Huge Jerk in shifting from P to D or R
 

I had posted this earlier, but didn't get much luck in resolving this.
Whenever engine is cold and I put car from P to D or R, the car gets huge jerk, As the engine gets warm, P to D/R shift become smoother. My car has 2 codes P1400 (EGR) & P0325 (Knoc Sensor) and I am sure none of these codes cause jerk like this.
Any idea what might be wrong?

tranny flush?

I was also hoping Tranny flush would take care of it, and I change tranny fluid this morning, but jerk is very much there.
googling more on this, basically if car is put in gear with motor idling more than 900rpm, there will be jerk. My car idles at 1500rpm in morning & slowly comes down to 800rpm in about 6-7 minutes, so this explains why jerk goes away when car is warm and why my cars motor mounts are broken!!!

Now the problem is how can I bring initial rpm down, I have put in new TPS, and cleaned TB,
or if anyone know something else?

Did you "accidently" shift into Park while the car was moving?

I did that one 4am morning while fixing the car, pushing it up the drive way. But it's gone away.

Your's might have something to do with the pressure...

I recently got this car, doesn't know much about its history,
I have no idea if previous owner did accidentelly put car in gear. But this doesn't explain why jerk stops when car is warm up.

I searched old posts and figured out at least part of the puzzel, the initial idle on car is high because I changed TPS. I need to Adjust TPS, let car warm up to correct idle and then remove battery for 2 hrs!!!

From stickies...

How to adjust IACV -

Warm the engine up to operating temp.
Turn off the engine.
Disconnect the TPS.
Start the engine and adjust the idle speed using the stop screw on the throttle body to 650 RPM's.
Turn off the engine.
Reconnect the TPS and restart the engine.

If the IACV is working correctly your idle should be correct. If it's a bit low, try adjusting the screw on the IACV bypass to get your idle speed to ~700 in neutral with no load. (no load means no lights or A/C)

I think thats what you need to adjust to set RPM. I did. G'luck.

Ok I had a similar problem, and in the process of diagnosing it and ultimately fixing it, I came to realize that our cars are more sensitive to electronic rather than mechanical malfunction. shadyonedeath gives you the procedure for manually adjusting idle air control timing, but only do this as a last resort as in my case there were a few small problems throwing things off and offsetting the base timing can make a problem more difficult to locate. My intake tubing had a bit of looseness in it which was resulting in all sort of extreme compensations from the ecu, but I too was getting a P0304 Knock Sensor (which stopped when I changed in a 300zx fuel filter) and decided it was time to replace it anyway, now no problems. I highly recommend that you replace your knock sensor and harness with brand new oem units (up to $200 for both). The install is in the stickies, look about for it, its relatively easy if you don't have fat hands. It sits in the V of the block 6-8" below the UIM. Unbolt, remove, and replace with extreme care, you don't want to beat up the new sensor at all because it is very sensitive to concussive shock. Don't forget to remove the negative battery terminal either to discharge the electrical system... Reset your ecu after you're done and give it a few minutes to register.

Whenever buying a used car from someone who had a questionable history with their vehicle, expect to have to go down the proverbial rabbit hole (or money pit) with it until everything is back into specifications. Look at the bright side, once you fix it, you know your maintenance is going to ensure that it lasts til the wheels fall off. Personally, I had to get new tires, new starter, new battery, new alternator, new exhaust, new belts, new plugs, new headlight bulbs... but now I'm happy :doublethu

Thanks Everyone,
I have a new KS with me, I tried a lot to change it, but couldn't get it out. And sometime while trying to take KS off, I was worried that I may not be able to put it back.
I tried to adjust idle by letting the car warm up and then taking battery off. That seem to have worked, car idles steady at 700rpm, but the original problem of jerk from P to D/R is still there, though significently lesser now.
One more thing I noticed that there is no voltage from ECU to TPS!!!

So far I have added New battery, Complete Tuneup (Plugs, Fuel Filter, Coolant, Belts, etc) New bulbs, interior shampoo, And soo on. Hopefully its all worth it.

Did you use the IACV directions to get to 700?

Glad to here you fix PART of the problem..

Whats KC?

As you suggested I cleaned up IACV, and let the car warm up for good 10mins, Then turn off car & removed battery for good 2 hrs. Now car starts up at 1300rpm and within a minute idle comes down to 700. I didn't need to change IACV screws.
Sorry It was meant to be KS : Knoc Sensor
Once again Thanks a Lot.

So does the idle stay steady and doesn't fall down to 500rpm when you go into D?

At Idle your RPM should be :

Park or Neutral @ 700 rpm.
Drive or Reverse @ 650rpm

The things, i aleady tried cleaneing the iacv by taking the hose off and spraying some CRC TB carburator cleaner, but it seems that it didn't solve my problem, should i try taking the IAVC off and cleaning it or should i try fiddling with the black adjustment screw on the IACV?

sorry if i sound like an idiot, but what is this talk about removing the battery for 2 hours?? or is that just your method of resetting the ecu?

Thats not Cleaning buddy...

To clean it, you need to remove the IACV from the Intake manifold, take it apart carefully and clean the internals thoroughly.

You'll know what i mean once you take it out. :thumbsup:

lol, that's what i thought :) How hard is it to do? Is teh IACV really complex inside?

No, not that hard. Just be careful and remember where everything goes.

I could be wrong, but this may very well be your problem. have someone shift the car for you while you look in the engine bay. if the engine jerks violently, the bad mounts may be the cause of the thump that you're feeling. i'm also thinking that this can explain why you don't feel it as much when the car gets warm. the engine wouldn't move as much when the idle drops. Once again this is just a theory, maybe someone can shed some more light.

My mounts need replacing as well, and i'm experiencing something similar to what you are going through.

A failing transmission will also cause this problem (the jerkiness from P to D or R).

could also be bad motor mounts.....

Agree with the motor mounts...

In my case jerk was caused due to high engine rpm.
You can easily check this by letting the car to warm up fully so that idle comes down to 900 and then put car in D or R.