2.3L ('83-'97) Problems with 94 2.3 running lean

[Nytfury]

Somewhat recently i got an old 94 that had sat for many years but only had around 100k miles on it. I've put some money into it and got it running but have been chasing problems with it. Currently im getting a code 172 which causes the engine light to turn on and off while driving. The truck also starts rough and bucks under load at somewhat lower rpms. We haven't done much modification to it other than taking the cat off, but im wondering if maybe this has given the engine enough flow to outrun the stock injectors? Any help is appreciated.

 

[alwaysFlOoReD]

Temporary removal of cat will not outrun stock injectors. But maybe injectors need cleaning or replacement?

 

[lowspeedpursuit]

'94 doesn't have downstream O2, and functional cats are generally considered non-restrictive. I would look elsewhere.

Air leaks? Fuel supply? At 100k mi., the O2 sensor itself is probably due anyway.

 

[franklin2]

Catalytic convertors do create a minor restriction, and that does cause your EGR to not flow correctly without it. It all works together. Would it be enough to make the engine buck and jerk and not run correctly? I doubt it.

If you want to take the O2 sensor and the computer trimming the fuel out of the equation, just unplug the O2 sensor and run it like that and see what happens. Once the engine warms up enough the computer will look to the O2 sensor for fueling information. If it doesn't get any info, it reverts back to the factory memory tables to fuel the engine.

 

[Nytfury]

Temporary removal of cat will not outrun stock injectors. But maybe injectors need cleaning or replacement?

Injectors have been thoroughly cleaned and i've ran some 93 octane and seafoam through it aswell.

 

[Nytfury]

'94 doesn't have downstream O2, and functional cats are generally considered non-restrictive. I would look elsewhere.

Air leaks? Fuel supply? At 100k mi., the O2 sensor itself is probably due anyway.

I have replaced the o2 sensor because the original one was damaged, the fuel pump was also replaced and i checked fuel pressure and the pump was creating pressure within the OEM specifications. I have also thoroughly checked for air and vacuum leaks.

 

[Nytfury]

Catalytic convertors do create a minor restriction, and that does cause your EGR to not flow correctly. It all works together. Would it be enough to make the engine buck and jerk and not run correctly? I doubt it.

If you want to take the O2 sensor and the computer trimming the fuel out of the equation, just unplug the O2 sensor and run it like that and see what happens. Once the engine warms up enough the computer will look to the O2 sensor for fueling information. If it doesn't get any info, it reverts back to the factory memory tables to fuel the engine.

I'll try this when i get a chance, i didn't know the computer had built in tables it would revert to, thanks for the info.

 

[scotts90ranger]

The fuel table works off of airflow and rpm, that's it, it's running lean because it is sensing less airflow through the MAF and the O2 sensor is correcting more than expected... If you haven't cleaned the MAF I would do that before doing anything silly...

 

[Nytfury]

The fuel table works off of airflow and rpm, that's it, it's running lean because it is sensing less airflow through the MAF and the O2 sensor is correcting more than expected... If you haven't cleaned the MAF I would do that before doing anything silly...

There's a long story to go with the MAF, but its clean and functioning properly.

 

[scotts90ranger]

If the MAF is functioning properly, you have good fuel injectors and are getting lean codes, you have an air leak "somewhere" where unmetered air is getting around the MAF, as dumb as it sounds it could be the PCV valve stuck open. I get a lean code on my '97 occasionally, haven't looked into it too much... on a '94 I might suspect a cracked lower intake manifold gasket where it meets the head... my turbo engine had some gasket chunks missing there and it ran odd...

 

[Blmpkn]

Injectors have been thoroughly cleaned and i've ran some 93 octane and seafoam through it aswell.

93 octane doesn't clean anything, FYI. All grades of gas have the same detergent packages in them.

 

[Nytfury]

If the MAF is functioning properly, you have good fuel injectors and are getting lean codes, you have an air leak "somewhere" where unmetered air is getting around the MAF, as dumb as it sounds it could be the PCV valve stuck open. I get a lean code on my '97 occasionally, haven't looked into it too much... on a '94 I might suspect a cracked lower intake manifold gasket where it meets the head... my turbo engine had some gasket chunks missing there and it ran odd...

i could always try pulling the manifold off, i've done the old spray starting fluid and see if the idle rises, but thats not a perfect test by any means. additionally i'm not aware of a my truck having a PCV valve, its just a tube running from my valve cover to my throttle body.....

 

[scotts90ranger]

I don't remember where the PCV is on a '94, on my '90 the 3/4" hose ran forward out of the oil separator then turned up behind the alternator, the PCV was the transition to 3/8" hose then it went behind the throttle body. On my '97 the PCV is in the middle of the intake manifold halves I think, it's been a year since I pulled the upper intake to change that half of the spark plugs...

 

[lowspeedpursuit]

'94 2.3L PCV couples two hoses of different sizes, right around the oil pressure sender, down a bit from the back-driver's corner of the head. Smaller top hose connects to the bottom of the throttle body. Per the manual, all trucks come with one, so I assume it's just harder to locate on manual-trans models because all the EGR equipment is directly in the way.

 

[Nytfury]

Thought i should post an update, the issue was probably that the plug wires for cylinders 3 and 4 were swapped on the drivers side coil. I swapped them and its running and starting much better, still have the CEL but i'll clear it and see if it comes back. I'll post another update in here when i know for sure.