Need Help With Stock 1986 GN

Country Nate

New Member
Jul 7, 2014
To make a long story short, I own a 1986 GN with 57,000 miles on it. I purchased the car new in 1986 when I was 19 years old. I drove it a lot the first couple of years, and then very little in the last 20 years. Mostly sat in storage. I know the car does not run like it did when it was new. It seems a little sluggish, and it idles a little rough, especially when cold.

At this point, I have decided to get the car running correctly again, so I found this website, and I have been reading, and reading for the last couple of weeks. Time for me to start asking questions.

Everything except the torque converter is stock, even the chip. In 1998 the torque converter was replaced because my dad was racing the car around and somehow managed to burn it out. He took it to Cottman Transmission to be replaced, and I have no idea what they put in it. I wasn't paying attention. I took the cover off last week, and it is 12", and bright orange. Only numbers I can find are C48 4802 A7. Whatever it is it, "stalls out" around 2000 rpm's. When I say "stalls out" I used two methods. When braking, the wheel starts turning at 2150 RPM's, and the boost starts to light up at about 1900 RPM's. From what I gather on here, I should replace with one that stalls out a little higher around 2500???

I got a scan master a couple of weeks ago, hooked it up and here are the readings:

o2- bounces all over the place while driving around. WOT, it's about 830 until I hit third, and then it drops back into the 790's.

Knock Sensor is almost always on 0. Even WOT. I did see it jump up to 1.4 once for about half a second under WOT.

AF- 3 when I turn the key on. 4-7 during IDLE. about 214 WOT. The WOT number should be 255 right?

Bat- 13.8

INT and L8- I haven't been paying attention. If I need it, let me know, and I'll post back.

BL- moves from 115 -140.

MPH- seems to be right according to the speedometer.

CLT- 185- 190

ATS- Varies with the outside temp.

TPS- 42 4.56

IAC- Bounces around in the low thirties.

CC 0 -250. It usually jumps up in increments of 10 to 20.


Rpm- 775 to 800.

Under WOT my boost gauge says 12. Shouldn't it be 16 17?

I have ordered a TT 5.7 chip.

Fuel pressure is 30 at idle and 38 with the vacuum hose off of the fuel regulator. Shouldn't it be 42 43 with the vacuum hose off, and 33 at idle with the hose on? I don't have a long enough hose to check it WOT.

It has fairly new plug wires and spark plugs.

Brake master cylinder has been replaced. Crack in the header has been fixed. I really would like to get it running like it did when new, or even a little better. I just want a quick street car that I may take to the track once when I get the motor right. If I could get her in the 12's, I would be very happy.

I'm guessing I should start with a fuel pump and a torque converter. Any suggestions? I would prefer not to have a hot wire kit. It would like to leave the turbo, intercooler, and injectors stock.

Is what I want possible?

What am I missing?

Sorry to be so loooong winded, but as I'm learning, these cars can be complicated!!

Thanks in advance, Nate

Torque Converter. Anybody know what kind it might be?

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You'll probably see 255 on the airflow if you can raise the boost to 17 or so. The reason your BLMs are maxed out at 140 is most likely due to the fuel pump not keeping up PLUS starting out with low pressure.

If you want to leave the stock injectors, chip, pump and omit the hotwire.... park the car and just look at it.
Why would you not want a fuel pump hot wire? I've seen low mileage TR's with less than 10 volts to the fuel pump on the factory wiring.

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I have the TT 5.7 chip ordered. No problem getting a pump. Sorry if I wasn't clear on that.

I would prefer not to change things unless I have to. If it's absolutely necessary to get hot wire kit to get it to run good, I'll do it.
That's one of many things. along with every hose under the hood, check valves, injectors, timing set, valve springs, etc....
The benefits of the hotwire (added voltage to fuel pump) outweighs the negatives (non stock appearing engine bay). If your fingers turn black from the vacuum hoses then it is time to replace them. Can't give you much info on the converter but you could try calling the gsca in GA You should also get a fuel pressure gauge either on a long hose that you can place under the windshield to check the pressure occasionally or get an electric one that you can mount inside the car next to your water temp gauge, oil pressure gauge, boost gauge, knock gauge, volts gauge, egr temp gauge, trans. temp gauge, etc. etc. Can't have too many gauges in these cars ya know.
BLM could be low due to a vacuum leak (or low fuel pressure). You won't know for sure until you bump up the FP. Should be 128 +- 10 . I think 150 is maxed out.
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Looks like just a repaint and re-stall on a regular 2004r converter if its stalling that low, stock D5s stall higher then that, and don't go by the factory boost gauge lights their not even close to accurate.
Thank you for the replies.

I agree on the fuel pump, hot wire kit, and mabie even a adjustable regulator. Looks like Kirban has a nice set up for that.

I agree on the torque converter as well. Would the PTC 10" be a good torque converter for it? Any other good choices?

Earl, you mean set the timing according to the instructions above?

What do you mean by "Check Valves"?

What do you suggest I do with the injectors?

Since the factory boost gauge is wrong, I guess I need a boost gauge? any suggestions? Can I adjust the boost?

Sorry so many questions. I'm trying to learn, because I want the car to run right.

IS there a way to check for vacuum leaks other than just looking at the hoses? mine have been replaced as needed over the years. They look ok. What I'll do is get the fuel pump issues straightened out, and then see if my BLM reading improves.

GNRick, I had no idea these cars ran that fast! lol... Thanks for the GS link. I'll start looking into all these gauges. :vomit:;)
Best way to check for vacuum leaks is with a smoke machine. I bought mine from craigs list, from a mechanic closing his shop. There are utube videos on how to use it and how to make your own. A bit pricey but well worth it if you can find a used one. You should also replace your stock MAF with a set up from Full Throttle. They sell a "Translator" which converts the signal from a MAF off an LT-1 motor (or LS-1) into something the Buick ecm can understand. You might find the MAF cheaper at Advance with their internet discounts or just buy it from Full Throttle and support a vendor. The LT-1 maf is much more reliable than the stocker if you plan on driving your car very much. Cc BUMAFT iTpStatus 0 Tp Bc
It won't look stock but is worth it. Your MAF numbers should then go to 255. As for the injectors they can get dirty/gummed up from sitting. If you already ordered your chip then it sounds like you intend on keeping the stock injectors which is fine. You might want to remove them and send them off to have them professionally cleaned. You won't be able to adjust the boost with a stock turbo as the factory didn't provide an adjustable wastegate. This is probably a good thing if you want your motor to live a long life ;). You should also do the spring cleaning After doing all the stuff I just told you, only one last thing to do.....enjoy your car!:D
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As above the fuel pump needs voltage to produce work. You wouldnt expect the any electric motor to produce without the proper voltage. Then comes the amperage, you have to supply it or it can't make the volume and pressure your engine needs.
Hit the and look into the spring cleaning.
I understand your desire for original as like you I bought my 87 new when I was 19 also. Most wouldn't be able to tell what is original anyway. Having it run well is way more important to me but I do like a nice stock "appearing" one.

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