FungsterRacing

iTrader: (4)

I'm hoping the progress continues!

Thanks a lot for the navigation to the proper procedures, will definitely save me some time! I will keep this updated with news on whats going on

FungsterRacing

iTrader: (4)

Well, unfortunately it seems that I cannot do anymore testing due to lack of necessary tools (and essentially some background in this area). I read over the testing procedures, so obviously there is a module that is malfunctioning for some reason - That or the wiring harness is bad somewhere. Connectors I can check, and general wiring, but modules seem to be out of the question.


If anything else new comes up, I will definitely keep this updated!

Edit: Looking at the following link:

http://foxed.ca/rx7manual/2003mazdar...html#wp1025486

It appears that the two codes I am currently seeing have two commonalities: EPS and Keyless Unit

Now, I cannot say that it would be one of those two, but it seems plausible. It is difficult knowing where to start when it comes to this electrical stuff, especially when I do not have the necessary equipment for diagnostics. Also should be noted that I installed four (4) new plugs, as I initially thought it was a flooding problem.

Edit #2: After reading the following:

http://foxed.ca/rx7manual/2003mazdar...255430W05.html

According to the top portion of the page, it appears that the two codes I have (U1900 & U0073), it states that those two are associated with CAN system communication error, but NOT Wiring Harness Open or Short Curcuit, as there is a separate code associated specifically with that (U2516). So from this, and I ask you this, does that imply that I can safely assume that I have a module malfunction? That page makes me think so. Meaning it could be: PCM, TCM, DSC HU/CM, EPS, Keyless Unit or Instrument Cluster. I unfortunately cannot test all of these items, but can test some.

Is is agreeable from the above link in Edit #2 subsection that it is in fact a module malfunction? Note that this includes a connector being loose, but does not include a wiring harness issue. Please let me know if my thinking makes sense or if I am missing something here


Edit #3: Please note that this relates directly with the original post and Edit #2, so please read those if you have not yet. On the following page:

http://foxed.ca/rx7manual/2003mazdar...255430W01.html

It asks: Are any other DTCs other than the following displayed? <--- That is the section. Under there it states: PCM: U0073, U0101, U0121, U0155 as well as: TCM: U0073, U0100. For the keyless and other ones, it reads these codes (again, as in that first box): U1900, U2516.


So the question is, Does the above mean that U0073 is associated only with the PCM and TCM? (As it is listed only with them) Also, U1900 is my other code, which is associated with Keyless, etc. I am getting confused with all of this, trying to put the strings together to figure out this mess. It seems that some codes are associated with a limited number of modules, so essentially I am trying to figure out which ones are not working, and these pages and diagrams are (possibly) misleading me or directing me in the right direction.

My gut for some reason is pointing me to either the Keyless Unit or the PCM. As for the keyless unit, for verification, is it the box under the dash on the passenger side with 3 harness's going into it? I had found a picture once that showed differently but cannot find it

FungsterRacing

iTrader: (4)

Just realized with my model, I do not have the DCS HU/CM or the TCM as mine is 6MT, also do not have Steering Angle Sensor - Leaving: PCM, Instrument Cluster, EPS, Keyless Unit. From this I am ASSUMING, but NOT AT ALL SURE, that it is one or more of these four units which are faulty as there are communication errors U1900 and U0073 as described in earlier posts.

RIWWP

iTrader: (2)

In the US, having a 6MT didn't automatically include or exclude DSC/TCS. Check for the switch near the dash light dimmer, left of the steering wheel. If there is no switch there, you don't have it, if there is a switch there, you have it. If you don't have DSC, it is likely that you don't have the Steering Angle Sensor either, as I think that DSC is the only place that it's used.

I would agree that the combination of codes and 'possible causes' is pointing to a module malfunction in the PCM, EPS, and/or Keyless. The symptoms you have been having point to PCM (driveability problems) and Keyless (things connected to locking/unlocking)


Unfortunately, having a look connector can exhibit the same symptoms as a broken or shorting section in the wiring harness. Think of "loose connector" as being the same as "loose electrical connection", which can occur within the wiring as well if it was pinched, broken, melted, etc... If a circuit board has also gotten an internal short on it, then it could exhibit the same symptoms too, all depends on what shorted where.

You are almost certainly going to have to need a dealer's assistance at some point, hopefully after you narrow down the problem and obtain replacement parts yourself. They will still need to do the stuff to link the new modules with your car, but you really don't want to pay dealer retail prices on those modules.

FungsterRacing

iTrader: (4)

Well if the pcm is gone, would that not mean that the instrument cluster would not work also? We attempted to pull start, but no luck.

I'm checking over throttle body right now, as to do with the P0506 code. Also just noticed that my VFAD plug came off

RIWWP

iTrader: (2)

A damaged circuit board doesn't always mean completely fried/dead. Computer hardware is a good example, where you can be having weird issues from say, a network card, from the board being damaged, but still have a connection here and there.

Another example would be my 99 Miata. At some point I fried an internal resistor in the ECU, specifically the O2 sensor resistor. It was possible that it would have broken the connection completely, but what happened instead was that the sensor was getting the full 12v un-resisted. Caused plenty of open/closed loop switching issues, I'm sure it was killing the sensor faster, etc... The ECU still ran the car just fine though.

A damaged board could literally have any single aspect/component of the board is damaged with other stuff still working fine. It's part of the nightmare of diagnosing electronic failures.

FungsterRacing

iTrader: (4)

Ok, so here's a weird update. I am no longer getting CAN network error codes - I cleared them once, and we have started the car a few dozen times since, and the only code I am getting is now P0506.

Here is a video of what the car is running like. It is at idle, until my dad puts his foot right to the floor, and it refuses to even try revving - Won't go above 1k. Note that the car was running perfect before it was put away.

RX8 Diagnosing - YouTube

RIWWP

iTrader: (2)

That sounds like you are only running on 1 rotor, or maybe only one or two faces of a rotor?

I don't expect engine damage, it hasn't been running to have caused damage since it was running fine before. I would guess that the ECU simply isn't firing the plugs or the injectors when it should be, but that is simply a guess.

Ash8 and Ray from BHR might be able to point you in the right direction here, I think I'm at the end of what help I can provide.

FungsterRacing

iTrader: (4)

My initial thoughts - just lack of error communication codes is odd.

Thank you RIWWP for all you're help, it has gotten me much farther than I would have without it. If we had a thank button you'd get one!

Hopefully Ash or Ray will pipe in on this issue

FungsterRacing

iTrader: (4)

I'm considering buying a used PCM off eBay for example, just so that I don't get charged out the *** for one at the dealership. I have the N3H6 18 881K... seems eBay does not have this one specifically, but very close ones (...881J for example)

Might go this route, as they are only $150. I will hopefully get a hold of Ash or Ray for guidance here

RIWWP

iTrader: (2)

Yeah, Ash will be able to tell you what part numbers might be compatible. You definitely don't want to get, say, an automatic PCM for example.

FungsterRacing

iTrader: (4)

Got that right! For the most part the ones sold via eBay do specify that right off the bat, but I'm not sure about compatibility from there.

If my PCM is not successfully telling the car when to fire, etc., I wonder what the chances are of plugging in a compatible PCM and it working enough to drive it to the dealership?.... My gut tells me it would be best to just get it reflashed and configured at the dealer, but knowing me I would try

RIWWP

iTrader: (2)

Yes, if you can limp it to the dealer under it's own power you will be far better off financially, and probably for more than just the tow cost.

FungsterRacing

iTrader: (4)

Perfect. I may try to contact Ray regarding this, if not I will PM Ash and hopefully get some feedback once he's up.

For the (average) $150 price tag on a used PCM, I'm pretty willing to throw the money in that direction and see if it makes a change. I'm convinced that is the issue. We took the intake off and started it to verify the throttle body was opening when I depressed the gas pedal and it was, so that must be fine.

Damn I've learned a lot in the past few days

ShellDude

iTrader: (12)

hrm ... this doesn't sound like it's PCM related at all any longer. One can guess that after sitting for a while dust and what not had collected and caused some initial unwanted resistance, hence all the U**** codes.

But since they're now gone and all you're left with is the low idle CEL then perhaps the path is mechanical... possibly ignition / spark ... possibly a stuck injector ... possibly a combination of both.

I'm gonna go out on a limb and suggest stuck injector but would expect you to get more than just the P0506.

FungsterRacing

iTrader: (4)

Well its a difficult one to call. I can see the PCM having some negative effect on timing, but something being stuck makes sense. We took the intake off and cranked the engine, and heard a strange sound which I am not sure is normal - It sounded like the exhaust was coming up through the intake. It sounded like a valve on a piston motor - 'pfft pfft'

Might try to get a video of it later, but a mechanic locally said that when internals get moist that there is some flap that can crack and exhaust gets pushed through the intake but I have never heard of this on this car

FungsterRacing

iTrader: (4)

We think we MAY be onto something:

As we are, for some reason, hearing noise coming through the intake when cranking (we take MS intake off the throttle body and can hear it), we think an apex seal may be gone. We have come to this possible conclusion because:

1) As in the linked YouTube video above, it is not firing properly. It seems to not be compressing and igniting properly on all faces of the rotor (probably #1, as a misfire code came up during testing, but has not come since) It sounds like it is functioning correctly on one face, but no others

2) As said above, we hear a "pfft" in the intake what seems to be once per rotation when cranking, as if the exhaust is being pushed up through the intake port

Does this make sense? If you hear the video, specifically when my dad tries revving it up, it sounds like it is only firing once every so often (1/3 times I believe). I can blame the PCM for timing, but I think it may be a mechanical error, such as one apex seal gone - One gone would explain why one side is still firing, but the other sides are not and the exhaust is able to come back up through the intake as well as the exhaust.

You can see in the video quite a bit of smoke - It is cold out where I live, about -10 C. So I can understand some smoke, but that is quite a bit, especially when he is attempting to rev. It could mean a coolant seal gone as well.

Let me know what you all think about this theory! If that is the case, I think I may try to get my hands on a new engine and have it put in (As I live 900KM away from the car), or have it rebuilt, whichever is more effective and makes most sense financially (Though that is not a problem)

FungsterRacing

iTrader: (4)

I thought I would give an update on my next steps towards fixing the problems, or diagnosing them first for that matter.

As seen in the video and from descriptions, the car now starts, barely idles, and will not rev. It is essentially just, bluntly put, 'bucking'. After my last update I had to go back to AB for work, and will be returning to the car at the end of the month / early May. Here is what I think I can check over. Please note some of the items may have been checked over before, but I will re-do many of the inspections:

- Wires, plugs and coils. Also check for proper seating on both the coil pack and plug, and use an inductive timing light to test if all coils are firing. Although this won't help for timing, it will tell me if there is an issue with firing at all.

- ESS Surprisingly enough, this is one thing I failed to check when I was diagnosing before. I know if has an issue of causing idle issues, but I am not sure it would also cause the car not to rev. Regardless, it will be checked and cleaned, and hopefully I can check its resistance as well (1.1 ohm or so should be good, correct?)

- MAF Although I had checked and cleaned it, I will do so again. Visual inspection may not be enough, though. Anyone have any idea for the actual sensor testing?

- Backyard Compression Basically just doing this to see if one of the faces / rotors has zero compression. I highly doubt it, but its worth a check. Please Note: A proper compression test will be performed at some date, but all my testing will be done before that happens.

- Fuses and Relays May as well check them all again!

Things I Cannot Check, But Will Get Checked After My Testing:

- Compression

- PCM and CAN Network Although this means towing the car over an hour to a good friends shop so he can hook up his computer, it will be worth it once I finish my testing.




I also have the Android app Torque, does anyone have any suggestions on which values I should be looking out for while the car is idling? Although I was getting CAN communication codes, once I cleared them and started the car several times, they never appeared.

As of now, the only code appearing is P0506 (Cannot reach idle). I did once get P0301 for a misfire, but it never came back in all the starts and rev attempts we did after that one time. My initial thoughts for this was the Throttle Body, so I will be searching for a good way to test it. We did manage to see that it does open and close properly when idling and attempting to rev.

If anyone has any suggestions or comments please throw them in, as everything is as always appreciated.

RIWWP

iTrader: (2)

Idle should be 5g/s, or 4.8-5.5 range, too high and it's probably a MAF problem, too low and there is a vacuum leak (air is getting to the engine that isn't going past the MAF).

Idle short term fuel trim should be within -2% to +2%, ideally 0%. 4% or higher and you probably have a vacuum leak, -4% or lower could be a number of problems, including stuck injectors.

If you can't get it to idle, then watch AFRs as it dies to see what it's doing, too much or too little fuel? If the fueling is right on, then it's either getting an airflow choke, insufficient compression, or the spark can't keep it alive.

FungsterRacing

iTrader: (4)

Awesome advice, thanks! I will check all these when I am back out. The exhaust had a really strong fuel smell to it, which led us to think that the air was not getting enough air (Maybe was coolant smell, but smelt more like fuel) Had white smoke, but was -10 C out.

Now some past history of the car: P0139 was an often code. Presumably a vacuum leak, though I could never track it down. Realized that with the intake on, the previous owner had not removed the VFAD, which I did and plugged the hole (did that while diagnosing these issues before). Any places to look for a vacuum leak? That could has not come up yet during all of our testing, but I do remember it coming up often enough last summer.

RIWWP

iTrader: (2)

A vacuum leak could be nearly anywhere between the MAF and the engine, including every inch of every vacuum hose attached to the UIM. The common culprits are the service nipples on the LIM, and the three hoses that are on the accordion just before the throttle body. I've also had a vacuum leak from accidentally pinching a gasket between the UIM and LIM on one of the side intake runners.

A smoke machine is really the only "perfect" way of finding a leak, everything else is chancy on whether or not you will find it. Unlit propane or carb cleaner, sprayed around points of possible failure is often the go-to.

FungsterRacing

iTrader: (4)

Will check over the entire LIM. I was thinking of using just a soapy water solution on the hoses, though I now realize if there was a leak that could cause problems


That P0506 one is baffling me, though. I realize it could very well be intake related, just seems so odd that the car won't even rev up, just bucks. I think my first targets are the LIM and the coils/plugs/wires, though it could be a failed PCM. So many routes to go!

RIWWP

iTrader: (2)

Can you define "bucking" more clearly? I relate that word to not-smooth clutch engagement.

FungsterRacing

iTrader: (4)

Sorry! I should be much more clearer with that. In the video that I have uploaded here (Post #57), you can hear what I am talking about when I ask my dad to put the pedal down to rev the car.

When I mean bucking, I mean that it sounds like the timing is off, 'buck buck, buck buck, buck buck'.

Horrid description, I know. The video definitely does it more justice

RIWWP

iTrader: (2)

Ah, right, that. Same reply stands as before. 1 rotor or less than 1 rotor. It's not a single apex seal missing. That would be far smoother.