Tach signal or PW spikes

southspeedescort · Post by **southspeedescort** » Tue Dec 13, 2005 11:38 pm

ok i've been driving around my MS1 for about 2 weeks or so now. It's been working great. It sings out to redline no problems. Recently the car has been sputtering like crazy after about 3K RPM. I thought it was the injectors so I changed them to ones that I knew were working well. Still with the same thing. I just want to know if anyone here has seen similar problems and can eliminate a possibility for me.
i'll attach some datalogs if they can help.

my setup:
MS1 with MT 2.25b627
Tech Edge 2AO
stock 4AGE reading RPM from - coil

southspeedescort · Post by **southspeedescort** » Mon Dec 19, 2005 9:22 pm

I know it's not conclusive, but if it helps I put all my stock wiring back on and the car runs perfectly like before. I'm wondering if I have a loose connector?

Karl_Skewes · Post by **Karl_Skewes** » Tue Dec 20, 2005 2:24 pm

hmm.. well you're triggering off the negative side of the coil right?

So, I would check:
1) Coil negative wire is not touching ht leads, and connectors are soldered and good all the way back from coil to MS.
2) Grounds for MS are good... soldered and not loose.
3) R10, the main resistor for the tacho is not touching on anything else, and is not discoloured.

What size is your R10 currently?
Standard is 390ohms IIRC.
On our 4AGE's, we normally had to increase this. Up to 5000ohms or so at one point.
Too little and it would spike, too much and it would have an artificial rev limiter.
We always ran a Dave Cap (details in Mega Manual).

southspeedescort · Post by **southspeedescort** » Tue Dec 20, 2005 2:37 pm

I just followed the standard assembly procedure, it is 1k ohms.

Should I solder in a 4k or 5k resistor?

Becuase the TPS MAP signals are directly proportionate and very very smooth, but the RPM and PW go crazy once I start to rev it past 3k RPM or so.

Karl_Skewes · Post by **Karl_Skewes** » Tue Dec 20, 2005 2:51 pm

ok.. if the other items check out, then you can try increasing the resistor. probably better to go in 1k steps max though.

however, it's quite possible that something else is the problem as this worked before.

southspeedescort · Post by **southspeedescort** » Fri Jan 20, 2006 9:28 pm

I think my brain was installed backwards.
my ed cap. was not installed for some reason.

I think this is the solution for my tach noise.

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Tach signal or PW spikes

Tach signal or PW spikes

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