Weird idle fluctuations when in 1st gear
 

Anybody have this before? My car idles just fine, 750 with the lights off, 850 with the lights on, 17 inches vacuum at both speeds. EXCEPT when I have it in 1st gear with the clutch in. The idle will settle to 850 for a moment, then start cycling to almost shutoff, then bounce to 850, then die. If I pop it out of 1st gear as the rpms are falling from 850, they pop right up to 850 and it idles normally. Idles normally in neutral and all other gears. Makes 1st gear creep in the market parking lot a real bitch! This only started recently, and I did search...

So I dug around a bit last night. Here's what I found: My idle speed control solenoid is reading 12.5 ohms at the ECU connector, which is a little bit out of range (manual calls for 10.5 to 12.2 ohms or so), AND my 1st & 2nd switch gives continuity at the wrong positions, namely, the 1st gear position does NOT give continuity like it should, but rather gives continuity in neutral. No continuity for the 1st position sensor in any other gear, only neutral. The 2nd gear position works fine.

The relationship chart in the manual shows the 1st & 2nd switch effecting turbo controls (unlikely active at idle?) and the air pump, but I don't know in what way (typical manual... juuuuust enough info to make you go WHY!!).

So I'm ordering a new 1st & 2nd switch, and will pop that in there when I can. I was wondering a couple things: Does ANYone actually know what this switch really does wrt the ECU? And is that ISC reading too far out of whack?

Thanks for any help, and I WILL post the results of the new switch when it gets in there.

Thanks!!

resistance readings are temp dependent. if it was hot or cold it may put it just out.

Yeah, that actually was my thinking. The engine was still just a bit warm (probably 110F or so), which would raise the resistance. So that's probably ok then.

Just got off the phone with a REALLY busy Ray at Malloy. Have the 1st & 2nd switch on it's way ($27.44 for the switch, a dollar and some for the relevant gasket). So we'll see if this fixes it!

1st gear switch...tells AWS not to do it's thing.

I know that's nothing to do with the problem. But how is your AWS? act funny or just cherry?

AWS bees a-woikin' fahn ovah heah, boss!

Sorry... I always tap the accel on startup, but have tested the AWs to make sure it's shooting the moon. HATE that rev up...

Plot thickens. I was erroneous in my claims that all other gears are fine. All other gears cause similar condition, that is, you put it in a gear at rest with the clutch in, and the idle dies. IF the lights are on. Or IF the blower is at 3 or 4. Or IF the rear defrost is on. Ooohhhh... E/L sensor, anyone? How do I test that lil' bastid, anyways? Hmmm....

1st gear switch affects more than AWS.

Anyways, you already diagnosed the problem.

The ISC readings are a symptom, the 1st gear sw is the problem.

About half way down I wroteup how to test the E/L and the other sensors you're working with.

https://www.rx7club.com/showthread.p...hreadid=303907

Re: Weird idle fluctuations when in 1st gear
 

what page/section?

i think i have the same problem..today was pretty damn hot, like almost 90 and i just drove the 7 for like 20 min, everything was fine but i guess the outside temp plus the engine temp was too much, it prob killed some sensor and my idle was funky letting off 1st gear.. in neutral, it would be at 1000rpm, but i do my normal driving and it would bog like crazy leaving 1st gear, sounded and felt like i was a beginner 5spd driver, it would bog and jerk..now my water temp at this moment is like 210-215f, i have the fans running at that moment and its 90 degrees outside..i would have to rev like to 2500 for it not to bog..i guess when i do the normal 1500, then let off, the idle was so messed up, it would drop to almost stalling.. it has to be the heat right?

so do you think the extreme total heat just snapped off some sensor to make it this way? cause after startup and during the spring months, (55, 60, 65 degrees etc) the car would act totally normal, only during the hot summer months is this car doing it.. i had the same problem last summer in my talon..

could be the isc?

Re: Re: Weird idle fluctuations when in 1st gear
 

Hey Dubs. I'm looking at page F-196, and it's showing the 1-2 switch (MT) having relations with the Turbo Pre Control, Waste Gate Control, Turbo Control, Charge Control, Charge Releif Control,and Air Pump relay. But it doesn't show the nature of those relations. Interestingly, it DOESN'T show a relationship with the AWS. Most curious....

Thiis is the test he's talking about.

"I tested the E/L unit by grounding the TEN connection at the diagnostic connector, and attached a small lamp to the FEN (I think this is right, but don't have my FWM with me right now) and B+ connector. With the ignition key on you can test each E/L input one at a time, plus neutral, clutch, etc. The lamp lights (ECU only supplies 20~30 ma so this has to be a very small lamp, or use your VOM in series) when the ECU responds to each input switch, thereby testing the entire circuit. Check out section F of FWM on Electric Load (E/L) Control System, around F-135 or so I think."

So if I have my DVM connected via the current measuring leads to the B+ (i.e. battery voltage) and the FEN connections on the Diagnostic box, I should read ~ 20-30 ma when turning on any of the relevant control devices for the E/L unit with the ignition on, right?

If I'm reading page F-67 correct, it's the MEN connection, not the FEN. Thanks for the tip, I'll check these tonight!

sounds right...I don't have the manual in front of me. But if what FDjunkie said is correct, you could measure the amperage.

Spurvo - how did the test turn out???

Worked late, couldn't get to it! Grrr....

Now the post is moved so it'll NEVER get seen, huh? J/K!

OK, here's the skinney so far...

With the engine off, the key turned to the run position, and the TEN connection on the diagnosis box grounded.
I measure no current between the MEN and B+ connections. If I turn on the parking lights, I read 36.3 milliamps between the MEN and B+. Turn the lights off, current stops. Turn on the blower fan to position 1 or 2, no current at the MEN to B+. Blower fan to 3 or 4, and I get 36.0 mA between the MEN and B+. Turn off fan, current stops. Turn on defrost, 36.0 mA results at the MEN to B+. Turn off the defrost, current stops. Turn on fans to low speed (relays 2 and 4 grounded) I get no current at the MEN and B+. Turn fans to medium speed (grounding which ever relay is controlled by the thermoswitch, sorry I don't have my FSM handy) and I get 35.6 mA at the MEN and B+ trerminals. Stops when the fans are turned off.

So the E/L is working correctly, which I suspected as it was modifying the idle at the appropriate times. So I wait for the 1-2 switch, and will probably order a new ISC. Kind of fun to have to rev the engine all the time at rest when driving at night to keep it from dying. Feel like a RACAR!!!one1!

More when I know more...

Ouch! 250 bones for that (I heard.)

I think I might be able to find you a used one...(probably not the greatest thing)...but you can use it for a test to see if yours acts different.

pm me...if you want to run the test.

Malloy quotes $277.38 for the ISC. Ray said he's been getting a lot of requests for these lately, so he's stocking them. Honestly, I've stopped blanching at anything under $500 or so with this car. Fender for ONLY ~$190? Hah!

Anyway, one thing at a time. 1-2 switch replacement first, then we'll reconsider.

i have a ISC ill sell you. 50 bucks plus shipping. works perfect.

spurvo - any findings on the 1-2 switch?

I gotta ?uestion about the yellow wire???

it appears to connect to a blue connector and a white connector just inside the firewall, I can't seem to locate this pin outs in the wsm.

any idea what this wire is linked too? has input for?!?

Update: (sorry it took so long, I was in Nashville)

So I was a little confused about the operation of the 1-2 switch. I received the new one from Ray at Malloy (only about $30, so it was easy decision) and tested it naturally to see how much better it would be than my old, supposedly bad one. I was WRONG about how it is supposed to operate. In fact, the switch is SUPPOSED to allow continuity across the 1st gear wires (lesee here.. that's the yellow and white wires) in any gear BUT 1st, as well as neutral. Not only do I deduce this from the new switch itself, which exhibits this behavior, but also a closer reading of the manual, which shows there to be battery voltage at pin 2K on the ECU when the car is in 1st (i.e. when the switch has no continuity), and only ~1.0 volt when in any other gear (i.e. when the switch has continuity between the yellow and white wires). Had I read that carefully, I would have seen that the wiring diagram is a little "hazy" here, in that it implies that there would be continuity between the yellow and white only when you are actually in first, rather than the other way around.

Following the logic, the switch provides continuity between the red and blue wires when the switch is fully pushed in, that is, when you engage second gear. From the ECU test procedure, there should be ~1.0 volt at pin 2L when in second gear (i.e. when there is continuity between the red and blue wires), and battery voltage when in any other gear or neutral (i.e. no continuity).

So my 1-2 swicth is not the problem.

More: I tested the ISC resistance on dead cold engine. 11.6 ohms, right in the middle of spec. Might be ok, then. BTW, the way I'm testing this is to connect the voltmeter on resistance setting between the blue with green stripe wire, pin 4Q, on the top connector for the ECU, and the black with white stripe, pin 1B, on the bottom connector for the ECU. This bridges the common ECU connection for solenoids (#16 in the round circle on page B1a of the wiring sheet) and the appropriate pin for the ISC control. Quite the contortion act to get down in there with a light, the book, and the ohmeter!

I tested the AWS solenoid as well (it's right there), and it read 12.6 ohms (brown with yellow stripe, pin 4P, top connector, opposite side from the above ISC wire). Out of spec by around 10%. Hmmmm... so I went and disconnected it at the solenoid to see if this was the problem. Nope, I still get a dying idle with an electrical load when I put the car into gear. Sigh... kind of nice that the rpms don't shoot for the moon in the morning, though. Seems like the driveability is a little better too? Hmmmm some more!

So I'm back to square one. Maybe air pump circuit related? The relationship chart shows the 1-2 switch effecting the air pump somehow (but how exactly, is of COURSE not revealed), but then am I sure it's 1-2 related, and not neutral switch related (dies when taken out of neutral)? I must admit I've not tried checking the idle speed with the TEN connection grounded to see if it's correct, so that's the next easy thing to check (like maybe the ISC is able to control idle, but only barely, and the E/L shoves it out of its range of adjustability? Hmmmm....).

I can't believe you've read this far!

Dubs, which yellow wire where, exactly? blue and whire connectors inside the firewall are ECU connections, yes? Although with the fan recall wiring update, I think there's an extra chunk of harness involved that's not in the wsm, which may be your confusion... if it's the same yellow wire listed above, then there's your answer! 1-2 switch...

have you tried adjusting the air bleed socket?

Yeah, I did that. idle went up a little, down a little as I move the socket in and out with the screwdriver. Just like it's supposed to, right? And grounding the TEN connector with the engine running makes the idle go up just a bit, to say 800 rpm (lights and loads off). Anyway, not sure what the problem is STILL! It's perfectly driveable, except in the dark you gotta play with the throttle more. Sigh...

I had too ;)

Thanks bud, you did answer my question. I haven't had the chance to test yet...

I'm wiring an E6X (haltech) and the "how to" for tranny harness, just says cut these wires out of these connectors.

I've got the (tranny) harness fabbed, but I wanted to know what I was cutting and why. The Yellow wire from the 1-2 switch is cut and is the only one that isn't connected to anything.

Cool! Minor update: Now the idle wants to live above 1000 rpm unless I wilggle the shifter a bit. Went under there and tested the neutral switch. Most inconsistent thing I've run across! Put it in neutral, the switch has continuity. Put it in gear, the switch loses continuity. Put it back in neutral, the switch remains discontinuous (neat word, huh?), I wiggle the connections I'm using to test, then there is continuity. Oh. Sticky switch?

Ordering new neutral switch after I write. Further, the 1-2 switch is not all peachy as well, in that it behaves correctly in 1st and neutral, but putting it in 2nd only gives a blip of continuity, not continuous. So that needs replacing like I thought. Too damn bad the switches are at the TOP of the damn tranny. I forsee a difficult weekend ahead... more when I know it!

might as well get a flywheel (and clutch??) while you're in there :D

just a thought ;) BEST OF LUCK TO YOU!

Upitty date: So as I feared, the new 1-2 switch did nothing to fix the problem. The switch was indeed not giving continuity through the entire range of the 2nd gear position (you push the switch in a bit and get the cut for the 1st position, then the switch gets a little harder to push in, that's the 2nd position close), and now it works fine. For those of you who don't know, the switch is the 4 wire one on the pass side of the tranny, just above the speedo sensor, which is itself just above the frontmost bolted-on cross brace. Anyway, it's a 15/16" wrench, or 24mm (they're the same), but you need to remove the cross brace, remove the bolt on the speedo sensor and swing the sensor mount tab down, and probably bend back the heat shield for the cat as well. All that, and no better.

So I got smart-ish and tested both the neutral switch and clutch switch connections at the ECU. Turns out the neutral switch is flakey at best, giving intermittant contact in neutral, mostly only with the shifter just about to go into 1st. The clutch switch doesn't switch anymore, just sits and does nothing. Oh. So a new one of each are on the way, and from what I've read on this forum, the clutch switch failing can be the cause of many an idle problem.

Last issue: anyone have ANY idea how to remove the neutral switch withOUT removing the transmission from the car? The switch is right at the top of the tranny, just in front of the plate that is in front of the shifter mount. I can get a crow foot on it, but I can't turn it as it binds up against the body of the tranny. Anyone worked this one out yet? I think I'll try grinding some clearance on the crow foot, but I'm not sure this'll get me anywhere.

Kinda wierd that ALL of the tranny related signals to the ECU have failed. I'm REAL sure these will be the last sensor failures I evar have... ;)

Spurvo,

Not long ago, I saw a post showing some tools. There was a set of Craftsman wratcheting end wrenches. I thought that would be a pretty nice item to have. I don't know if that tool would help you, but I thought I would mention it.

I'm still with buddy!

Man that really stinks that you've replaced some failed switches and still nothing has improved.

the wratcheting end wrenches that Adam mentioned are really nice to work with...again I have no idea if these will help you???

check out my wiring project...

http://www.nopistons.com/forums/inde...0&#entry554955

I'm going to need to tap that speed sensor you talk so fondly of... ;)

**couple pics if you scroll up.

Have you checked the clutch switch? I know it can cause various idle flakiness.

Dale

dc, you bet! Dead as my.. well.. we won't go there ;) Anyway, a new clutch switch is on its way, so hopefully that will cure some of the ills.

The neutral switch is right at the top of the tranny. I wonder if there's room to get the ratchet box end in there? Hmmm.. I'll get a 15/16 (if Sears has one) and give it a whirl. Thanks guys!! I'll be sure to let 'yall know!

Dubs, ya maniac! Rewire for different ecu?

:cool:

Cool deal - I had a buddy whose FD had a bad clutch switch, cause some SERIOUS weirdness with the idle. Seems like it wouldn't be such an important input, but I think the computer flips out when it's not there. Go figure.

Dale

upidaytimus... ;)

Well, YAY for me! Clutch switch solved the problem about 98%. Put the new $9.75 switch in, and the idle fluctuations with the electrical load were almost completely gone. There was a little hunt left though, so I got creative.

I went to Sears, got a 3/8 drive 15/16" deep well socket. Went after it with a dremmel and cutting wheels (two screwed onto the end). I cut one of the sides off of the socket, basically along the length of two of the "points" on the side. Went up about an inch, then made a cross cut. Any of you who've used one of these for O2 sensors know what I'm a talkin' about. So i went after the Neutral switch. The missing section went right over the wires, and the socket stuck out over the edge of the tranny just right to get a socket wrench on it. A nice firm tug later, and off came the switch. YAY! No dropping the tranny...

The old one had black goo along the sleeve for the ball, and sure enough, pushing the ball in only occaisonally gives continuity. Replaced it using the same tool. Very easy, very nice. 15 minutes tops.

I tested the connection (green with white wire on the lowest connector on the ECU) and sure enough, there is continuity every time I'm in neutral, none when I'm in gear. Yay some more (I might be happy here...). :D

Now the car purrs absolutely steady when putting it in gear with the lights on. Unflappable.

Oddly enough, fixing these switches has made the shifting and driving easier. I attribute this to the neutral switch not sticking anymore, and the clutch switch allowing the ECU to correctly allow the engine to decelerate into the next gear. MUCH easier to drive, less bucking and weird behavior between the gears.

So. Problem solved, all for less than $70.00. So, you guessed it... YAY for me!!!

Addendum: 15/16" is the same as 24mm, not 23mm, like I mistated above. Sorry 'bout that. The 1-2 switch and neutral switch (and the backup switch for that matter) are all 24mm, or 15/16".

That s great that you finally solved the problem, and the car is running like its supposed to. Maybe its time to upgrade that intake :)

Congrats

HAH! One step ahead of ya! Got it done last night. Not sure I like that wierd off note yet, but I think I'm liking the temp numbers I'm seeing at the mouth of the primary turbo. Runs ambient of the freeway now, which it didn't before, but I'll post all that in your thread, adam ;)

Now it's on to the MONSTER axle hop during regular driving when the car is cold. I'm guessing bad diff mount bushings, maybe control rod (or whatever you call the longitudinal member!), and a not so nicely resurfaced flywheel from the reman. Sigh.... at least it idles ;)

Please post your results on my thread. I am very curious to hear what happened.