No power under load

Its at the shop now - I will get it back tomorrow. The nissan dealership said they checked fuel pressure and it was good, but im having it checked again today. When I get it back tomorrow I will jack it up so the front wheels turn free and put it in gear and see how it does.
I have also changed all the motor mounts but it still vibrates. It does not stall out when you put it into gear, but I have noticed that sometimes when you put it in gear the rpm drops down to like 500 rpm then gets back up to around 750 and stays there. It idles steady around 750 rpm but the motor shimmies like its starving for gas - if you let off the brake and let the car roll the vibration stops, but it runs like its bogged down until you get to around 35 mph then it seems to do a lot better. The transmission does not slip at all. Its been doing this for about 2 years - I thought it would get worse but never has? Ive cleaned the throttle body and relearned the air idle. I pulled the intake and checked the butterfly screws and they are all still in place and no intake leakes. The air inlet does not have any cracks or anything. Ive replaced the PCV valve because it was leaking into the intake. Il let you know the new results of the fuel pressure and how it runs up on the stands.

Thanks for the reply

I really felt like the torque converter was trying to lock up at idle so I took it to a transmission shop. I just got it back from the Tranny shop - The guy is supposed to be the best in the area & he assured me it didn't have anything to do with the Tranny or the torque converter. So I don't know what to think? Ill let you know the results time I get them.

Thanks again

This took so long because I had to get the nissan key for car monitor. I jacked it up and let the car idle. It idles perfect - put it in drive with brake on and the motor vibrates just like in the video. I take the brake off and the vibration stops. This is just like it does while on the ground. I hooked the computer to the car and here are some of the results I got. Let me know if something is off.

Idle RPM in park - 725 - 750 in Drive - 575 - 615
Shouldn't this be closer to the same?

MAF B1 g/s in park - 2.23 in drive - 3.30 and up past 4
I dont know if this is correct. Why would the reading stay the same in park and keep rising when in drive?

H02S1 B1 - park - (0.08 - 0.70) drive- (0.08-0.9)
H02S2 B1 - park - (0.29) drive- (0.29)

B/Fuel Schdl(ms) park - 3.1 drive - 5.8
Inj Pulse - B1(ms) park - 2.7 drive 4.6

IGN Timing (deg) park 11 - 12 drive 11 - 12
With motor off and ign on timing reads 110
When something like the air condition is on the timing reads around 15 when put in drive.

I have taken it yet to another trany man and he says that is is not the torque converter that he thinks is either fuel pump not having enough pressure are or the throttle body has a problem with one of its sensors.

Thanks again for your help
Terry

I didnt look like the computer I checked the car with was showing the voltage signal sent from the MAF so I manually checked by back probing with a multimeter. Here are the results.

Yellow/green wire - 2.9V all the time idle or revved Or in drive.

Red/green 12v car off and 14v car running.

Solid Red - 5v all the time

Black - n/a

White- 1.2 volts at idle 725 rpm & 2.5 volts at 3000 RPM

I thought this sounded closer to being correct - does these readings sound good to you? If so I guess Ill get a Throttle body replacement.

When I hooked the computer up to the car.
I am curious as to why it was showing
MAF B1 g/s at 2.23 all the time as long as it was in park & 3.3 when put in drive and it kept going up past 4 the longer it idled in drive. I thought maybe this was some other reading other than voltage from the MAF.

Thanks for the help again and thanks for your time

Terry

Im sorry to bother you with this, but Im having a tough time finding terminal 72 white wire. There are no markings that I can see & there is more than one white wire. Also the way the wiring harness is made it would be almost impossible to back probe it. I guess if I could find the correct wire I could just pierce the wire to get the reading. If there is a schematic somewhere I could see it would help.

Thanks again for all of your time and help

Terry

I found a schematic and got the volt readings.
Idle in park - 1.27 V
Idle in drive - 1.45 V
2500 RPM - 1.83 V
4000 RPM - 2.22 V

When you use the pedal to bring idle up to 750 in drive the motor still vibrates about the same.

When you use the pedal to bring idle up to 750 in park its smooth.

Also I haven't noticed this before, but the cover on top of the motor gets extremely hot. Hot enough you can't hardly touch it, but the temp reading is normal. Maybe its always been this way and I just have not payed much attention. Coolant level is good.

Here are some temp readings I got the other day
ECT ( °C) 94 = 201 F
INT / A Temp ( °C) 55 = 131 F
Fuel Temp ( °C) 30 = 86 F

Some surface temps
Top Motor cover - 140 F
Exhaust Header - 240 F
Exhaust coming out muffler - 190 F

Sorry this is so long just trying to get all information I can.

Thank you
Terry

I checked today for leaks - I even sprayed the intake and vacuum lines from under the car. I couldn't find anything. Also two other people have looked for leaks and couldn't find any.

Going by the tach in the car here are some more numbers. (I don't have the computer anymore)
Car Idle in neutral or park - around 725 RPM
When you put it in drive - it dips to just below the
500 RPM mark (almost stalling for just a second) then it comes up to around 600 - 625 RPM and stayes there. I know these numbers are a little different than the last numbers I give you. Sometimes it seams to vary a little - but still runs the same.

I sprayed just a quick shot of carb cleaner straight into the intake and it stalled the car. I guess this was because of the MAF.

Ive checked timing chain and guides and all is good. Harmonic balancer looks good. Also dropped the oil pan looking for maybe some metal from the engine, but all looked good.

One mechanic told me to change my transmission mount & 3 others said it was fine. I think the trany mount is good. A cpl people told me they think changing the throttle body would fix it because it is electronic & one of the sensors built into it may be off a little causing the problem without throwing a code.

I just wanted to eliminate everything I could before I went that route.

What do you think. I know something is causing my idle to be lower than it should be and I also know there shouldn't be that much difference between my idle in park and my idle in drive.

Thanks again
Terry

I tried to get fuel pressure but I can't find the port to check the pressure. The computer I used to check everything with didn't give the fuel pressure either. How can I check the fuel pressure?

The compression is
Cylinder
#1 - 165
#2 - 165
#3 - 160
#4 - 165

Car has 80,000 miles on it

Thanks
Terry

It starts to run smooth when the car starts moving. If I put it up against a wall and have it in drive with brake off it still does it. I thought this model didn't have a fuel filter. Does it have one? None of the part houses carry a filter for it - I was under the understanding it only had the strainer in the tank.

Dunno if you ever figured it out yet, but 1 thing. Difference in idle speeds between park and gear is due to timing. No power under load is most likely one of two things. Bad cat or, if the car does not have coil packs and coil is mounted in distributor or on/close to the motor, coil will get hot from engine surface temp and the coil will crack, throws no dtc, not visable, but will cause car to fall on its face under load.

I replaced cam sensor and crank sensor and spatk plugs fixed the problem