HELP! Car Misfiring FIXED!

[atc250r]

I've been battling this misfire for close to 6 months now. Every time I think I've fixed it, a few months later it comes back /ubbthreads/images/graemlins/banghead.gif. The first time it happened it finally got bad enough to start happening at idle and it gave me a code #41 which is "Injector not continuously driven for 4 seconds during cranking or idle operation." I replaced the CAS plug and all was well for about 4 months. About 6 weeks ago it started the same misfire, above 3000-4000 rpm under load and making boost. I wiggled the CAS plug and wires and the miss went away again. I cleaned the connections in that plug and all was well until I went to the track where it started again /ubbthreads/images/graemlins/mad.gif. I tore open the wiring harness from the CAS across the intake at the track but saw no visible damage. I taped everything up very tight, put it back together and managed to get one clean run in before it started missing again. I removed the pins from inside the CAS connector, removed the wires, installed all new wires all the way to about where the harness is fastened to the back of the intake. It was fine for about 3 weeks and then last week it started missing a little when it was cold and I was getting onto the highway leaving work. Today it's back to doing it just as bad as ever. I replaced the plugs a few months ago and the wires aren't that old either. All the connections I've made were soldered and heat shrink insulated so that should be fine. I've been soldering for nearly 20 years and have 4 years of electronics classes so I'm sure that I did a good job on that. Has anyone had something like this happen before? I thought it was the CAS so last time it happened I switched it with one out of car that was running perfectly and it made no difference. My only guess would be the igniter or coil packs but I don't feel like rolling the dice on a couple hundred dollars worth of parts. I'm at the end of my rope with this damn car. I expect sh*t to go wrong but it's nearly impossible to diagnose something when you have to be driving down the road to make it happen. Hopefully someone out there has had a similar problem and fixed it permanently. I may try rigging my COP coils to eliminate the coil packs as the problem but the last time it happened I tried a set of nearly new ones from Underground's car and that didn't help at all. Someone please help before I part this thing out.

John

 

I have been having the same issue for a long time too. I can't figure it out either, but I did build a COP set up, and it didn't help either. I changed all the ignition components many times, and nothing works. I am going to probably just put in a new harness, and call it done. I have no idea what it is, I have even tryed a new ECU.

 

[atc250r]

Thanks for the input Jon. Are you going to try a brand new harness or one from a donor car? I noticed that the time it happened before this it was immediately after I installed a new KD chip. Obviously it isn't due to any problem with Jeff's chip but maybe it is on the ECU end of the harness since that's the area I disturbed that time. I'm going to try wiggling some wires down there tomorrow after it acts up and see if it goes away. Strangely enough CAPS shows two different harnesses, one for 1991 and one for 1992. What is really interesting is that the 1991 harness is $700 while the 1992 harness is "only" $466 /ubbthreads/images/graemlins/confused.gif. I'd probably be willing to buy a new one for $466 but $700 is too much.

John

 

[powerplay]

John, next time it acts up go to the test part of logger and turn off the injectors one at a time and see if you can isolate the cylinder. Since we have a waste spark system it might only get you close, but if it is misfiring you should be able to shut down the cylinder and not notice much change in the running of the engine. Of course, it will fall on it's face when you shut down the good ones. It might help to get a little closer to the problem. As you said, it is hard to trouble shoot a problem while you are driving, but the logger should help if it shows some flaky readings when it is happening. Jeff might know how to monitor the CAS pulses to the ECU, or maybe the signal going out to the igniter. It would be nice to have a scope on the passengers seat to look at some of the signals when it is happening. Don't give up and part it out. There has to be an explanation and a solution.

Scott

 

[atc250r]

I was thinking about trying that, Scott. I'll charge the logger up tonight and see what I can find tomorrow. I tried watching injector pulse to see if it falls off or remains constant when in should be rising. I'm sure Jeff can shed some light on what the ECU uses the CAS signal for and that may point me in the right direction too. I also may try hooking my timing light up and that way I can watch to see if spark is dropping out. I'm also going to sit down with the service manual and see if its any help.

John

 

J, try checking the ECU connectors at the ECU.Ive had to tweak a few connector terminals myself.Recently, I was getting a knock error and traced it down to a intermittent ECU connection.Also, the CAS and TPS connectors seem kind of crappy IMO.Without those wire clips holding them on, they're very loose.The ignitor and coil connections on the other hand, seem to be alot more solid.

 

John,
As someone else suggested, first you need to figure out which cylinder is missing. I've had so many ECU's in and out of #1886 that one of the injector wires broke inside. I used the logger to disable each one, until I figured out which one wasn't working. Then, using the ECU pinout on VFAQ.com, I ohmed out that injector wire to ground. I think all the rest of them tested like 13 ohms, but that one was open, of course. This is one of the main reasons I stopped repairing ECU's.

 

[atc250r]

Alright I put some time in this afternoon and came up empty. The logger cannot disable an injector except at idle so that whole plan is out the window. I can't get stupid MMCD Tools to upload any of the logs into the PC /ubbthreads/images/graemlins/banghead.gif. Can anyone help with that so I can hopefully make some progress with this POS? I don't see anything wrong with any of the logs but the ECU has code #41 saved even though the CEL never came on /ubbthreads/images/graemlins/confused.gif. Also, my VSPD is all over the place /ubbthreads/images/graemlins/confused.gif. Standing still it bounces all over and driving at a steady speed it does the same thing. HELP!

Edit: Alright, I've managed to get the logs onto my PC but I have no where to host them. If anyone would like me to email them to them please let me know.
2005-12-09 16:17:45
English Units Datalog
TIME FLG0 FLG1 TIMA COOL FTRL FTRM FTRH FTO2 EGRT O2-R BATT BARO ISC TPS MAFS ACLE RPM KNCK INJP --- AIRT O2-F ---
12/09/2005 16:19:33 22° 186.1°F 0.72V 69.0% 503.2Hz 3813 6 12.29ms 50
12/09/2005 16:19:33 14° 186.1°F 0.82V 68.6% 635.3Hz 3969 6 14.34ms 60
12/09/2005 16:19:33 14° 186.1°F 0.78V 67.8% 691.9Hz 4188 18 15.10ms 67
12/09/2005 16:19:33 9° 186.1°F 0.70V 67.8% 723.4Hz 4344 22 15.36ms 71
12/09/2005 16:19:34 9° 186.1°F 0.72V 67.8% 767.4Hz 4500 22 15.87ms 76
12/09/2005 16:19:34 9° 186.1°F 0.66V 67.1% 798.8Hz 4563 21 16.13ms 78
12/09/2005 16:19:34 10° 186.1°F 0.74V 61.6% 830.3Hz 4781 21 16.13ms 82
12/09/2005 16:19:35 10° 186.1°F 0.70V 62.7% 861.7Hz 5063 20 16.38ms 88
12/09/2005 16:19:35 11° 186.1°F 0.70V 62.7% 912.1Hz 5188 25 16.13ms 89
12/09/2005 16:19:35 9° 186.1°F 0.76V 65.5% 937.2Hz 5250 31 16.64ms 93
12/09/2005 16:19:35 7° 186.1°F 0.80V 67.1% 981.2Hz 5438 30 16.64ms 96
12/09/2005 16:19:36 7° 186.1°F 0.80V 67.1% 1025.3Hz 5594 30 16.64ms 99
12/09/2005 16:19:36 7° 186.1°F 0.82V 68.2% 1037.9Hz 5781 29 16.38ms 101
12/09/2005 16:19:36 9° 186.1°F 0.80V 83.9% 1050.4Hz 5875 29 16.13ms 101
12/09/2005 16:19:36 9° 186.1°F 0.78V 100.0% 1050.4Hz 6063 29 15.62ms 101
12/09/2005 16:19:37 9° 186.1°F 0.72V 100.0% 1044.1Hz 6313 32 15.10ms 101


Next:

12/09/2005 16:17:18 28° 182.8°F 0.86V 93.7% 220.2Hz 2750 0 5.89ms 17
12/09/2005 16:17:18 27° 182.8°F 0.84V 100.0% 239.0Hz 2906 0 6.14ms 19
12/09/2005 16:17:18 27° 182.8°F 0.82V 100.0% 257.9Hz 3063 0 6.40ms 20
12/09/2005 16:17:18 28° 182.8°F 0.80V 100.0% 289.3Hz 3219 0 6.91ms 23
12/09/2005 16:17:19 28° 182.8°F 0.82V 100.0% 339.7Hz 3469 0 7.68ms 28
12/09/2005 16:17:19 28° 182.8°F 0.84V 100.0% 396.3Hz 3719 0 9.47ms 37
12/09/2005 16:17:19 23° 182.8°F 0.84V 100.0% 509.5Hz 4031 0 12.29ms 52
12/09/2005 16:17:20 18° 182.8°F 0.84V 100.0% 723.4Hz 4313 5 15.10ms 69
12/09/2005 16:17:20 15° 182.8°F 0.78V 100.0% 836.6Hz 4938 23 16.38ms 86
12/09/2005 16:17:20 9° 182.8°F 0.53V 100.0% 893.2Hz 5125 29 16.38ms 89
12/09/2005 16:17:21 8° 182.8°F 0.59V 100.0% 987.5Hz 5313 28 16.64ms 94
12/09/2005 16:17:21 8° 182.8°F 0.53V 100.0% 1019.0Hz 5500 28 16.64ms 97

 

[powerplay]

Those files should be uploaded automatically to your PC when you hotsync. Sorry about the injector disable snafu. When you cradle the palm and push the sync button does it complete the process?

 

[atc250r]

Figured that out, thanks Scott. I postd my logs as best as I can but I'm such a noob when it comes to this kind of stuff. I've got one more log to post if I can get it uploaded. It looks like it's leaning out but I can't figure out why. I think if it was an ignition problem it would go really rich since the engine isn't lighting off the mixture. I'm thinking more and more hat there is a problem in the signal from the CAS to the ECU and maybe Cruce is right that a connection at the ECU might be shitty. I also have the VSPD going all over the place, the baro at 0.00psi, and the AIT at -72*F. I know that Jeff locked the IAT and BARO inside the chip but the -72 reading seems a bit out of whack. I'll PM Jeff again to see what he says.

John

 

[powerplay]

John, you are on to something with those readings. I would follow up on checking you connections and give Jeff as much information (readings) as you can. The baro. should be locked at 14.5 or 1 atm and that temp. is definitely wrong. I know he will steer you in the right direction. Let me know if you want me to take any measurements or readings from my car for comparison.

 

[powerplay]

Looking at the logs, if I am reading them correctly you probably are getting lean on the top as you are at about 100% duty cycle on your injectors and you are getting alot of knock so the ECU is pulling timing. I assume during these two pulls you were getting the "missing"? Do you remember at what rpm it started to occur? I would like to look at that point and on more closely.

 

[atc250r]

Quote:
if I am reading them correctly you probably are getting lean on the top as you are at about 100% duty cycle on your injectors



The 100% you see is the throttle position. The injectors were at about 70% max. I'm looking at one log right now where the DC is 73% at 5300rpm but the O2 dropped down to .37V /ubbthreads/images/graemlins/confused.gif. With 720's I shouldn't be anywhere near leaning out at only 5300. Looking at another log it did the same thing and as soon as the 02 voltage dropped from .83V to .78V it shot straight to 23 counts of knock which is where it starts "stuttering" really badly. I wonder if the fuel pump isn't starting to crap out or maybe the fuel filter got clogged up. If I'm leaning out with 720's under these conditions there has to be a problem with either the fuel delivery to the rail or maybe the amount of duty cyle the ECU is telling the injectors to open for is not how long they're actually opening. I have a fuel gauge on a hose at work so I'll hook it up on Monday and watch what the pressure does but for now I'm going to get a new fuel filter and see what happens. I can try another pump since I know someone that has an RX7 TT pump laying around. Maybe it isn't a CAS problem at all, maybe it is just losing fuel. Thanks for helping me Scott, it's great to have someone to bounce ideas back and forth with. PS, Jeff said the readings on the logger for IAT and BARO are just what the wire into the ECU says, not what he has it locked at inside the chip. Could you watch the VSPD on your logger and tell me what you see, Scott?

Thanks.

John

 

[powerplay]

Are you talking about the VSS under the Baro reading on tab 2? Yea, what conditions do you want me to check it? Idle, moving along, etc?

 

[atc250r]

Yes, that's the one. I'm ASSuming that it should read true vehicle speed but I remember Jeff saying it would float around when the car was stationary. Check it standing still and then at whatever speed you'd like. I tried pulling the ECU out and tweaking the pins put that didn't help. I'm going to replace the fuel filter and fool with it more tomorrow. I've got a family party today that I was hoping to drive the GVR4 to but I'll just get aggrivated driving it like this.

John

 

[powerplay]

I will take some readings. I fully understand your feeling about driving the car when it is not running right. I am in the middle of doing up the Christmas tree so I will get to it later this afternoon.

Scott

 

[atc250r]

No rush, I won't be working on it anymore today.

John

 

[powerplay]

Heres what I found.

Sitting with the key in the "on" position I got 64-66. Once I started to move ant the TPS went up it jumped to 130. BTW these numbers are raw data numbers. If they hold true to the other sensors it has a range of 0-255. So they are just the data bits the ECU reads. As I drove around it stayed pretty constant at 130 for about a minute. Then it dropped to 2 and it started to vary back and forth between 2 and 130. It was at 130 more of the time than 2, but it would switch back and forth. It was not dependent on TPS% or RPM value. There were a few instances when it would hit 0,34,59,63,73,82,89,91,93, and 255 but mostly 130 and 2. These numbers appeared randomly. mixed in with the 2s and 130s. Sitting after my 12 minute drive around the hood it was reading 2s and 130s at idle. Turn the engine off and the key on on at it went to 64. It sounds like mine is doing the same thing as your. Let me know if you need anything else.

 

The speed sensor should NOT change when the car isn't moving. It should always read ~228, if I recall. I would suspect that you possibly have a bad reed switch. If you disconnect the speed sensor, and it still changes, you have ECU issues.

 

[atc250r]

I finally figured it out. The connector on the #4 injector was not making good contact. The reason that it was fixed for a while everytime I fooled with the CAS plug is because the #4 injector plug is right next to it /ubbthreads/images/graemlins/banghead.gif. I pulled every injector plug off, slightly twisted the pins inside the injector, and loaded some di-electric grease in there. The pins on #4 were actually a bit black from the acring that was probably going on in there. Thanks to everyone who helped me with this problem. Now I get to start tuning pretty much from scratch again but I'm just glad to have the car back in action.

John