I had my battery disconnected overnite. i connected it and started the engine. After about 10-15 seconds it will run great. Steady 725-750 rpm. But if I rev the engine a couple of times and rev above 3000 rpm, it starts idling bad, raising and lowering between 750-1200, over and over.
If I shut the engine off and disconnect the battery for a few minutes, then restart it, the engine will be back to a good idle until it is revved past 3000 rpm again.

What could be causing this? I can't find anything like this by searching for it.

 

Start by pulling the codes first.

 

Codes is a good start. Could be an issue with your tps? Try checking it with the lights they sell for adjusting them.

 

When was the last time you set the idle and adjusted the tps to spec?

 

you have a 1990 TII?..
Limp mode most likely a bad OMP..TPS should be set too.
List your Modifications,please,If any.

 

I pulled the codes but the only codes pertained to the missing emissions sensors.

 

I set the tps and timing last week and re-verified them today.

 

I have the Rtek 1.7 with the OMP removal, street ported, 3 inch straight thru exhaust, FMIC, 550/720 cc injectors, Walbro 720 fuel pump and no emissions except BAC.

I did get it to run a little better by swapping out the leading coil. Now both leading plugs are firing on the mark but the #2 trailing plug is firing 90 degrees or more off the timing mark. The #1 trailing plug actually fires right between the trailing and leading marks.

It doesn't seem to be missing too much when accelerating quickly but misses badly if accelerating slowly. It starts missing around 1800 rpm and seems to even out above 3000.

 

What method did you use to test/set the TPS?

Read through this thread if you're not familiar with setting/testing the TPS:
https://www.rx7club.com/showthread.p...&highlight=tps

 

I used the 1v method and verified it by the 1k ohm method.

Maybe I should start a new thread, since the problem now is not the problem that the thread was opened with.

 

Maybe I should start a new thread, since the problem now is not the problem that the thread was opened with.

The engine will idle at around 800-850 fluctuating. The timing is set dead on with the L1 plug firing on the first mark but the T1 plug fires almost in the exactly same place, within a degree or 2. The L2 plug fires at the first mark but bounces between the first mark and a couple of degrees above the second mark. The T2 plug will not cause the timing light to fire at all.

What would cause this? CAS, ECU, gremlins.

 

I was reading some old posts and now I'm thinking that all -or at least most- of the timing mark problems are probably being caused by an older/cheaper timing light.
I'm going to pick-up a new light and recheck the marks and see if the problem still exists.

 

induction style timing lights have to be "JUST so" in order to get a good read.
Placing them Near the spark plugs is the best bet...They are a finicky thing.