Hey all

Got a 97 Eclipse RS

Idles kind of high, around 1300

But when I turn on the AC, or even just the front window defroster, the idle shoots up to 2400+

This makes driving with the AC on quite embarrassing, as you come to a stop and the engine races to 2400rpm.

Would this be a vac leak, or EGR problem, or Idle control?

I have searched on this but haven't found answers.

My vac lines seem to be OK - I do get intermittent CELs for the EGR valve but the light will be on one day and off the next.

Want to know where the idle adjust screw is at. Got the 420A layout diagram but still cannot locate it. (Does it exist??)

Thanks

Originally posted by falling-debris
vac leak

Bingo

There is no idle speed adjust on the 420A, short of drilling out the tin cap behind the "arm." When you're looking at the "fin" on the throttle cable arm, you'll see it rests against a little plug coming out of that "arm" on the TB. If you drill out the cap on the other side, you can use a torx/allen wrench to adjust the TB plate open a bit more, but this won't help your problem. It will raise the idle across the board. So if you crank idle up by 100, the AC thing will be +100 too.

Target idle is 750+/-50. If you're running higher than that, it's more than likely a vac leak. Road///Race sells a "Larsen Hose Kit" that comes with all the sizes you need to do the engine bay in a number of colors for about $25. You can also snip 1/8" off each size you need on the car (leave the rest in place so you don't forget what goes where) and go to Autozone to get the cheap rubber hose in those sizes.

Thanks Dr

Currently the PCV valve which is supposed to connect to the intake tube is WITHOUT any hose at all. Previous owner has installed a large cone filter with a 3" pipe connected to the TB. There is no PCV breather hose, just the bare nipple (heh heh) coming from the head cover.
Also, since I am new to the 420A, I didnt notice any sort of MAF sensor on the intake. I have researched this here on this forum and I have seen that this motor doesnt have a MAF??? True?? That's what I thought was throwing the CEL, was the short ram intake. But I saw nothing to plug into the stock airbox.....

Next, there is another short 90-degree rubber hose at the top of the TB and it is completely dried out and cracked.

The EGR valve - I checked it by standing under the hood, and manually opening the throttle to watch the valve. It never moves. Should I see movement in there? I can see a small steel shaft in there but that's it.
Connected to the EGR valve is what appears to be a plastic version of itself with an ecu connection. Everything is plugged in, but this plastic EGR valve looks way out of place, it's literally floating between the downpipe and the block.
Interestingly, when I removed it from the car and started it, the CEL disappeared.

True, we don't have a MAF. We use a speed-density algorithm to derive the fuel/spark terms.

The bare nipple on the VC won't harm anything, just leak oil/fumes. If the one on the intake is left off, I'd think the idle would be more like 5k. I just have my blocked off because my PCV would leak backwards under boost.

The cracked 90* elbow is a vaccuum feed to the EVAP canister, and it'll cause your idling problem if it is indeed cracked open.

The EGR can be tested with a cheap vaccuum tester from about any store with automotive stuff, just d/c the lines to the diaphram and pump it up to 15"Hg or so, and it should open up. If not, then it's bad. The mini plastic version is it's control solenoid valve, and if you leave it unplugged it'll throw a code.