CEL + TCS on Solid / 4k RPM limiter / HELP!

[NSX-Files]

There have been posts about these symptoms with CTSC equipped cars. I don't have a CTSC but my 1991 started acting up today.

I have had about 10-15 occasions during the last 8 months of ownership where the TCS light comes on and I feel the momentary ignition cutout feeling. After shutting off the ignition and restarting it goes away. I've also had 2-3 occasions where the TCS comes on and the CEL also flashes on then goes off.

Now though, both lights are staying on. With the car idling, feeling the exhaust pressure, I can tell the left pipe doesn't have as much air pressure coming out as the right pipe (JGTC Parallel - I think the left pipe is the front bank). So it's apparently missing or running on 5 cylinders. I'm getting the 4k RPM limiter and my idle is at 1200 RPM whereas it was usually around 850 RPM when running right. I assume the 4k limiter is some kind of "safe mode".

I haven't done the paperclip in the blue connector yet to pull the codes for the TCS or CEL yet. I thought I'd search here first. BTW I have 215/40/17 front and 265/35/18 rear tires. I would have preferred 275/35 on the rear, but the wheels came with these mounted. Would these sizes cause TCS problems? Would that then lead to the CEL problem I'm having? My TCS Off switch never lights up and I don't think it even works.

I would add that I recently (2 days ago) removed the Taitec "silencers" that restrict the flow (and noise volume) of the JGTC Parallel exhaust. They had been installed for about 1 month. My car has test pipes instead of CATS, although I'm planning to buy and install Hi-Flow CATS as the smell and the raspy sound at 3500 RPM is truly obnoxious. TIA for any advice.

David

 

[Larry Bastanza]

Step 1. Forget the TCS light
Step 2. Get the CEL Codes
Step 3. Post them here

 

[nsxtasy]

I have 215/40/17 front and 265/35/18 rear tires. I would have preferred 275/35 on the rear, but the wheels came with these mounted. Would these sizes cause TCS problems?

No.

Stick with the 265/35 rears. While neither rear size will cause TCS problems on your '91, the handling will be better with the 265.

 

[NSX-Files]

Step 1. Forget the TCS light
Step 2. Get the CEL Codes
Step 3. Post them here

I jumpered the bright blue service connector and turned on the ignition (without starting). The CEL stays on solid; the only flashing light is the TCS light which gave a code of 3-1, which I read as PGM FI ECU. Note that my car has the SOS sticker on the ECU box. Is there a connection between "chipped" ECUs and these kinds of problems? Would an AEM EMS solve the kind of problems I'm having or is the trouble somewhere outside the ECU? Let me add that the original problem with the TCS light coming on has often been in circumstances where I just started the car and am not even moving yet.

Am I doing the right thing to get CEL codes? Again, it stayed on solid with the jumper connected.

UPDATE: After initially getting the TCS code above, I reset the codes by pulling the clock fuse. I even disconnected the battery for 20 minutes then went for a drive.

The car is still not revving over 4k and the idle is high. TCS and CEL lights stay on constant. Now when I jumper the blue connector, CEL stays on and TCS light goes off once then stays on.

Now what?

 

[NSX-Files]

UPDATE:
I've tried multiple times again to get a trouble code from the CEL. It just stays lit with the jumper inserted. Is this a code in itself? In other words, if there is no problem, does the CEL normally go out after 2 seconds when the jumper is inserted? If so, this means I have a CEL code of zero.

With the jumper removed, and engine running, both CEL and TCS stay lit and I have the 4k rpm limiter. I'm not even getting the TCS 3-1 code anymore that I got earlier before resetting with the clock fuse.

I pulled all the coilpacks and spark plugs. They are all the same - whitish/tan porcelain insulator, shiny silver center electrode, tan/brown side electrode. None of them were wet, fouled or looked like they weren't firing correctly. So, why did I feel less exhaust pressure from the tailpipe of the front bank? Is this normal or is it a symptom of the the problem?

Tomorrow, I'm going to put my multimeter to the coils to check them all, although I suspect that they'll be fine given the condition of the plugs. The coilpacks looked fairly clean.

I'm probably going to do a compression test while I have the plugs out - not to solve this problem but just to know the condition of the engine.

In looking at the DIY/trouble_codes.htm in the FAQs, the MIL Code "0" (which I assume is zero blinks) is "ECM Internal Circuit Failure." I'm really wondering if my SOS Superchip is an issue here. Like maybe its coming loose or something.

I didn't know one way or the other before, but I pulled off the air filter box. l have the OEM scoop and box, and I don't have a big bore throttle body or headers. The only I/H/E components I have that are not stock are test pipes and JGTC Parallel. I'm wondering if my car should even have the SOS chip given the lack of the other I/H/E aftermarket components?

The 1991 Service Manual page 11-16 has a troubleshooting guide. It says zero blinks on the CEL is the ECU. It also says that "When the CEL and the self-diagnosis indicator are on, the back-up system is in operation." Page 11-25 describes the ECU Back-up systems:

Fail-Safe Function - When an abnormailty occurs in a signal from a sensor, the ECU ignores that signal and assumes a pre-programmed value that allows the engine to continue to run.

Back-up Function - When an abnormailty occurs in the ECU itself, the injectors are controlled by a back-up circuit independent of the system in order to permit minimal driving.

Self-Diagnosis Function (Check Engine Light) - When an abnormailty occurs in a signal from a sensor, the ECU lights the CEL and stores the failure code in erasable memory. When the ignition is initially turned on, the ECU supplies ground for the CEL for two seconds.

* * *

Seems to me, given the ECU code I'm getting, my car is running in "Back-up Function," and the engine missing I'm feeling is the cutout of the fuel injectors because the injectors are being controlled by a back-up circuit. This is also limiting the RPMs to 4k as some kind of "limp home mode." I'm tired of limping, I want to RUN!

Basically, it seems the manual is suggesting to substitute a "known good ECU" and recheck to see if the CEL goes away. Trouble is, I don't happen to have a known good ECU laying around.

Searching through old posts, I read some about cracked solder joints on a main relay. Is that something I should examine? If so, where do I look for that? I'm running out of ideas, here.

 

[NSX-Files]

UPDATE:
I pulled all the coilpacks and spark plugs. They are all the same - whitish/tan porcelain insulator, shiny silver center electrode, tan/brown side electrode. None of them were wet, fouled or looked like they weren't firing correctly.

Here's a pic of one plug. They all look basically the same. Note they are NGK Iridium BKR6EIX-11. Are these ok to use?

<img src="http://www.nsxprime.com/photopost/data/1087/medium/DSCF0093.jpg" />

I also measured the resistance of the coils between terminals A and B. All of them read exactly 1.0 ohms. The factory spec is 0.9 - 1.1 ohms, so I'm ok with all of them.

I did a compression test with the following results:
CYL 1 - 199
CYL 2 - 194
CYL 3 - 190
CYL 4 - 190
CYL 5 - 195
CYL 6 - 194

This is using a fairly pricey MATCO compression test kit that always seems to read lower than the cheapy gauge I bought from Autozone. The nominal reading according to the manual is 199, so I think I'll trust this gauge from now on over the cheapy one.

Searching through old posts, I read some about cracked solder joints on a main relay. Is that something I should examine? If so, where do I look for that? I'm running out of ideas, here.

I believe this is the main relay. Anyone see any abnormalities here?

<img src="http://www.nsxprime.com/photopost/data/1087/medium/DSCF0096.jpg" />

<img src="http://www.nsxprime.com/photopost/data/1087/medium/DSCF00941.jpg" />

<img src="http://www.nsxprime.com/photopost/data/1087/medium/DSCF0095.JPG" />

I'm kind of at the end of my rope here. The manual is suggesting to substitute a "known good ECU" and recheck to see if the CEL goes away. So.... anyone that can help me out in this regard? I've taken out my ECU.

It's really very easy to get to and remove - probably a 5-minute job. Now I just need another one to swap out for a quick test. I have a feeling doing that will make it run normal again. If so, then I'll know what needs to be repaired.

<img src="http://www.nsxprime.com/photopost/data/1087/medium/DSCF0097.JPG" />

<img src="http://www.nsxprime.com/photopost/data/1087/medium/DSCF0098.JPG" />

Are there any known issues with the SOS chip I have? I really want to solve this problem!

Thanks in advance for any advice or help.

 

[NSX-Files]

http://www.scienceofspeed.com/products/engine_performance_products/NSX/ScienceofSpeed/NA_tune/ecu/

According to their website, when SOS does the SuperTune ECU, they also apparently supply the customer with a factory calibration ECU chip. Does anyone have one of these that I could borrow or buy to plug into the ZIF (zero insertion force) socket of my ECU to see if maybe that's where the problem is?

David
[email protected]

 

[Larry Bastanza]

If you are not getting codes, most likely the jumper is not making good contact. I use a paper clip, and every so often I need to sand it off to get the tarnish off of it, to get the codes.

Give it another try.

HTH,
LarryB

 

[NSX-Files]

UPDATE: The car is running great again! Here's what I did:

I removed the ECU from the car and opened it up (front and back) to see if I could find anything obvious. I removed and reinserted the SOS modified chip into the ZIF socket. I didn't see any obvious faults inside the ECU so I put the covers back on and left it to sit overnight. I reinstalled the ECU the next day and what do you know, runs great with no CEL or TCS lights on and the 4k RPM limiter is gone.

It could have been a loose connection in one of the harnesses connecting to the ECU or the main relay. Those were the only two things I messed with between when it ran bad until now. Or else maybe the overnight slumber without power to the ECU cleared the fog from its brain. Either way, next time it does this I'll know what to try first.

The positive from all this is I had the reason to pull and inspect the plugs, test the coils and do a compression test with pretty strong results. So I have some peace of mind for a while. Now, it's on to fixing my leaky CV boot... and changing the tranny oil... and fixing a leaky spool valve o-ring... and fixing the erroneous brake lamp failure indicator... and you get the idea.