I have an 87 GN completely stock. Running about 20lbs of boost. The car ran perfectly fine when I got it. Now the car takes off fine, but when I get down harder on the throttle it starts to break up real bad and will no longer run out as it would before. I can mash the throttle down keeping it steady after a certain point and the boost will fluctuate between 10-16lbs while spark knocking. I've had a scanner on it before and whenever we try to check the timing it will kick off the scanner, not giving us a reading. The coil pack, control module, and wires have been replaced. Messed with the fuel pressure maintaining at about 45lbs with the stock 30lb inj. Like I said the car breaks up really bad while not wanting to run out What could the problem possibly be?
spark knock/breaking up
- Thread starter awdunton
- Start date
Kevin87TurboT
How many can I own??
- Joined
- Jul 29, 2005
awdunton said:
Just like Sooner said, 20 lbs of boost is too much on pump gas. Do you have race gas in it? Your options are to either put race gas in it or lower the boost to 16-17 lbs on pump gas, or install an alcohol injection kit. I prefer the alky injection option. You can drive the car on the street on pump gas and the alky kit comes on only under boost.
Thanks.
I have put 100 octane and it does the exact same thing as it does with 93. Also, when I got the car the Auto Meter guage would peg 20lbs and have no problems at all. So I'm not quite sure what may have went wrong.Possible computer? Also, about how much timing should these have at 16lbs.
Thankyou
I have put 100 octane and it does the exact same thing as it does with 93. Also, when I got the car the Auto Meter guage would peg 20lbs and have no problems at all. So I'm not quite sure what may have went wrong.Possible computer? Also, about how much timing should these have at 16lbs.
Thankyou
Kevin87TurboT
How many can I own??
- Joined
- Jul 29, 2005
awdunton,
With a stock GN like yours, you should be able to get by with 16 lbs of boost and with around 18 degs timing on pump gas. The timing is controlled by the chip and you'll have to determine what chip you have. If it's a pump gas chip, most all of them with have the timing between 16 and 19 degrees. If it's a race gas chip, it may be in the low to mid 20s. It was a good idea to try your car on 100 octane, but if you already had some 93 octane in the tank, then the 100 octane would have been diluted to something between 93 and 100 octane. A better test would be to run your gas tank nearly to empty and pour some VP C16 racing gas in it. If that doesn't fix the misfire, then you may look at the engine tune or computer.
Good Luck.
Kevin
With a stock GN like yours, you should be able to get by with 16 lbs of boost and with around 18 degs timing on pump gas. The timing is controlled by the chip and you'll have to determine what chip you have. If it's a pump gas chip, most all of them with have the timing between 16 and 19 degrees. If it's a race gas chip, it may be in the low to mid 20s. It was a good idea to try your car on 100 octane, but if you already had some 93 octane in the tank, then the 100 octane would have been diluted to something between 93 and 100 octane. A better test would be to run your gas tank nearly to empty and pour some VP C16 racing gas in it. If that doesn't fix the misfire, then you may look at the engine tune or computer.
Good Luck.
Kevin
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