Ford EFI Gurus, 2002 Ranger driving me nuts

[airbatica]

Originally Posted By: punisher
Simple stuff first.

The idle trims you posted- they are at idle? Have you screwed with the base idle?

If your idle trims are Ok at idle, you can rule out vac leaks (lean) or MAF (rich at idle).

My advice- verify base idle with IAC disconnected. (engine at op temp etc) After that, disconnect battery/clear PCM memory and reset idle strategy.


Yes, the trims are idle, with A/C off. Base idle screw hasn't been touched since it left the factory. Disconnected the IAC, and the engine ticks over at about 500RPM. I've disconnected the battery and cleared the PCM memory several times over the course of troubleshooting it.

This afternoon, I pulled the the connectors off the PCM, the body harness where it joins the engine harness, and the TPS sensor and hit all of them with LPS NoFlash electrical contact cleaner. We'll see if that makes any difference.

 

[TFB1]

Originally Posted By: eljefino
Is the airflow from the canister purge really that big that it can cause idle changes? My GM stuff make the hose super tiny, 1/4 to 1/8" diameter.

Maybe you can restrict your hose just as a diagnostic aid? Jeez, you could plug it, but get a CEL, and could plausibly over saturate the charcoal left alone too long. If it's rubber (not vinyl) you could put a vise grips on it like a hemostat and drive around.

I'd go this route, but somehow I can't imagine the purge valve would only cause a issue with A/C on...

Also I'd clean the MAF meter, they'll cause a lean condition when dirty that can cause some strange drivability problems...

 

[eljefino]

So how do the blend doors move in the HVAC system? They draw a vacuum? Can you plug that hose?

 

[punisher]

If you do have a purge valve acting up, it will really skew your trims. If you see any purge flow at idle, there is a problem (usually with the purge flow sensor).

Like I said before in another thread- If you want a quick MAF diag look for rich trims at idle, and lean trims at cruise/WOT.

TP- when your TP sensor/idle switch is flakey, your IAC is going to go almost 100% duty cycle. When a TP flakes out, you will know it. RPM will hang ~2K mark as the IAC is opened up.

It would not hurt to verify base timing. I admit it is just about near impossible for a change of base timing to occur, but since you have gone so far with the diag. Retarded timing will cause the large Manifold vac delta, and possible idle concerns.

Just throwin' that out there.

 

[1kickbuttranger]

Mine does the ac idle hang since day one. Something tells me to look into the speed sensor in the trans. I know on some AOD's if it wasn't plugged in, the idle would just drop instantly...

With 306K on mine, I would like to have all the parts you pulled off of yours!!

 

[wander2039]

Mine was a vacuum leak under the dash. The AC worked great also except pulling a few extended hills in Arkansas. Not sure how the dealer diagnosed that.

 

[01rangerxl]

Originally Posted By: 1kickbuttranger


With 306K on mine, I would like to have all the parts you pulled off of yours!!

Hot [censored], I remember when you posted pics of it when it was a little over 200K or thereabouts. You really put some miles on that thing!

 

[Whimsey]

This happened recently with my 2002 F-150 with the 4.6 v-8 and 5 speed manual. Out of the blue it would hang up at ~2,000 rpms. In fact if I slowed down in gear to say 1,000 rpms it would jump back to ~2,000 rpms. My mechanic did the analysis and determined it was the IAC. He also cleaned the throttle body. He did that first but it still idled at ~2,000 rpms. After the IAC was replaced it idled fine most of the time. Occasionally it would hang at 2,000 at first. But as time goes on it does it less. I attribute this to the computer's relearning phase.

Whimsey

 

[airbatica]

The latest reset of the keep alive memory and connector cleaning seems to have helped. It only hangs very infrequently now with the A/C on. I had some time to look at the PIDs for the evaporative emissions this morning. This Ranger does not have a flow sensor, just the vent solenoid at the canister, and the purge valve that connects to the manifold. The canister vent solenoid shows 0% Duty Cycle at all times (normal according to the Ford Emissions/Powertrain manual). The purge valve on the other hand is opening at idle, at a duty cycle of around 25%, and rises to 85% and then closes again. The PCM shouldn't be commanding it open at idle if my understanding of the Evap system is correct. Also, LTFTs at hot idle for banks 1 and 2 are up to around 8-9%. STFTs are still fluctuating around +/-1%. *Beats head against the desk*.

 

[punisher]

If your scan tool shows the PCM ordering a duty cycle for the purge valve, ignore it for now. If there is no purge sensor I guess the PCM is using the fuel vapor pressure sensor to verify purge flow or looking for an O2 sensor swing when the purge valve opens, so a flow sensor may not be required on that vehicle. Anyway, that purge duty cycle is a PCM output, which is not something to bother with now.

Are the LTFTs trending towards "0" when going through a drive cycle? I can't remember when a MIL comes on due to LTFTs. I seem to remember about 25% last time I worked on a 4.0 OHC truck (intake gaskets/orings). If the trims trend to 0 under load(high MAP)that indicates a vac leak, or a leak between MAF an throttle body. Goes without saying, before relying on STFT/LTFT data, verify fuel pressure. Bad regulators, or fuel pressure sensors on a returnless system, renders trim data pretty much useless.

 

[1kickbuttranger]

Originally Posted By: 01rangerxl
Originally Posted By: 1kickbuttranger


With 306K on mine, I would like to have all the parts you pulled off of yours!!

Hot [censored], I remember when you posted pics of it when it was a little over 200K or thereabouts. You really put some miles on that thing!


You remembered that!! Wow!!

 

[SHOZ]

It definitely is some sort of vacuum leak. Disconnecting the IAC when the engine is hot and idling should kill the motor. If it still runs with the IAC disconnected rap on the cylinder with a screwdriver handle to see if it is sticking.

One thing I use to do on my Taurus SHOs when this would happen is to reset the idle screw. I know you are never suppose to touch it but.... This gives the PCM more headroom and better control over the IAC.

With the engine warm and idling adjust the screw so the idle is around 1500 rpm. Disconnect the electrical connector and adjust the screw back out until it is idling about 400-500 rpm.

Plug the IAC back in. Turn off the engine and disconnect the battery. If there is an idle relearning process go through that. Usually is is shifting into gear and turning on the AC allowing the idle to settle down each time.

 

[airbatica]

The LTFTs do trend towards zero at load. Fuel pressure is on spec at 55PSI. I think I found the issue. I monitored the PIDs for MAF Voltage and Flow on the way home. There are several flat sections of road where I can maintain a steady speed and load (no A/C) for several miles. Even with my sluggish scan tool, I was seeing deviations of around 30% in flow and voltage. I'm going to clean the MAF sensor again tomorrow and see if that helps.

 

[yonyon]

If you're seeing the MAF change that much at steady state you're not going to do anything my cleaning it unless there's a foreign object such as a burned bug rolling around in there.

 

[OVERKILL]

Originally Posted By: yonyon
If you're seeing the MAF change that much at steady state you're not going to do anything my cleaning it unless there's a foreign object such as a burned bug rolling around in there.


Agreed. He needs a new MAF most likely. Maybe even one from the wreckers. Perhaps a previous cleaning "fixed it to death"

 

[01rangerxl]

Time to get that one from Rock Auto.

I have one of the closeout Motorcrafts, they are good. All new sensor guts in a used housing.

 

[airbatica]

Yep, ordered the closeout Motorcraft from RockAuto. Should be here in a couple of days. I probably did clean it to death last time (spraying it with the nozzle too close). It wouldn't be the first time, and certainly won't be the last.

 

[airbatica]

I got the new MAF sensor today, installed it, and cleared PCM. The idle strategy relearn is a [censored]. I let it idle 10 minutes from cold with the A/C off, and then 5 minutes with it on. The truck finally quit jerking after driving around for 15 minutes. Kind of reminds me of doing a motherboard and CPU upgrade with Windows XP. I'll update again in a couple of days.

 

[01rangerxl]

Good to hear the new MAF seems to be doing the trick.

 

[airbatica]

Originally Posted By: 01rangerxl
Good to hear the new MAF seems to be doing the trick.


Figured I would check in with the final update. The closeout remanufactured Motorcraft MAF sensor was defective. The response time was fine, it killed the idle hanging problem. However, it was so widely off on the airflow (guessing it was miscalibrated) it was reporting to the PCM that it set a P0171 and P0173 (LTFT was near -28% at all speeds). I put the old sensor back in, returned the Motorcraft one as defective, and ordered a brand new Delphi AF10128. With the Delphi, the idle hang is gone. Fuel trims are right where they should be. The truck now runs just like the day I drove it off the lot.