AFR/Stealthram 355, SD 7730. The car ran great until about 3 months ago. I am not even sure where to begin on this seemingly electrical problem.

Symptoms:
Tach accurate below 2800rpm. Beyond that, it jumps to zero and holds.
The car feels sluggish and bogs under full throttle. The timing sounds retarted at idle but have not got a light on it.
The alternator is running hot - burning to the touch after 10 mins of driving.
Low and rough idle.

Any ideas on where or what this could be? A combination of problems? Any leads appreciated!

 

Sounds like a possible bad battery connection. Your alternator is hot from compensating for the battery. Check to make sure your connections are tight and not all corroded.

 

Does it only do it when the car is warm? Also does the car kind of follow the tack when it bogs, like if the tack dropped the car would stop accelerating? I had a problem similar to this it ended up being a loose ground wire. I would check the grounds on the backs of the cylinder heads which was my problem, make sure the wires on the starter are tight (uncle had a similar problem this was the cause), and the ground on the front of the engine block passenger side. Remember, they have to be on there tight.

 

The tach only reads up to 2800, rather hot or cold. The engine revs basicly normal and does not follow the tach when the tach jumps to zero. I can punch it and it responds normally. It feels much slower though, like maybe full advance isnt coming in properly. It is not a ground issue for sure. I have a MEGA ground strap on it because of the rear battery.
The first thing I searched for was a short or a partial short, but I have had no luck finding any poor connections or worn wiring insulation. Thanks for the input . I'd love to hear some suggestions as to why the tach bounces around.
edit: I replaced the ignition module today but that didnt help. :-(

 

I'm going to try a pick-up coil tomorrow. I'm really tired of throwing parts at it and it gets expensive. Will the stock pick-up coil work with my MSD pro billet? I'll soon find out! Thanks for the input y'all.

 

Had to get an MSD pickup coil--luckily one was in stock at the local speed shop. UNluckily, this did not fix the problem. Same thing is going on with the tach, and sometimes the tach doesnt work at all.

edit: Still me, just forgot I was on a friend's computer

 

You don't have an aftermarket ignition installed do you? Like a MSD box? Symptoms sound alot like what happened to a friend's Z28...it was a bad MSD 6A box.



HTH

 

Yes, I have a Crane HI-6S ignition box. That was the first thing I bypassed when we started the diagnosis. It runs the same with or without the box. Thanks for the suggestion. The problem is very deep. The motor bucks and surges now, and it has no tach. I need to get a scan tool on it and look at the critical values. I wonder if the computer has the correct rpm signal.