Mistifying 2000 Venture problem

OK...a week ago I posted up about my 2000 Chevy Venture problem. This all started when I tried to pass someone and it acted like the engine missed on me. Barely got it back to my in-laws house. We got it home and my mechanic is just aggravated with it. He did replace the fuel pump with an AC Delco pump as he said the old pump wasn't holding pressure and sometimes wasn't pumping at all.

He said the van starts and idles PERFECT..no missing, not running rough, etc. Drive the van down the road and after it warms up...it starts acting like it misses. Pull over and put it in Reverse...it doesn't miss....doesn't matter if you are in 1, 2, 3 or OD. Slip in in neutral...runs FINE with no missing. He also said sometimes it will stop if you stomp on the gas...sometimes it will stop once you put it in reverse and go back forward. They have had one of the expensive Snap-On scanners hooked onto it...NO CODES WHATSOEVER...ran the van with it connected the whole time and when it would act up...NO CODES...I think I am going to drive him to drinking with this one....the biggest problem is that it is RANDOM..it won't follow a set pattern of doing it! NOW one code constantly came up that is gone now was the P01404 I believe which was something with the EGR...there was a loose vacuum hose coming from the PCV Valve, seen below circled in blue in second photo (this is a photo of the old one so it's not kinked like that), I replaced that and the code hasn't come back..not sure if it was because of the vacuum hose or something happened with the EGR...

Any suggestions...things we have done...

I pulled off the PCV Tube on accident, replaced with NEW Circled in red in second photo
NEW AC Delco plug wires
NEW Fuel Pump
NEW Fuel Filter, FRAM which is what was on there, this was replaced a day or so before the pump...the gas had black crap in it on the gas tank side....black stuff was NOT in the tank so it was coming from the pump.
All work prior to this was just regular maintenance, I had the head gasket replaced this time last year though, had the dancing needle, the leak wasn't bad enough to have junk in my oil.

http://www.illuminationsfx.com/venture/ventureblackstuff.jpg

I don't mean this to sound condescending, because it is not, but does your mechanic know how to read the real-time data coming into the scanner rather than just hoping for a code? He should be looking at the real-time datastream to see if anything is going out of whack while the problem is occuring. I'm not familiar with the Snap-On scanner but I'm sure it has a record function so he could take it for a test drive and slowly accelerate while looking for spikes in the TPS or MAF or MAP values to indicate a poorly operating sensor. Saying that it is OK if you put it in neutral really doesn't mean much. In neutral there is no load on the engine and it shouldn't have any problems keeping up. See if he can record while you drive and he watches the datastream. Then, go over the datastream recording to see if there are any glitches.

I just spoke with him and he said he was reading the live data....and NOTHING was spiking or out of range....which is why he said I better bring him a bottle of the best when he figures it out....because it isn't, according to the computer, running wrong....

Question...replacing fuel pumps...doesn't require a PCM reset does it? The only out of ordinary thing that has happened just before this...was the van started misfiring, blinking SES light...ended up being one of the BACK plug wires had laid on the manifold and melted...we replaced all the wires...my wife RIGHT AFTER that went straight to Raleigh, NC..which is about a 2 hour drive...she said it shuttered once when she was getting off the interstate. Got to her mothers and the next time it was driven was by me...which is when the above started...

Van running fine with EGR P01404 code
I messed around and must have jiggled the wires which caused the flashing SES light and burned wire
Replaced vacuum hose running from PCV Valve, shown above
Replaced Spark Plug Wires
drive to Raleigh
Stutter started once down there

That is the chain of events leading to this...

Help guys....

I took the van to the local dealership to have it diagnosed today...and I have to say I am confused and...confused. As I stated before, the van had NO CODES as read by fairly top of line Snap-on Scanner....only codes it pulled up were two tensionor air bag codes...it was scanned last night before it was towed...it was started an moved into the parking place and started to pull into the bay....they come back and say there are two codes...P171 and P174. P171 is Bank 1 Lean and P174 is bank 2 lean....I had a new pcv valve and tube in the van for them to put on...no problem there. However, they say there is a transmission code being thrown...but couldn't give it to me...they told me that the engine problem was fixed...which it ISN'T if it is still bogging down after getting warm...they charge me 162 bucks for from what I understand is putting on a flipping pcv valve and pcv valve tube...then tell me there is a transmission code...which I think the Snap-on should have caught....then said I would have to pay an other 97 bucks for the transmission issue...which MAKES NO SENSE TO ME...

If the van idles fine...then warms up and bogs down under load....WITHOUT SHIFTING HARD...IN ANY GEAR...however, bogs down in ANY GEAR...except Reverse where it will not bog down but turn off if you let off the accelerator...I mean there has NEVER been any transmission shifting issues....It feels like the tech couldn't find an engine issue so passed it off to being a transmission issue...but I don't see where it COULD be a transmission issue...Again..these codes just appeared...is their scanner system that much different where it would pull codes not seen by a rather top of the line scanner by Snap-on...when this bogging down happens...the vehicle isn't bucking....it is bogging down...you can hear it in the engine......is it possible that its maybe a bad torque converter? Can they act like that?

I still think the "technicians" are relying too much on the computer to tell them what the problem is. You really need to find out what is happening when it bogs down. Is the fuel pressure good when it bogs, is the computer trying to dump more fuel but it isn't seeing it in the o2 output, is the airflow good, is the transmission stuck in 4th gear when it should be dropping into 2nd, is the torque converter locked up and not releasing, Is the o2 seeing a rich condition and de-fueling even though it isn't running rich, is the throttle position sensor dropping out at a certain range making the computer think you've let off of the accelerator pedal, are the brakes binding, when does it happen (only in closed loop?), is the exhaust unrestricted (a clogged catalytic converter will cause some serious bogging), etc.... The computer isn't there to "tell you what's wrong", it's there to monitor the sensors and let you know if the sensor is out of spec. A modern computer controlled vehicle can mask a lot of issues that would have popped up much sooner in an old carbureted car. If there are now lean codes that may be where to start looking. Something as simple as a disconnected vacuum hose can introduce enough unmetered air into the engine that the computer throws a lean code because it is outside of its paramters. Sorry this was so long, but a decent mechanic needs to look at it and start with the basics, fuel - air - spark, then move on from there.

Yeah...I think they are lost...They said it is a torque converter which makes NO SENSE...I called two transmission shops and they asked me what was happening and they said...it doesn't sound like a transmission issue...the key to them on the torque converter...after warm up...and by warm up I mean a 1/2-1 mile drive which to me isn't enough time for the transmission to get hot...anyway after warm up if it bogs down...if I barely keep my foot on the gas...it will SMOOTHLY go from first to second to third...no knocking, no kicking, etc. OK...I push the accelerator and it bogs down...I can stop the van...put it in reverse and drive to China without it bogging down...THAT is when the transmission guys said its NOT a torque converter as if the converter was locking up at the time in 1--3 it would also be doing it in R. I brought the van home and am having yet another person look at it. As far as a restricted exhaust system...can I just take out the sensor before the cat to test that?

I wouldn't be so quick to dismiss the torque converter diagnosis. I know it's a totally different car, but we had the EXACT same problem on a Hyundai Excel at about 40k miles which we had purchased new way back in the 1980s. The engine ran like a top in neutral or park from idle to high revs and back down again. As soon as you put it in drive and attempted to drive, it would sputter exactly like a car with a misfire. It took a long time to diagnose, but sure enough, it was a bad torque converter. When I first read your post I was going to suggest it as a possibility but I didn't because I knew everyone would think I was crazy.

Could you throw it in reverse?

I don't mind getting the transmission rebuilt if that is whats needed..the prices are all over though...dealer wants 3200 for a new transmission with 3 year/100000 mile, or 2800 for a rebuild...everybody else is 1550-1800 for 24 month/24,000 miles...the dealers 100000 mile warranty really means nothing with the 3 year tacked on there...

I really do not recall if reverse made a difference, but if I had to guess I'd say it did not. It's been a long time. Also, that car just needed a new torque converter, not an entire tranny rebuild. Your problem could be totally different, but I only mentioned it to answer the simple question of whether a bad torque converter can produce the engine conditons you described. The fact that it was such an odd and difficult to diagnose problem (and so frustrating!) is the only reason I remember it after almost 25 years.

Usually, if the torque converter is staying locked up the engine will stall when coming to a stop. Yes, you can take out the O2 sensor before the cat. to see if there is excess backpressure. You could also unplug the TCC solenoid on the transmission and see if it helps at all.

Put a fuel pressure guage on the thing. Get some readings from there. For the expensive Computer diagnosis, you could buy a half decent scanner youself and be just as good as those fools.

Check this dude out: http://www.amazon.com/Equus-3160-Professional-Diagnostic-Vehicles/dp/B001QIUGVI/ref=sr_1_1?ie=UTF8&s=automotive&qid=1266901341&sr=1-1

I do have someone else looking at it...he seems to think it is the TPS...we will see. lesterl, the fuel pump is brand new and pressure is where it should be. He said when he had the scanner on it the TPS voltage wasn't right...can't remember exactly what he said, but he said it was all over the place when it shouldn't be....will post back tomorrow when he comes back.

"He said the voltage was all over the place". There you have it. A scanner will only help IF you know what you are looking at. Keep us posted.

I found a guy that fixed it all....the voltages WERE all over the place....because I had wires in TWO locations that had melted and fused together....one on the manifold and the other somewhere else. It had gotten hot and melted the two wires together and caused all of this....he traced all wires from the sensors and pulled them apart and re-insulated them. I also had to replace my crank sensor, cam sensor and TPS sensor. I also had a cracked ICM. Been driving the van around the last three days...he did say that the grounding out could have damaged my PCM...so we are watching for any funny codes coming up to see if that happened. Basically...the van at start up was running fine because it was running in what I would call default mode...when the vehicle got to operating temperature and started running based on data coming from sensors...the data coming from the sensors was whacked out....

That's called "open loop" and "closed loop" modes. That's where a better tech would know what to look for to start piecing the puzzle together. That's really one of the first things to check for when diagnosing driveabilty problems. Does it happen in open loop, closed loop or both. Glad to see you finally got it fixed.

TPS is used in both OL and CL modes....