M20 Frankenstein build help

[chase_mull3r]

I have a 1986 325e with a super eta block and an entire I swap to the top side of the engine. Head, manifold, afm, ecu, etc. the problem I am having is that my car still redlines at 4500 rpm. The ecu I am using is the 173. Which makes no sense to me, am I missing something or??? Any help would be appreciated

[packratbimmer]

Did you change tachometers and code plugs?

[chase_mull3r]

The tach on my car doesn't work so I have an aftermarket one connected to my ignition coil. I'm not to sure what a code plug is though? Is that something that is needed?

[squidmaster]

The coding plug he's referring to is a tach coding plug that adjusts output signal to the stepper motor in the stock tach. Since that's not the case you don't have to worry about it.

Is there no engine speed signal output to the ECU then? That will need to be connected using the stock hall sensor that's mounted on the front of the block that reads the crank cog teeth

[ak-]

I hit a brick wall @ 4500~ when my CPS wasn't close enough to the teeth of the wheel. It was actually kind of loose now that I think about it. Another thing to check.

[chase_mull3r]

My speedometer works and everything it's just my rpm gauge on the cluster that is broken. Also I just replaced my cps, it's on there pretty tight. plus my car would be running all wack if it was loose wouldn't it? My car runs totally fine it's just not getting up to where it should. As soon as my car hits 4500 on my aftermarket tach the car won't go any higher. Can't help but thinking it's an electrical issue somewhere I mean what else could it be?

[ak-]

Mine ran fine actually till I fixed the issue. See if the CPS isn't close enough to the wheel rather than just being loose.
Check the dist. cap and rotor as well - points could be corroded.

[bblazen]

I had this same issue and it ended up being a bad coil.

[suruba]

i had a problem like this, sputtered out at about 4500 and felt like a redline, but it was a piece of metal on the cps shorting it out. didn't find it till it killed my cps.

[chase_mull3r]

Thanks, I'll give both of those a look when I get off of work. I'll let you know how it goes!

[chase_mull3r]

Does anyone know the gap distance that is supposed to be in between the cps and crank gear?

[squidmaster]

1mm from the specs I've read

[chase_mull3r]

Well I slipped a 1mm feeler gauge in there and it was pretty spot on. Just the tinyest amount of restraint so that all checks out

[chase_mull3r]

Well it turns out the tach I have is for a v8 so it wasn't picking up the signal correctly... probably something I should have checked right from the start 🙄