Fairtax4me Posted December 15, 2015 Share Posted December 15, 2015 Could be a Vacuum leak. Double check all of the PCV and breather hoses. Did you remove the intake manifold? Used new gaskets? Link to comment Share on other sites More sharing options...
White95Legacy Posted December 16, 2015 Author Share Posted December 16, 2015 Cleaned out the 16 pin engine-chassis connector with a small flat tip screwdriver to scrape the pins clean, and then sprayed with PB Blaster and then sprayed with isopropyl alcohol and then blew it dry with air. Hooked up the oscilloscope then we drove 15 miles with only very slight stuttering. I had the scope hooked to ingitor and fuel injector wires and I was watching but the stuttering was so minor I didn't catch a glimpse the 2 times it stuttered for half a second. We will drive it some more but I believe that is the cause. The hesitation was worse after engine job cause we disturbed that connector. I hooked the 5v MAF TPS and Temp Sensor circuit to the positive of my multimeter, set the meter to DC volts, and I hooked the ground of my multimeter to ground, but I didn't see 5v, I guess cause the circuit is isolated from ground, must have to probe the 5v and one of the other sensor feedback wires that run to the ECU. Link to comment Share on other sites More sharing options...
White95Legacy Posted December 16, 2015 Author Share Posted December 16, 2015 We used new intake manifold gaskets, new exhaust manifold gaskets, new cat gasket. We took out PCV and put it in a cup of diesel for a couple hours and swashed it around, the plunger inside moved without issue, then put it back in. Link to comment Share on other sites More sharing options...
Cougar Posted December 16, 2015 Share Posted December 16, 2015 I don't think the return for the 5 volt supply is different than chassis ground but I may be wrong on that. You may have found that the 5 volt supply isn't working. Link to comment Share on other sites More sharing options...
mikaleda Posted December 16, 2015 Share Posted December 16, 2015 (edited) Sounds like dirty connectors were the problem. I've found that those connectors are problematic, a good cleaning of all your connectors might eliminate the rest of your issues. I would suggest getting some electrical cleaner instead of penetrant. Probably wouldn't hurt to check all you ground connections as well Edited December 16, 2015 by mikaleda Link to comment Share on other sites More sharing options...
White95Legacy Posted December 17, 2015 Author Share Posted December 17, 2015 The connections inside the 16 pin were still corroded after the PB Blaster attempt. He is trying some corrosion dissolving techniques of his, involving vinegar. We got some CRC QD Electronic Cleaner to use for a final cleaning, and then blow drying it with compressed air. 1 Link to comment Share on other sites More sharing options...
White95Legacy Posted December 18, 2015 Author Share Posted December 18, 2015 We cleaned the 16 pin connector again and it still hesitated a few times while we were driving today, not nearly as much hesitation the first day we drove it after putting the engine back in before we cleaned the 16 pin connector. I had the oscilloscope running and the fuel pulses cut short during the hesitation, ignition pulses kept sparking away like they were supposed to. I noticed there were 2 switches on the clutch pedal and not just 1 like I would have assumed. Sometimes the starter motor seems to not want to start unless the clutch is released and then pressed again, then earlier it refused to start after releasing and re-pressing the clutch 4 times, eventually we push started it since we were parked on a hill. Since then it has started fine. Might be an engine ground. We could also try bypassing all 16 pins of the connector with jumpers as a test to eliminate that connector as the problem, but that would involve alot of jumpers and risk shorting something out, or taking the female connector apart and scrubbing the female pins and making sure each one has decent friction when inserted onto the male pin. The OBDII scanner should be here next week hopefully. Link to comment Share on other sites More sharing options...
ocei77 Posted December 19, 2015 Share Posted December 19, 2015 Use emery boards to clean the contacts. Unfortunately I left my diagram of pins for the harness where I won't get back to for a few days. In either case looking at the back of the connector #1 is Br, 2 is LG, 3 is LR and 4 is YL. Check resistance and see if one/more are much higher than the others. This may help you to narrow down if only one or two pulsing low. O. Link to comment Share on other sites More sharing options...
White95Legacy Posted December 29, 2015 Author Share Posted December 29, 2015 Got the OBDII Bluetooth wireless code reader. Paired it with my laptop and displayed a bunch of graphs on my screen while driving. When the hesitation occurred throttle position worked fine, grams per second of air kept reading fine, but both front and rear oxygen sensor voltage dropped to 0. We will probably inspect the oxygen sensor wires real good. Probe them to see if they are getting shorted out or a wire is disconnecting. Inspect main relay connector B47 wiring since it supplies both oxygen sensors with 12v. Link to comment Share on other sites More sharing options...
White95Legacy Posted December 29, 2015 Author Share Posted December 29, 2015 Here is a photo of my screen during a hesitation that happened between 165 and 172 seconds, right where the oxygen sensor voltages drop to zero, engine rpm spiked from 1200rpm at 172sec to 2700rpm at 173sec, I didn't downshift to boost the rpm, so power came back around 172sec. Link to comment Share on other sites More sharing options...
Cougar Posted December 29, 2015 Share Posted December 29, 2015 Since the 12 volts seems to be having trouble I suggest you replace the Main Relay. It supplies power to the ECU and to various engine components. There could also be a connection problem going to the relay coming from the fuse panel. Both of those things are good possibilities for this trouble. The O2 sensors use the 12 volts for the heater sections only. The output voltage is generated by the sensor itself. Link to comment Share on other sites More sharing options...
Fairtax4me Posted December 29, 2015 Share Posted December 29, 2015 I can't remember, have you replaced the MAF sensor on this? Link to comment Share on other sites More sharing options...
Numbchux Posted December 29, 2015 Share Posted December 29, 2015 (edited) I see a few interesting things. I'm not sure any of them definitively point to anything, but I'll post them.... Narrow band O2 signals can be difficult to read, but the fact that they both agree means it is probably not the sensors. The only thing those 2 have in common (other than the ECU itself, which I'm not ready to assume is the issue), is the main power wire. The O2 sensors, and the purge solenoid are the only things that get power from that side of the main relay. So a main relay issue (not unheard-of) could easily cause a drop in supply voltage to those 3 things, and nothing else. Easy enough to check.... More likely, though is that they are just reading the lean condition that is causing your hesitation. I think this is supported by the condition at 142 seconds, falling rpm and closed throttle means no fuel (I assume either between gears, or just coasting). I also see the fuel trims bumping into the positive. Which would lead me to believe that the computer is trying to enrich the mixtures to compensate for the lean condition. This completely contradicts what you're seeing with the injector pulses.... Assuming the TPS actually reflects movement of the pedal at the time, that looks normal. MAF looks unaffected. Edited December 29, 2015 by Numbchux Link to comment Share on other sites More sharing options...
White95Legacy Posted December 30, 2015 Author Share Posted December 30, 2015 I can't remember, have you replaced the MAF sensor on this? Nope, too expensive for my friend, taking a more diagnostic approach. Link to comment Share on other sites More sharing options...
White95Legacy Posted December 30, 2015 Author Share Posted December 30, 2015 (edited) I see a few interesting things. I'm not sure any of them definitively point to anything, but I'll post them.... Narrow band O2 signals can be difficult to read, but the fact that they both agree means it is probably not the sensors. The only thing those 2 have in common (other than the ECU itself, which I'm not ready to assume is the issue), is the main power wire. The O2 sensors, and the purge solenoid are the only things that get power from that side of the main relay. So a main relay issue (not unheard-of) could easily cause a drop in supply voltage to those 3 things, and nothing else. Easy enough to check.... More likely, though is that they are just reading the lean condition that is causing your hesitation. I think this is supported by the condition at 142 seconds, falling rpm and closed throttle means no fuel (I assume either between gears, or just coasting). I also see the fuel trims bumping into the positive. Which would lead me to believe that the computer is trying to enrich the mixtures to compensate for the lean condition. This completely contradicts what you're seeing with the injector pulses.... Assuming the TPS actually reflects movement of the pedal at the time, that looks normal. MAF looks unaffected. We'll as long as that was not a hesitation at 142 seconds, which I don't remember if it did, but I don't think it did, that would prove that a lean mixture can make the O2 sensors read 0.0 volts. I think the O2 sensors just use the 12v from the relay for their heater, and the sensor elements generate a voltage which the ECU reads. I guess I should probe the O2 sensor leads for voltage to see what the 2 wires going to the ECU are doing to see if I am wrong about that theory. So the fuel pulses go really short during a hesitation causing a lean condition, the O2 sensors read 0 volts (wikipedia said a heated O2 sensor would read 0.2 volts during a lean condition, I guess if it is very lean it could read 0.0 Volts?), the MAF and TPS keep reading just fine otherwise the ECU would not be reporting that to my laptop, the ECU recognizes the lean by reading it's O2 sensors and is trying to adjust it's fuel trim to +25%, but the injector pulses go short. I'm starting to think the ECU has a damaged circuit internally, something to do with the injector drivers. Maybe I can convince my friend to buy an original ECU from a junkyard or ebay, we could install it and see if it fixes the problem, if it doesn't fix the problem we reinstall the old ECU and sell or return the one we bought. We can check if the ECU can be taken apart and then I can carefully look for damage. Another idea is one of the hundred wires going to the ECU is getting shorted or overloaded or crossed with another data wire and causing the ECU to act stupid. On the other hand I never did check to see if the 12v from relay to injector circuit is staying on, maybe the short fragments of pulses I see on the oscilloscope is just interference from something else and not injector pulses at all. On the other hand the MAF is working fine and it gets 12v from the same power relay circuit as the injectors and the ECU switches the individual injector grounds to pulse them, and since the car still had the same hesitation with the MAF disconnected I assumed the injector/MAF 12v from relay was fine. And here in the scanner reading we see the MAF working fine so I still doubt the injector 12v is turning off. Edited December 30, 2015 by White95Legacy Link to comment Share on other sites More sharing options...
Numbchux Posted December 30, 2015 Share Posted December 30, 2015 If you do try the ECU, FYI, it's unique to '95. Might even be more specific, as every '95 I've worked on had a MAP.... Link to comment Share on other sites More sharing options...
White95Legacy Posted December 30, 2015 Author Share Posted December 30, 2015 I should probably tag along when my friends family goes on a long drive and play with all the features of this software to see if any abnormalities are happening in unexpected places. Link to comment Share on other sites More sharing options...
Fairtax4me Posted December 30, 2015 Share Posted December 30, 2015 (edited) Nope, too expensive for my friend, taking a more diagnostic approach. Okay.When you initially described this problem, it sounded more like a hesitation or a surge issue. What I see in the data is a total loss of power for the same time that typically occurs when the MAF signal drops out. You just cant see this in the MAF data because the signal drops and returns too quickly for the scanner to observe it. The 95-99ish model 2.2 cars do have a known issue with the MAF signal dropping out intermittently, caused by a cracked solder joint inside the connector housing of the MAF. This momentary signal loss causes the ECU to freak, so it cuts the fuel for a few seconds. If the car is still moving when the fuel is returned, the engine will resume running as normal and you drive away like nothing happened. No lights come on on the dash, because as far as the dash is concerned, the engine is still running. Eventually, if the problem gets bad enough it MIGHT set a code for the MAF sensor, but usually these symptoms happen for quite a while before the computer ever sets a code. If sitting still, the engine stalls, you cycle the key and it usually starts right back up again. The signal drop is pretty much instantaneous and can happen so quickly that a typical OBD2 scanner will not be able to pick up the change in signal because the data sampling rate is too slow. But you have an O-scope, and that should be able to pick up on the signal loss. You can probe the signal wire at the MAF and ride around and watch the scope for the voltage to suddenly dip. That dip should coincide with the loss of engine power. Most of the time you can get the engine to stall while idling if you start wiggling/tugging on the wires to the MAF sensor. If you pull the wire just right, it will flex the bad solder joint and cause the signal drop. This can usually be fixed by cutting out the silicone sealant on the top of the sensor and prying the top up. Re-solder the joints where the pins connect from the plug to the pins on the PCB. Then put the top back on and re-seal with silicone or RTV sealant. Edited December 30, 2015 by Fairtax4me Link to comment Share on other sites More sharing options...
White95Legacy Posted December 30, 2015 Author Share Posted December 30, 2015 (edited) Okay.When you initially described this problem, it sounded more like a hesitation or a surge issue. What I see in the data is a total loss of power for the same time that typically occurs when the MAF signal drops out. You just cant see this in the MAF data because the signal drops and returns too quickly for the scanner to observe it. The 95-99ish model 2.2 cars do have a known issue with the MAF signal dropping out intermittently, caused by a cracked solder joint inside the connector housing of the MAF. This momentary signal loss causes the ECU to freak, so it cuts the fuel for a few seconds. If the car is still moving when the fuel is returned, the engine will resume running as normal and you drive away like nothing happened. No lights come on on the dash, because as far as the dash is concerned, the engine is still running. Eventually, if the problem gets bad enough it MIGHT set a code for the MAF sensor, but usually these symptoms happen for quite a while before the computer ever sets a code. If sitting still, the engine stalls, you cycle the key and it usually starts right back up again. The signal drop is pretty much instantaneous and can happen so quickly that a typical OBD2 scanner will not be able to pick up the change in signal because the data sampling rate is too slow. But you have an O-scope, and that should be able to pick up on the signal loss. You can probe the signal wire at the MAF and ride around and watch the scope for the voltage to suddenly dip. That dip should coincide with the loss of engine power. Most of the time you can get the engine to stall while idling if you start wiggling/tugging on the wires to the MAF sensor. If you pull the wire just right, it will flex the bad solder joint and cause the signal drop. This can usually be fixed by cutting out the silicone sealant on the top of the sensor and prying the top up. Re-solder the joints where the pins connect from the plug to the pins on the PCB. Then put the top back on and re-seal with silicone or RTV sealant. We were driving around the neighborhood a few weeks ago, I pulled over, disconnected the MAF, started up the car and it drove ok, but the hesitation still happened occasionally without the MAF even being connected. Car drove exactly the same without the MAF, hesitation/total loss of power was just as often. Edited December 30, 2015 by White95Legacy Link to comment Share on other sites More sharing options...
White95Legacy Posted December 30, 2015 Author Share Posted December 30, 2015 I just tested the injector 12v from the relay, I probed the yellow wire right by the injector and ran the wire inside the car, started the car and it read 14v, drove for a while and had a hesitation for a good 5 seconds of total power loss and the voltage stayed at 14v. So it is not a fuel injector positive supply issue. The injectors ground is switched by the ECU. We took apart the ECU and everything looks fine inside, no cracked solder joints, no cracked board, no burned components, no severed terminals. But one of the components could be worn out internally, maybe a switching controller for the injectors. We were browsing ebay for ECU's and they are only $30-$50 used, numbers match up, so he is ordering one. Link to comment Share on other sites More sharing options...
Fairtax4me Posted December 31, 2015 Share Posted December 31, 2015 We were driving around the neighborhood a few weeks ago, I pulled over, disconnected the MAF, started up the car and it drove ok, but the hesitation still happened occasionally without the MAF even being connected. Car drove exactly the same without the MAF, hesitation/total loss of power was just as often. Normally you'll get a big loss of power and a rough idle with the MAF unplugged. The engine will run, it just wont run very well. But there was no change at all? Link to comment Share on other sites More sharing options...
White95Legacy Posted December 31, 2015 Author Share Posted December 31, 2015 Normally you'll get a big loss of power and a rough idle with the MAF unplugged. The engine will run, it just wont run very well. But there was no change at all? It might not have run perfect, but after a few minutes of driving with MAF unplugged it lost power for a few seconds, more than once, same hesitation problem the car has had since they bought it. We didn't test the performance too much, but it idled ok, seemed fine. We tried the same with the TPS, unplugged it and drove around, that too made almost no difference in performance, car drove ok, but still lost power/hesitated occasionally, more than once. We tried unplugging both the MAF and TPS and the car refused to start, but unplugging just one of the two allowed it to still be driveable, but didn't isolate our problem. Link to comment Share on other sites More sharing options...
crazyhorse001 Posted December 31, 2015 Share Posted December 31, 2015 (edited) When you clean the terminals in a plug, you should put a dab of dielectric grease on them to protect against new corrosion. It will also stop current corrosion from progressing. Our robots at work always get this whenever we disconnect a plug. We have a nice spray can of grease, i'll get the name brand when i go back monday. Its not cheap, but what insurance is lol I'm still blown away at your diagnostic efforts, they're absolutely herculean! Awesome info in this thread Edited December 31, 2015 by crazyhorse001 Link to comment Share on other sites More sharing options...
White95Legacy Posted December 31, 2015 Author Share Posted December 31, 2015 When you clean the terminals in a plug, you should put a dab of dielectric grease on them to protect against new corrosion. It will also stop current corrosion from progressing. Our robots at work always get this whenever we disconnect a plug. We have a nice spray can of grease, i'll get the name brand when i go back monday. Its not cheap, but what insurance is lol I'm still blown away at your diagnostic efforts, they're absolutely herculean! Awesome info in this thread I told them to buy dielectric grease a year ago for other projects, now their solar system has terminal corrosion, maybe electrical problems in the future will teach them to diagnose problems and find solutions, but they will probably just think god broke it. Thank you Link to comment Share on other sites More sharing options...
White95Legacy Posted January 7, 2016 Author Share Posted January 7, 2016 (edited) Grrrrrr, was not the ECU. We put a different ECU in and same exact hesitation/total loss of power. This is why I used to be a mechanic, but now I ride a 20lb road bicycle with a powermeter 10,000 miles a year. Lot less to go wrong with a bike, and I can brag about how my wattage output gets better every month. Has a rear rack that measures 40cm x 65cm and can carry 70lbs. Can average 14 mph without getting sweaty, 20+mph if I wanna get somewhere fast. Think were gonna tear the wiring apart and check everything, gonna tell my friend to google for some new wiring harnesses. First we should check all the grounds, not just the grounds that are easy to reach. I hope we don't need to tear the dash apart to find the ghosts. Does anyone think it could be a connection to the crank/cam position sensor? There was no data for those sensors in the ScanMaster-ELM software I was using. I know it's a 20 year old car that some would say get rid of, but we're still having fun digging deep into the engineering behind it. Thanks all. Edited January 7, 2016 by White95Legacy Link to comment Share on other sites More sharing options...
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