Fuel Question, and a few other topics!


GM EFI Founder/Editor
Jun 11, 2004
So since I have just moved from So Cal from Ohio a few months back I have to say it's a total culture shock.

Having said that, my '87 GN was recently delivered and it feels great cruising my GN around the greater L.A area. However, I've noticed what seems like a drop in power. I not sure if it's been the change in elevation, the climate, or the two point drop in octane rating (used 93 back home), but my Buick doesn't feel as fast as it was back east. Maybe it's a combination of all of the above?

I was curious as to what all of the guys are running out here in regards of fuel, and although it's quite costly, I was thinking of running a blend of 91 and maybe some VP race fuel, just to bring the octane rating up -and then some.

I've owned my car for a little over three years, I know quite a bit about Buicks (although I'm still learning), and I've been in love with these cars since 1987. I don't want to sound like a total newb, but what's a safe and relatively cost-effective solution to the 2-point dip in octane?

Also, occasionally it likes to stall while at speed once I let off of the throttle. I'm thinking it's either the IAC, MAF, or the cam sensor. It even makes a sort of burping or popping noise on occasion. It started doing this right before I left Ohio. Any thoughts?

It's a basically stock, bolt-on car (mods below). Any help will be welcomed. Thanks.
I am assuming you are NOT running Alky (or Meth)? This would greatly reduce knock. I doubt the elevation is the issue unless your MAP sensor is bad. When you turn the key on, the computer reads the MAP to know the elevation before your start the car (at least it does on newer fuel injected cars so Im assuming the Buick is the same, correct me if Im wrong). I honestly would recommend running a Alky kit from Julio. Then have a chip burned for that, turn the boost up and hold on! Even with 91 octane you will be fine.
The MAP sensor is just for the boost gauge. There is no MAP input to the stock ECM. More than likely without putting a scan tool on the car to see you are experiencing knock retard due to the drop in octane all things being the same. Alcohol injection works really well I'd suggest getting an alky set up for your car and a Turbo Tweak chip then see if you can twist Mike Benards arm to help you get the car tuned.

If you unplug your MAP sensor, I doubt the only thing that will happen is your boost gauge not working.
I run Chevron Supreme (91) and Alkycontrol, and there is not an issue with power.

That said....on this Cali 91 octane, if you are running more than 14 lbas of boost, you better be shooting alky too....

For your other issue, Lou could help you out.
I'd start by making sure you have a good set up plugs in there (AC Delco R43TS have never done me wrong personally) and verifying your fuel pressure is good at idle and under boost. Could also make sure your ICM or it's base are not loose....just grab the coil pack and see if it wiggles.
TPS is easy to check if you have a scan master...can also be done with a voltmeter and a good set of narrow tip probes.
Not only are we stuck with 91 octane but we also have a special Summer and Winter blend of gas. I would check your car for knock just to make sure. Do you have 100 avaialble around you?

Thanks for the link. What I said is true, the MAP sensor is only for the boost gauge. Cars with digital dash don't even have one. They have a pressure switch instead for the two lights that are on the dashboard. Unplug it and nothing will happen except the boost gauge won't work.


Interesting. Yeah I couldnt find much info on the OBDI (or prior) vehicles. I usually deal with OBDII and I know the MAP sensor is used for various other inputs (baro pressure, EVAP function tests, Clear-Flood-Modes for testing, etc) I even had a car that would intermittently not start because of the loose connection at the MAP sensor. Soldered the wire back on the connector and the problem went away. Thanks for the info Neal!
Welcome 02WS686GN!! Did you have the car at a shop recently in Ontario, CA? A buddy of mine whom owns a shop there said he saw a GN at another shop getting a fuel pump installed. He spoke with the guy. He said he just moved here from back east.