I've been breaking in my 13b non-turbo rebuild with about 1300 miles on it upto now. I noticed it was lacking some power intermitantly while driving the other day and when I came to a stop the RMP would drop to about 400 and on the verge of stalling. When I got home put my timing light on th L1 wire and the strobe would work intermitant and I shook the wire to the Lead igniter and it would act up. I removed the connecter tighten the female spring prongs reconnected it and timing strobe was constant. However for some reason my idle would stay up around 1500. I figured I would check the idle setting and when I put the jumper in the check connecter it would go right down to 750 RPMs. I take the jumper out, rev it up to 2000 and it only dropped to 1500, put the jumper back in and idle would go down to 750???? Can any one give some advice to what could cause this and why the jumper wire does this???? Thanks, Gary

 

I don't know anything about how timing lights behave, but whenever there's an unstable idle (rotary or boinger) a vacuum leak is one of the first suspects...

ttyl,
Amur_

 

Attached is a page from the manual that mentions the timing lite. It might be applicable to you. Its note C. On the leads I see that all the time, the loss of a flash for long periods of time. Its obviously not the missing of the engine and just a lite problem. You can prove that to yourseld by disconnecting the trail plugs completly and checking the timing with just the leads firing. If the plug was really missing the engine would be shaking all over the place. As for the 750 good and correct idle with the initial set coupler in but high rev's without it......duh. For a clue, with the initial set coupler out, pull the bac's plug off and see what happens. I doubt an air leak because the idle is 750 with the initial set coupler engaged.

 

I have an 89 N/A w/ a bad idle(it surges up and down, once and awhile it will sit at 1100, once in awhile at 750,. normally between 600-900 bouncing though).

You say vacume leaks are the most common, how do i figure out if there is a leak, and which ones are leaking if they are?

Thanks
journey

 

the most common method (without having to search with a vaccum pump/gauge) is to spray carb cleaner all around and try to listen to the engine. If you spray CC in an area and the engine revs-up after a second or two, then a vaccum leak is somehwere in that area....just to be safe, replace all vaccum hoses in there

 

>>spray carb cleaner all around and try to listen to the engine. If you spray CC in an area and the engine revs-up after a second or two, then a vaccum leak is somehwere in that area

To expand on that, the idea is that the vacuum leak is altering your mixture, (i.e. running lean.) When you spray over the leak, the carb cleaner is drawn into the line and then through the sys into the combustion chamber. Having this momentary shot of extra combustable material briefly brings the mixture a little closer back to normal, so the engine will run more smoothy for a moment.

Instead of blasting every hose right away, go one hose at a time, a few inches at a time. You'll have a better chance of finding the exact location this way, and then replace the offending line.

If you don't want to/feel like spending the time on it, call around and try to find a shop with a smoke machine. This machine dumps a little bit of smoke into the air intake and then the mechanic watches to see if that smoke leaks out anywhere. I don't know what a typical charge is for this service... Can't be much.

Another easy thing to go after is the (less likely) possibility of old or worn/damaged spark plug wires. A good replacement aftermarket set can be had quickly without spending a fortune.

ttyl,
Amur_