So my tachometer all of a sudden decided to act up. Its not showing the right rpms that i am actually at. when im at idle it will sit at 700-800 like a normal idle but when i go to rev it up or move the needle will bounce around and never give correct readings. for example if i rev it out to 8+k, it will go up to 3-4k and drop completely then continue going up and only makes it back up to 4-5k with some bouncing inbetween, ill try to get a video later but ive searched this with no results and here are a few things i have tried. First i pulled the cluster out and checked the wires actually going into the cluster but there seemed to be no issues. So i started thinking it may be a grounding problem. I did the TSB where you ground one of the wires from the boost sensor to the water filler neck on the motor. same issue. So i did a few voltage drop tests getting between .4-.6 ohms one the upper right and lower right pin of the far left connector on my ECU so i did a little more research and found a better way to ground the wire that goes underneath my IC bracket. now my ecu is getting 0hms resistance but the tach is still acting funny. I was beginning to think it might be the cluster now but i would like to get a second opinion before i condemn it.

 

Try disconnecting the 4 wire plug to the trailing coil and then reconnect the plug after cleaning it up a bit and applying some dielectric grease. Also, check the condenser for the tach which I think will be bolted to your slave cylinder. Lastly, does your shift light work properly? If it does not then the signal from the trailing coil is not good.

 

lol my shift light has never worked properly, actually, since i had the cluster i was like "hmmmm shift light bulb.....gone!" and just threw it across the shop

 

checked the connecter, the clip that holds it together was broken but besides that, it looked clean on the inside, no signs of burning or anything. so i did what you said and zip tied it to make sure it stays together but the tach is still doing the same problem.i was mistaken before, the tach actually never goes past 5k rpms but the engine is obviously turning faster. the engine sputters a little bit around 3k and it seems to correlate as to when the tach decides to be not functional. for example the tach drops when it sputters and when it decides to continue rev the tach continues from where it dropped to. i know it sounds confusing, but a video will explain it all.

 

That condenser goes to the oil pressure gauge, has nothing to do with the tach.

 

Then why not tell him where the one for the tach is located?

 

If the tach circuit had a condenser, I might.

 

Yes it does. To the original poster I apologize for the incorrect info but the item should be located near the trailing coil.



Another thing you could do is look at the blue arrow which points to a black wire with a tube like ending. There are two of these, one each located by both coils. Jumper a wire from the one by the leading coil to the one located by the trailing coil and see if this provides you with a better acting tach.

 

Take the plugs wires off at the trailing coil and check spark.
My thinking is that since the tach takes its signal from the Trailing coil.,the coil itself can be acting up or failing.

 

http://s17.photobucket.com/albums/b8...0-10-07-32.mp4

Video!

 

How long has this problem occured. In the video you provided, the Boost, Temp and Fuel gauges are not working. Have these always not worked or did their problem coincide w/the tach problem?

 

No, it doesn't.
That condenser is located on the leading coil, the tach draws it's signal from the trailing coil.

 

aftermarket boost guage, i'm pretty sure its the fuel sending unit that is not functional when i fill up the tank it will read a full tank of gas then read empty by the time i have 1/2 a tank or less, and the temp kinda works, it will go up 1/4 of the way and stop(only time ive seen it go higher was when the motor overheated once) motor was just cold.

but i went ahead and started the motor and started pulling wires off my coils, my L1, L2 and T1 had a very strong spark, T2 was extremely weak, you can hear it arc, but only when the wire was actually inside the coil, all the others would arc everywhere while its running.

Edit: could there be an underlying problem causing the lack of spark in my trailing coil or is the only solution the coil itself? are there any differences between NA and TII coils?

 

The wire connected to the condenser connects to both coils and not just the leading coil. The condenser related to the oil pressure is for gauge purposes. Why would the one associated w/the coils not be for gauge purposes and if it isn't then what is its purpose?

 

There are two coils in the trailing coil which fire independently of each other. This is made so by the ECU via pin 1U which is known as the "select" signal.

Also, you could just disconnect the 4 wire plug from the trailing coil as a test and run the car off just the leading coil and check if the tach works and if the problem persists with the tach then you know the trailing coil is not at fault as it relates to T2 spark.

 

if i had a trailing coil laying around and i knew the T1 was bad and the T2 was good can i swap the T2's? ill give that a try right now

disconnecting the 4pin connector on the trailing coil makes the tach completely inoperable.

 

With everything connected you ought to bridge the two black check connectors as it will send a different signal to the tach so you could check to see if the very same problem exists.

 

are you talking about the bullet connectors on both of the coils (blue arrow on the above pic)? or the red arrow connectors you pointed out?

 

Bullet connectors.

 

just bridged the bullet connectors and got a working tach, guess my trailing 2 coil is the problem, thanks alot for the help =)