Stock tach reading incorrect.

[DJ19885.0]

I am running Ford TFI Ignition on an 88 mustang. I am using MSII Board V3.0 MS2.89000 firmware. I am also using the ford eec-iv adapter board. The tach signal in MS as seen on my computer is perfect. No noise, well at least not noticeable anywhere in logs. My problem is that the stock tach sticks at 2000 rpms at anything under 2000 actual rpms. It occasionally jumps down sporadically. After 2000rpms, the stock tach seems to work fine. Other than that, it just sticks at 2000 usually. It used to work fine with the factory computer. Any ideas?
Thanks!!

[Matt Cramer]

Could be a settings issue - please post a copy of your MSQ and I can check them.

[DJ19885.0]

Also no matter what I change I CANNOT get a smooth idle below 900 rpms, I have tried everything... It seems to have a consistent missfire feeling and reps drop about another 100 once it dips below 900 rpms. Maybe a related problem?? I have spent hours trying to get it, but i just have to keep idle at 1000 for now. Here is my msq in the attachment.

mpg premium.msq

Thanks!

[Matt Cramer]

Set your Maximum Spark Duration to 8 - this will get it to emulate a TFI signal.

[DJ19885.0]

Thanks for the response, but now the tach reads exactly 2x normal after entering the 8 in max spark duration. This didn't help the idle issue either.

[Matt Cramer]

Just checking - guessing by your MSQ and nickname, this IS a 5.0, right? Just wanted to be sure this isn't a 4 cylinder here.

[DJ19885.0]

Yea, its a stock 5.0 with a msd pro billet stock replacement dizzy so, TFI.

[DJ19885.0]

I guess I am not as concerned with the tach as much as the idle issue. I did notice that as soon as it gets the rough idle, it instantly goes lean. Because it is a "steady misfire" feeling, and I have my injectors up to bank fire 2 cylinders per side, I have a feeling that one of the banks just shuts off below 900rpm for some odd reason. PW 1 and PW 2 are "reading" correctly in tunerstudio when this happens. What can I do to fix this??

Thanks again for the help!!

[Matt Cramer]

To deal with the idle issue, I'll need to see a data log of the engine attempting to idle. Also, does the timing you see with a timing light stay matched to the timing in MegaTune throughout the RPM range?

[DJ19885.0]

Here is a hot start. The idle is bad, rough when it is first started and stays bad until rpms go up and hang around 880. O2 also goes rich as soon as it starts to idle well. The idle then gets rough again near the end as seen by a drop in rpm to 750 ish and lean o2 drop.

bad idle.msl

[Matt Cramer]

Try adjusting your spark advance table - try 22 degrees at 700 and 20 at 900. Also make sure that's what you are actually getting with a timing light.

[DJ19885.0]

Haha, wow, that was an easy fix! Thanks a ton for all your input. You guys really stand behind your excellent product and I really appreciate it! A couple of my friends think it is so cool, and may be potential customers soon! This is easily the best vehicle modification that I have ever attempted!