93 Transport Intermittent problems

This issue has plagued this van since it was handed down to me in June of 05. A quick history of the van.
Grandfather bought it in 93, only owner. Handed me the van with 100,000 miles. Issues before the van was given to me:
* Speedometer did not work correctly. Engine computer was replaced and fixed this problem. The computer was replaced and not more than a few days later (after sitting in a driveway for 3 days) a seal around a hose broke shooting fluids into the engine compartment a few days before the van was mine.

Since the day I received the van in June I have been having a serious problem. June was the first time ever, my van will randomly miss while changing gears. When the van would try to change gears you would feel a jolt and the tack meter would go crazy (only when issue occured, no other time). I took the van to a Accurate Auto in Euclid, OH. Good mechanics, had the van for two days, could not find the problem. After that I took the van home. On the way to Lakewood, OH about a 30 minute highway trip my van started jolting and the tack was going nuts. I got off the highway and my van stalled at a red light. Took it to a pontiac dealer. they had the van for 2 days. Drove it a toatl of 60 highway miles, could not get the van to do it. A week after I got it back , it started happening again. Took it to a friend who has been a mechanic for over 25 years. He had it for 4 days, drove it over 100 miles issue wouldnt happen. Hooked it up to a machine, there wasn't any bad output (dont know what the name of the machine is). Until october it would happen like once a month. October it started happening again. Nov 31 I took the van to Rochester. I went from Cleveland, OH to Buffalo, Ny with no problem. After Buffalo it start jolting for a few minutes and stopped. In rochester at about 3 am I go to start my van it's jolts like crazy, engine made some crazy noises, put it in drive and stalled. Started the van and didnt have the problem the whole rest of the trip. yesterday, the van stalled twice and didn't stop jolting. Today was the last straw, I was slowing down toward a red light and the van stalled and I couldn't use the brakes. Quick thinkingly I threw it in park at 5 mph......GAH.. Anyways its running fine now but I need some type of solution.... After stalling yesterday and today it took a good amount of time to get the car running again. I am thinking that the new computer is causing these troubles. All mechanics said the van is in great shape. This van will have 122,000 miles on it when I leave work today, I am not giving up on this van. Any suggestions?? Thank you very much in advance guys.

Your problem sounds something like mine, and I don't have a solution. At ~75,000 miles it started losing 12 volts momentarily. It *usually* only loses voltage for a second or two, but the effect can be strong. The tach flies up, as the speedo does sometimes. Sometimes the warning lights come on briefly. It also takes the auto. trans out of gear--apparently some 12 volt solenoid is required to be on to keep it in gear. The problem happens in every gear, sometimes in Park when idling. If the engine isn't spinning fast and the 12 v loss is longer than 1 or 2 sec., the engine quits. Real fun when I'm cruising along the highway in OD, because the engine will NOT crank if I put the gear shift in neutral. It HAS to go back to Park, which means I have to come to a full stop!

It always fires up immediately after putting it in Park, and the weird thing is that it will also start in Neutral, but won't crank after the voltage loss UNLESS I return it to Park.

Local dealer couldn't find anything wrong. Wanted to replace the "wiring harness" but they aren't available from Pontiac anymore. I bought a new ignition switch in the hope that the orig. one is the problem, but I have to remove the steering wheel and air bag first--thus my other post.

I may try to run a wire right from the battery to the wire leaving the ign. switch (assuming I can find it). Because the problem happens several times per hour, it won't take long to see if *that* fixes it.

Benessero : this "starter does nor crank at all" problem with park/neutral is probably linked to a worn out transaxle position switch, since there is no other logic that wires and switches in that circuit.
www.avigex.ca/xport/starterdiagram.jpg

Finalhour216: what engine do you have?
just in case, do you have the Check Engine Lignt to come ON when this happens ? THis is a '93 and you can pull the codes using THIS (www.avigex.ca/xport/readingdiagnostics.jpg)
And while power brake fades out if you press the pedal more than once or twice with dead engine, it will still brake the car if you push hard enough (much harder) but this will not satisfy emergency braking situations....

[QUOTE=LMP]Benessero : this "starter does nor crank at all" problem with park/neutral is probably linked to a worn out transaxle position switch, since there is no other logic that wires and switches in that circuit.

LMP,

Thanks for the reply. The baffling part of this is that the starter WILL crank in neutral EXCEPT when this "12 volt" loss occurs-then it must be placed in Park.

I'll try this today--when it stalls, I'll stop, put it in Park, and then put it in neutral and see if it'll crank.

LMP:
I have the 3.8l engine on the trans sport. When this happens the Check Engine light does not come on. Thanks for the quick tip. I should have thought about using the E Brake eh but what the hell crap happens. Anyways I spoke with my grandfather again today. He does know a good amount about repairing cars, just doesn't have the space to do major jobs, but that's beside the fact. He told me that my uncle had the same problem this week. He was driving on the highway and after a certain speed his van jolted. He pulled off to the side of the road. After two or three minutes leaving it off he started the van got back on the highway with no problem. it ended up being a fuel pump problem. I'm going to talk to my mechanic friend and inform him of that and have him take a look at the fuel pump. If you think this may not be related let me know as it may save me a few dollars. Thanks.

-Rob

Fuel pump is an instant regular suspect....and sometimes it ends up being the culprit. But I'd go with a fuel pressure test before dropping the fuel tank.
www.avigex.ca/xport/fuelpressuretest.jpg
Unhappily, unless someone can install a rig that will provide pressure reading during actual driving, pressure test with engine at no load may not prove revealing .
An inexpensive first try would be to change the fuel filter...its under the car , and it is a maintenance item, anyway.
However, all of this seems only loosely related to the other symptoms you have mentioned....I'd rather think about ignition problem....but I'd expect CEL to go on with these...although several with crank sensor or pickup coil problems (see recent thread on this) did not have the CEL.

I also have the 3.8 engine, and I am sure my problem isn't related to fuel or the fuel pump--it's purely electrical.

Good thing for LMP's post. Today I discovered that my "starting inhibitor" switch is indeed shot. It won't crank at all now unless it's in Park. But my electrical problem started BEFORE the switch failed, because it USED to start in Neutral-no problem.

I think I'll just wire-bypass the switch. I'm not concerned with starting this beast in gear--it's the lowest HP vehicle I've had in many years and "suddenly jumping ahead" is not on its menu.

I had this very same issue after i fitted my new engine 2 weeks ago......
Thing would run fine and then keep loosing 12V on and off.

In the end i tracked it down to the + 12v power distribution block near the battery. ( The one with the Red cover ). I removed all the Connections on the block. Sprayed with Contact Cleaner / Lubricant. put all the conections back and tighened them down real tight with a Ratchet.

Now shes perfect.

Paul Taylor,
TS SE 3800 TPI.
UK.