ok well im about to buy a gtu that has a jdm motor T2 1990 about roghly 30k miles. it has an idling problem when the engine gets warm the idling goes up and dow from 1,000 to 1,500. i figure maybe a tune up will do since it may be a misfire needs new spark plugs or i should look for vaccum leaks. wat can cause this? has anyone ever gotten this. im thinking can it be the turbo? can anyone help me a bit? its ok when its in high rpm. when driving

 

i posted this twice i noe i need information because im about to buy this rx7

 

Surging idle can be cured most of the time with correct TPS and idle speed adjustments. First, make sure the TPS resistance is set to 1000 Ohms, engine fully warmed up. Then go back and adjust idle speed (initial set connector shorted) to the 700-800 range. When the idle speed is adjusted too high, the system will send a fuel cut signal which drops the idle. When the idle drops too low it then raises it to the preset level but that's too high again so it sends the fuel cut signal. You end up with the up and down idle which is basically harmless, but very annoying.

 

It could also be a vacuum leak. I had a bunch of problems with rotting gaskets on my old N/A engine and it made the engine surge between 1000 and 1500. Eventually took the whole Intake manifold off and replaced all the intake gaskets, Some of the vacuum tubing, and the injector O rings. Ran great after that. Its a fairly easy job to do if you have the time to do it.

 

every problem ive seen like that has been to do with vacuum leaks, check, then check again, then check again, its happened to me more than once