1996 Pontiac Grand AM SE engine stalling issue
As you know I am a regular on this site as far as supplying many answers to people's questions as well as asking a few. I've been away from it for a while but tonight I have an 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. :wink2:
For the last couple months I have been experiencing an odd stall out of my engine and it is very intermittent. What happens is that I will be driving and go to turn a corner into my neighborhood or navigating a parking lot 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 knock her into neutral and it fires right back up and keeps going just fine. This always happens to me while turning with NO throttle pressure exerted by my foot. It never ever happens while driving in a linear direction and never happens while applying throttle pressure. I wonder if this is just situational or if there is a reason? :doh:
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. :banghead:
I have hooked up my computer to the car and there NO DTC's, however, there was freeze frame data and here is what it was: "U4665ol System High RPM." 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? 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? Thanks guys!! :thumbs:
I suspect the ignition system. Hook a timing light up to a random plug wire
and see if the firing is rythmatic and doesnt miss or do anything crazy.
Also, check for a steady idle. Hook up a tachometer and see if it holds
steady and doesn't race, go back down low, race up again.
The reason I suggest this is because it's happened to me before. It was a bad ignition module.
Well I did that with the computer to watch my idle speed and everything seems Kosher. There are no quivers in the engine and everything seems smooth. The reason that I steered away from ignition is the fact that the rev limiter is not functioning correctly and that works by killing the fuel system as far as I know. If my rev limiter not working right has anything to do with the stalling issue, then odds are the fuel system may be the culprit would you not think? This one has me thinking for sure, I am going to play with it and see what happens. Thanks for the ideas and if anyone else knows something as well, please let me know. You do have a good point about the ignition module though which has me thinking. How can I test that or watch it with the computer? :-)
This one has me out of ideas - Let me think about this one for a day or so
:doh: :doh: Have you noticed if this happens in a particular type of weather? Say like damp/wet/humid? Odd one!
No, this can happen when it is dry as a bone and a beautiful day, or it can
happen in humid weather or rain or whatever else. It has happened
probably 6 times in the last three months just at sporadic times. I really
think it is correlated to the rev limiter not working on the car correctly
like I have explained having something to do with the fuel system getting
trimmed to open loop and when it is at idle with my foot off the gas, that
kills the engine really quickly because now, the fuel injectors are not
being pulsed and therefore, she'll die. Someone else did bring up the fact
that the ignition module could be faulty too, killing my ignition. It is
just that the car runs fine 9.9 out of 10 times.
One thing that should be added as well is that when the car has sat for a while, particularly in the am when I get ready to leave the house for work, I will start the engine and the IAC system(air pump) kicks in to run the rpm a little higher because it is cold. This is normal, but after it runs for a few seconds, the engine faulters and stumbles a couple times and then resumes normal idle. I watched this on the OBD II computer screen as well and saw that when this happens, meaning the engine faulters, my fuel system pops to open loop for just a split second then returns to closed loop as it should be in. This is why I think I have something going on with the fuel system causing this stalling.
The question is, why is this happening? Does anyone know how the Crank Position Sensor would fit into any of this if at all or does anyone know what sensors the PCM uses to rev limit the engine? I know on some cars the limiter only works in park or neutral and that signal comes from the trans to the computer. Then you'd have your device telling the computer your engine RPM at that given instant. Would that be the CPS or something to do with the ignition system elsewhere? I know what the CPS basically does but I am not sure if this is the sensor that the PCM uses to say, "hey computer, the engine is spinning at 4800K and I am detecting that the transmission is not in drive or any other gear, therefore I am calling out an engine overspeed scenario and therefore, killing the fuel." I am just trying to take this situation and make something logical out of it, LOL. What do you think?
Does anyone know what "U4665ol System High Rpm" means for OBDII Freeze Frame Data? That is NOT a DTC, yet it is what keeps coming into the computer as freeze frame data every time this problem happens. :doh: Thanks for all your help! :thumbs:
Do you have the latest software for the scanning tool your'e using?OR, can you get access to GM's service website. That U4 code could be a Gm manf. generic code. Maybe tbaxley can come up with something. I'm lost :oops:
I dont know this one off of the top of my head. It may take me a day or two but I need to do some investigating. I am familiar with the Powertrain series Codes (such as P0171) but am not knwledgable of the U or Uart series code. You have me curious and am willing to learn
The U series codes are used to identify communication isues within the OBD2
system which uses Uart communication protocal. Since I am not an I&C
engineer, I have no clue as to what that means. A U4665 code is something
outside the format of an OBD2 code since the number 4 is typically either a
0 (generic) or 1 (manufacturer specific)
I suspect you are dealing with a GM specifc code dealing with a communication issue within the OBD2 system and its associated output devices
Ok, thank you for doing all that research to look into this. I honestly
have not had time to further explore it. I am going to try and call the
dealer today as there is a guy there I can always talk to who is quite
Pontiacs. I will see what he says and then post the results. Again, thanks for the help :-)
Well I called the dealer and it was basically as expected....."Bring it in." They dont know a damn thing unless you have an open wallet and they have the car. Forget that, I am going to figure it out. If anyone has any other suggestions, I would love to hear them. :thumbs:
I talked with an acquaintance @ a dealership (unfortunately he works for a Chrysler dealership) this afternoon. A U or Ucar type code implies there is a communications breakdown between the main CPU or ECM and another module such as an ABS module or an ignition module. The error code pinpoints exact modules which aren't talking thus where some wiring troubleshooting may need to happen. You are going to need to find someone with a GM factory service manual for the car to dechipher this one
Yeah, I need to go ahead and get the service manual for the car anyways so I will probably end up doing that. I cannot get the problem to occur again right now, LOL, so this is not going to be simple to figure when it won't do it. Anyways, thanks for you help. Where are you located? I was seeing in your profile you're in Southeastern TN. I used to go to Kingsport (NE) and Johnson City and such quite often. Are you near Knoxville or further south? :-) Thanks again!
What I think Tbax means is, the "GM FACTORY" manual, not an after market service manual. These manufactors, will put strange codes onto the system that they hold as proprietary information, which SUCKS, but it's one of their money makers.Gonna have to find a source for the definition of these U codes.
Yeah Lectroid, that is what he means. :wink2: I am going to have to probably order it. I have the manuals for all but this car. There is no use in having anything but the factory one as those aftermarket ones are a crap shoot. :-) I am going to have to find some info. on freeze frame data and GM U codes. I might even go to the makers of the AUTOXRAY computer system that I own which is the OBDII scanner to see if they have any light they can shed on it. Where is VWHOBO anymore? I have not seen him with any postings in ages. I thought he might read this and know something. Thanks for all the helps guys! :-)
Chattanooga is in the Southeast corner of TN, approx 1 1/2 hr from
Knoxville and 1 1/2 hr from Atlanta, GA on I 75. I lived in Colonial
Heights between Kingsport and Johnson City for 6 years until I got
transferred to Chattanooga in 1994. Upper East TN has some great
restraunts and good BBQ houses[/QUOTE]
Yeah it sure does have some great BBQ......What is the name of that place somewhat near the Bristol Motor Speedway up on this rural route rd. through the mountains and built into the side of the hill that has EXCELLENT BBQ and a smokehouse right there on the side of the mountain??? Jake(roomate in college and from Kingsport) and I used to go jet skiing on Boone Lake and then drive out there to eat. This was maybe 3-4 years ago or so. I remember it having a neat history and it is right in the side of the mountain. They carved out a piece of the hill and built the place right there. You just pull in, not tons of parking available, LOL. I cannot think of the name of that place for nothing. It is very well known in the kingsport area. I think that area of TN is very pretty and I like it. I am about 5 hours from there in Richmond, Va. I used to drive down there often with the jet ski and met up with friends and hit the water on Boone lake and Warriors Path State Park too. Ha, I am having a nostalgic moment, LOL. If you know what I am talking about, tell me! :-)
THAT IS IT,,,been there several times, LOVED it. That is one neat place and yes, the directions are exactly as you stated. Talk about gooood eatin. I ought to drive down there just to eat sometime LOL. That whole area is nice to me. I loved hanging out down there!! :-)