Dumbfounded. Engine Light Issues

[ronmsal78]

I have a 2003 Ranger 2.3l manual trans. I cannot keep the check engine light off. I have already done the cheap/easy stuff. I cleaned the MAF etc., I also checked for vacuum leaks... none. Since my scanner can only give me freeze frame data, no live data. I cleared the code and found that the code always set at one particular time... Starting in first gear. Here is the F.F.

Exactly as written on scanner:

CODE P0171
FUELSYS1 CL
FUELSYS2 NA
LOAD_PCT% 18.8
ETC(Deg F) 203
SHRTFT1(%) 14.1
LONGFT1(%) 24.2
RPM 890
VSS(MPH) 6
SPARKADV(Deg) 16
IAT(Deg F) 102
MAF(lb/min) 0.270
TP(%) 16.5
O2B1S1(V) 0.215
SHRTFTB1S1 14.1
O2B1S2(V) 0.000

I have a really good question about the above info. Why on God's green earth is the engine running (or trying to run) in closed loop during take off? I always thought accelerating was accomplished using open loop strategies.

I need some insight on what exactly is going on here. It makes no sense.

Any help is appreciated, Ron.

 

[Earl43P]

It SHOULD be in closed loop (using all sensors for feedback signals). Open loop would be triggered by WOT, which you clearly were not flooring the gas pedal (TP @ 16.5).

Those fuel trims are high.

I tried to replicate your scenario at lunchtime with my 2000 2.5, but in 2nd gear.
@12-15 mph, just a tad over 1000 rpm, I couldn't get either fuel trim over a 4 (steady state, barely touching the gas, TPS @ ~18). I saw a STFT @ 7 during an accel, but it wouldn't stay higher than that for any duration, while going those speeds.

Since you don't have a vacuum leak but are running lean, I can only guess that perhaps your IAC is stuck full open. If it were mine, I'd remove the IAC, slap some gasket material over the IAC ports, reinstall it and see if the idle drops really low. It may not idle at all until it has a chance to relearn idle with no air from the IAC.

The other thing I notice is your "after the cat" O2 sensor is dead, but that shouldn't affect fuel trims and definitely won't set a P0171.

Did you check your PVC plumbing and oil filler cap seal for sucking air? I ask because your symptoms look like a vacuum leak to me. I know you checked for that.

 

[ronmsal78]

Disabling the IAC is not a real option. The throttle blade on this dang thing seals 100%. It closes all the way and the engine relies on the IAC just to even run at idle.

Funny this is the truck runs great exept for this abnormally tough engine light issue.

oil cap: good, gas cap: good

I removed all vacuum operated accessories, even the brake booster, plugged the line, cleared the codes, and it still came back. It's a good thing Rangers are light, I couldn't have done that with my F150.

This light is a big pain in the rear.

 

[Earl43P]

At the very least, you should test the IAC.

Note rpm at idle, then select AC on and see rise in rpm.

Disconnect IAC and note drop in rpm (may even stall).

I hear what you're saying with the TB blade seal and IAC.
But I can tell you for a fact that a 2000 3.0 WILL idle with a solid gasket blocking both IAC ports. I also played with different sized holes in the gasket, trying to make it not hang rpms between shifts (and provide engine braking during decel like the good old days).

Doesn't the 2.3 DOHC have that variable intake runner system? I know it has specific OBDII codes, but I wonder if they are open passing more air than expected? IMRC is the acronym for that, IIRC. I know that system has been problematic on some Fords.

Doesn't it also have the coolant-heated PCV? You didn't mention eliminating a PCV leak, which would be about as bad as having no oil cap seal.

I try to do all my own diagnosis too, but this may be a case where a $100 Ford tech diagnosis is worth every penny. (perhaps not yet, but maybe soon).

 

[ronmsal78]

The secondary throttles checked out good. I put on a new manifold and gaskets. 2 mos. ago. (The variable manifold geometry decided to pop its plug out of the manifold. 8 codes on that one.) The PCV is the old school type and moves freely. The only code that I have is the lean code.

Also, my a/c goes to the defrosters at anything harder than 1/4 throttle. This seems to be the norm with these. I checked the system all tested fine. This engine just doesn't like making vacuum above 2000 rpm.

 

[Earl43P]

"Also, my a/c goes to the defrosters at anything harder than 1/4 throttle. This seems to be the norm with these. I checked the system all tested fine. This engine just doesn't like making vacuum above 2000 rpm."


^Smoking gun.
You have a vacuum reservoir with a checkvalve that prevents the Defrost going to its default position as you describe.

Believe what the code is telling you (lean) and the Defrost behavior confirms it.

Vacuum problem.

http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm


The PCV system has tubing. Inspect it, its grommets, etc.
Your engine is making vacuum or you would be complaining about a hard brake pedal. The brake booster also has a checkvalve but acts as its own accumulator due to its diaphram size.

 

[ronmsal78]

I'll check this out.

 

[ronmsal78]

Okay, I checked out the IAC it worked just the way I thought it would. I unplugged it and the engine shut off like I turned the key. I think I'm gonna start testing sensors. I'm pretty sure a sluggish O2 sensor might cause this problem. Any other insight would be appreciated.

 

[ronmsal78]

Should I just throw a whole lotta money at this? I have tested or replaced everything fathomable, yet the light still come on. I got it to come on at 36 mph once. Everything else matched the earlier freeze frame. Save the O2 volts at 0.224V. I think this truck is possessed. What are the chances of an intermittent Crank sensor malfunction?