Hi there,

So I picked up a 96 Ranger 2.3L L4 a couple months ago. Engine was trashed. I did a full rebuild - the works (I've done about 10 of these rebuilds on the old 80-85 stangs). New sensors are: PCV, MAF; TPS, CPS, CamPS, New fuel pump; new fuel regulator. Last guy put in two new coil packs. Has obviously new plugs and wires.
Truck starts up and idles great but has no acceleration at all; it pings pretty badly at higher RPMs (25-35mph in 1st). Tried hauling my empty little trailer today and could barely pull 50mph. If I had to guess, I would say this is major fuel starvation and it may be why the previous owner toasted the engine.

Seems to be no vacuum leaks; EGR is blocked off and CAT is hollowed out and a 12 inch cherry bomb so no restrictions there. I tested the TPS and MAF with my multimeter just to be sure they were good and they look ok. Fuel pressure is at 35-45 psi. No CELs.
I have disconnected the MAF and it ran like always (except the idle of course). Tried the same with the upstream 02 sensor - ran the same as always. IAC - same thing; ran as always.
I ran a couple of cans of Seafoam through it. No effect.
I do have new injectors coming next week.
Any other ideas what this could be? I am running out of options here. I have a diagnostic ODBII coming this evening. I am going to run it with Torque to try to get some sensor data.

Any help would be great!

 

I would test compression on al least 2 cylinders just to take that off the table, 160psi is expected
Or use a vacuum gauge 18-21" is expected, lower means low compression(valve timing issue)

Yes, pinging at higher load can mean Lean mix so fuel pressure was dropping under high demand
When you tested pressure did you raise RPMs above 2,000 and then hold there for 30+ seconds to see if it was slowing dropping pressure(weak pump)

 

Thanks Ron,

I believe I tested the pressure throughout the rpm range. - but I could borrow the tool and check it again.

Got my ODBII reader. These things are the bomb. Vacuum is 18 at idle; 18 at stable 3000 rpm. Would seem to indicate compression is good (which I would expect with a rebuild).

Torque gave me this: MAF up to about 55 gps at WOT going 45mph and but never over 55 even at higher RPM in 1/2 gears. TPS data was good. Should Intake Air Temperature be 122 (its currently 41 degrees outside)?

Fuel Component System widget gave me something I wonder about - it reads open loop using O2 sensor (but if the MAF is functioning and the TPS, why would this be?). Anyone know what this is indicative of?

Thanks!

 

So I checked the fuel pressure; 35psi at 2000+ rpm. Tested vacuum with Torque Pro. 21 at idle and at 2000 rpm.

I am attaching the Torque graph of a run from 0-50 or so. I think I need to remove some sensors to make this thing intelligible.



Here is a better graph of another run.



Does the MAF usually look like this? It was floored the entire time. It was pining beyond 30mph in 1st gear.

 

So I have been going over the data and it looks like volumetric efficiency is inexplicably low - well under 50%. Does this sound like a bad MAF? I am going to replace it even though the previous owner did as well.

 

Where the IAT(intake air temp) sensor is located matters, its also called ACT(air charge temp) sensor
I think this sensor is on the intake manifold on a 1996 2.3l
So 122degF may not be out of line, but does seem a bit high

Try looking at temp before cold start or just after cold start that should be close to outside temp

And yes, a higher FALSE air temp would cause pinging and loss of power, as the computer would calculate/run a lean mix, but...................the O2 sensor would "see" that leaner burn and computer would add more fuel to compensate and would then set a Lean code.

 

The IAT is located just before the throttle body on the plastic intake tube. That high value may have been a spike due to the code reader/software connection. Today its readings are normal.

 

At that location I would expect + or - 10deg of outside air temp

 

So I installed a new MAF today and reset the computer - MAF values under load are going 60-70 gps now (and calculated VE up to VE is up to around 80 at times) so the MAF was definitely bad before. Looks like there was some gunk cooked on there. Truck is detonating much less (still does it though) but still 20 seconds to get to 50 MPH so there is still something to look at.

 

Do you have a vacuum gauge or compression gauge?

As much as I like computer controlled systems I still think they need to be tested against "real world" values

There is no "vacuum" sensor, so its a calculate value based on optimum engine values

 

Hey Ron,

I grabbed a vacuum gauge. 25 in/hg at idle; 22+ at stable 2500 rpm.

 

That's high, good

Can't see any obvious reason for the lack of power

 

So I was doing some thinking last night - and I borrowed a compression tester. 170+ psi on cylinders 2 and 3 with the engine cold - which seems pretty high from what I understand. So guessed that this shows too much cam advance, which would make the numbers a little high. I pulled the cover and I noted that my pulley was set to 3 degrees BTDC which would be great for just a little more bottom end. BUT if the cam pulley was off by a tooth, the advance would be (38/360) + 3 = 13.5 BTDC which is way too much and would explain the detonation. I pulled it back to 10 degrees ATDC on the pulley markings, which, given the hypothesis of one tooth off, gives (38/360) - 10 = + .5 degrees BTDC. And the truck works right now - MAF readings of up to 80; VE up to about 70. No pinging and keeps pulling up to at least 70 mph (didn't test on highway). Not much torque under 4000 rpm so I will probably go back and set the absolute cam advance to around 6 degrees later. Right now I am just glad its working right.
Next up - electric fan and new injectors.

Thanks for the help here Ron.

 

Well the 1996(1994-1997) 2.3l runs 9.4:1 compression ratio, so 170psi cold would be about right

But glad you got it running better

 

So truck was running ok - not great because there was a throttle response issues. The next day, it would BARELY run at all. I pulled the timing cover and the bolt that holds the tensioner was too long - so the tensioner was letting things jump. The oil pump and thus the camshaft position was going all over the place. I put in a shorter bolt, reset all the timing and put the cam advance to 10 Degrees BTDC and it is purring like a kitten (a slowish kitten). Great throttle response and no pinging at any RPM (I run 93 octane).

Thanks!

 

Good stuff