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Hi Xylus,
I hope this doesn’t insult your intelligence…you’ve done a lot of work, and it sounds like you have been careful about it. Before going any further, I would suggest changing the oil and filter again. Let the engine run until normal operating temperature is reached, then change the oil after that. After doing an extensive job on my engine as a result of coolant in the oil, I was surprised how much coolant was still present. This can accumulate in the bottom of the oil pan too, after a significant leak. Here is a picture of the inside of my oil pan during the job.
At first I thought either the head gaskets or the intake manifold gaskets were still leaking. After changing it the second time there was no more coolant present.
A second suggestion would be a compression test on each cylinder. It sounds like you intend to take the plugs out anyway to check for coolant in combustion chambers. This might be a first step to ruling out head gaskets failure if compression is good…just a couple quick things I might do first if faced with your challenge. Best of luck to you…
I would check the main wiring harness at the fans to make sure there is no sign of a bad connection (burned or melted plastic). Additionally, you might check the temp sensor unit ECT (near the thermostat, see image link below). Here is a helpful article if you have access to a scan tool: http://troubleshootmyvehicle.com/gm/3.1L-3.4L/how-to-test-the-thermostat-3 Best of luck with this…
http://troubleshootmyvehicle.com/images/articles-300-399/320/323/image_1.jpg
I would check the main wiring harness at the fans to make sure there is no sign of a bad connection (burned or melted plastic). Additionally, you might check the temp sensor unit ECT (near the thermostat, see image link below). Here is a helpful article if you have access to a scan tool: http://troubleshootmyvehicle.com/gm/3.1L-3.4L/how-to-test-the-thermostat-3 Best of luck with this…
http://troubleshootmyvehicle.com/images/articles-300-399/320/323/image_1.jpg
Thanks JTF,… I did use a straight edge on the plenum to see if any warpage was present. I didn’t see any. However, I did not check the intake manifold. I will do as you suggested. If minimal warpage is present, would you suggest a layer of rtv in addition to the gaskets? It did seat well with the gaskets in place while on the bench.
tomatofarmer1
Thanks JTF,… I did use a straight edge on the plenum to see if any warpage was present. I didn’t see any. However, I did not check the intake manifold. I will do as you suggested. If minimal warpage is present, would you suggest a layer of rtv in addition to the gaskets? It did seat well with the gaskets in place while on the bench.
tomatofarmer1
It’s been a while since giving an update. The vehicle was back on the road for a while, with the misfire. After discovering that the lower intake was beginning to leak coolant again, I discovered something else using a cheap cigar and heater hose smoke test…this was after two high tech smoke tests at a friend’s shop. I’ve included a couple video links below. I tried to load the videos here but wasn’t successful…Check it out; it shows what I discovered and an inexpensive fix… Will keep you posted when I get car back together…
It’s been a while since giving an update. The vehicle was back on the road for a while, with the misfire. After discovering that the lower intake was beginning to leak coolant again, I discovered something else using a cheap cigar and heater hose smoke test…this was after two high tech smoke tests at a friend’s shop. I’ve included a couple video links below. I tried to load the videos here but wasn’t successful…Check it out; it shows what I discovered and an inexpensive fix… Will keep you posted when I get car back together…
Update:
The GM 3400 misfire issue is greatly improved, but not yet completely resolved. Last week I found the fuel rail line had a leak at the top (back side). Also, the number 5 injector seemed to not be seated correctly in the plenum. It’s hard to even see this area with a mirror. There was no raw fuel odor noticeable which was unusual. I happened to hear the fuel rail releasing pressure after the car had been off for a couple minutes. I was lucky to hear it. After replacing an o ring in the rail and reseating the injectors last weekend, things improved quite a bit. However the misfire was still present. Idle conditions improved and the misfires were not as prevalent.
This might get me kicked off the forum, but I have sinned… Yes, I threw a few bucks at the car and replaced the 7x and 24x crank position sensors this weekend. Things improved dramatically. For the first time, the vehicle produced no hard misfires at all during a test drive. Also, it performed wonderful at idle in traffic and performed well over all.
I am still experiencing some hesitation at certain speeds, 15 to 25 mph mostly. Here is my plan forward. I will again take the car to my professional mechanic friend and do the CPK relearn procedure. Also, I’m going to ask him to really check out the fuel trims, pressure, etc.,
I appreciate all of the collective wisdom on the forum. Many of you suspected a vacuum and/ or fuel issue which were true. Special thanks to Eric the car guy, DF Ranger and Fredsmythson for expertise and experience. Thanks to all who offered help.
The car will sit this week as the power steering reservoir is leaking…will repair Friday. I’ll send another update after I get the car to my friend’s shop.
tomatofarmer1
Update:
The GM 3400 misfire issue is greatly improved, but not yet completely resolved. Last week I found the fuel rail line had a leak at the top (back side). Also, the number 5 injector seemed to not be seated correctly in the plenum. It’s hard to even see this area with a mirror. There was no raw fuel odor noticeable which was unusual. I happened to hear the fuel rail releasing pressure after the car had been off for a couple minutes. I was lucky to hear it. After replacing an o ring in the rail and reseating the injectors last weekend, things improved quite a bit. However the misfire was still present. Idle conditions improved and the misfires were not as prevalent.
This might get me kicked off the forum, but I have sinned… Yes, I threw a few bucks at the car and replaced the 7x and 24x crank position sensors this weekend. Things improved dramatically. For the first time, the vehicle produced no hard misfires at all during a test drive. Also, it performed wonderful at idle in traffic and performed well over all.
I am still experiencing some hesitation at certain speeds, 15 to 25 mph mostly. Here is my plan forward. I will again take the car to my professional mechanic friend and do the CPK relearn procedure. Also, I’m going to ask him to really check out the fuel trims, pressure, etc.,
I appreciate all of the collective wisdom on the forum. Many of you suspected a vacuum and/ or fuel issue which were true. Special thanks to Eric the car guy, DF Ranger and Fredsmythson for expertise and experience. Thanks to all who offered help.
The car will sit this week as the power steering reservoir is leaking…will repair Friday. I’ll send another update after I get the car to my friend’s shop.
tomatofarmer1
Thanks Eric and DF Ranger…When performing the work, I had both heads off the vehicle. The machine shop checked the valves and pressure tested the heads. They checked out fine. I did replace the valve seals before reinstalling the heads. The vacuum gauge test is a wonderful idea. It would be a good learning experience for me. Eric I don’t know the fuel trim numbers. My mechanic friend was looking at them and simply said they looked fine.
I wholeheartedly agree with the philosophy of not “throwing parts” at the car. I am tempted to change out the crank position sensors to see what happens. Fredsmythson’s post from a couple days back answering my questions almost describes the symptoms exactly. He said the PCM did not throw a DTC for about 6 months. Even then, it was a knock sensor code rather than the crank sensor itself. I found a really good price on Ebay. Don’t throw a wrench at me.. 🙂 bad idea? I’m tempted. Again, know my thanks for your time and knowledge is sincere..thanks very muchThanks Eric and DF Ranger…When performing the work, I had both heads off the vehicle. The machine shop checked the valves and pressure tested the heads. They checked out fine. I did replace the valve seals before reinstalling the heads. The vacuum gauge test is a wonderful idea. It would be a good learning experience for me. Eric I don’t know the fuel trim numbers. My mechanic friend was looking at them and simply said they looked fine.
I wholeheartedly agree with the philosophy of not “throwing parts” at the car. I am tempted to change out the crank position sensors to see what happens. Fredsmythson’s post from a couple days back answering my questions almost describes the symptoms exactly. He said the PCM did not throw a DTC for about 6 months. Even then, it was a knock sensor code rather than the crank sensor itself. I found a really good price on Ebay. Don’t throw a wrench at me.. 🙂 bad idea? I’m tempted. Again, know my thanks for your time and knowledge is sincere..thanks very muchI want to say a sincere thank you to Eric and the rest for your help and interest with this troubleshooting issue . This has been my first time on an automotive forum. The experience has been positive and encouraging.
Today, I met with a friend who is a professional mechanic and one of the most knowledgeable persons I know locally. Unfortunately the problem persists after these services/ tests were performed.
* He did the crank position relearn procedure successfully with his scanner. However, the misfire persisted afterwards.
* Secondly, he did a smoke test to check for a vacuum leak. No leaks were detected during this test.
* Next, he checked the fuel trims and injectors, etc., with the scanner. He said it all checked out within specs and fine.
* He did find an intermittent misfire in cylinders number 3 and 4 with the scanner.
Here is why this is confusing….cylinders 3 and 4 are on opposite sides of the engine. They are controlled by separate coils. Again, the coils are relatively new as are the plugs and wires (all original AC Delco).I checked the plugs, wires and connections to the coils. All seems to be fine. The plugs look healthy, dry and are a good color. No signs or carbon tracking or wires crossing, etc.
So I am still scratching my head here. I did find this post on the International Automotive technicians network. I am unable to read the solution and answers. Also, I am unable to join as one has to be an ASE certified mechanic. Maybe one of you guys would be kind enough to look. It sounds like it may be describing the same issue. Here is the link: http://www.iatn.net/techhelp/69/28017/2003-chevrolet-venture-ls-3-4l-misfire-mil-lamp-on
Pressing forward…thanks again
I want to say a sincere thank you to Eric and the rest for your help and interest with this troubleshooting issue . This has been my first time on an automotive forum. The experience has been positive and encouraging.
Today, I met with a friend who is a professional mechanic and one of the most knowledgeable persons I know locally. Unfortunately the problem persists after these services/ tests were performed.
* He did the crank position relearn procedure successfully with his scanner. However, the misfire persisted afterwards.
* Secondly, he did a smoke test to check for a vacuum leak. No leaks were detected during this test.
* Next, he checked the fuel trims and injectors, etc., with the scanner. He said it all checked out within specs and fine.
* He did find an intermittent misfire in cylinders number 3 and 4 with the scanner.
Here is why this is confusing….cylinders 3 and 4 are on opposite sides of the engine. They are controlled by separate coils. Again, the coils are relatively new as are the plugs and wires (all original AC Delco).I checked the plugs, wires and connections to the coils. All seems to be fine. The plugs look healthy, dry and are a good color. No signs or carbon tracking or wires crossing, etc.
So I am still scratching my head here. I did find this post on the International Automotive technicians network. I am unable to read the solution and answers. Also, I am unable to join as one has to be an ASE certified mechanic. Maybe one of you guys would be kind enough to look. It sounds like it may be describing the same issue. Here is the link: http://www.iatn.net/techhelp/69/28017/2003-chevrolet-venture-ls-3-4l-misfire-mil-lamp-on
Pressing forward…thanks again
Thanks DF Ranger…I was hoping to avoid the dealer… 🙂 might I ask just a few follow up questions?…I see you are busy, so know it is much appreciated…
* Would this relearn be necessary any time the new balancer comes off, say for a repair (if not a different balancer)
* Would the same be true anytime in the future I unplug the crank sensor, or clean it?
* If sensor itself is replaced, is the relearn procedure necessary?
* Finally, would you replace sensor before relearn? The Car has 224k at this point. Trying to get at least one more year out of her…
Thanks very much again.Thanks DF Ranger…I was hoping to avoid the dealer… 🙂 might I ask just a few follow up questions?…I see you are busy, so know it is much appreciated…
* Would this relearn be necessary any time the new balancer comes off, say for a repair (if not a different balancer)
* Would the same be true anytime in the future I unplug the crank sensor, or clean it?
* If sensor itself is replaced, is the relearn procedure necessary?
* Finally, would you replace sensor before relearn? The Car has 224k at this point. Trying to get at least one more year out of her…
Thanks very much again.
