1997 Pontiac Transport Montana 3.4LThis story is a long saga but I think it would help to have all the information.The van has had intermittent problems for about 5 months, shifting weird and losing power, never giving a single code from the begining to the end of the story. Before anything was done it would run exellent for about 3 minutes in the morning, then it would bog like there was no power. I had to floor it to keep up with traffice off of the light. It would hardly accelerate and struggled to keep a constant speed of 35. I replaced the plug wires and ignition module with no effect. I then took it to a shop because I was at a loss. They said the catalytic converter was plugged. So I took it home and did that job. You could see through the honeycomb in the old one but I swapped them out anyway. No change. I took it back to the shop and mentioned the shifting issues and asked if the transmission could be at fault. They kept it another day and said the next day that they believed it was the tranny. Since this is the wife's car I took it immediately to a tranny shop and told the story. They kept it overnight and drove it and said it was definitely toast. I told them to rebuild it and they did. I go to pick it up and it drives the same... So I then started looking at the van again. I noticed that the camshaft position sensor retainer bolt had fallen out and that the plastic flange around it had completely broken off. I had a thought that perhaps it was inching out of the hole and only worked when cold because of no thermalexpansion (seemed plausible at the time). I used a bar of metal to try to tap it slightly back into the hole. It didn't appear to move but I gave starting it a try. It wouldn't start after this. So I thought, yippee I found it. I disassembled it. While disassembling I recalled reading that some systems have a magnet on the camshaft. So I rotated the motor by hand and noticed there was no magnet. I panicked and read on the internet that this was not the case on this motor and that there would just be a gap in the ring on the cam, (relief). So I reassembled everything. Then tried starting it. While doing this it appeared that it wanted to start so I kept trying. I made sounds like it had fired during an exhaust stroke and burped out the exhaust a few times. Then it fired, what must have been, way before TDC and everything slowed and made a horrendous sound from the starter. I think it rotated in reverse causing a huge amount of torque in the starter because the nose broke off of it. So now I've replaced the starter and I've also replaced the crankshaft position sensor under the crank pulley too. Still no start... It seems to behave the same way as it did after I replaced the camshaft sensor. There has been a few pops and a few instant stops and then the starter manages to get going again. I have stopped fiddling with it for now. I have worked on and fixed plenty of cars before but this one has me stumped and approaching broke. Any help would be massively appreciated, Thank you!
Country: United StatesMake: PontiacModel: Trans Sport MontanaYear: 1997Engine: 3.4L
Camshaft Position Sensor
Crankshaft Position Sensor
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Yep, still waiting. I don't really have other avenues to go down until I give in and have the car towed away and fixed at a shop, which I'd rather not do. How long does it usually take to get an answer?
Hello I'm Neal and I am here to help resolve your issue. If I cannot help I will opt out and refer your question to another expert.
Wow, that is a tough one. Everything thing you have done makes sense and sounded like it was reasonable. Have you checked the fuel pressure?
I have not checked the fuel pressure. I find it very unlikely, however I will check it out. I have to rent a pressure guage from Autozone or the like to do this so I'll come back in a few days or so and let you know the results.
I think it is worth it to rule it out at this point. Let me know what you find.
I just walked out to the car to recall where the connection was for the pressure check and decided while I was there to wiggle some wiring connectors. I played with about 7 of them and then tried the ignition. It fired right up... Now to find the offending wire, wires or connector. It still runs a bit rough but now I have a pretty good lead on what to look at, even if it is the entire engine wiring harness...
I'll still look at the fuel pressure too, I'll let you know.
The low tech wiggle test is a valuable tool, with it running try and see if you can make it react by wiggling the harness.
Neal,I forgot to update this as my progress moved along. I replaced the MAFsensor, knock sensor, both crank sensors, cam sensor, air filter, swappedout the ignition module with a spare, swapped out the throttle positionsensor, transmission rebuilt (ouch!), swapped in an extra coil I had ineach position. No effect. Compression check was good, fuel pressure wasgood. It's been drivable not getting worse so we've been driving it. Thenit started ticking really really loud. I took off the front valve coverand found that a rocker bolt had backed out. It backed out because it washelicoiled with the wrong size in a previous life and then driven with animpact wrench (I assume) back together. I'm sure it was quickly sold to meafter that. The rocker has a huge wear spot in it and the pedestal it sitson is all dented up, the valve head looks good but the retainer is beat upbut working. I"m blessed that the retainer held it's keepers or I'd begiving up.So the way forward is a keyed insert. I have purchased a 12.5mm drill anda 14.5mm tap. I'll be using a spare rocker pedestal drilled out to 12.5mmat work so that I can make sure I drill straight. I also have a sparerocker and pedestal from a 3100 motor I got free years ago on craigslist.If this isn't it I'll drive it into the ground anyway. I'm stupid forspending so much money but I always thought I was on to something andsuccess was around the bend. I could have swapped a newer 3400 from ajunker GM car for $350 ($175 on half price day) and my own labor with afriend although I don't have a garage so that would have been difficult.I'll try to remember to update you when done.Aaron
Wow! You have been through a lot on this one! I hope the rocker repair goes well and you can get some more good miles out of it to compensate some of the time and money you have put into it.
Success! The van runs like a champ after I finally figured out it was the rocker and fixed it.
Glad to hear it is fixed!!! I hope you can get a lot more miles out of it.