4.8 swap tach reading high
10-09-2012, 03:45 PM
#1
4.8 swap tach reading high I am working on finishing the little things on my swap, Thread Here, It is a 2000 sierra 4.8 in a 98 s10. I just installed an instrument cluster with a tach from a 2008 blazer because my cluster had not tach. It works but reads best I can tell double what it should. At an idle it is showing 1500 rpms, at 65 on highway its up over 3000 rpms, I know its not spinning that fast. I have searched and searched and found only a couple helpful posts, one where someone said something needs to be changed in the cluster itself, a resistor or something, another post said that I would have to change it with Hp tuners in the PCM, On the current performance website, it says I will need a module to correct the signal then goes on to say you don't need to correct it for ls1 swaps, that it should read right.
Does anyone know for sure?
If it is a tune correction, is it simple, would I have to send it off several times to get it calibrated right? Would it be another $100 or more for just a tach calibration or would something like this be cheaper?
I am real close to just buying HP tuners, if I knew I could fix this problem with it I probably would.
Any help is appreciated.
Does anyone know for sure?
If it is a tune correction, is it simple, would I have to send it off several times to get it calibrated right? Would it be another $100 or more for just a tach calibration or would something like this be cheaper?
I am real close to just buying HP tuners, if I knew I could fix this problem with it I probably would.
Any help is appreciated.
10-09-2012, 04:17 PM
#2
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With using HP tuners, there is a tach resolution signal parameter that changes the tach output signal from the pcm to the cluster.
That needs to be changed from I think 4 to 6, but I cant remember for sure.
Had the same problem with my 97 sonoma with an ls1, and now the tach reads correctly
That needs to be changed from I think 4 to 6, but I cant remember for sure.
Had the same problem with my 97 sonoma with an ls1, and now the tach reads correctly
10-19-2012, 03:16 PM
#5
Received HP tuners last night, got my tach and fuel guage fixed or so it appears.
Tach high/low resolutions were set at 3/3, I changed them to 6/6 and that seemed to work, It's a little bit off from what HP tuners shows but only a tiny bit.
As for the fuel guage, the perameters in the 2000 sierra were at 0 ohms empty 150 ohms full, I reset them to 49 ohms empty and 240 ohms full. I have not checked my sender to see if that was correct, I found those numbers on a forum somewhere and the guage seems to work better. Time will tell.
Also, noticed that I have a very lazy oxygen sensor using the VCM scanner suite and my long term fuel trims are in the +15 range. Hopefully with a new one my mpg will improve. Will do some logs with new o2 sensors and see if this thing really wants more fuel.
Tach high/low resolutions were set at 3/3, I changed them to 6/6 and that seemed to work, It's a little bit off from what HP tuners shows but only a tiny bit.
As for the fuel guage, the perameters in the 2000 sierra were at 0 ohms empty 150 ohms full, I reset them to 49 ohms empty and 240 ohms full. I have not checked my sender to see if that was correct, I found those numbers on a forum somewhere and the guage seems to work better. Time will tell.
Also, noticed that I have a very lazy oxygen sensor using the VCM scanner suite and my long term fuel trims are in the +15 range. Hopefully with a new one my mpg will improve. Will do some logs with new o2 sensors and see if this thing really wants more fuel.
