1G 90 help with tach

[adamsg]

ok so i got a 1990 tsi awd..the kid i bought it off of is supposedly a dsm 'guru'.my car has a 7bolt head( 6 bolt block ) my tach is hooked up to a noise sensor he put on the block? so after idle my needle either spazzes up and down or down to zero. he claimed the only way to get it to work is to put the 6 bolt head on. it wouldnt bother me so much if i wanted to keep it stock. but i want to do a gm maft and it requires accurate rpm readings to be useful. this also confuses me on how can my ecu give me correct fuel trims if it doesnt know the true rpm.

help.. how can i get my dash tach to work accurately? i dont even know where to start

 

[brian9397gsx]

What a fxxking idiot, he must of tapped into the knock sensor. is this the stock tach or aftermarket?

 

[adamsg]

its the stock tach. idk what is going on with it. hes convinced theres no way around it. i dont even know the true benefits of having the 7 bolt head but im half tempted to buy a used 6bolt head or get one from dsm graveyard because its real frustrating.

 

[steve]

It's not the head, it's the coil pack and power transistor he likely used along with the 7 bolt head.

There are tons of threads here on the issues with 90's and tach problems. You need the 90 tach gate, noise filter to make the 90 gauge cluster tach work correctly. You can use the 91+ coil pack and power transistor as long as the signal for the tach comes from the 90 tach gate.

The ECU doesn't use the tach signal for RPM, it gets that information from the CAS.

 

[adamsg]

okay thanks. i think ive got it figured out. i talked to the kid i bought it off of, he said that i dont need the dash tach to work correctly. so im just going to think of it as a luxury i dont have haha. but he said that the noise filter is bad? idk why he couldnt just say that in the first place

 

[rlacasse1]

You need the 90 coil pack as already said above.

 

[steve]

He doesn't really need the whole coil pack, just the 90 tach gate from the bottom on it. The actual coils are pretty much the same.

 

[NeMiZiS]

Well I just replaced this part here on my 90 Tsi.
I was told it is the noise filter and that it is what sends the signal to the tach..

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But I still don't have my tach working.
Then looking at this thread here, it says a different piece is the tach filter?
http://www.lilevo.com/turbo/tach/body_tach.html
Some one help me out please, do I need the "filter" in the link above?
Or should this noise filter have fixed my tach?
I've already ordered a new cluster, I'm just waiting on that to come in the rule it out too.

 

[steve]

This is the 90 tach gate I was talking about.

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Does your coil pack have 3 or 4 pins on it's connector? Is the sender on the bottom of the coil pack as shown in that link?

The 90 noise filter is the one in the guys hand. It connects between the tach gate and the ECU/gauge cluster and mounts to the intake manifold stay.

 

[Kapok6]

its the stock tach. idk what is going on with it. hes convinced theres no way around it. i dont even know the true benefits of having the 7 bolt head but im half tempted to buy a used 6bolt head or get one from dsm graveyard because its real frustrating.

Yeah, you should definitely get that 7 bolt head off there and put a 6 bolt head on and sell me the 7 bolt head.

 

[NeMiZiS]

The plug has a 4 pin connector on it.

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The Tach gate, does seem to be on the lower side of the coil.
I just put in a new noise filter, I bought from Mitsubishigraveyard this week end.
I also attempted to pull the whole coil pack out.
I took the 3 mounting bolts off and it still didn't really want to move, so I just put the bolts back in.
(Is there a trick to getting it out?)
I was mainly working on the oil return line that day and didn't have a lot of time to mess with the coil.

 

[NeMiZiS]

Sorry double posted...
When my computer froze.