ZR-1 Net Registry Forums - View Single Post - Diagnose - 2,500 rpm Stumble Miss - 1991 8k mile ZR-1

SteelBlueZR1 · 03-24-2013

Sorry for the delay in updating. So, I had previously installed the new Jerry's Gaskets sourced oem map vacuum line as the old one was a hodgepodge of cobbled together rubber and plastic vacuum lines and completely soaked with oil.
I thought I still had a fuel / secondary problem, as the stumble problem continued; but on a whim, I removed and cleaned again the new vacuum line, which still had some remnant oil in it. Maybe the MAP sensor connector being unplugged and plugged in 2x's also cleaned the contacts?
Now the car idles perfectly (Nickel stood on edge for :30) and there is no hesitation when the secondaries open, and the car pulls amazingly strongly and smoothly to red line.
I guess it just took some time for the oil to work its way out and allow correct MAP readings. There was tons of oil in the original MAP line and only a little in the new OEM map line.
I drove the car 30 miles tonight, and the LT5 has never run this well before!
A Big Thanks to Jerry of Jerry's Gaskets for talking me down from buying the fuel pumps pre-emptively and focusing on the MAP sensor vacuum hoses.

03-24-2013	#19
SteelBlueZR1 Join Date: Aug 2011 Location: Evergreen, Co. Posts: 344	Re: Diagnose - 2,500 rpm Stumble Miss - 1991 8k mile ZR-1 Sorry for the delay in updating. So, I had previously installed the new Jerry's Gaskets sourced oem map vacuum line as the old one was a hodgepodge of cobbled together rubber and plastic vacuum lines and completely soaked with oil. I thought I still had a fuel / secondary problem, as the stumble problem continued; but on a whim, I removed and cleaned again the new vacuum line, which still had some remnant oil in it. Maybe the MAP sensor connector being unplugged and plugged in 2x's also cleaned the contacts? Now the car idles perfectly (Nickel stood on edge for :30) and there is no hesitation when the secondaries open, and the car pulls amazingly strongly and smoothly to red line. I guess it just took some time for the oil to work its way out and allow correct MAP readings. There was tons of oil in the original MAP line and only a little in the new OEM map line. I drove the car 30 miles tonight, and the LT5 has never run this well before! A Big Thanks to Jerry of Jerry's Gaskets for talking me down from buying the fuel pumps pre-emptively and focusing on the MAP sensor vacuum hoses.