Tach Fubar After Chip Install

[funcrew]

I installed a name-brand chip bought from the manufacturer in my bone-stock M20B25. DME is a 173. As soon as the engine started up after the install, the tach was wandering all over the place, erratic, and reading approx. 30% too low across the rev range. Tach was working perfectly prior to the chip swap. Engine starts easily and runs very strong.

I haven't had time to put the OEM chip back in for confirmation, will do that this weekend when I have time. I tried to leave a message with the chip vendor, but their inbox is full. Will try again tomorrow.

Has anybody heard of a chip screw-up causing tach problems?

[blocke]

Never heard of that. But on my miller maf conversion it required splicing wires at the DME. Did this chip have anything like that or just straight plug ang play swappage?

[JTapper]

Never heard of that. But on my miller maf conversion it required splicing wires at the DME. Did this chip have anything like that or just straight plug ang play swappage?

I'm doing the Miller MAF and WAR chip in the spring, care to elaborate on this?

[kamotors]

its super easy just cut one wire and solder it onto another.^

to OP I'm not sure how a chip could effect your tach.

[blocke]

its super easy just cut one wire and solder it onto another.^

to OP I'm not sure how a chip could effect your tach.

What he said. Clip one wire, tap it into another, and insert chip with the notch on the chip matching the notch on the board. Very simple.

[Lunner]

I'm doing the Miller MAF and WAR chip in the spring, care to elaborate on this?

It's a piece of cake, and Miller has it explained 100% in their instructions pdf on their website.

[lennon]

did you mess with the c104 plug, perhaps on accident? its right down there by the ECU.

[funcrew]

did you mess with the c104 plug, perhaps on accident? its right down there by the ECU.

Well, I screwed up something, and it's not the chip's fault. After talking to the chip guru, I swapped the OEM chip back in, and tach was still fubar. So I guess now it's time to either:

A. Go though the standard diagnostics for a funky tach (someone please post a link if there's a good thread on that)

OR

B. Ignore it. It's not like the tach provides any meaningful input for driving around on the street anyway. Lots of other POS "vintage" BMW problems to solve that would yield more bang for the buck time-wise.

Thanks to all who replied.