3.0 Idle and rpm dips

[kamps989]

Hey guys I am coming to my wits end about this issue, I have dug high and low on the forums to no avail.

So I have been having rough idle issues and my engines RPMs dip under acceleration in 2nd and 3rd gear. The dips generally aren't that large but on a handful of occasions it feels as though my truck is all the sudden being pulled backwards as it lugs so much. I just cleaned my MAF sensor and put a new fuel filter on (long overdue since I have 115,000 miles and I am 90% sure that was the original one). These tweaks helped my ideling and cold start issues I was having however the RPM dips continue. My truck is throwing the beloved flex fuel sensor code however in the past 2 years this code has come and gone and I haven't paid much attention to it as I don't want to replace it (not for the real one but for an emulator as I never run more than E10).

So what do you all think, has my flex fuel sensor finally caught up with me or should I be looking for a vacuum leak or EGR issue?

 

[RideFord94]

Well if the dips are intermittent I doubt it is a constant leak. It never hurts to give your egr a good cleaning as it is just carbon that builds up on the diaphragm and causes it to stick. Have you cleaned your IAC? Not much you can do about the rough idle. The only way I solved it was rebuilding the heads although I don't know if that's actually what solved it. Any cans of sea foam through the intake/fuel?

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[RideFord94]

I mean it sounds like your losing fuel or air somewhere along the line so I wouldnt put it past that sensor depending on what the side effects of a malfunction are.

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[kamps989]

I have not cleaned the IAC, however the rough idle is significantly better since I did my little bit of maintenance so I am not very concerned with that. Though I will say that my worst idle occurs when my worse RPM dips do. I have never run sea foam through anything but the gas, which I have done a lot of. Does it really work wonders when used in the intake? I am a huge sea foam advocate as I have seen it work wonders mixed with gas in small engines.

 

[RideFord94]

Yea it's basically letting the solution sit on your valves and piston faces. Anyway. I do. It still seems like your losing fuel or air somewhere. Is the idle funky and not constant or just rough?

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[kamps989]

Usually just as generally rough idle, every now and then it gets funky where you can visibly see the RPM's drop and rise. Now I am getting a misfire on #2 code again, an issue I thought was resolved however may also be related to my troubles.

 

[RonD]

Sea Foam in the intake is to clean off carbon build up that may occurs from a long term rich fuel/air mix.
Symptom of carbon build up is pinging/knocking when accelerating.
If done incorrectly it can cause engine damage, i.e. broken piston or bent push rod.

Your symptom doesn't read like carbon build up.

Couple of things that would be easy to test are the TPS and the EGR valve
The TPS(throttle position sensor) tells the computer how far down you are pushing the gas pedal, how far open the throttle plate is.
It is a simple sensor, works like a volume control or light dimmer.
Computer sends the TPS 5 volts, if throttle is closed .8-.9volts come back to computer.
As you push down on the gas pedal the TPS increases the voltage from .9 up to 4.8volts for wide open throttle
If there was a dead spot in the TPS so when it hit a certain spot the voltage going to computer dropped, say from 2.5v to 1.5v the computer would think you just took you foot of the gas, so RPMs would drop.
Easy to test this with a volt meter, center wire on the TPS is the "return voltage wire"
Peirce it with a sewing pin then turn key on, with meters black probed grounded and red probe on center wire pin you will read under 1vDC, .9 is spec.
Now slowly open throttle plate, you should read a nice steady increase in voltage, no jumping around, go to full throttle, above 4.6v is spec, then slowly close it, repeat a few times just to be sure.

Next is the EGR valve.
Locate the EGR valve and it's top vacuum line, follow that line to where it connects to DPFE sensor, unplug it and pull line out so you can reach it with your mouth and not get chewed up by the fan, lol.
Start engine
With engine idling suck on the EGR valve line, engine should start to stall out, release the vacuum and idle should return.
Turn off engine.
If nothing changes the EGR valve is probably stuck and is causing the rough idle and dip in power.
Remove EGR valve

If engine does start to die with vacuum at EGR valve then connect EGR vacuum line back to DPFE sensor.
Remove that line from EGR valve end and plug the vacuum line with a bolt or ??
Star engine and go for a drive, see if you still get that dip in power, if not then DPFE sensor is probably bad and opening EGR valve when it shouldn't

 

[kamps989]

Thanks for the ideas on testing these items, I will get all over it tomorrow. I did the sea foam through the brake booster line today, even if that wasn't the cure (which it wasnt) the motor actually seems to run a little better...in my mind at least haha. I have had the DPFE sensor go bad previously and replaced it however I was getting an engine code for that. Although I hope that is it as that would be a stupid easy fix as that thing is in a location begging for me to take it off!

Any thoughts on the symptoms of a flex fuel sensor finally giving its death rattle? Or should I continue to ignore it in the manor I have grown accustomed to?

Also could an EGR issue cause a misfire on just one cylinder?

 

[RonD]

The Flex fuel sensor issues have usually just been connector issues.
There is a connector under the drivers seat that can cause all sorts of issues.
Ford issued a TSB for 2000/20001 Rangers because of all the problems.
TSB
01-5-2
Publication Date: MARCH 2, 2001
FORD:2000-2001 RANGER
Some vehicles may exhibit a rough idle, Anti-lock Brake System (ABS) warning lamp illumination, inoperative or erratic speedometer, Diagnostic Trouble Codes (DTCs) P0500, P0501, P0503, P1721, P0176, P1000, ABS DTC 9, RABS DTC 16, or a delayed or harsh shifting automatic transmission. This may be caused by water intrusion at connector C309 (2000 model year) or C340 (2001 model year) under the driver's seat.

ACTION:
Inspect affected connectors; clean or replace connector pins as necessary. Install new sleeve and boot assembly over -14401- connector (interior). Refer to the following Service Procedure for details.

Verify water intrusion in connector C309 for 2000 model year or C340 for 2001 model year applications by removing bottom half (male) connector located on -14405- wire harness assembly under driver's seat, outside, beneath vehicle's cab. If water is present or pins are damaged, remove connector sleeve and perform the following:
INSIDE CAB
Remove driver's seat
Remove driver's door scuff plate
Peel carpet or vinyl lining back to gain access to top portion of connector C309F (for 2000 model year) or C340F (for 2001 model year)



EGR could effect just one cylinder but it would mean that one cylinder was also dealing with another issue, lean fuel mix or weak spark.
Suggested EGR leaking was more for the loss of power over all, at lower RPMs

 

[kamps989]

Just attempted to do the EGR test however I ended up not doing it because it was spewing water droplets (I presume it was water anyway!) and air out of it and wasn't all about drinking what my ranger has to offer! Is this normal and I should just literally suck it up!?

 

[RonD]

"Spewing water"??

Out of what?
The DPFE vacuum hose

Or the EGR valve?

Neither would be normal

If EGR valve then remove and replace the valve, EGR diaphragm has no connection to exhaust flow unless there is a hole in it, exhaust gas contains water also outward pressure.

And clean out that vacuum line then check if DPFE and its other vacuum lines have been water logged, lol.

 

[kamps989]

At the DPFE, there is only 2 hoses going to it and both were doing the same thing. However I just removed the hose leaving the top of my EGR valve directly and hooked a hose up to that and sucked on it and my trucks idle immediately slowed as it seemed to not like that very much. So i am assuming the valve is functioning.

 

[kamps989]

Just volted my TPS sensor and it appears to be working within spec. Thought there was a drop at first but i could not recreate it after repeated tries.

 

[RonD]

Good news on the EGR valve, that is a correct result.
And on the TPS as well.

Sorry, yes DPFE sensor hoses will have outflow with engine running.
The hoses on the DPFE sensor are connected to the EGR's exhaust tube.
One measures exhaust pressure the other measures pressure near EGR Valve, the pressure difference is used by the computer to determine exhaust gas flow into intake when computer opens EGR.

Just to test if DPFE is working correctly I would remove the vacuum line from the EGR valve and plug that line, screw or bolt in the end, so no vacuum leak.
Then drive around and see if symptom goes away, you will get a CEL since EGR is unhooked.
If idle and RPM drop improve then DPFE is probably the issue

 

[kamps989]

Can't thank you enough for your help on this issue Ron.

I just went out and tested as you said, plugged the line coming off the valve and was still getting the dips. Seemed like the Idle may have gotten slightly rougher when I reconnected the line but ever so slightly.

Could we be talking about separate issues perhaps? If so I am certainly more concerned with the dips while underway. Where to go from here is the next big question I suppose!

Just for some more info the dips only occur under acceleration when I am in a gear that would almost seem to high if I had a manual albeit no excuse for it to dip and rise like that. It only dips once then once I hit higher revs it subsides completely, the TPS really sounded like the issue on paper. Perhaps the TPS only malfunctions from time to time and with a few more testing sessions I will find it faulty?