Engine idle surge on a all stock low mile car

gn.87

Time Capsule
Joined
Sep 8, 2007
I have an original low mile Grand National that I am selling. I’ve owned many low mile Grand National’s over the years and they all seem to have some sort of minor surge at idle especially when it’s cold. The issue that I’m having is the gentleman who is thinking about buying it send an inspector who is going to make a note of the surge in his report. He advised me to do a little research to prove to the buyer that this is usual and customary with the stock chip. Anybody here on this board that can chime in and explain this is usual and customary for a stock low mile car with an original chip. In the past I have ordered a chip from Eric Marshall at turbo tweak in my surges of all gone away. This car still has a stock chip.
 
It might be best to verify the changes Eric makes on his chips. I believe he disables the EGR valve, and possibly makes some tweaks for the stock injectors and IAC?

I am running a low miles stock motor with Eric's 5.7 and stock injectors and trying to find the cause of an intermittent rough warm idle? BLMs are good 128-129. I believe it is the old stock injectors.
 
I have an original low mile Grand National that I am selling. I’ve owned many low mile Grand National’s over the years and they all seem to have some sort of minor surge at idle especially when it’s cold. The issue that I’m having is the gentleman who is thinking about buying it send an inspector who is going to make a note of the surge in his report. He advised me to do a little research to prove to the buyer that this is usual and customary with the stock chip. Anybody here on this board that can chime in and explain this is usual and customary for a stock low mile car with an original chip. In the past I have ordered a chip from Eric Marshall at turbo tweak in my surges of all gone away. This car still has a stock chip.

You didn't mention what year GN you have. If it's a 86' or 87' it should have the ACXA or BBKJ recall chip in it. The idle surge is a common problem with the stock chip. I had a customer with a low mileage 86' GN (11K miles) with the same problem. Some shop charged him $600 to change the fuel pump to fix the problem. Low and behold the problem was still there. I put one of Eric's chips in it and problem gone.
 
The tt 5.7 chip solves the idle surge problem. Iirc among other reasons The old factory recall chip is not suitable for todays fuels.
 
I would start with a basic comb over. Check for vacuum leaks. A common one that's hard to pinpoint is EGR gasket.

Make sure the TPS and IAC are set correctly.
 
You didn't mention what year GN you have. If it's a 86' or 87' it should have the ACXA or BBKJ recall chip in it. The idle surge is a common problem with the stock chip. I had a customer with a low mileage 86' GN (11K miles) with the same problem. Some shop charged him $600 to change the fuel pump to fix the problem. Low and behold the problem was still there. I put one of Eric's chips in it and problem gone.
Thanks
 
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