I've got a 98' RS-T. What it's doing is randomly, if I've driven it for a while, maybe 30 mins or so... when I come to a stop or depress the clutch to let it idle the rpms drop down to around 500 and sometimes shuts off. When it does that I'm only reading around 8htz of vacuum and around 12-12.5 AF ratio.

I checked the CEL and it came up EGR, Ignition Misfire, Speed Sensor, and IAT.

The car is turbo, ebay T3/T4, walbro 255hp, vortech s-fmu, stock injectors, and electronic voltage clamp. Engine is out of a 95 Eclipse. For some reason vacuum is only around 12-15 at idle and it fluctuates.

I have removed the EGR valve and solenoid (explaining the EGR code). The speed sensor is broken so the ecu is not reading speed at all. I'm pretty sure that the IAT is just bad and it has a random miss I can hear at idle and it feels a little sluggish when normal driving not in boost.

The dropping rpm is completely random. Sometimes I can drive for a hour and not have a problem, and then other times it just does it at a random time while coming to a stop or a slow turn. When I let it sit for a while, it will start and idle fine until I drive it for a period of time and it does it again.

I bought an IAT today and attempted to install it and apparently the sensor is suppose to fit a 98 when it has a 95-96 plug so I have to either find another sensor or grab a plug off a older model. I'm picking up a egr solenoid the next couple of days just to satisfy the CEL, and I have a speed sensor I haven't swapped yet since it's not driven daily.

Any suggestions or previous experience with an issue like this is greatly appreciated.

For one, get a new speed sensor. With no speed sensor, the ECU will not know when the car has come to a stop, and it will not adjust the IAC appropriately. This typically results in a dropping idle.

Also, pull your IAC, clean it thoroughly with either brake cleaner or electric motor spray, and reinstall. May also want to OHM out the TPS and make sure it is still to spec.

What should I be reading on my tps?

Originally posted by eclipserstturbo
What should I be reading on my tps?

TPS resistance should read between 3.5 to 6.5 k-ohms if its in good spec.

+2 on the speed sensor. Mine was damaged from an accident and car would shut off randomly when I came to a stop.

Well, guess I'll be swapping out speed sensors today due to popular demand. I'll let you guys know what happens.

Okay, so today I installed the new IAT and connector, egr solenoid, and speed sensor w/ a 95-96 connector. It supressed the CEL, however I am still not reading speed at all. Not on my speedo or on the turbo timer. Any ideas on what to try next to read the speed? It's not that big of an issue since I know speed by rpm, but I would still like for it to work.

I haven't driven enough to see if it still drops rpm yet, but I am about to embark on that journey in a few minutes. I'll keep you guys posted. Thanks

pull the speed sensor back out, carefully remove the pinion gear, and spin it in a drill with the car on. Does the speedo move? Then the sensor is good.

If that's the case, stick your finger down in the speed sensor hole and feel for the speed sensor ring gear. If it's loose, pushed off the diff, missing, or you can push it around with your finger, then it's probably not engaging the speed sensor pinion gear and not spinning the sensor.

Okay, took the car out today. Did great the entire ride to work. Did fine the entire ride to the meet. Almost the entire ride home, it tried to die everytime I tried to let it idle.

I haven't attempted the speed sensor trick yet. I'll give that a shot tomorrow. However when I installed the sensor, I realized that the gear that clips to the sensor is just kind of chillin in the tranny. I don't think its actually in the gear. Should I take the new one out and unclip the gear and try to push it down in the tranny, then put the sensor in?

I've noticed that when it tries to die, if I just push the pedal down a little bit to around 850-1000 rpm it runs okay but as soon as I let the pedal go it'll die. Almost like it's not getting enough air in. My A/F is at around 12.5-13 when it does it.

I finally realized today that my thermostat is stuck open. When I got home I cut the heat off and the fan for the ac condensor and the temp gauge went from below the "C" line to the normal line after a few minutes of idling. The only thing cooling the radiator is the condensor fan because I didn't have enough room to put the smaller fan on the driver side. So I have to fix that tomorrow.

hey I was wondering did you ever fix the problem??? Because I am having same issue with my eclipse and I can not seem to find the problem at all. I thought it was vacuum leak at first sealed the leak, still having the problem and I do not know what to check next