madkiwi

I am not going to start celebrating yet, but I may have solved the "random and unpredictable going into safety boost" problem. Looky here- That is the EFI harness connector for the knock sensor. The black wire is the shielding ground wire. Completely broken. I have talked to 2 different people who believe an unshielded knock sensor sub-harness may indeed result in spurious noise causing the ECU to interpret it as knock signals from the sensor. And being completely random.

I had to send the USB Consult tool I purchased back to the seller due to the weird stuff it was doing to my car (HICAS error, not reading the speed etc). I am going to buy a new one, just waiting to get it. Then I will get the Nistune software and get those maps. How can you measure the AFR? IS this one of those deals where you either install a wideband O2 sensor or put it on a dyno with a sniffer attached to the exhaust? Here is where someone in Denver mentioned a bad JWT ecu- http://www.twinturbo.net/nissan/300zx/forums/technical/view/1146182/No-issue-in-Denver-doing-14psi-on-stockers.html Thanks

So here is the latest on my progress (or lack thereof). I had the compression tested, high was 171 and low was 148 psi. Like a new engine. Verified that the mark on the crank pulley lined up with 0 on the advance indicator when #1 was at TDC. With the plugs out for the compression test my mechanic inspected the cylinders with a borescope. Apart from normal carbon deposits, nothing to report. I can report that the FSM manual has an error in the testing protocol for the MAF. On page EF & EC 174 it says that voltage from b to ground with the key ON should be about 0.8 volts. I purchased a used N62 sensor last week and installed it, it has a voltage of 0.45 volts and my old one was 0.44. Both show the expected voltage at idle (1.216 and 1.245). And it did nothing to solve my safety boost problem. I just ran a tank of gas with a bottle of Redline Si-1 fuel system cleaner in it to clean up the injectors/valves. Happy to report that it has already helped my fuel economy a bit, just got the highest mpg in mixed driving in a long time (17.59 mpg, or 13.37 l/100km) but still getting the safety boost issue. I have not changed the base timing to 12 degrees (or lower) as suggested yet because I have been doing other things and seeing if they help first. Don't want to change a bunch of things at once and not know which one made the difference. Is there a way to examine the fuel maps programmed into the JWT ECU without spending a fortune on software? Because with the lack of anything else I am wondering if there is something wrong in the ECU. On twinturbo.net someone did say that a tuner had found an issue with a 1995 dated JWT chip that was running super-lean. I am not sure what the date is on mine, short of pulling the carpet/plywood out of the passenger footwell, which I don't feel like dealing with right now. I will before my next phone call to JWT, because I may have to ask them about it. Thanks.

I got one of those (from a US based seller) and ended up returning it. On my 1993 TT it would not read the vehicle speed, it caused a HICAS error code, and put the car into "high speed steering mode" which reduces the power steering assist so you really needed 2 hands at low speeds. Did not matter if the computer was connected or not, and you had to cycle the ignition to put everything back to normal. Apart from all that, it worked just peachy. You will need to download drivers for the FTDI serial-USB chipset, all they put on the disc was the free Nissan Data Scan. You can get them here- http://www.ftdichip.com/Drivers/VCP.htm Your experience may vary...

You are kidding, right? :saddam: When I wanted to buy mine I was looking on Ebay (US) and Craigslist and figuring no matter what I was probably going to have to fly somewhere and drive it back to Montana. With my luck, it could have been in Florida (2,800 miles by road). But I ended up finding mine in Hamilton Montana, about 45 miles from where I am typing this post. 1993 TT, pristine leather interior, Cherry Red Pearl and immaculate body and paint. (I won't mention the deferred maintenance items that had to be dealt with...) Only bad thing (I thought) was it was an automatic. As other people have pointed out to me having an auto turbo is pretty nice for acceleration, you never lose boost for gear changes. The UK isn't that bad by comparison.

I am such a retard. You know how they say be careful when you are reconnecting the ECU connector to the ECU? Don't over-tighten the bold that holds it on? Well, don't UNDERTIGHTEN it either. Because if the connector isn't fully seated, then weird things happen- like pin 11 that feeds ignition signal for coil #4 to the PTU doesn't connect properly. Obviously I discovered this AFTER troubleshooting the PTU, the ECU-PTU harness and finding absolutely nothing wrong. Until I started reconnecting the ECU and realizing I was tightening it more than I had previously... OH ****ING HELL! On the plus side, all the PTU connectors are now clean and full of dielectric grease.

Today I checked the wiring between coilpack #4 and the PTU, good continuity. The connector between the harness and the PTU was green, used a bunch of electronics cleaner and a Dremel to clean up the contacts. Going to check the wiring between the PTU and the ECU tomorrow. Wondering if the ECU connector pin is not making contact. The first Google search I did for "300ZX code 21" came up with a thread on 300zxclub.com where the guy's problem was the female connector on the ECU harness connector backed out of the plug. I did have the ECU disconnected the day before the new CTS came in, when I was checking the wiring of my new CTS plug. After I make sure the wiring/connectors from the ECU to PTU is good, then I will test the PTU. See what I am doing? Check the inexpensive stuff first. A PTU here is $158, don't want to assume it is knackered until proven so.

If it isn't one thing, it's another. I replaced the CTS (checked the new one was within specs first) and started the car, it was running like crap. Dragged out the laptop, plugged it in, pulled codes. Code 21- No ignition signal. Tried a power balance test, #4 is not running. Only thing I can think of is that when I was manipulating the harness to replace the CTS plug I must have either broken a wire or dislodged one of the PTU connectors. Because if the PTU is actually bad I MUST be cursed. I did not have time beyond step one of the diagnostic procedure (EF & EC 119-121) to trouble-shoot. I work for myself, but I had to go take care of work stuff and so... tomorrow. Ever seen a grown man cry? I came close...

Got home too late to install the new CTS, let alone go for a test drive. It is supposed to be 85 F tomorrow (29.4 C) so a great day for seeing if the detonation comes back. What do I need to incorporate the Nistune stuff in my car?

Well that is a new one to me. Not only is the CTS bad, it is completely open. No resistance at all. Wiring checks out fine (total resistance was 0.2 Ohms). I wonder why that just happened. I know you in the UK complain about Nissan raping you on parts, but we get some of that here. MSRP on a CTS is $29.75. My local stealership has one in stock, they want $35.70 (Courtesy Nissan has them for $22.31). I want to get the car running today, so pay I must. Can't wait 3-5 days for Courtesy to send it to me. Oh, I called the place that has a dyno here in town. They specialize in diesel truck stuff. The tech basically told me unless I have my own knock monitoring equipment and software, there is nothing they can or will do for me. So that is a dead end.

Oh, and the aux. fan did not come on. Sorry, overlooked answering your question.

I'll strip down the plug connections and make sure the splices are good. Actually even if they are, I have a new yellow connector w/pigtails in my parts box, I will just replace it. Then connect my multi-tester to ECU connector pins 28 and 30 and make sure I get good readings. Thinking out loud now- maybe this has been my problem all along? A bad connection or not-quite-good-enough connection that has been flaking out randomly, telling the ECU that the engine is too cold for boost? Maybe not, once the engine sees higher temps again, then it would allow boost. So, never mind. Plus I have not recorded any CTS codes before. I'll let you know what I find tomorrow. Mark

I am going to do that, tomorrow when I have 20 minutes to deal with it. But Noz, if you are still reading- something new happened today. After a normal start to my day I made my first stop, and when I returned to the car a few minutes later and started it, the idle jumped to 1500 rpm, then stepped down slowly over the next 5 or 6 minutes to normal idle (800 rpm). Thought that was a little weird, stopped at the next place I had to go, and the same thing when I got back in the car. After the 3rd time this happened, I plugged in my laptop to the Consult plug. Turned on the ignition and the coolant temp was showing it was 70 degrees (21 Celcius). This was after the car was sitting for only 20 minutes, and it was an 80 degree day. I started the engine, same wildly high rpms, and I sat in the parking lot until the temp on the computer showed it was 176 F (80 C), took about 5 minutes. Idle was where it should be after car is warmed up. Drove to my next stop, computer showing temp around 180 F, shut car down. Turned key to ON position, temp on the computer showed 75 F. Started the car, idle ran to 1500 rpm, then ran down to 0. Yes, for the first time since I purchased the car 4 years ago, the engine stalled. Transmission in Park. Started it again, and the car was in "cold start" mode again, with high idle, but it stayed running. Drove home, idle is a little high, 900 rpm, temp on laptop showing 178 F. Shut down when I got home, started the engine again, and once again it stalled. Stayed running the second time I started it. Checked codes, of course it is Code 13, CTS. But that doesn't explain the symptoms- I had a bad coolant sensor when I purchased the car and the auxiliary fan ran all the time. Idle was a little high, but not 1500 rpm. The CTS and the connector were replaced together, and I definitely soldered the new connector. I did a full temperature test of the CTS about 6 weeks ago, it passed with flying colors. Thoughts?

Last things on the checklist done- checked the injector resistances. What made the job easy was discovering I could do it from the ECU connector, pretty neat that I did not have to try to get all those connectors off (and remove the balance tube). #1- 12.1 Ohms #2- 12.3 #3- 12.1 #4- 12.1 #5- 12.1 #6- 12.0 That includes all the resistance in the wire to the injectors, theoretically 0, but what it tells me is the damn injectors are doing what they were designed to. After eliminating the unlikely, then that leaves only the impossible- my petrol sucks. Here in Montana all our gasoline comes from a refinery in Billings (about 300 miles from here) and they make 87, 89 and 91* (note below) AKI with 10% ethanol and 91 AKI ethanol free. It is intended for "Snowmobile and off-road use". * I was told that the refinery makes their Super 93 AKI, because it is also sold in Washington and in the Dakotas. More economical to just make one Super formulation, and sell it both here and at lower elevations. All the pumps here are marked 91 AKI, but because you are getting higher octane than you are paying for it isn't an issue. I am wondering if I should just give up buying the ethanol-free gas (who knows what they get away with putting into outboard engines and ATVs) and just buy the ethanol-gas blend. Then budget for a set of later-model injectors and the adapter kit when my current ones die from the ethanol. I have run out of ideas. I think I have checked everything. I will still take the car and have it run the dyno. We'll see if that finds anything, but I can't imagine what. Maybe I should just take it out behind the barn and shoot the damn thing.

Last things on the checklist done- checked the injector resistances. What made the job easy was discovering I could do it from the ECU connector, pretty neat that I did not have to try to get all those connectors off (and remove the balance tube). #1- 12.1 Ohms #2- 12.3 #3- 12.1 #4- 12.1 #5- 12.1 #6- 12.0 That includes all the resistance in the wire to the injectors, theoretically 0, but what it tells me is the damn injectors are doing what they were designed to. After eliminating the unlikely, then that leaves only the impossible- my petrol sucks. Here in Montana all our gasoline comes from a refinery in Billings (about 300 miles from here) and they make 87, 89 and 91* (note below) AKI with 10% ethanol and 91 AKI ethanol free. It is intended for "Snowmobile and off-road use". * I was told that the refinery makes their Super 93 AKI, because it is also sold in Washington and in the Dakotas. More economical to just make one Super formulation, and sell it both here and at lower elevations. All the pumps here are marked 91 AKI, but because you are getting higher octane than you are paying for it isn't an issue. I am wondering if I should just give up buying the ethanol-free gas (who knows what they get away with putting into outboard engines and ATVs) and just buy the ethanol-gas blend. Then budget for a set of later-model injectors and the adapter kit when my current ones die from the ethanol. I have run out of ideas. I think I have checked everything. I will still take the car and have it run the dyno. We'll see if that finds anything, but I can't imagine what. Maybe I should just take it out behind the barn and shoot the damn thing.

Still got to see to the dyno run (if I can) but will investigate that next week. To your list- Spark plug rating too hot- Installed NGK PFR6B-11B, colder than stock Incorrect base timing- Double checked, it is a hair under 15 degrees. Call it 14.5. Faulty CAS- removed CAS connector and checked for corrosion etc. it was fine. Will take it apart and clean (as well as examine the cam key for wear) tomorrow. Fuel delivery issue (eg. weak pump, blocked injectors)- Checked fuel pressure at idle, with vacuum hose off the regulator and while driving. Plenty of pressure. Low grade fuel- Unknown. Pump ethanol free here is US 91 AKI. I am at 3,300 ft above sea level, so that is what they sell. Carbon build up on piston crowns- Just had the Motorvac treatment done Compression too high (skimmed heads, NA engine)- Engine is stock TT. Lowered fuel RON due to oil ingestion- Burn no oil at all, exhaust gases are white steam on startup, clear after that. Because my engine is running rich most of the time (safety boost) I have some black soot on the bottom lips of my exhaust pipes. Poorly mapped ECU (timing set too advanced; fuelling set too lean)- Don't know how to see that, or if I can ask JWT if that might have happened. Too much boost- Out today trying to get safety boost to kick in my max boost was 0.78 bar (per my Blitz DTT) which is only 11.3 psi. Intake charge temps too high- Ambient temp was 80 F (27 C) today, no safety boost. Also I do have Z1 SMICs installed (put them in Aug. 3rd) which should help lower charge air temp. Also checked my coilpacks today, they were all 0.7 or 0.8 ohms. So really good. Tomorrow I will test all the injectors. PITA to get the connectors off... By the way, here is the raw data that goes with that video of my instruments. If anyone can look at the data and let me know if any of the numbers look out of whack. One thing that surprises me is that the time drops back to 19-20 degrees BTDC at full throttle, high boost, whereas slight throttle gets 42 degrees of advance. ecutalk1392014_video.xlsx Thanks, Mark

Wish I had the resources to fly you out here. I know there is one shop in town that has a dyno. I will call tomorrow and see what they can do. I actually heard the detonation a couple times, right as the safety boost kicked in. I am familiar with what it sounds like, owning a Pathfinder teaches you that. At first I really thought it was loose change rattling in the ashtray. Getting back to your comments about setting the AAC to 15%, how exactly is this accomplished? Neither of the software packages I have (ECUTalk and OBD Scan Tech) have the ability to change anything there. Is it just a matter of adjusting the idle screw while monitoring the AAC on the software? Forgive my ignorance, not a mechanic by trade and getting help in this 1 horse town is frustrating when they all know less than I do. Thank you for taking the time to even help.

I was so hopeful I had it figured out. My MAF failed one of the Service Manual tests, so shouldn't it be assumed it is bad? My ON (engine not running) voltage was measured at 0.44 volts, manual says it should be 0.8 volts. Removed and cleaned it, same result. What is really weird is ECUTalk shows the not running voltage as 0.08 volts. My running at idle voltage was 1.245 V (manual says it should be 0.8 to 1.5). I have stock turbos, with the JWT ECU and 12.5-13.5 psi boost jets. What else would cause safety boost? I thought it was only 4 things- -Engine is cold -Bad Engine Temperature sensor -Car is detonating -Bad detonation sensor Engine not cold when it happens, Temp sensor was checked and is good, detonation sensor replaced last year. NO CODES! Everything is Code 55. I am still stumped.

Back to my problem now... I just noticed something on my graph that makes me think. Between 22.10.5 and 22.17.1 (6.5 seconds elapsed) RPMs increased from 4650 to 5912. That is an increase of 27.13% In the same timespan MAF voltage increased from 3.29 V to 4.16 V, only a 6.12% increase. Considering the engine is just a big air pump, if the engine is running 27% faster shouldn't the air going through it also increase by 27%? This presumes the MAF sensor voltage output is linear, which I believe it is supposed to be. This would explain my high boost detonation. The ECU is not receiving the full story on how much air is going through, and is supplying fuel at the incorrect ratio- leading to a lean condition. Am I smoking crack here?

I realized later that the 24% from the AAC was during the cylinder drop test. The software (OBD Scantech) actually increased the rpms before the test started to 850 from my normal idle of 750 (actually from my recordings it wobbles around from 737 to 762). Point is, the 24% is not my normal idle number. I have not had a chance to check what it actually is, in between work and wondering if the Ebay seller is going to replace the Consult tool I have not had the time. Plus yesterday when I thought I may get a chance, I decided to install my new cooling fan and fan clutch. That took longer than I thought, and I ran out of my allotted time to run the Consult again... The fan had some pretty good cracks in the hub- but the primary reason for replacement was because the clutch had the same amount of rotational resistance hot or cold so I was pretty sure it was not functioning correctly after 21 years. I also found one of the recirc hose clamps was completely loose! When I replaced the recirc valve a couple weeks ago, and changed all the hoses to silicone, I missed one of the clamps. That may explain my lack of boost... When the car goes into safety boost no codes are generated. Because everything is functioning normally. I have no knock sensor code, because my knock sensor is working, you only get a code when the ECU cannot communicate with it. I have been in email contact with Peter Collins, the author of ECUtalk (as I guess you know having purchased one of his LCD displays) and he is pretty sure the Consult adapter is causing the issue. Pretty obvious really, the problems happen even if it is not plugged into the computer... I will try to get some time today to plug the computer into the car again and figure out what is my AAC duty cycle actually is at idle.

I thought it looked a little high, then I found this on the Z32 Wiki- "...generally, when warm, the duty cycle is around 30%. If the number is 15% or lower, this often means a vacuum leak is present, as 15% is the lower threshold of the AACs operation, and this indicates the ECU attempting to lower the idle speed." http://z32.wikispaces.com/Consult+Quick+Reference It was the only reference I could find to what the AAC duty cycle should be.

I remember that part of the recording, I took my foot off the gas (technically throttle was at idle) to slow down as I was catching up to traffic (happens quickly when I am doing 115+ mph and they are doing 75). Apparently the better correlation is throttle voltage and airflow. Here is a graph of RPM, throttle position and airflow. Time is first 1:52 of the of the youtube video. One thing I learned from graphing it was that there is a lot of shakiness in the airflow, especially at closed throttle. That indicates vacuum leaks. And I thought I was on top of them...

This is what I recorded yesterday using ECUtalk. I edited the video down to 4:15, just from the time I got on the interstate and exited again. Apologies for all the clicking picked up by the microphone, the only thing I can think is it was rubbing on the leather seat? I think everything looks normal. Car did not go into safety boost, which is what I was hoping I would get so I could record what the engine was doing when it occurs. My theory of a faulty MAF seems to be disproved by this recording, at 6,000 rpm with 3.26 volts on the throttle (and about 10.5 psi boost) the MAF was at 4.16 v (this is at approx. 110 mph, in 3rd gear- automatic transmission). However, the MAF was showing a bad reading with the ignition ON (engine not running) of 0.44 with a voltmeter, ECUTalk recorded 0.08 volts. Service manual says it should be 0.8 volts. ECUTalk could not read the speed, I believe the consult adapter I got on Ebay is faulty. It also causes a code 14 Speed sensor fault, and sets off the HICAS warning light, and to make things just peachy it puts the power steering into "high speed mode"- fine for the freeway, not so great on city streets. Removing the consult adapter from the vehicle's plug restores everything to normal. So I am asking the seller for a replacement adapter, assuming this one has some kind of internal short. Also did a power balance test when I got home using OBD Scantech. Got an rpm drop on every cylinder, so presuming I have no misfires (at idle anyway). Is it worth re-running the balance test at higher rpm (I saw that as an option)? Power Balance Test Summary On 9/13/2014 5:08:33 PM Coolant Temperature: 189 Deg {F} Idle Air: 24 % Cylinder # 1 Cylinder On Stablized For 2 Seconds Average RPM When Cylinder Stablized... 845 Rpm Cylinder Off Sampled For 3 Seconds Average RPM When Cylinder Is Off... 802 Rpm Average RPM Drop Result... 43 Rpm Highest RPM Drop... 95 Rpm Amount Of Data Sampled When Cylinder Off... 182 Cylinder # 2 Cylinder On Stablized For 2 Seconds Average RPM When Cylinder Stablized... 869 Rpm Cylinder Off Sampled For 3 Seconds Average RPM When Cylinder Is Off... 827 Rpm Average RPM Drop Result... 42 Rpm Highest RPM Drop... 69 Rpm Amount Of Data Sampled When Cylinder Off... 187 Cylinder # 3 Cylinder On Stablized For 2 Seconds Average RPM When Cylinder Stablized... 877 Rpm Cylinder Off Sampled For 3 Seconds Average RPM When Cylinder Is Off... 817 Rpm Average RPM Drop Result... 60 Rpm Highest RPM Drop... 114 Rpm Amount Of Data Sampled When Cylinder Off... 191 Cylinder # 4 Cylinder On Stablized For 2 Seconds Average RPM When Cylinder Stablized... 873 Rpm Cylinder Off Sampled For 3 Seconds Average RPM When Cylinder Is Off... 815 Rpm Average RPM Drop Result... 58 Rpm Highest RPM Drop... 110 Rpm Amount Of Data Sampled When Cylinder Off... 186 Cylinder # 5 Cylinder On Stablized For 2 Seconds Average RPM When Cylinder Stablized... 864 Rpm Cylinder Off Sampled For 3 Seconds Average RPM When Cylinder Is Off... 817 Rpm Average RPM Drop Result... 47 Rpm Highest RPM Drop... 76 Rpm Amount Of Data Sampled When Cylinder Off... 185 Cylinder # 6 Cylinder On Stablized For 2 Seconds Average RPM When Cylinder Stablized... 869 Rpm Cylinder Off Sampled For 3 Seconds Average RPM When Cylinder Is Off... 817 Rpm Average RPM Drop Result... 52 Rpm Highest RPM Drop... 106 Rpm Amount Of Data Sampled When Cylinder Off... 186 Can anyone tell me if this is all normal? Thanks, Mark (Crossposted to every 300zx forum I am a member of)

So I purchased one of those Consult USP boxes on Ebay with "Nissan-14" on it, downloaded VCP drivers for it from FTDIchip.com. All seemed to work on my Windows 7 laptop, and when plugged in to the 300zx TT. Connected ok (COM 9) and went through all the steps of choosing gauges to display. Everything seemed fine- except for one anomaly. It would not show the speed. I tried both imperial and metric (mph and km/h). My speedometer is working perfectly. Once I started driving with the laptop plugged in, about a mile from my home the power steering suddenly stopped working, and within a minute the HICAS light came on. I pulled codes, it said I had a code 14- vehicle speed sensor circuit error. After a shutdown, everything seemed normal. Drove a couple blocks, HICAS light came on and the power steering went off again. Unplugged the consult box, shut down, restarted and drove 4 miles home- no problem at all. No HICAS light, power steering worked fine. Now I am a little nervous about doing a full boost run with the laptop plugged in trying to find out what causes it to go into safety boost when I hit 11 psi. If I am going to lose my power steering every time I have this running... that doesn't inspire me to try 90+ mph runs. One thing I did find was that the MAF is definitely sending bad signals in the ON position (engine not running). My logs show it was 0.08 volts- supposed to be 0.8. Anyone know what the deal is with the speed sensor when a consult plug is running?

Thanks guys, I believe the boost leaks have all been dealt with, the last thing was my carbon canister which has now been eliminated. lonezedder and Noz- part of my problem is that I live in a smallish city (65,000 people) in a remote area. I know of one other TT in town, and am fairly confident a meeting of the Montana 300zx Owners Club could be comfortably accommodated in a corner booth at Pizza Hut. My mechanic, while very skilled and knowledgeable, does not know that much about the 300zx, and the local Nissan dealer has nobody that old (and they are so bad they installed the wrong spark plugs). Point is I do not have some of the resources available to others. The nearest Z specialists are in Seattle- 500 miles (800 km) away. I will put a request up on all the Z forums that I am a member of and see if someone is prepared to loan-by-mail a known working MAF sensor. Maybe I will get lucky.