Problems after filling tank with 87 octane, but no knock?

[bishir]

I posted the other day about my doofus of filling my tank with 87 instead of 93. Well, I ran the 87 out of the tank just by driving around last week. When the needle touched E I filled with 93. I figured it would take a while to run the little bit of 87 still in the lines so I waited to lean hard onto the car. When I did it's still bucking and popping. The funny thing is I'm not getting knock. Is that because of the alcohol? I thought if I was having octane problems it would be because of knock, but the scanmaster isn't showing anything unusual. This is only happening at high revs and any boost amount over 13-14lbs. One time it bogged in 2nd and I felt like I had no power at all. I'm going to try to add some Xylene to the mix and run out this tank, but the no knock part has me concerned that it's something else. Any suggestions?

James

 

[badboy86gn2]

Im not sure or sure you already know but whats your alky set at pump speed sounds like its too rich and 02s are different when you run alky

try to get gas at known gas station ie (cheveron)
try pulling some gas out with fuel press regulator
turn down pump speed
how about coil pack???

start form the basics meaning put boost stock and dont run alky also fuel press and chip and see if it still happens

whats your combo and what dose scan master tell you

Johnny

 

[bishir]

OKay, I just took a big trip in the GN and ran through 2 tanks of 93. Octane isn't the problem.

The other day I put on drag radials and a powerplate. I've checked for leaks around the powerplate and I can't feel, hear, or see any. The car will run fine up to 15lbs of boost. Anything over that it will spit and sputter. I turned off the alky and the same thing happens. It will run fine to 15lbs and over that it will spit and sputter, but show knock. Before I put on the powerplate and tires, the car would run 19lbs with alky no problem.

Does it sound like a coil pack to you? It's the original with a date of 11/11/86. The car is basically all stock except for exhaust and alky.

Thanks,

James

 

[scottyb]

I'm sure there's a host of possible causes, but my coil pack did the same thing. You can take it to Auto Zone for a free test if you don't have a ohmmeter.

 

[GNX]

Sounds like the coil pack. Mine went out 2 years after it was brand new in '87.

 

[bishir]

You can take it to Auto Zone for a free test if you don't have a ohmmeter.

Thanks for the help everyone! I have an ohmmeter. What is the correct method of testing the coil-pack? Also, from reading on the forum I heard the module could be bad and show the same symptoms. How can I tell? Thanks! BTW, Postons is only 45mins from my house so I will probably take a trip up there if necessary. Let me know if you've had bad luck or good luck with their equipment.

Thanks,

James

 

[bishir]

BTW, Scotty I was just in Jacksonville picking up a set of rims and tires. Too bad I didn't get a chance to meet you. Sounds like a nice car..

James

 

[scottyb]

Originally posted by bishir
BTW, Scotty I was just in Jacksonville picking up a set of rims and tires. Too bad I didn't get a chance to meet you. Sounds like a nice car..

James

Drop a line next time. Thanks, it's just an old worn out Buick.


Look on gnttype for testing method, I don't remember. You test the resistance across 2 matching posts, and also across 2 matching connectors on the bottom. If you can't find it there, then just call the clowns at Auto Zone, they'll tell you after you have to thouroughly explain it to then about 7 times.

 

[bishir]

I think I found the solution. I'll let you know once I get a new coil pack if it's the cause. I took my multimeter out to the car and measured across the terminals on the coil pack and the outer two both produced between 11-13k ohms. The middle two did nothing. Looks like I need a new coil pack according to www.gnttype.org. I feel sorry for those people who worked on these without the internet!

Thanks,

James

 

[trbojo]

had the same problem. i even went up to 103 octane fuel. turned out to be the coil pack and a set of wires. btw, like i've read before on these posts, a coil pack can ohm out ok and still be bad. mine ohmed out fine, but under higher heat and more boost, they crap out because of the increase in resistance.

 

[Roger]

My last coilpack ohmed good when cold. When it was warm it measured over 75k ohms across 1 section.

 

[ijames]

This a little late but since lots of guys mix pump and race gas I'll post it anyway. I don't know if you pumped the tank dry or just drove it so it was low, but there's almost always some gas left in the tank. If you ran the 87 down to maybe 4 gallons and then put in 14 gallons of 93 octane you are still only at (87*4+93*14)/(4+14)=91.7 octane, approximately. To get rid of effectively all of one kind of gas you really need to run the tank down to 3 or 4 gallons, fill up, run the tank down to 3 or 4 gallons again, and then fill up again. Course, if you can run it lower or pump it almost dry it takes less flushing . As for 87, I've run it when I had to with no problem. You just need to make very very very sure to control that right foot .

 

[bishir]

Ran through 3 tanks of 93 and still had the same problem. Luckly, I found out how to test the coil pack and that was my real problem.

Thanks,

James

 

[bishir]

**********PROBLEM FIXED HURAH!*******************


Just got the coil pack from Kirbans today. I put it on and it cured the problem! Good thing too, because the old coil pack kept getting worse and worse. Great deal 49.95 at Kirbans.

Thanks,

James