Transmission Hesitates To UpShift

[HeavyEX]

Ok,
I have a 1999 AWD 5.0 with the po171 p0174 codes. I have been looking and looking and replacing parts but I cannot for the life of me find a vacuum leak... so far I have replaced the EGR, DPFE Sensor, EGR VAC solonoid, upper intake manifold gasket, fuel rail o-rings, PCV valve and hoses, plenum gasket and I have inspected and backprobed the TPS sensor, IAC valve and MAF sensor with instructions I found on this forum. I have used a small brake bleeder vacuum pump to test all the lines I can find without any significant loss of vaccuum. I also have used a cigar to blow smoke through the air intake and the only place I can see any smoke coming out is the IAC valve and the EGR valve. When I block those off no smoke seems to escape. I spray everywhere with carb spray and cannot notice a change in the motor speed. I took the console out and looked at the transmission. There was a long hose coming from the side going up by the engine compartement that was just capped off. I cut it down shorter, capped it with a bolt and silicone and used part of the hose to replace the other little hose coming off the top of the tranny because it seemed a little loose and had obviously had fluid splashed up in there which made it seem a little swollen.

Now, my shifting seems to be getting worse...presumably due to the vacuum leak I can't find. If I am accelerating I almost have to let off the gas and let the RPMs drop to get it to shift sometimes. Otherwise my RPMS will go up but my speed will flatten out...as if the transmission were slipping.

Am I right in thinking this could be due to my vacuum leak or am I way off? Is there something in particular you guys think I should check or do that would be causing both these problems for me? Since I am having this problem with the Transmission I am assuming the p0171 and 0174 codes are not due to a fuel delivery issue. Does the 1999 have a vac modulator on the transmission that could be bad?

Thanks in advance for any help you may offer.

 

[gonenuke]

Was there a plastic cap on the hose you caped off with the bolt? Kinda sounds like your transmission breather hose.

 

[windsors03cobra]

No vacuum modulator, I would try to change the fluid in it and see if it improves, how many miles are on the transmission ?

I've never backprobed a MAF but I would have changed it long before I did all the other stuff you did, 5.0's rarely have intake leaks and injector o ring leaks are almost unheard of, thats deep work too.

It does sound like you may have some neccesary vents plugged, good for them to be able to breathe to prevent pressure which will push fluids out seals

 

[delexploder]

Unplug the breather vent hose and check the vaper recovery lines and cans and then there's the vacuum ball in the fender I think its under the battery tray. Dose your heat work and your vent selection?

 

[HeavyEX]

All of my air controls seem to work and I have visually checked all the lines I can under the dash...all seem intact. I will take the bolt out of the hose and put the plastic cap back in and report back. There is also a hose coming off the top of the transmission which I determined today actually goes to the vent tube that hangs down the side of the transmission. It is not plugged, I blew air through it and it flows freely. Apparently there is no vacuum going to the tranny...at least none I can see. I guess it is all electronic.

I have visually checked the vac canister under the battery and the hoses going to it with no holes found. I also ran a hose down there by it while running and listened for a leak but couldn't hear one. I will take the battery out next week on my day off and take the canister out to give it a more thorough check.

Also, since the transmission problem does not seem to be related, I will buy a pressure guage and check the fuel pressure. I replaced the fuel pump a year and a half ago with an AutoZone cheapy so I guess it could be weak.

As far as the manifold gasket...yes, I wish I had not done it. It was several hours of work for me and with all the parts I replaced I am a few hundred dollars deep with no return on investment. My only hope is that those parts will last longer than the ones that were on it and I won't have to do the work again soon.

Oh, and the car has 85k on it. I assume it is the orig tranny.

Thanks for your replies.

 

[HeavyEX]

Unplugged the line and replaced fuel pump AGAIN. It seems like it may have fixed all my problems for now. Truck accelerates better and shifts smooth. Thanks a lot for your info.