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Michael Mobile Technician
Utah
Michael
 

Timothy, There are some adjustments in Tunercat for fueling. I just have not found one that makes any difference. With stock injectors, it should not be over-fueling if the MAF is curved correctly. The aftermarket cam sensor is adjustable.

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Bob Technician
Massachusetts
Bob
 

Have you tried driving it with the maf disconnected to put it in speed density mode?

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Michael Mobile Technician
Utah
Michael
 

Bob, From what I can see there is not a MAP sensor on this vehicle. I do not recall what happened when MAF was disconnected. Maybe it stalled or would not stay running? I do recall at least trying that in the shops lot.

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Mike Educator
North Carolina
Mike
 

I am sure that you have already given it a thorough visual inspection. Did you notice any aftermarket parts? It is hard to find a bone stock turbo regal after all those years. Usually the fuel pressure regulator has been replaced or beaten with a hammer to put more tension on the spring. Lots of guys also use a later model MAF and a translator. If you have an old scan tool you should be able…

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Michael Mobile Technician
Utah
Michael
 

Hi Mike, The car is quite changed. The fuel regulator is adjustable. It has gone through 3 sets of injectors. 30#, 40# and stock. I thought maybe the 40# injectors could not be sloped by Tunercat, so I had them install stock injectors. Same problem. Did the MAF and translator. CAM signal has been tested through the whole RPM range including when dogging out. Square wave is steady as a rock.

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Alan Owner/Technician
Mississippi
Alan
 

Friend of mine had one back in the day. It was a beautiful vehicle. I remember the very first thing he did to that car was order a aftermarket high performance chip. That's about the same time it would start randomly fouling spark plugs. He put every brand and heat range of spark plug known to man trying to eliminate the issue. He was unwilling to accept the fact that the eeprom chip maybe the…

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Zeb Diagnostician
California
Zeb
 

Pretty sure these had boost specific MAP sensors (oe position above right wheel well). Don't have any first hand experience but in the 80's each sensor had to be individually checked - might have better results nowadays using a scope vs. a DVOM. With all these mods has it ever run correctly?

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Phillip Technician
Tennessee
Phillip
 

Need to know all the mods done to this vehicle. What boost levels are you running when you are over fueling?

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Michael Mobile Technician
Utah
Michael
 

Phillip, We never get to boost when going rich. WOT in the parking lot out of gear will kill the engine.

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Timothy Owner/Technician
Wisconsin
Timothy
 

Generally not going to get to boost with all those mods unless the thing is loaded going down the road…at least my turbo racer wouldn't. Does it still bog when accelerating under load?

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Michael Mobile Technician
Utah
Michael
 

Tim, It does not matter if in gear or not. Falls on it's face. Let off throttle and it gets it's composure back. This happens from a dead stop.

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Timothy Owner/Technician
Wisconsin
Timothy
 

Just a SWAG. This thing has way too many mods. to be easy. Reminds me of all the fun (NOT!) I had tuning my old racer…

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Jim Technician
New Jersey
Jim
 

Map sensor is only for the dash boost gauge. Does NOTHING inside the ECM

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Jim Technician
New Jersey
Jim
 

Can you ID the injectors? Did you put a stock chip in it? DO you have a way to burn a chip? I can email you a prom file if you can give me injector size and rough mod list. I used to tune them trackside every weekend, and send chips all over the country.

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Michael Mobile Technician
Utah
Michael
 

Jim Testa, They replumbed the turbo exhaust side to lower restrictions. 90mm MAF with MAF Translator. This is in fact a 1985. (hot air model, no intercooler) I listed as 1987 since the ECU was updated to 1987 version. This was a suggestion as there are more parameters in table to correct. I do have a burner and Tunercat program. The IAT was turned off in Tunercat. Injectors are back to stock…

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Eric Owner/Technician
Wisconsin
Eric
 

Michael, I worked on several of these years ago. My brother owned some along with some T-Types. I can tell you that the 1985 models were a difficult vehicle to work with. Any changes made to the system made the car perform worse. Trying to make a 1985 work like a 1987 is going to be a nightmare. My brother finally got rid of his 1985 and bought a 1987 T-Type, much nicer all around and much…

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Michael Mobile Technician
Utah
Michael
 

Eric, I hear what you are saying. I still have the 1985 ECU if needed. The same problem has existed with 1985 ECU and stock EEPROM. The newer ECU was suggested because there are more adjustments in the tune. I was told that beyond the intercooler, there were no changes to wiring or electronics. I have not noticed any differences between the two. Still thinking it is something like Chris has…

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Jim Technician
New Jersey
Jim
 

That is incorrect. The maf is different. If hes using the hot air maf that could be your probldm. There is a wiring change needed as well if you want to use the MAT. Although the tables are zero’d out unless you have a chip using Turbolink and the boost harness. Cam sensor timing wont affect your fueling that much. Only if the sensor is 180 out will it run weird.

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Grant Technician
Illinois
Grant
 

You confirmed my suspicions. If I had a dollar for everytime someone suggested a mod for my 85 that only applied to the 86/87…

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Eric Owner/Technician
Wisconsin
Eric
 

Michael, I'm pretty sure there are more differences between the 1985 version and the 1987 version than you were told about. I remember my brother stocking up on parts for his 1985 and then after he purchased his 1987 listening to his complaints about how “Nothing is the same on the 1987 compared to the 1985”. I remember him having all kinds of problems after he installed several known good…

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Jim Technician
New Jersey
Jim
 

So you have stock injectors right now? 28.2? Stock turbo or how big? Cammed? Let me get my laptop fired up and send you a few files. Whats a good email address? Youre sure its a 1227148 ecm? Hot air ecm is different. I think I have some hot air files too tho

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Michael Mobile Technician
Utah
Michael
 

Jim, Stock Turbo and injectors. Engine from Jasper so assuming stock or near stock profile. 1227148 ECU. my email is …

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Jason Mechanic
Florida
Jason
   

Hey there mike as a owner of a 87 grand national I feel your pain. There is a guy that builds these cars that I’ve talked with several times. he owns Steve v automotive these cars are his specialty you can find him on Facebook or google search. Ask for steve …

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Pierre Owner/Technician
California
Pierre
 

I wonder if someone filled the tank with ethanol possibly? It might have mismatch Injector and Maf. Even the Maf location might be part of the problem. Good luck Michael.

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Scott Owner/Technician
California
Scott
 

Hi Mike, Can you log RPM, MAF & MAP during the WOT event and share it here? Also, are they doing anything special to increase rail pressure under boost?

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Chris Owner/Technician
Ohio
Chris
   

As Jim Testa stated the MAP sensor is only for the factory boost gauge on an analog dash car. The digital dash cars didn't even have a map sensor installed from the factory as there was a two wire pressure switch for boost. A yellow and a red lamp is all that ran. The fuel pressure increases under boost proportionally so long that the vacuum line is connected. That vacuum line has manifold…

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Scott Owner/Technician
California
Scott
 

Understood Chris, My request was so that I could hopefully see what the ECM is interpreting as cyl/air. MAP is not going to provide me with any metrics to support the cylinder air flow but it will let me know how much boost is being generated. I've tuned a ton of race cars and have seen all sorts of creative fuel pressure control systems so this is why I asked. I always preferred to set up the…

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Michael Mobile Technician
Utah
Michael
   

Scott, I should probably invest in some sort of datalogging. I don't expect to do anything with OBD I again though. The tools I have are very limited. I am told that the Mastertech in Tech 1 mode can be tied to a laptop with serial connection. I do have a Mastertech. This is one of those cases where you wish you would have never taken on a project. Just a big time burner with little reward…

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Steve Diagnostician
Arkansas
Steve
 

Hi, I owned an 84 Olds Cutlass Supreme, was having similar problems, under wot. I adjusted the throttle position sensor, had multimeter hooked into the ECM , adjusted until it was within a certain range, can't remember now. But it made a world of difference, it was a stock ECM and engine, also found two EGR ports slightly clogged in the intake under the carb, cleaned out. Just a thought, good…

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Jim Technician
New Jersey
Jim
 

Totally different fuel system. This buick is sequential fuel injection. With maf.

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Timothy Owner/Technician
Wisconsin
Timothy
 

I feel your pain! Once I find that a vehicle has been modded out, I refuse to take them on anymore…

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Michael Mobile Technician
Utah
Michael Update
 

Guys, I really appreciate all the support that has been given on this vehicle. I am currently testing products that will help datalog and graph the few PIDs available so I can get a better picture of what is going on. Meanwhile the Broadband Oxygen sensor decided to die. So customer purchased and installed a new one. My days are extremely busy so it is hard to carve out time for a time burner. I…

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