Hello,

Last night, I installed a 4g93 manifold on my 03 es. I have ported the runners to match the gasket and I opened the plenum to 60 mm in prevision of my 1g tb. As of right now I still have the stock tb.

Once I finished hooking every thing up, I repluged the battery, started the car and let it idle for a few minutes. As it always does when reseting the ECU, the rpm jumped to 3000 then to 2000 and it started to come down as the engine warmed up.

Once the car was warm, the rpm started to fluctuate between 800-1500 rpm, I could hear the IAC valve opening and closing to prevent the car from stalling. I turned the car off, rechecked every vaccum connection, and again reset the ecu. This time since the car was kinda warm, the rpm took less time to drop down and it started to bounce again. I listened for a vaccum leak, nothing.

I was suspecting the throttle cable but I tried different adjustments without success. Is the throttle plate supposed to be completely closed at idle?

Any other ideas? I had never experienced a similar problem before. My only other engine mod is a K&N intake.

 

The throttle plate should be completely closed at idle, that might be why you're having an issue.

 

check your injector ring seals. The ribber O's that go in between the injector and the intake manifold. They get really brittle and leak...

 

About the throttle plate: that is what I tought too, just wanted to confirm. Thank you.

As for the injector O-rings can you elaborate? I reused the stock ones and they looked fine by me, no cracks no apparent wear. But when I think about it, I was suprised to see that they did not really fit tight when I put the fuel rail back on, should I oil them?

I will also check for more vaccum leaks using some brake cleaner tomorrow.

 

From what I remember the O-rings just sorta fall in place.

 

when I did my mani swap i had a weird idle problem like yours afterwards. I tried everything, ISC, TPS, throttle plate adjustment, new coil packs, new sparkplugs...but nothing worked. So i made a compression tester with a bike pump and a couple of couplers hooked up to the throttle plate. While pumping it constantly air will exit thru the exhaust(some exhaust valves are open still) but air will also leak thru where ever there is a leak. You can use some water in a spray bottle and spritz it on the areas where you suspect a leak. If it bubbles or hisses then you have a leak there. Try it out... BTW the o rings around your injectors should fit snug to make an airtight seal. The rubber gets brittle and fractures sometimes causing an air leak.

 

Okay, so I've checked for leaks everywhere with a can of brake cleaner. The only place where I could notice an amelioration is when I sprayed around the injectors. After a while tough, it went back to normal. So I'll just order new injector seals and see.

Any other ideas?

 

I bet you its those injector ring seals.....