Hey guys, this is my first post on here but only because the car I'm asking about is my girlfriend's. I do a lot of work on cars, including hers, but know my limitations when it comes to the tools I have and my knowledge. I'll try to summarize the keys points of the issue that I'm hoping someone here may have suggestions for causes/fixes.

Car: 2005 Nissan 350Z @ 65k miles with bolt on mods and a tune. No turbos, supercharger or significant hp improvements.

Work being done: Clutch replacement. Original clutch was still in the vehicle but started slipping. Purchased replacement clutch kit from Z1 with mid-weight flywheel, full face clutch and mild pressure plate. Nothing crazy. Since I don't have a lift, I had a local, very reputable mechanic do the work.

Issue: Clutch was installed with no issues. Went to fire up the car and it starts fine but won't idle or rev properly. If left to idle, RPMs fluctuate up and down in a rhythmic pattern like someone is revving the car. Clutch was pulled apart at least 4 times now to verify installation and alignment. The mechanic even brought in a local import mechanic to look at it and he brought with him a Nissan tech that he knows. Both verified the installation was correct (crank to flywheel alignment) and confirmed the flywheel from Z1 matched the factory flywheel regarding perimeter notches for the sensor pickup, diameter and gear tooth spacing. Crankshaft position sensor was replaced twice with sensors from 2 different manufacturers (Hitachi and Duralast) with no change. Procedures were ran several times for the throttle body relearn with no change.

We are all at a loss as to what could be causing this issue. Anyone with a similar experience or knowledge on this? Any help would be greatly appreciated.

Our next step is to reinstall the original flywheel with the new clutch and pressure plate from Z1. If the issue persists after that, I can only suspect that the problem is electrical.

 

Have you tried pulling the codes yet? Even though the SES light isn't on, there may be a stored code.

Other than that, just random guesses - fuel pump? MAF sensor?

 

Thanks Heel. Codes were pulled but I don't have the exact list. I remember discussing them with him and most if not all were related to the crank and cam sensors. He cleared everything out earlier today to see if it would make a difference but the car ran the same.

Your random guesses make sense but that would have to be a major coincidence. Car ran fine prior the work and he never touched that stuff. I'll certainly keep those in mind but hopefully we don't get to that point...

 

Is it possible when they were torquing the flywheel they turned the engine backwards and jumped the timing chain?

 

Sounds like classic crank position sensor (abbrev. "CPS" in this post) issue(s). There are tons of posts that start with "I just changed my clutch and flywheel and now.... FUBAR."

Double check all the codes again. Recurring P033x codes with two new sensors (despite not being OEM parts) usually indicates a mechanical issue (typically misalignment) or that the sensor is in some way getting erroneous positioning reads possibly due to an electrical short such as...

Simple things first: check the harness going to the CPS, these can get brittle and suffer wire breakdown or the pins in the connector itself get gunked up (especially from the first time it's been pulled off - old pins/wires can get pulled loose and/or gunk shoved into the contact when reinstalled). If it "looks" OK, get some electronic contact cleaner (don't use caustic cleaners like throttle body spray, it needs to dry clean and fast) and clean the connector with spray and wipe up any residual dirt/grime.

If that all looks good, need to ask: How was the flywheel installation checked? Was it removed and checked that it was positioned correctly? Rare, but not impossible to mis-align the flywheel to crank. The bolt circle is consistent but can be installed one hole off. I've heard of a time when the crank dowel was flattened or pushed through making it next to impossible to assure the FW was properly installed. (Which explains why this piece is pretty readily available.) Obviously, this requires teardown of the entire trans/clutch assembly. Again, not likely, but a slim chance of the FW being misaligned.

Comparison between the stock FW and new one. You mentioned the ring gear. Is it possible you got the wrong (or inferior) part? Is it tooth for tooth (exact number) identical? I've found that non-OEM parts - even the known good ones - can sometimes be wrong and a simple one tooth difference will still allow the motor to crank but the crank timing is still off by a few degrees, enough to cause rough running, hard or impossible starting.

Finally, use only Nissan branded crank and cam sensors. Hitachi did make them for Nissan but the OEM spec units seem to be more robust and accurate; especially the "new design" units with the metal sensor covers. These are available from any online Nissan parts shop, e.g. courtesyparts.com

Good luck, please post your end results to close the loop for others seeking advice on the same issue. (And believe me, probably 7 of 10 requests for help never have an end "fixed and how I did it" followup.

 

Thanks for the responses so far guys.

For Ponyryd, not impossible but highly unlikely. This guy is pretty good and has done a lot of clutches on different performance cars. I doubt he would make that mistake.

MicVelo,

• I would tend to agree on the CPS and really that was the first thing I went after during our discussions. The original CPS wasn't bad but we replaced it anyway just in case. All three had the same result. They were all checked with a multimeter and had the same readings.
• I'll grab codes after he swaps the old FW back in, assuming it's still running the same. If that's the case, I agree the next main culprit is the harness. Man I hate electrical problems...
• As for FW alignment, it was literally removed at least 4 times and checked, even by the import mechanic and Nissan tech. I wasn't there when they did it but I would hope they weren't all wrong. Probably 80-100 years of experience under that car at the time verifying alignment. One funny thing to note on this point is that when he initially removed the FW, there was never a dowel pin in the crank. Just the hole where it is supposed to be. Not sure that really matters though as long as they ensure the small hole on the FW aligns with the crank hole for the dowel.
• Regarding the FW comparison, all 3 of those guys compared the 2 and took measurements, even interlacing the gears of both and rotating them to see if there was any tooth binding. Nothing. Everything checked out well.
• I hear ya on the sensors. As mentioned above, my gut tells me this is electrical but should know for sure tomorrow when he gets the old FW reinstalled. I'll let you guys know what I find out.

 

Were your replacement crank and cam position sensors OEM or aftermarket?

 

Cam sensors weren't touched. I assume they are original but would have to verify to be 100% sure.
Crank sensors tested were both original and aftermarket (original, Duralast and Hitachi). All were tested with a multimeter and yielded the same results both from the meter and when installed.

 

For whatever reason, the Z is very particular when it comes to those specific sensors. Even though they may test the same with your multimeter, non-OEM will still cause problems.

 

Ok, so here's the latest... Original flywheel was reinstalled with the same result. Engine starts but throttle continues to surge up and down quite a bit when left to idle. The mechanic borrowed a Nissan scanner and did some investigative work. I'll need to get the codes from him (we just spoke on the phone) but basically everything is pointing to the throttle body or something that is causing the throttle body to do this. There is a suspicion that with the tune that was previously conducted and the fact that he disconnected the negative terminal on the battery that something happened as a result. This is pretty much as far as he can take it. I'm going to try and contact the shop that did the tune and see if any of the stuff that was done could've impacted the tune itself. It shouldn't have especially since we've disconnected the battery in the past with no issues, but who knows.

Not sure where to go with this now but it's getting really frustrating...

 

The more I read on this issue the more frustrated I get. Lots of complaints about this surging throttle body issue but most start with people cleaning the TB or MAF. A couple I've seen started with disconnecting the negative terminal on the battery, just as the mechanic did for the clutch replacement. When the relearn procedure doesn't work (which my mechanic tried multiple times), people start throwing lots of money at it up to and including complete ECU replacement. Really??? I hope this doesn't turn into that.
No offense to you 350Z guys, but I'll gladly stick with my Corvette. My girlfriend can keep this thing...
I'll continue to post as I learn more.

 

Might be worth contacting a decent tuner to see if a battery disconnect can cause a change like this. I really don’t see how it could, but worth a call to ask I suppose.

 

I don't think there is Any Way to Cause a Proble to the ECU, or the Data in the ECU just by discounting the Battery.

And Certainly having the Car Tuned before would have No Affect Either........

 

I fully agree, but it seems like this is what he’s thinking. Only way it could be an issue is if the tune doesn’t allow a stock throttle body relearn, and it needs to be relearned by the tuner….dunno though, tunes can do wacky stuff sometimes.

 

Ponyryd, that's exactly the concern the mechanic had with the tune...that it won't allow the relearn procedure to take hold. Granted, he's an excellent mechanic but also admits he's not a tune specialist. As a result, I did call the shop that did the tune. Big shout out to Hal at Dynosty. He was very helpful and left the door open for further questions as I continue to troubleshoot. I didn't ask specifically if the tune would prevent the relearn but he confirmed the tune itself wouldn't be causing this or would have been affected by the battery disconnect. He also gave me some possible procedures to start with that I haven't read about yet. One interesting point that I brought up with him was that the car has been running very rich for a while now. We just always thought that was normal due to the tune. He confirmed that is not the case and the tune they used shouldn't be doing that. Not sure that little tidbit has anything to do with this issue but at least I know it's not normal and can work to fix that too.

My next steps... Since we know the clutch/flywheel isn't causing the issue, I asked the mechanic to put the new flywheel back in and button everything up. I don't want a mix of new and used parts installed or have to do this again in the near future just to replace an old flywheel. Although the idle is f'd up, I believe I can drive the vehicle the 1-2 miles to my house. At that point, it goes in the garage and I start methodically working through relearn procedures and component troubleshooting.

I'll try to keep you updated on the process. I do realize and appreciate the importance of info in these forum threads. This is my first time on the 350Z forum but I have taken advantage of the vast amount of knowledge on the Corvette forums for a while and it looks like this forum is similar. Thanks guys.

 

Well at least you’re getting somewhere, lol. In all honesty my next step would be to do a thorough “wiggle test”, this sounds funny but is a legitimate diagnostic procedure used in the trade….It’s all done by hand, but a scanner with a live data function helps immensely.
If the car doesn’t idle you may need a helper to run it for you as you do the testing, but you’re basically going to grab any wiring you can see, and just give it a “wiggle” or flex with your hand-don’t yank on the harnesses, but work it in a similar fashion to shifting on a slow cruise. Basically what you’re trying to do is just give it enough pressure to see a change in the running, at which point you’ve likely found the source of your issues. If no change get the car up on stands, and look at any of the wiring connectors and harnesses that may have been affected by the clutch work-the engine would have been tilted down at the back to disconnect the bellhousing bolts, so check any wiring that may have been stretched/pulled/affected by that.
If these tests come up with nothing, you’ll next be looking for a shop that can graph data on a lab scope, this will be costly but they should be able to graph each CKP/CMP sensor and watch for a variance in the signal. Without this test you’re just wasting time and money throwing parts at it. Also, don’t insist that this is the source of your problems, have them do a full diagnostic on it.

 

Quick update... The mechanic put the new flywheel back in and buttoned everything up. I got the car back to the house this evening and started by looking for any codes using my BlueDriver tool. No codes popped up at all. I then tried multiple times to do the ECU relearn and Idle relearn with no success. RPMs at idle continue to oscillate and don't go away. I found this video showing the exact same thing I'm seeing. Only difference is his oscillations start after about a minute but mine start immediately. I decided to pull the plug on the throttle body and start the car. When I did this the car immediately settled down and idled perfectly. Shut the car off, plug it back in and back to the oscillations. Do you guys know what provides inputs to the throttle body? Any tests that I can run to isolate the bad input?

 

The pcm controls the throttle body, it will adjust the idle based on several different parameters.

 

Update
Been running various tests over the last two days to try and determine the cause of this idle revving/oscillation issue. These included tests/inspection of the MAF, Throttle Body, IPDM, PCV, battery connections and numerous attempts to run relearn procedures. Nothing has corrected the issue or pointed to a cause. Today I decided to quickly check the Accelerator Pedal Sensor. I simply pulled the plug to see what would happen. Engine started and idled high (~1500 RPMs) but it was very stable. No revving or oscillation.

• Could it be that this sensor is providing the bad input to the ECU and subsequently the throttle body to cause this type of issue?
• Is my logic correct? I've removed one input of several to the throttle body that resulted in a stable running car. Thus, that input is causing the problem.

I ran some multimeter tests on the harness side of the pedal sensor. Supply voltages were good at 5V and grounds were good. Didn't check any sensor signal voltages back to the ECU though. That could be another test I could do if I dig out the ECU and get someone to help me run the test.

 

If you unplug the app, it will go to a limp mode setting, so yes, staying high sounds about right, since it has no reference point, so it will default to a high rpm so the owner can limp home above idle.
If the throttle is surging and stalling, it’s very likely that the ecm is trying to compensate for something by causing the surge, it it could also be as simple as a failed throttle body, and the ecm cannot control it precisely enough to allow a relearn.
FYI there are 2 sensors in the throttle body and they must match to pass the initial self-check upon startup, if not you should get a dtc. Did you say you only had cam/crank codes?