Rpms drop when clutch pushed in!!!

[DSM Chase]

I have had this problem now for months... I cannot figure it out all my link numberes are good. When the clutch is pushed in while changing gears or at a stop light the rpms will drop, Also when i rev it up and let off the gas it rpm drops.... sometimes even shut off . My ISC motor tested good all coils at 29 OHMS...

Also my BOV is resirculated...
7lb lighter than stock flywheel
simulating idle switch on LINK
Link idle setting at 1k
battery at 13.5v

TPS is at 0.68 at idle and 5.0V at WOT so its good?

ECMLINK Log file.... Its towards the end of the log i am driving down the road and then when i go to turn into my driveway when i pushed the clutch in it happend... Im going about 13MPH when it happens drops to around 400-500RPMS then shoots back to 1000...Log is at the bottom In the Attached Files..

Quick video of it rev RPM dropping, does same thing with clutch in or in neutral


RPM Drop ISSUE - YouTube

 

[DSM Chase]

My car idles fine it's just when I get on the gas and then let off or push the clutch in while changingin gears they drop... Also I can't find the tps display in link?

 

[TrystanGST]

It should be an option under displayed values. If not, then you'll have to make sure Link is tracking it by adding it to captured values.

I mentioned idle because fixing that solved some driving issues I had as well. But it sounds like your RPMs just drop too quickly when you lift?

 

[DSM Chase]

yes they drop very fast if i dont get back in the gas or put in in a gear it will drop or die within a second

 

[TrystanGST]

I don't think the lighter flywheel is the problem, but it is certainly making it worse. When you depress the clutch and put the car into neutral, car should go into idle. Sounds like yours isn't. That's why I recommended all that throttle body idle adjustment stuff. If you leave your car idling, hook up Link, and turn off the TPS adjust, do you still see idle sw set to 1-?

 

[pazsion]

BAd throw out bearing.

Most crankwalk stories begin with "my pedal drops to the floor when i turn" left, 4g63. right, 420a. This happens because the steering linkage is allowed to push against the play in the crank. And it moves. Causeing the clutch to be pulled or pushed. The pedal will drop or pull up on it's own. It may or may not make a noise or vibration.

I think the clutch is not fully disengauging. a bad throw out bearing could be part of this. It'll cause there to be more friction when not under load. But when engaugeed things could operate seemingly fine. Until it completely fails.

Also check for leaks or low clutch fluid. If you notice bubbles or there is no fluid...it won't engauge or disengauge properly. If there are bubbles you'd have to drain out what you got, fill it and bleed it, like brakes. kinda. You should check for leaks etc while do this.

Syncros gone bad. If these get too warn out, either because of speed shifting negligently, or improper fluids being used...they'll move out of their proper location, or dislodge completely...rubbing against things and causeing a situation similar to what you describe. But often in this circumstance it would also be extreamly difficult to get in and out of gears. And it wouldn't feel like it's set into gears. Maybe even jumping out of gear.

Recirculateing boosted air? If you don't adjust this right...when you let off the throttle you'd flood the engine with air. stalling it. You could adjust the idle a bit higher or make the fuel richer...

 

[DSM Chase]

it does it in neutral occasionally, I Will hook up my link in a little while and check it out... So the TPS display Is it a raw value or does it just say TPS in displayed values?

The transmission is a brand new shep stage 3, Everything has less than 1500 miles, the 6 puck clutch, Trans,throw out bearing, Slave cylinder, Xfer case, All of it

 

[pazsion]

oh, there is also a Multi purpose relay...I think turbo's have this too...In the n/a's i believe it's called a MFI relay.

I've had similar issues before when these have gone bad. The ecu will also use this circuit to kill the engine if there is an over voltage, or something it's told is crucial shorts out or becomes faulty. crank sensor, cam sensors something not hooked up right etc.

This is also part of the ignition system.

Have you checked any of the fuses or relays under the hood?

Can you make & link a video?

 

[DSM Chase]

also just a minute ago i got a Crankshaft Positioning Sensor Circuit Malfunction on Link, I cant get it to come back up i cleared it amd hit update i even restarted it and it wont come back up. Could a CPS Malfunction cause rpm drop?

 

[99eclipse420]

Just throwing this out there, did you re-program, for the upgraded injectors, could it be possible that you are flooding the motor???

 

[EclipticalGS]

Did you adjust your BISS, ISC position and TPS when you made the switch to 1000rpm idle?

There are how-to articles on this site that explain the adjustments needed to BISS screw (get a new oring as well) and setting the tps switching point, as well as the base timing. Ecmlink has a base timing mode that makes this really easy.

Ensure your tps switch is set with a feeler and multimeter, then hit the base timing check box in ecmlink and adjust the BISS until it matches the idle you set in link (1000 in this case), and then set base timing to 5* btdc (base timing set only applies with use of a 1g CAS). Then uncheck the base timing box.

Now, log your normal idle and you should see a ISC value of 30 IIRC, and make sure the gram per rev value is correct (not sure of this value of the top of my head) but 25 sounds right. Correct me if I'm wrong on the values, if someone could post the link to that howto that would help

Lastly you can fine tune the BISS under normal idle to try to match the ISC pos and the gram per rev values previously stated.

Update. Read this article where it talks about ISC position and learned idle adjust.
http://www.dsmtuners.com/forums/newbie-forum/321158-biss-adjustment-iac-position.html

Make sure you first set the TPS switch with a feeler (not in the article posted above) then the 98-99 eclipse/talons have no timing connector ground so dsmlink must be used there's the check box. Adjust your BISS so that all of the values stated in that link are close as possible (grams per rev isn't included but you should see 20-25) also Learnedidleadj value does take a minute to change so don't be discouraged if the BISS does nothing immediately

Hope this helps

 

[TrystanGST]

^ has a good point. I set my TPS etc for my 900 idle. When I was having a lot of issues it was due to my CAS/CPS wiring. I had gone from the odd 95-96 two sensor setup to a 1G CAS, and once I got it wired properly it resolved a myriad of issues. So a CAS/CPS sensor could cause issues.

 

[DSM Chase]

Im starting to believe its starting to walk or The CPS is bad, for all those who keep telling me to log my grams per rev, ISC, and TPS, all of those are good. My ISC is at 30 At idle the BISS o ring is brand new. The grams per rev at idle is 0.25...

Im about to lay under it and check for crankshaft end play

 

[EclipticalGS]

Well I didn't even see that you had a cps harness ECL...that could be a problem. Can you get a log of your car fully warmed up idling, and then press the clutch in? That would help a lot, log as many values as possible. I doubt your engine CW'd its got the split thrust bearings. You can do yourself a huge favor and just switch to the 1g hall effect CAS and the Magnus 1g CAS harness. That is if the CPS is faulty. My car used to die randomly from intermittent cps signal.

 

[DeadlyScone]

This may be a silly question but, is your BOV recirculated before or after the MAF?

IDK if it matters if you have a GM or just a 2G MAF but my BOV was recirculated after the MAF and it would do the same thing yours does. i moved it upstream so it recirculates before the MAF and it doesn't do it anymore.

 

[DSM Chase]

I found this video, Its of a 1G but its exactly what mine does sometimes....
Video - TinyPic - Free Image Hosting, Photo Sharing & Video Hosting

Anyone still with me on this?

Could this be a BOV issue? Like if its not functioning properly? but it does it even if there is no boost built

Well I didn't even see that you had a cps harness ECL...that could be a problem. Can you get a log of your car fully warmed up idling, and then press the clutch in? That would help a lot, log as many values as possible. I doubt your engine CW'd its got the split thrust bearings. You can do yourself a huge favor and just switch to the 1g hall effect CAS and the Magnus 1g CAS harness. That is if the CPS is faulty. My car used to die randomly from intermittent cps signal.

So could a bad CrankShaft positioning censor cause the rpm drop sometimes?

 

[VRP]

This shouldnt be crankwalk, If u turn left and ## clutch pedal is still good and u dont shut off, Its not walk...

 

[EclipticalGS]

This could be many things I stated before the ISC, tps, BISS you sound pike you have that covered. This could also be a bad ground wire somewhere, if you've relocated tour battery you can't just use the a ground in the trunk, front o2 sensor acting up, crank sensor/ cam sensor, maybe you need to use the maf clamp setting in dsmlink, also if you raise your idle, you must set the FC coast value in dsmlink to the difference of the stock idle, in your case 1000-750 equals (250).

This thread explains the maf clamp idleair [ECMTuning - wiki]

Also you may want to use the simulate idle switch position.

Try all three of these settings and see if that helps. Set your FC coast to 250, check idle air clamp and play around with values, and try the simulate tps

Also if you have cams, they may need to be dialed in, what's your vacuum reading at warmed up idle?

 

[DSM Chase]

so my coasting fc offset should be at 250 right? And im at a -25 vaccum at idle... Just did a boost leak test no boost leaks, BOV is good also, everything holds at 30PSI no leaks anywhere...

 

[EclipticalGS]

Yep coasting FC is set to 250. Something does sound weird about -25 vacuum at idle. Stock dsm pulls 20-22, usually any type of performance mods take your vacuum down.. sounds like not enough air is getting past the ISC or TB. Did you try the maf clamp feature , or the simulate idle switch yet?

Honestly, I've found with use of a lightweight flywheel, and other intake mods that maf clamp is almost essential. My car has no ISC, although hard to start in the cold (which I never do anyways) maf clamp and coast fc is the only thing keeping my car from dying stoplight to stoplight on decel.

Also get a log file of your idle if you can. It would make things easier on my end

 

[tfaulk21]

I had this problem in my na ###### not what your having just a thought. Is your AC on when this happens cause mine would be on and it would do that sometimes even stall my car out

 

[DSM Chase]

Ok, well my v3 lite doesn't have Maf clamp so ill mess with the fc offset later today, I may just bite the bullet and go Evo 8 Maf or speed density...

 

[DSM Chase]

fc offset at 250 did nothing... Same issue

 

[EclipticalGS]

Well shoot me a log file of when your car bogs so I can tell you for sure if your ISC pos dips down at the same time. That's the only true way to check

 

[gsxtreme1987]

Any updates on this OP? You figure out the issue?

 

[DSM Chase]

Car still has this issue, Although i daily drive it its not that bad... Ive noted that it Does it worse on a rainy day... So that makes me lean towards a MAF issue.