98 v8 mountanieer shift issue. Please help

[travis1460]

So I just bought a 98 5.0 automatic awd mountanieer today. I test drove it yesterday and everything seemed fine except the front shocks felt like they needed to be replaced. Well after paying the guy for the mountie my wife drove it away and 5min later called me and said the check engine light came on. When we got home I drove it and noticed when you floor the gas the rpms shoot up to 3000 and stay there and its like the truck dont want to budge past it like a governor is on or something. If you let off the gas it accelerates fairly well but push the gas down again to downshift and same thing. Could this be because the truck might be in limp mode, or a tranny issue. When in park you can hit the gas and the rpms go all the way up no problem. I seriously hope its nothing major because the reason I bought the vehicle was to have an extra vehicle since my car has been acting up.

[96eb96]

Welcome to the Forum! Get the code read and report back(Do not pay - most major parts stores could do it). Limited power at high RPM could be a partially clogged cat converter (just a quick guess). A shift issue is possible too but usually the o/d light would be on.

[travis1460]

I just went to oreily auto and pulled the codes. I get p0171 and po174 which says its running lean on bank one and bank 2. The guy said he put new injectors in and looks like he did so that could be the case with those codes but don't know why new injectors would do that. I also did a key on engine running test and it said that the overdrive circuit was out of test range. The overdrive light is not flashing though. I can manually shift through all the gears but same thing once I hit 3000 rpms it feels like it governs out unless I let off the gas a little bit and then it shifts and seems to work ok. Its just when I give it gas to like pass it will downshift but stay at 3000 rpms

[gonenuke]

Try cleaning your MAF sensor.

Look for vacuum leaks in hoses, maybe a vacuum line is cracked or not pluged in. While the truck is running, spray starter fluid around the intake and see if you get a change in how the engine is running. If it picks up revs then you have a leak in that area.

Check your DPFE sensor make sure the hoses are not cracked.

All the things are explained in diffrent post. Just search for:

How to clean MAF sensor

Checking for vacuum leaks

Maybe when the injectors were put in the upper or lower intake gaskets were not seated properly, or bolts not torqued right.

[jremington59]

Does it feel like the tranny is slipping? You very well could be correct about it going into limp mode.

As for the check engine light, you can bet the guy reset them before you test drove it and lucky for him it didn't come on immediately. It's best to have a reader that can check stored codes when buying a vehicle so this doesn't happen.

A code P0171 may mean that one or more of the following has happened:
•The MAF (Mass Air Flow) Sensor is dirty or faulty
Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
•There could be a vacuum leak downstream of the MAF sensor
•Possible cracked vacuum or PCV line/connection
•Faulty or stuck open PCV valve
•Failed or faulty oxygen sensor (bank 1, sensor 1)
•Sticking/plugged or failed fuel injector
•Low fuel pressure (possible plugged/dirty fuel filter!)
•Exhaust leak between engine and first oxygen sensor


A code P0174 may mean that one or more of the following has happened:
•The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
•There could be a vacuum leak downstream of the MAF sensor.

[Turdle]

Good advice.

I would check the PCV valve hose and the grommet. The larger vacuum lines under the driver side of the upper plennum run back to the very center of the very rear of the lower intake manifold. The line ends with a pcv valve attached. It may have popped out, or, the grommet which seals it into place could be leaky. Since the prior owner did remove the upper intake to change the injectors, I bet there is indeed a vacuum hose loose.

The fuel pressure regulator is also vacuum controlled, however it allows higher pressure as vacuum drops.

Another quick isolation for vacuum leak is to try the ac. Do the vents switch good? Can you switch from vent to defrost and back again, with air blowing out the correct duct? If not, this tells you the leak is on the hvac side. You can the work from there.

[travis1460]

.

[travis1460]

So I went out and checked the maf sensor and it looks pretty good and has no leak. I tried to find the pcv valve with no avail but noticed there was a vacumn line that was spliced pretty bad so I attempted to fix it. I also noticed right next the the firewall there is a valve/switch looking component with an electrical connector and three vacumn ports coming off of it with the 90 degree rubber elbows. 2 out of the three have elbows and the other one in the middle only has the elbow but it is not plugged or anything. Looked all over for a vacumn line and could not find one. I beleive the component is an air bypass valve or something. It has a top that looks like it could be turned or something. Its black with a wiring connector and 3 vacumn ports coming out the bottom. The middle one has nothing connected to it, what could it go to? Could I just plug it off?

[travis1460]

I just looked on oreily autos website and saw the switch/valve I was looking at looks like an egr vacumn solenoid. It only shows two vacumn ports on the one in the picture but mine has 3 on my truck. Its right behind the upper intake toward the passenger side right by the egr valve. Does anyone else have 3 vacumn lines coming off of it?

[gonenuke]

Are you talking about this? Just saw your new post Mine only has 2 vacuum hoses attached. Mines a SOHC 4.0

[Turdle]

Now you are onto something. I have never seen one with 3 ports.

[jremington59]

A new one is around 25 dollars. But I will say if it weren't working properly it should set ofF the CEL with an EGR issue.

[travis1460]

Yes gonenuke it looks just like that. One electrical connector and three ports for vacumn underneath. two are used and one has a rubber elbow but it is not plugged.

[travis1460]

Just went and pulled the lines off and it only has 2 ports. The vacumn line had like an extra port attached to it by a tab to use as a spare I guess. It looked like it was directly attached to the valve. I cleaned the maf and iac sensor and reset the CEL light. Going to drive it to work and see how it does.

[travis1460]

So I drove it to work and it still does not seem to downshift very well. I can feel it downshift but the tack stays around 3000rpms and acts like the governer turned on or something still. I let off the gas and it will pick up speed at an ok rate and drives. I push the overdrive switch and it will pick up speed faster as long as I don't give it enough gas to try and downshift. Transmission issue or engine problem do you think?

[bronchole]

TPS going bad? Drops out at WOT? Pretty much a long shot since TPS usually go bad down where they spend most of their life operating.

[Turdle]

I think you mean to say it will not "upshift" into the next gear?

[jremington59]

I think he might mean it won't "seem" to shift up. I think his tranny might be slipping and when he lets off the gas it "grabs", you might say.

I had a guy once put 2 bottles of lucas tranny fix in prior to a test drive. The stupid ass left the empty bottles on the ground outside his garage. He tried saying it was for another vehicle but you could see it clinging to the dipstick. Some people don't care if they make it someone elses problem...

[travis1460]

Well I don't know I just know when I punch the throttle the rpms go slowly up to 3000 rpms and stay there. I would assume it would be downshifting because it would be trying to shift from od to 3rd to 2nd to first going down in sequence. I can hold the gas and it does the same thing. Let off just a little bit and it starts picking up speed. I checked the transmission fluid before I bought it and it was normal color no smell of burnt bands or anything. I can shift manually through the gears and it will go above 3000 rpms in all the gears unless I punch it and it stays at 3000 rpms in any gear. I'm going to try a new tps sensor to see if that does anything. It keeps throwing lean codes on both banks of injectors. I cant find the pcv valve anywhere. Can someone post a picture or link or something please. Thanks everyone

[travis1460]

So I was finally able to get my tps sensor off. I had to take the throttle body and cable off to get the screws loose because they were tight! I measured the voltage before doing anything and it was 1.26volts. I drilled the holes like three times until I didn't think I could go any further without breaking the ears off. I got it to 1.07 and it made a huge difference in throttle response and seemed to have more power. My mountie did not want to start hardly at all until I cranked it the fifth time after the mod and even had the negative cable off the whole time so it would set the computer. If I cant get closer to .96 with this tps sensor does that mean I need a new one? If so what brand tends to work the best?