2.9L Running Rich

[Javve]

I have a 91 Ranger XLT Super Cab. Truck seems to be running a little rich, along with slow acceleration and a top speed of about 65 mph. It also likes to lose speed on steep hills (both speed and rpm). I have replaced the 02 Sensor, MAP Sensor, Oil Filter, Plug Wires, Cap, Rotor, coil, and cleaned (and checked the gap) of all spark plugs. Some of which could have been affecting it. (Wouldn't start before changing the cap/rotor). The old MAP sensor was for a 4.0 which was the origional engine of this truck. I do think they are the same part number though. It also likes to have a tendancy to die when first started unless revved up a couple times. When revved up it blows white smoke after starting and it goes away when you release the pedal. I haven't held it down for a long period of time though to see if this stops. I've taken the IAC off and cleaned it thoroughly. The plunger to push the shaft doesn't seem to budge. Not sure how it's operated internally but even using a screw to get a good grip on the center piece it did not even move.

I tested the throttle position sensor, and it goes from roughly 500 ohms to about 3.1 Megohms with no major jumps, so it tests good as long as resistance measurements are within range.

The other thing that can cause the problem is the water temp sensor, and the Idle Air Control Valve. I know the slow acceleration part may be the transmission which I'm prepared for if that's the case. I'm half tempted to convert the truck to a manual transmission. Anyone done this and know if you have to do any major changes other than cut a hole for the shifter, get the clutch pedal assembly (and related parts) etc?

I'm thinking of going to the origional 4.0 Engine. The truck was given to me with a siezed 4.0, got the 2.9 cheap. (and put in the 2.9 harness/ecu).

So far the parts that I've replaced have helped the truck a little but not fix the main underlying problem of slow acceleration and top speed. When I'm more away (tomorrow) I'm going to look up the hp / torque difference between the 2.9 and the 4.0. The 2.9 also has a knock in it that increases when you are going faster but doesn't knock at the same rythm all the time. I'm thinking lifter or rod.

*Truck does not have the EGR system, and ran great with the current ecu for a few months. The 10 mpg is killing me right now while trying to find the underlying cause*

 

[IMenriched]

you'll, in all likelyhood, be much happier with a 4.0 back in place.
Lots more add on goodies and far better power band , and most important parts availability. Pretty rare if folks have 4.0 and swap back to a 2.9.

That said, the 2.9 is prone to cracking heads,,,"puffs of white smoke", is not a good sign, even if it is just after start up. Are you loosing coolant?

AIC plunger need to be able to move for it to work.

HAs the fuel filter been changed?? ALso check to see what your fuel pressure is , check the FPR.

 

[Javve]

It would have been great to stick with the 4.0, but 2.9 was a great price and was available at the time. The 4.0 was already sitting in back of the truck. I should have kept it and rebuilt it. You know what they say about hindsite! I was in an area where just going to a salvage yard and pulling one wasn't the easiest task.

I changed the fuel filter but have not been able to check the fuel pressure. The vaccum line to the FPR does not have any fuel on it. It's likely that I'll have to buy a checker specifically for this.

 

[Javve]

Replaced IAC with one from salvage yard. Old one the plunger would move but didn't use something small enough. Cleaned one out from salvage yard real well. Will see if things improve. It seems to be doing a little better. Going to clear the computer and see what happens.

I also have to look up the codes 12, 13, 77, and 74. I did a self check and those are what came up. I have it bookmarked so will see.

 

[Javve]

12 and 13 have to do with idle.

74 has to do with brake being possibly depressed (which it wasn't touched) and 77 about a goose test.

Nothing seems to add up.

 

[IMenriched]

12 and 13 have to do with idle.

74 has to do with brake being possibly depressed (which it wasn't touched) and 77 about a goose test.

Nothing seems to add up.

what kind of vacuum pressure are you getting?? and also what kind of fuel pressure are you getting??

How clean was the upper intake of the 2.9 prior to the swap?? might have carbon build-up covering a vacuum port.

 

[Javve]

I have to get the testers in order to answer your question about vacuum and fuel pressure. I didn't have the upper intake apart at all so have no idea on cleanliness. I did spray the heck out of it with intake cleaner (no I didn't use carb and choke cleaner )

I'm seriously thinking about pulling the motor and tranny out of the truck and put the 4.0 in. Can get everything I need for under $250, just have to pull it myself at a junk yard :|

 

[IMenriched]

I have to get the testers in order to answer your question about vacuum and fuel pressure. I didn't have the upper intake apart at all so have no idea on cleanliness. I did spray the heck out of it with intake cleaner (no I didn't use carb and choke cleaner )

I'm seriously thinking about pulling the motor and tranny out of the truck and put the 4.0 in. Can get everything I need for under $250, just have to pull it myself at a junk yard :|

If the 4.0 is running prior to getting it....that sounds to me like a pretty good deal.

If it can't be verified that it runs....shoot them a lower price, (If you feel that wouldn't take much to get it runnning...meaning compresssion is even across all cylinders, looks fairly clean, no coolant in the oil & vise-versa...etc)....you're already doing the work of removal. I'm sure that if that one doesn't work out that ....somewhere there is a running 4.0 for near that price.

IF your stuck with 2.9 for awhile need to get it running...the tech library has excellent info about getting codes and vast array of other thngs. http://www.therangerstation.com/tech_library/OBD_I.html

and for codes http://www.therangerstation.com/tech_library/2digitcodes.html
maybe you found this already??

the 74 may lead back to ground wire issue...the other 2 you listed earlier (12 & 13) are AIC related.....so maybe recheck grounds and connections

 

[Javve]

I had found the thing on the codes, but seen on another thread about an orange wire that is in the same loom as the O2 sensor. I checked and checked and checked... well you get the idea... and no orange wire grounded to the rear of the engine inbetween the firewall and engine. I pulled the loom off and only orange wire in there is the one going to the O2 sensor itself. So now I'm trying to figure out where the wire is supposed to origionate from, so I can trace it and see if it is grounded at all or just broken/cut and left in the loom. The donor vehicle I pulled the harness out of already had the top half of the engine missing, so it's very possible it was just cut.

 

[IMenriched]

I had found the thing on the codes, but seen on another thread about an orange wire that is in the same loom as the O2 sensor. I checked and checked and checked... well you get the idea... and no orange wire grounded to the rear of the engine inbetween the firewall and engine. I pulled the loom off and only orange wire in there is the one going to the O2 sensor itself. So now I'm trying to figure out where the wire is supposed to origionate from, so I can trace it and see if it is grounded at all or just broken/cut and left in the loom. The donor vehicle I pulled the harness out of already had the top half of the engine missing, so it's very possible it was just cut.

I can't speck directly to your vintage, yours' being a 90' & colors more than likely changed as well as wire loom/harness design ....but...my 86' had a orange wire ground from the TFI section of the harness....it grounded to the back side of the head/block. I think I counted like 5 grounds in the engine bay area.

You're in the spot where getting a wiring harness schematic for your vintage is a good idea.
or look at a neighbors or anothers buddys to see what is where.

 

[Javve]

There's some at the salvage yard here. I may have to burn a couple bucks to enter and look in hopes of saving tons in fuel cost. I found about 4 2.9's and all are almost complete. Maybe I'll be able to find where it origionates from. I checked a wiring schematic and could not find it. All I found were mostly black wires going to ground. Hope to be able to report something positive tomorrow.