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So, I finally got around to dealing with this.
First off, I’ll start by telling you all that the car has a header, and therefore has an extension on the O2 wiring to attach to the O2 sensor which is now under the car just before the flex pipe.
I was suspicious of that extension cable, so I pulled it out, and went over it. I did find nicks in the insulation on two of the wires, hard to be sure if they were significant enough to case any shorting, so I repaired the harness, and reinstalled it. When I was seeing the 1.3 volts with the O2 disconnected, that entire harness was unplugged, so it was not the cause.
With the harness reinstalled, I was still seeing 1.3 volts for the primary O2 in Torque. Next up, I removed the old O2, and replaced it with a new Denso O2 sensor. When I started the car up, I was still seeing 1.3 volts until the new sensor warmed up, then I saw voltage drop to nearly 0 briefly, and then it began cycling between about .3, and .8 volts just like it is supposed to. I also saw my fuel trims which had been at about -20 LT and – 8 ST climb to 0 LT and +4 ST.
So, apparently, when the ECU is getting no signal from the O2 sensor, for what ever reason what I see in Torque through my blue tooth OBD2 adapter is 1.3 volts. I don’t know why, but that is what was happening. New sensor in, everything works fine, engine runs amazingly, no crazy readings, life is good.
Thanks to all who offered up their advice!
After doing a bit of thinking today, I came up with a theory: My theory was that the whole issue was indeed a crazy O2 sensor. My assumption was that the O2 was sticking at 1.23 volts, which would tell the computer that the engine is crazy rich. I then assumed that when the computer attempted to push the O2 sensor lean, it was going way lean attempting to get the sensor to flip. With the long term fuel trim holding at -18, and short term pushing close to -30, but since the sensor wasn’t responding properly, the computer was still seeing what looks like a rich running engine.
Every once in a while, the O2 sensor would jump to life, and readings would change to .3, .4, 1.0, or even 0. At 0, the opposite effect would take place, and short term fuel trim would go to 40 or more positive. At 1.0, the short term fuel trim would make radical swings from positive to negative trying to sway the O2. I then set up Torque on my phone, and set up real time data to show me LTFT, STFT, O2, as well as manifold vacuum, voltage and a few other things, and was able to see some of this happening while I was driving. I theorized that my misfire was indeed a lean miss, caused by the computer compensating for a bad O2 reading.
This would explain the engine running fine when I got into the throttle hard enough, as it switched from closed loop to open loop. I figured if there were a mechanical issue like leaking injectors, EVAP issues, or a leaking fuel pressure regulator, then I would continue to have problems even in open loop. To test this, I disconnected the O2 sensor, which forces the computer to run in open loop, and as I expected, it runs fine with the O2 unhooked.
I will check the wiring from the connector to the O2 sensor tomorrow to make sure there aren’t any problems there, and if that checks out, then I guess it is time for a new O2 sensor.
In the end, my troubleshooting made this more complicated that it needed to be, but I’ve never seen a car run this poorly due to an O2 sensor. Every time I’ve had one fail before, fuel economy got bad, and then the check engine light came on, but drivability never really suffered.
Hmm, reinstall the catalytic converter . . . you really think that could be it? That could be the cause of my intermittent misfire? I’ll have to give that a try. Kind of surprises me that the car would run fine for 2 years without it, and then suddenly develop issues.
There seems to be no real pattern to when, and how long the misfire / bog lasts for. It acts, and feels very much like a lean misfire. When it is happening, if I get into the throttle, somewhere around the 2/3 to 3/4 area the engine snaps to life. I can watch the STFT jump up to 0, or slightly positive at the exact moment that the engine comes back to life.
Occasionally, I will see my O2 reading drop from 1.3 to .5 either at the onset of the misfire / bog, or at the end of it, and then slowly climb back up to 1.3 Most of the time it just sits at 1.3. I haven’t seen any crazy movement in intake pressure numbers to suggest something odd happening with the MAP sensor. The TPS also shows no signs of bad behavior. The ECM is reporting steady voltage of about 13 volts at all times, and I still have no check engine light. By now I would have expected one for the primary O2 being slow since it has sat at 1.3 volts for most of the day today, and possibly for voltage too high on the primary O2.
Is it possible that the computer is not going into closed loop, and that is why I am seeing the high, stable voltage? I would then assume that during those moments when the voltage drops to .5 or so, that the computer is in closed loop, but for some reason switches back to open loop. Of course, then my next question would by, why, and why isn’t it throwing a code if something is preventing it from going into closed loop.
Then again, maybe the whole issue is the O2 not doing what it should be, and keeping the computer from going into closed loop, but that still leaves me wondering why no CEL for the O2.
Oddly enough, I’m seeing 1.3 volts on my scan tool even with the O2 disconnected. Checking the wiring for the O2 connector (end that goes back to ECU) I see 12v on the heater, and only .4 on the O2 . . but scanner still says ECU is reporting 1.3. I’ll fully admit I am lost here, so if anyone can shed some light on this, I’m all ears.
Upstream O2 is at 1.3 constantly, I don’t see any fluctuation in it at all. Downstream O2 is not present as the car has not catalytic converter on it.
Fuel trim is generally running positive around 8 or so, but goes very negative when the misfire is present. Misfire can happen at idle, and also at driving RPM. Snapping the throttle will often clean up the misfire, sometimes only momentarily, sometimes longer term, and generally if I open the throttle up enough it will clean up and run pretty well, so seems to happen at part throttle, and idle mostly.
I did smell fuel around the engine after it was misfiring this morning. No visible leaks anywhere. I pulled the vacuum line off the pressure regulator and ran it for probably about 3 or 4 minutes to see if any fuel was getting past the diaphragm, didn’t see anything there. The fuel odor seemed to be mostly on the passengers side of the engine. Only things over there are the charcoal canister, and the pressure regulator. No visible leakage around either.
I haven’t noticed any black smoke, but the misfire mostly happened after dark last night, so I could very well have missed it, I will keep an eye out for that.
I was replacing a CV axle on my mothers Dodge Caravan, in front of her house. I’d done quite a few CV axles over the years, but never one on a Caravan. Got the wheel off, van up on jack stands, spindle nut off, no problem. Removed the pinch bolt for the lower ball joint, pried the collar apart, but the damned stud wouldn’t come out. I tried everything, including lifting up the lower control arm a bit to see if that helped. Finally, I cut a short length of steel dowel a bit smaller than the ball joint stud, and used a puller to press it in from the bottom, and force the ball joint stud out. It was working amazingly, and I was so proud of myself right up until I realized that I still had the lower control arm on the jack, raised up, with plenty of tension on the strut.
Unfortunately, I realized that just as I was making that last critical turn on the puller, and at the exact moment that it started to strike me that this was a bad idea, BANG . . . out comes the ball joint, violently, and thanks to the tension on the strut, the steering knuckle shoots out, catching me in the cheek just below my eye, and knocking me flat on my back on the ground. My wife lets out an oh my god. My mother hears it from inside and comes running out to see if I am still alive, and all I can do is lay on the ground, holding the side of my face and mumble holy s*%^$t.
Thankfully, I wasn’t hurt beyond a bruise, and a hit to my pride lol. Lesson learned about the tremendous energy stored in springs, and making sure that you understand where that load is going to be applied, and what is going to happen when you remove parts.
Usually with the inner race, I cut a groove through as much of it as I can with a dremel, stopping just short of getting into the hub, then set a chisel into that grove, and give it a good wack or two. That is usually enough to fracture the race, and get it to come off. DO wear safety glasses when doing this though, it is not unheard of for a chunk of that race to splinter off, and go whizzing through the air.
If the gauge was showing no pressure when you started, then you have a significant leak somewhere. In addition, the system has been exposed to atmospheric pressure. As the previous poster stated, you need to locate the leak, have the gas recovered out of the system, replace the leaking part, as well as the receiver / drier since it has been exposed to atmosphere, replace the proper quantity of oil for the leak, and what ever part you are replacing, and then vacuum, and charge the system by weight so as to have a proper charge in it.
Agreed that often there are multiple weak spots in the cooling system at the same time, patching up one increases the pressure in the system enough to cause the next one to fail quickly.
As for the A/C and coolant, I’ve never seen them actually built into the same unit. In my experience, the A/C Condenser is a thinner, separate unit that is mounted directly in front of the radiator. Often, it’s location, and the way it is mounted, may make it appear as if it is part of a thicker assembly that includes the radiator, but in my experience, they are always two separate units.
When I added the can (I can’t speak for the reported yearly topping off that was done before I got the car) the low side was in vacuum, and high side was a bit under 100 PSI with literally no cooling effect happening. After adding the can, the low side is still at only 20 PSI. I am pretty certain I didn’t overfill the system. I stopped where I did because of the higher than expected high side pressure, and only added the can because I wanted to verify that the system was indeed working before putting time and effort into replacing parts.
I do have a local mechanic whom will recover the charge from the system for me, and I always use him before opening any A/C system up for work.
I swapped the relays for the primary cooling fan, and the condenser fan. Still, the condenser fan was the one that sputtered and died, so that ruled out the relay as the culprit. I next went to playing with the wiring, that didn’t produce any results, so I tapped the fan blade. Ding ding ding. Every time I touched the blade and pushed it forward a bit, the fan sputtered to life, then died again. Half a can (not really quite that much) of silicone spray got it running for a bit. A/C was then able to maintain around 50 – 60 degrees depending on outside temps, even with the car sitting still.
At this point, I just received a new condenser fan motor in the mail yesterday, as well as a set of new O rings for the system. The fan motor will go in either today or tomorrow, and then I need to wait for a day when I have the time to tear the rest of the system apart. I now know that with that fan installed, everything is working properly. I am reasonable confident that it is a bit under charged, and that it has air in the system, leading to higher than normal operating pressure on the high side. This gives me complete confidence that once I replace the evap and condenser cores with the new ones I have (as well as the expansion valve, since I already have that as well) and O rings, and properly charge it, I will have wonderfully cold air just in time for the summer heat here in NY.
I will post again once I’ve finished the job, and everything is working as it should.
I would say pressure test the cap to make certain that it is holding the proper pressure. As a previous poster pointed out, at lower pressures, the coolant will boil at lower temperatures, so if the cap is releasing early, say at 8 or 10 psi instead of 18, you could be boiling over before the cooling fans can pull the temperature down.
I was kind of thinking the same thing about the head gasket, but I didn’t want to be the one to suggest it. At any rate, always best to start with the simple, and inexpensive things first before assuming the worst.
Without a set of manifold gauges at the very least, and some idea of what you are doing, the possibility of causing significant damage (perhaps over $1000 worth) is pretty high.
Why did the system need 3 cans of gas? What is the capacity of the system to begin with? Did it have any charge in it when you started? There is a fair chance that the system is either grossly over charged, or has a considerable quantity of air in it. My honest advice is to seek the help of a professional before this becomes a very costly mistake!
It is possible that the bearing in the tensioner pulley is bad. Remove the belt, and try to rotate the pulley by hand. It should not spin freely, there should be some resistance, but it should be smooth with no grinding or grabbing. Any looseness, locking up, sticking, grinding, grabbing etc. would be an indication that the bearing has failed.