I have searched this forum inside out........85 SE V6 starts right up, idles perfect at 900, the tcc has been disconnected for 2 years, almost every time I put it in gear my rpms drop to about 400-500, sputters out dead. No vacuum leaks, new IAC, newer TPS, trans fluid is full, new fuel pump last year, great fuel pressure, and no SES light. Happened two days ago and for the life of me I am at a loss of ideas. I tested the MAP with a multimeter and did the hand pump test as well, all numbers came back acceptable. No EGR, it is blocked off. New 02 sensor last year too. Smells like running a little rich but not terrible. I am replacing the MAP Monday just in case. Any ideas where to proceed ? Thanks in advance your time and knowledge everybody!
Maybe your brake booster is leaking internally, that would cause a massive vacuum leak only as soon as you press on the brake pedal. You would need to press the brake pedal to put into drive..........
To test, use a pair of needle nosed vice grips, tips wrapped in a few rags to not damage rubber hose. Squeeze and completely block the hose that supplies vacuum to booster. KEEP IN MIND BRAKE PEDAL WILL FEEL "HARD", AND BRAKE FORCE WILL BE REDUCED, PRESS BRAKE PEDAL HARRRRRRD WHEN PUTTING IT IN DRIVE TO PREVENT CAR FROM MOVING.
------------------ "Discord" Red 1988 GT under restoration!
Does it keep running if you go past drive to neutral? Will it keep running if you give it gas ( point the car in a safe direction.. like not at ANYTHING) Does the car lurch when this happens or does it just bog down and die?
Yes, Booster and it's line can cause major vac leak.
May need ECM scanner too. Tran's NS Switch or wires to it may be iffy and ECM is not seeing the trans in gear.
Or Can be iffy engine/trans mounts pulling wires and causing ignition fuel etc problems.
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Originally posted by Easy8: Does it keep running if you go past drive to neutral? Will it keep running if you give it gas ( point the car in a safe direction.. like not at ANYTHING) Does the car lurch when this happens or does it just bog down and die?
Can't "go past drive to neutral"... Can go pass Reverse not drive. Yes... TCC locked will try to make car move in reverse or drive. Unplug TCC may not help here depending on exact problem.
IOW Solenoid really stuck open the TCC stays locked or enough to stall engine and try to move the car.
Only helps to unplug when valve is slow to close because dirt etc makes some more resistance for core spring closing the valve. Even if core returns to close position, valve "Rubber" can be bad and leak and keep TCC locked.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
New MAP sensor did not solve this issue. I can shift into drive but it stalls just like when I put it in reverse, if I shift back to neutral sometimes it recovers without touching the gas pedal. Ogre, if you could elaborate a bit more on auto trans sensors I’m all ears sir. I am not familiar with an IOW which you noted on your reply. I’m also replacing cap and rotor cuz they looked a bit corroded and it’s a cheap $20 AC Delco job which I should’ve done already anyways.
Did this gradually get worse, or start all of the sudden?
If gradually, I would clean the bore around and edges of the throttle body plate as well as the IAC passage. On high mile engines carbon can build up in these areas and start restricting airflow. You start to see if first with transitions from park to drive.
NSS is on the trans @ shifter. Bad or iffy NSS, Iffy Shifter and/or Cable, and other things can make NSS not "Sending" ECM "signal" car in/out of park/neutral. ECM scan tool quickly tell you this as you shift thru different points. See my Cave, Neutral Safety Switch for what it look like.
You already Unplug TCC in front of Trans right? Unplug usually stops TCC problems but not always or a lest right away. Sometimes have to wait until valve closes after solenoid got hot, binding from dirt or both. That can take minutes to hours or even more. But you have unplug for years so isn't same problem. Look at how fluidmaster works for toilets... (quick link @ ~ 2:30 min mark) TCC solenoid valve work similar to it. If "rubber" is torn etc and leaking AT Fluid internally then TCC can stay locked or part locked same a foot on clutch pedal pushing part way down. Most times enough load the car and will try move at idle and stall the engine unlike try to move a little at idle but TC works and won't stall.
Check the range switch on the transmission. There are different idle parameters for Park vs. Drive. It might be loose and not in the right position or one of the connectors could have gone bad.
Same sort of thing happened to my son's car once. Turned out to be a stuck/dirty idle air control valve. To check give it a little gas while shifting into gear.
In the first post you said it "sputters" at about 500rpm, so it sounds like it's running for a moment, not just shutting off. If I'm interpreting that correctly then it sounds like a tuning/sensor issue, not a locked TCC issue. If it was the latter the engine would just immediately stall. Was the car being driven consistently before this happened, or has it been sitting?
Can you keep it running if you give it throttle? Have you driven it at speed since this issue started? Doing so will allow the ECM to recalibrate the IAC position. Do you have a broken connector at the IAC? If it's broken then it can be plugged incorrectly. I also agree with cleaning out the IAC passages. If it's not been done then they're probably pretty grimy.
The ECM detects 2 statuses from the Neutral Safety Switch - in gear and out of gear. When you shift the lever into a drive position, the ECM will anticipate by opening the IAC (and maybe make early fuel adjustments, not sure). You can notice how the idle changes in that moment when you move the shift lever but the transmission hasn't actually engaged yet. If you don't notice the ECM reacting during that moment between moving the lever and actual engagement, then I suspect it's not getting the "in gear" signal.
The signals at the NSS must be documented somewhere. If you can find that info, then you could check that with a multimeter and try to determine whether it's reliably signaling the correct status. The easiest and best way to check this (and many sensor issues) is with a laptop running WinALDL or a "scanner", but if you don't have that, then it should still be possible to look into it with your meter.
I took advice from ogre and let it idle for over 20 minutes, outta nowhere it stalls out but gave code 22, I replaced the tps, issue continues. I tried to drive and it barely got out of the driveway, giving it too much gas stalls it too. Could this be a pick up coil failing?? No codes when I tried to drive it.Gonna test spark plug wires too
The signaling from the NSS needs to be checked. Check if it's working with either a scanner, or by probing with your multimeter (exactly how depends on the pinout, I'm assuming that info is out there), or at least observe if the idle changes when you move the shifter to a drive position. If the idle changes then the ECM is apparently getting the signal.
Check your +5V line at the TPS connector. This also goes to your MAP sensor connector - might as well check it both places. If it's not a consistent 5.0V then it's going to cause problems.
You should also be able to check the signal voltage by backprobing into the connector while it's plugged in. Try wiggling wires while checking these things. Look for anywhere that either the +5V or signal wire could be shorting to ground. Have there been any previous wiring repairs? Check that the wires aren't touching.
Sorry for the delay, but here’s an update. After replacing the NSS switch, issue persisted. Turns out the pick up coil and old gas were the culprits...Running great now. Thanks for your help everybody! The coil wires were exposed and corroded really bad. Glad it wasn’t the trans!!
