1996 Pontiac Grand AM Driving me crazy
Hey guys, Here I am again with a problem I posted earlier and still have
gotten nowhere with:
I still have this interesting issue going on with my 1996 Pontiac Grand Am SE 2.4 Liter DOHC 4spd automatic with lock-up torque converter that I would appreciate some feedback on if anyone in here has anything to add.
For the last couple months I have been experiencing an odd stall out of my engine under a certain set of constraints that I have been trying to narrow down.
What happens: I will be driving the car and go to turn a corner into my neighborhood or navigating a parking lot anywhere that there is a turn required and I will start to turn the steering wheel and with my foot OFF the gas while turning and all of a sudden the power steering gets very tight/goes out, all dash lights illuminate as the engine has stalled out while in drive range "D." I will knock her into neutral and it fires right back up and proceeds just fine. This always happens to me while turning with NO throttle pressure exerted by my foot. IT ONLY occurs (or has thus far) while turning LEFT. I have not been able to duplicate it turning RIGHT. It never ever happens while driving in a linear direction and never happens while applying throttle pressure. This has me BOGGLED!! :banghead:
When this problem first occurred, it did it once then never again for a good four weeks later. So, I chalked it up to a computer glitch of sorts. Now it seems to be occurring at the most random times and tonight, while backing, in reverse, from my driveway going to dinner and turning the wheel at the end of the driveway, it stalled and imediatly re-cranked no problem when placed in neutral. I got to dinner and coming home I turned into my neighborhood, it died again coming around the corner. It always re-fires and there are NO lights (aka DTC's) illuminated on the dash indicating a problem.
I have hooked up my computer to the car and there NO DTC's, however, the first time I took a computer reading I had freeze frame data and here is what it was: "U4665ol System High RPM." I wrote the code down and then cleared it to see it it came back next time I experienced the engine dying. It has not yet and I have had the problem and been able to cause the car to cut out by duplicating a left turn and no throttle pressure while braking slightly. Because the U code did not come back, who knows if it is correlated. If it is.........
I have a couple theories on this: Could I have a problem whereby the CPS (Crank Position Sensor) is mis-communicating the engine R's to the PCM and the PCM is thinking that I am excessively spinning too many R's, therefore it is sending the fuel system into "open" loop as it does with the rev limiter? Here is why I think this may be the case......I noticed a while back that if I floored the engine in PARK that it would hit the rev limiter and back off but then if I held it to the floor, that function would stop working after the rev limiter functioned correctly a few times and then she'd red line if I did not back off the gas pedal. Tonight, with this in mind and with the computer in OPERATIONAL DATA mode, I floored it and watched my Fuel System which went into OPEN LOOP every time the rev limiter limited the engine speed, then back to CLOSED and back to OPEN, etc....well when the rev limiter gave out and it accelerated into the 6K RPM range while I soon let off the gas, my fuel system was trimmed to CLOSED loop and never went to OPEN like it should have. Why is my rev limiter not working correctly and could this problem be the reason that I am intermittently stalling the engine? Bad CPS? Bad Ignition Module? OR is there another sensor that tells the computer when to knock the fuel system to open loop to limit RPM? Please help me here, I would think that a bad CPS would cause a DTC and I have none, but this is not always the case. The freeze frame data DOES point to excessive high RPM's. Any thoughts?
Yesterday, I hooked up the OBDII computer to the data link and took myself for a test drive. I placed the computer in CAPTURE mode so that if this happened while I tried to make it happen, I could hopefully record and view the freeze frame data of what the sensors/car were/was doing at the time. Unfortunatly, even though I did get it to act up while doing this so that it would stall, when the engine dies, I loss power to the data bus which causes communications to the computer to be lost because the data link powers down. This inhibits me from getting a snapshot that I could then upload to my PC, go on another drive, record more data at the point of failure again and then upload to the PC, graph them and see what is happening. :hi:
This problem is driving me crazy. What in the HELL would cause the engine to intermittently die while in gear and running normally and "seem" to only happen while turning and with throttle pressure? I orignially thought it was only happening with the A/C on but then yesterday I have gotten it to do it with the HVAC system turned off. I also have had this happen when turning and had the engine recover without having to recrank. The Tachometer will drop to zero and most of the time, stall.....BUT SOMETIMES the tach. drops to zero and then all gauge lights illuminate for a split second and then the engine recovers with all lights going off and everything is now normal? F**ked up huh? Yeah, that is what I think. I first thought it was fuel related but I am now thinking it has to be/good chance of ignition. Could my igntion module or coil be doing this? Maybe I am just deluded that this is happening under a certain set of constraints?? I can be driving in a straight line and VERY seldom my tach will drop to ZERO and Speedometer goes crazy and then it returns to normal, but has not stalled yet. I am really thinking this is a WEIRD ignition issue. I am just tring to narrow this down to a set of conditions but I cannot seem to do so!! :doh: UGH I AM STUMPED! :cussing: Any suggestions would be greatly appreciated.
Sounds like a simple problem to me. :banghead: ....................
OK - a couple of things. Idling RPMs, normal operating temp, out of gear. Then tell me idling RPMs, normal operating temp, in gear. Let me know those fiqures. Then I need to know manifold vacuum, normal op temp, out of gear, and in gear.
Well all, I figured I would write up what the problem was after some
investigation. To all of you who might have read this and wondered what in
the world and how you'd figure it out....I've done it.
After going on a test drive the other day and duplicating the problem while trying to capture the freeze frame data at the time the engine stalls with the computer....and having the computer data link power down when I lost the engine still with the key in the RUN position...I determined the following:
The only way that I could lose power to the OBD II data link connection while the key was in the RUN position whether the engine stalls out or not was if I had some type of intermittent power down of the PCM. Using this logic, I continued to drive the car through this weekend and observe the exact conditions if when this problem occurred. I noticed that it started happening when I hit abrupt bumps in the road and also if I would swerve hard ONLY to the left. I could duplicate it more and more often now and get it to screw up on demand. This told me one thing.....PCM power interruption most likely cause by a lose/faulty connection. I ended up under the hood with the engine running for about 2 minutes and the second wire that I checked coming into the FUSE box for power feed to the 10AMP PCM BATTERY in the fuse block was lose and when I touched it, the engine stumbled then resumed.....I moved it again and she died this time, but would immediately fire right back up only to stall again next time I jiggled it. SO, I pulled the wiring all out and re-wired that wire and PROBLEM SOLVED. Thank god I can do this stuff, I bet the dealer would have charged me 600 bucks and probably not found the problem as quickly as I did. :hi: :thumbs:
Good job -
I guess the moral to your story is to do "wiggle test" (i.e. wiggle wiring connectors to see if problem replicates itsself) as part of diagnosis. The Ucar codes describing earlier indicated some sort of communication bus problem but finding the info to know where seemed to be a pain in the butt
I am glad you found the problem
Success stories are always good to read. Wanna come look at the Grand Am in my yard?? :mrgreen:
Yeah glad I found it too, it was beginning to piss me off, LOL. What year is the GA in your yard and what is the problem? :hi: