OBD1 scan tool shows wrong number of cylinders
10-04-2022, 04:11 PM
#1
V8 Miata Fan
Thread Starter
OBD1 scan tool shows wrong number of cylinders
Does anyone out there know why? When I first start the code reader it is supposed to show the number of cylinders that the engine has. The car has a Ford 5.0 V8. The code reader shows the number 6. Otherwise, it reads the codes properly. Any ideas? -Brad
10-04-2022, 05:22 PM
#2
V8 Miata Participant
Ford part number off the ECU would be a bonus to try and track down the issue.
Bill S.
10-04-2022, 08:33 PM
#5
V8 Miata Fan
Thread Starter
E9ZF-12A650-AA
The scanner that I used is a Innova 3145. It is OBD1 only. I also have a Bosch 1300, but I did not try that one. Thanks in advance. LMK. - Brad
The scanner that I used is a Innova 3145. It is OBD1 only. I also have a Bosch 1300, but I did not try that one. Thanks in advance. LMK. - Brad
10-04-2022, 08:45 PM
#6
V8 Miata Participant
For the Bosch 1300 to work, you'll need an adapter cable:
https://www.boschdiagnostics.com/pro...iv-obd-i-cable
For the Innova 3145 , can't say I've ever used one, a quick only review shows it will work with the Ford EEC-IV, but unsure why it is not reading correctly, unless the frimware is out of date or somehow corrupted.
Bill S.
10-04-2022, 10:39 PM
#7
V8 Miata Fan
Thread Starter
Yes, I've got all of that stuff. I can read it with the Bosch 1300. I was just curious if anyone knew why it would misread the number of cylinders that the engine has. It's also showing a different weak cylinder every time I run a cylinder balance test. This last time it showed 3 weak cylinders. I'm half tempted to try a different TFI module. I had a guy tell me about a year ago that most of the modules that you can buy these days are junk. He has trouble finding a good one
10-05-2022, 06:21 AM
#8
V8 Miata Participant
Yes, I've got all of that stuff. I can read it with the Bosch 1300. I was just curious if anyone knew why it would misread the number of cylinders that the engine has. It's also showing a different weak cylinder every time I run a cylinder balance test. This last time it showed 3 weak cylinders. I'm half tempted to try a different TFI module. I had a guy tell me about a year ago that most of the modules that you can buy these days are junk. He has trouble finding a good one
Bill S.
10-05-2022, 01:27 PM
#9
V8 Miata Fan
Thread Starter
Bill, I suppose anything is possible. I've checked the DC resistance of all of the sensors and the injectors, and all is well in that department. I checked the sensors with a stethoscope with the engine running, and all are clicking. The spark plugs are all burning evenly. I did not however check for a square wave output at the BAP sensor. I don't believe that it should really matter because the problem is there even during cold startup when the computer is in open loop. The original problem was that the thing died 3 miles after unloading it from the transport. The TFI module went belly up and I replaced it with a NAPA TP31. The 6-cylinder notation on the code reader is a mystery to me. The distributor was stabbed correctly because the signature pip is in the right spot. The fuel pump sounded like it was about to die so I replaced it. I rechecked my fuel pressure yesterday and I have 39 lbs at idle and 43 with the vacuum hose disconnected. I've seen some postings that say the idle fuel pressure should be closer to 32. Do you think that 39 is too high? I did a smoke test and didn't find anything there. I did not check the vacuum hose routing because it ran fine for the first 3 miles. They had the BAP sensor connected to manifold vacuum which is incorrect for a MAF setup. I changed that but again it ran fine initially with it that way. There was some rust in the tank, and I spent 5 hours cleaning it. I even bent the baffles back to get as much as I could. It looks pretty good. I replaced the fuel filter. I suppose that it is possible since I disturbed everything that the injectors could have some debris. That's why I wanted to pull the upper intake and check them along with checking under the valve covers. It almost feels like an engine that I had many years ago that had a burnt valve. But I don't think that's possible considering it ran fine and then it didn't. The only other things that I did was to connect the VSS sensor between pins 3 and 6 and add a rocker switch between pins 30 and 46 so I could pull the KOER codes. I also checked to see that voltage was not present on pins 30 and 46 while cranking just to be sure. I ran a KOER test yesterday and got 2 related to Thermactor stuff which would be correct since there is no air pump. Plus, the 31 that I get because there is no EGR. I get the MIL after startup. I don't know whether these codes will set that or if it's residual from previous codes sent. I guess I should clear them to see. The thing that is frustrating is that you find something obviously wrong and fix that thinking that it will cure the problem and it does nothing. This can't be that complicated. I am light years ahead of where I was when I first started but I obviously still have a way to go. -Brad
10-05-2022, 02:46 PM
#10
V8 Miata Fan
Thread Starter
Update: OK, I switched out the TFI module. No better, maybe even worse. I went through all of the cylinders with my GTC 505 and I have misfires on several cylinders. You can feel it throughout the car. It seems like every time I check it with the tester, I show misfires on different cylinders, although number 5 has always been questionable. I don't know, maybe I need to replace the spark plugs again. This time with no anti-seize because I did get some contamination past the lower threads, although I felt like I got most of it cleaned off, I guess you can never be too sure. The misfires are so bad that the rpms shown on the tester are way off, sometimes by half. The tester displays rpms based on the number of pulses picked up from the ignition wire being tested. I am really wondering about that pip sensor. People say that if one piece is bad you should change the other. The only reason that I am unsure is because there are some cylinders that never show misfires. I would think that if it were the stator the misfires would be random everywhere. The other thing is leaking injectors. Could leaking injectors cause misfires? I think the answer is probably yes. Would there be any value in putting some injector cleaner in the tank? -Brad
10-05-2022, 03:22 PM
#11
V8 Miata Participant
Bill, I suppose anything is possible. I've checked the DC resistance of all of the sensors and the injectors, and all is well in that department. I checked the sensors with a stethoscope with the engine running, and all are clicking. The spark plugs are all burning evenly. I did not however check for a square wave output at the BAP sensor. I don't believe that it should really matter because the problem is there even during cold startup when the computer is in open loop. The original problem was that the thing died 3 miles after unloading it from the transport. The TFI module went belly up and I replaced it with a NAPA TP31. The 6-cylinder notation on the code reader is a mystery to me. The distributor was stabbed correctly because the signature pip is in the right spot. The fuel pump sounded like it was about to die so I replaced it. I rechecked my fuel pressure yesterday and I have 39 lbs at idle and 43 with the vacuum hose disconnected. I've seen some postings that say the idle fuel pressure should be closer to 32. Do you think that 39 is too high? I did a smoke test and didn't find anything there. I did not check the vacuum hose routing because it ran fine for the first 3 miles. They had the BAP sensor connected to manifold vacuum which is incorrect for a MAF setup. I changed that but again it ran fine initially with it that way. There was some rust in the tank, and I spent 5 hours cleaning it. I even bent the baffles back to get as much as I could. It looks pretty good. I replaced the fuel filter. I suppose that it is possible since I disturbed everything that the injectors could have some debris. That's why I wanted to pull the upper intake and check them along with checking under the valve covers. It almost feels like an engine that I had many years ago that had a burnt valve. But I don't think that's possible considering it ran fine and then it didn't. The only other things that I did was to connect the VSS sensor between pins 3 and 6 and add a rocker switch between pins 30 and 46 so I could pull the KOER codes. I also checked to see that voltage was not present on pins 30 and 46 while cranking just to be sure. I ran a KOER test yesterday and got 2 related to Thermactor stuff which would be correct since there is no air pump. Plus, the 31 that I get because there is no EGR. I get the MIL after startup. I don't know whether these codes will set that or if it's residual from previous codes sent. I guess I should clear them to see. The thing that is frustrating is that you find something obviously wrong and fix that thinking that it will cure the problem and it does nothing. This can't be that complicated. I am light years ahead of where I was when I first started but I obviously still have a way to go. -Brad
Update: OK, I switched out the TFI module. No better, maybe even worse. I went through all of the cylinders with my GTC 505 and I have misfires on several cylinders. You can feel it throughout the car. It seems like every time I check it with the tester, I show misfires on different cylinders, although number 5 has always been questionable. I don't know, maybe I need to replace the spark plugs again. This time with no anti-seize because I did get some contamination past the lower threads, although I felt like I got most of it cleaned off, I guess you can never be too sure. The misfires are so bad that the rpms shown on the tester are way off, sometimes by half. The tester displays rpms based on the number of pulses picked up from the ignition wire being tested. I am really wondering about that pip sensor. People say that if one piece is bad you should change the other. The only reason that I am unsure is because there are some cylinders that never show misfires. I would think that if it were the stator the misfires would be random everywhere. The other thing is leaking injectors. Could leaking injectors cause misfires? I think the answer is probably yes. Would there be any value in putting some injector cleaner in the tank? -Brad
No offense, but at the moment, you are your own worst enemy, yare all over the place, bouncing from one thing to another without starting with the basics. You need to start with the basics, find someone you can borrow an unadulterated ECU from and plug it in. Or buy one, that is your choice, but it needs to be done. Do not touch anything else, do not attempt to read codes, do not bother with your testers right now, most certainly do not open the ECU case. You want to pull plugs and change wires, maybe buy a distributor pick up for under the cap, and of course a new cap, go for it, otherwise, leave everything else alone. Fuel, Compression, signal for spark, and spark are all that you need to be concerned with until you can get it to fire and run at least for 10-30 seconds, then go from there.
The one thing I asked early on, did you pull the distributor and re-index it at TDC on a compression stroke, going back through my posts and yours, I fail to see where you did so..If timing jumped, that could be the cause of your issues, a bad distributor pick up ($17.00) could be the cause of some of your issues as well. However, the more you post, and again, no offense, the more I think you are in way over your head. Sorry, but just the vibe I'm getting.
Bill S.
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