TristanTII

Ok, so a recap of my idel problem, car idles fine at start up, once it warms up its gets a little rough (jumping up and down) If i've been driving hard (lots of highway driving, ect) it will stall sometimes.

Changed plugs and Fuel filter as part of routine maintaince. checked air filter

I checked for intake leaks using some WD-40, didn't find any.

tested the BAC by unplugging it, if cold the idle drops, still rough, if warm, it drops then stalls.

So I'm guessing it is a bad O2 sensor or bad air intake thermosensor, or both. But a couple things are bothering me about this, and I thought I run it by you guys before getting the parts and changing them out.

Can these sensors go bad without causing a warning light to go on?

and a more general question, how is the car supposed to idle at all if the bac is unplugged? Once it's unplugged doesn't it close, how would the engine get any air? Or to put it another way, if the ECU is getting bad data from a sensor, and this is causing the rough idle, wouldn't unpluggin the BAC fix the problem, since the ECU wouldn't be controlling the amount of air intake anymore.


Thanks for any help, and for making it through my ramblings

HAILERS

Ronald Regan was called the Great Communicator. I'm just the opposite. But I can tell that you desperately need to down load section 4A of the free factory manual at http://www.iluvmyrx7.com or at John Giblson site at fc3s.org(can't remember their url , . You have a basic problem in that you need to set the idle and the idle mixture. Its in section 4A. Easy to follow instructions and graphics. Its free. If I sit here and give you instructions I guarantee I'll leave something out. You have to jumper the initial set coupler, adjust the air screw and the variable resistor to set the idle, then unjumper. Idle should be 750rpm with the initial set jumper in. When you unplug it the bac, which obviously works, will keep it there when you put a electrical load on the engine. Theres nothing wrong with your car that setting the idle will not fix(most likely). The 02 sensor does not control the fuel mixture at idle. Drop that subject like a hot potato. Its normal on your year car not to get a fail signal unless the darn plug practically falls off. One more note, the bac is not there to set the idle. Your car should idle with the bac having gone **** up. The bac maintains the idle when a load is put on the engine like turning the a/c on etc. Remember, its free and its at http://www.iluvmyrx7.com FREE. (OOPS, THEY ARE WORKING ON THAT SITE AT THIS MOMENT TODAY, Nov, 25th...try this site http://www.fc3s.org/

TristanTII

just about all my info for trying to fix the problem came from this page

http://www.teamfc3s.org/info/articles/idle.html


I tried setting the idle speed before, using the initial set connector, but every I jumped it either the car stalled, or the idle screw didn't seem to have any effect. Maybe I'll try again.

TristanTII

If my check engine light Is Not on, will I get any ECU error codes, I assumed not, but if I could, I'll make up a lil tester and give em a check.

HAILERS

Does your car really have a engine check lite? I was of the impression that the 86=88 did not have one. I only have 86=87 cars. No engine check lite. Go out to your car and pull the plug off the air temp sensor on the r/h side of the dymanic chamber. Get a engine check lite? I know if i pull that plug off, the home made diognostic lites that I made from the teamfc3 site, will flash a code. I'm serious about whether or not a 88 has a engine check lite.???????????????????????? By the way, since you have been trying to set the idle and the air screw has no effect.....have you tried turning the variable resistor towards rich to see if that helps? Could be your going to have to remove the throttle body and set the throttle plates per the secton 4A. That should give you some more air. Or if you really want, there is a throttle stop screw on the front of the throttle body. It is held with a 8mm jam nut and the screw is only about a quarter inch long. its the passenger side of the tps, just a couple inches away. Might be covered with some goop so you might not see the slot in the head of the screw. I think you should try this last item right now. P.S. if you do mess with it, it WILL throw the tps setting off just a tad. Do you know where the variable resistor is?

TristanTII

I just went out and checked, and nope, no check engine light, I just kinda assumed there was one because we've got like a 100 little lights up there.


So I guess i'll try and head out to radio shack tomorrow to pick up the parts to make a error code checker, see if anything's gone bad.

TristanTII

Checked my ECU codes today, I didn't have any.

1.Like some other guy with a similar probelm on here having either my Headlights or Blower on (not AC) does help my idle problem a little, noticable, but nothing dramatic.

2Was runing some errands today and found a few things that make the idle worse (more likely to stall)

2a. going faster on the highway, if I'm doing like 80 the whole way, I'll almost always stall if I stop at the end of the offramp. As opposed to going 60 or so where I have a fair chance of not stalling.

2b. Starting up the car warm, ie after I finish filling it up at the gas station, or running into a store, I'll almost always stall getting out of the parking lot, but will be a little better once the engine gets warm(hot we are talking about 7s here)

3. holding down the gas a little (bring it up to 800ish), pretty much eliminates the roughness.

#3 makes me think that it isn't a air intake leak or a fuel problem, as I assume both of these would still be causing problems at 800 rpms.

I that one of the sensors that the ECU looks at for idle info is bad (Crank angle sensor, TPS, water thermo sensor, water temp switch, air intake temp switch, ignition switch)

Because of #2 I'm guessing it's either the water temp sensor, or air intake thermosensor.

I'm going to check the crank angle, and TPS this weekend. As well as try and check the output of some of the sensors while I'm grounding my ECU.

any advice for anything I should check while I have my IC off? thermo wax? can I / should I disable it, how would I?


And that's the end of another long (boring post) (unless you really dig rx7 idle problems)

Thanks again


PS. stopped by radio shack today to get a new DMM as my old cheap radio shack one got busted up. Picked up a nice one on sale ($30 or $40) it has software, and an output including cable for hooking up to a PC, which could be all sorts of usefull, especially if you have a laptop.

HAILERS

Just a reminder that at http://www.fc3s.org/ there is the download of a 88 fsm for free and in section 4a, at the beginning, there is a section called Control Unit, and there should be two pages that show what a readout for each pin on the ECU. Really seems like the idle is not set right with the initial jumper in, or the bac, even though working is'nt reacting fast enough to keep the engine from stalling. If you have the jumper in and can't get the car to idle at 750 using the air screw and the variable resistor, and you have no air leaks as you said, then maybe your going to have to take a look at the throttle body adjustments or crack the butterflies open a tad more using that idle stop screw. Any way, have fun with the meter.

Chance

What is the air intake thermosensor and where is it? I checked my codes and got one back for it. Thanks.

TristanTII

went out last night and tried resetting the Idle with the initial set jumped, and noticed that my variable resistor had been messed with. Tried adjusting with both the bac and VR, almost no effect.

going to retest all those components with my new meter