I've got a 6 port 13B wired open EFI, no o2 sensor or afm on Microtech Digi Pro Series 1 (old skool)..

Say I leave the car overnight, I start it in the morning and it idles smooth at about 1000rpm for 3 seconds, then watching the tacho the rpm starts jumping slowly until it gets pretty rough jumping between about 700-900 and misfires a fair bit. It's a steady jumping but im just wondering why it idles smooth at first and then goes all over the place.

The idle screw on top of the uim is in as far as it goes, and when shes warm standard idle is about 1200-1300rpm.

My OMP is setup locked on about halfway... if that makes any difference.

Ideas would be great, cheers..

 

first some Qs

how many miles on motor
what year 13b
does it smoke and how much


but for the high idle your thottle plates could be stuck

 

Whats a wired open EFI?

 

There's only about 15000 miles on it.

It doesnt smoke at all.

~1986 13B

5th and 6 ports are wired open... Always open, instead of normally being opened by actuators at about 3800 rpm.

I just cleaned out inside the TB couple weeks ago, it was actually after cleaning the gunk out that the idle increased..

 

Ya I know,,,hehehe...You are referring to the 6 port actuators tho not a wired open EFI (Electronin Fuel Injection) was just joking you.

 

Heh I didn't write it to be read like that They arent actually wired open - more the valves are completely missing and then any holes have been welded up...

Any thoughts on the problem?

PS. I have no thermowax.. but obviously for some reason its slowing down after a few seconds..

 

The sleeves are missing?

 

Bingo

 

Got a vac leak somewhere...My guess...

 

Does this usually happen in a hose, or could it be a gasket somewhere? I'll check all the hoses tonight. I dont have a UIM-LIM gasket as its welded - shouldnt leak there.

Cheers

 

Unless the weld cracked

Usually it's a gasket, or a block-off plate, I would guess...

At this point, it could be many things, including a sensor/wiring, if temps have anything to do with it. Make sure you have no vac leaks first, then you can start troubleshooting the crazy stuff...

 

Hmm between the TB and the UIM there is a thin (i think plastic) block which redirects some of the little air ducts around between the two. Should there be anything on either side of this to seal it? Currently the block just sits in there with nothing on either side. I thought maybe some sort of sealing compound should be on it, not sure about a gasket though, some of the holes ar equite fine.



thanks again,