Engine stumble when coming to a stop, while in gear.

[AK Ranger]

So, it looks like the idle has smoothed out and it doesn’t drop down so far, I expect it will learn and resolve the issue completely over the next few days of driving.

It was definitely idling rough when stopped at stop lights, but the idle didn’t fluctuate much at all.

On my drive today, the Check Engine light came on. I scanned it and came up with P0305 as the main code and P0175 was a stored

The truck has new plugs and wires, as well as air filter and fuel filter. When I was cleaning the IAC, I also cleaned the MAF. MAF specific cleaner was used.

 

[Brain75]

I wouldn't worry about the rich (175) since a misfire means you are sending unburnt gas down the exhaust and that is where the sensor will pickup too much residual (unburnt) gas and have a fit... Would worry about the misfire... could be as innocuous as a new plug wire not being solid on either end.

 

[AK Ranger]

I’ll check over it tomorrow

 

[AK Ranger]

Other projects got in the way…

The plug wire ohm’ed out within spec.
I could not figure out how to actually test the coil. The coil pack has only 3 coils inside so has MATCHED pairs
They are
3-4
2-6
1-5

There is no miss-fire on cylinder 1, so I am assuming the coil is ok.

We pulled the plug and it was super clean. I dropped a new one in just to give it a shot.

after a day of driving, the P0305 code came back. Through the process of elimination, does that make an injector the next step?

 

[AK Ranger]

Okay, we pulled the upper intake off and replaced the #5 Injector. The truck is starting to run better and better.
We still have an intermittent rough idle when sitting at a stop sign, or stop light.

We currently have two codes that have returned within 50 miles of being cleared.
P0175 - Fuel Mixture Imbalance
P0172 - System Too Rich (Bank 1)

Unfortunately, I will not be home for a few weeks to work on the truck.

I am curious if the cylinder 5 misfire issue was the injector and if that issue killed the O2 sensor.

I am considering replacing all three O2 sensors, as they are not really that expensive and it would be nice knowing all three are new. Not that you can't get bad ones, but I have had pretty good luck with Bosch in the past.

 

[Brain75]

one of those is bank 1 rich, the other is back 2 rich - so both rich.... I tend to look at a couple most likely issues. A) Bad MAF, B) vac leak (the air getting in is not metered or "counted" by the computer so it is too much air - which results in lean, the computer guesses all over the place trying to correct and gets rich - usually you will get lean first then both lean and rich)

172 most likely from engine-codes:

1. Faulty fuel injectors leaking or stuck open.
2. Malfunctioning mass air flow (MAF) sensor.
3. Vacuum leaks causing incorrect air-fuel mixture.
4. Faulty oxygen sensor providing incorrect readings.

175 most likely from engine-codes:

• Dirty or Faulty Mass Air Flow (MAF) Sensor
• Intake Air Leaks
• Exhaust Gas Leaks
• Fuel Contamination
• Faulty or Leaking Fuel Injectors
• Faulty Front Heated Oxygen Sensor
• Ignition Misfiring
• Incorrect Fuel Pressure
• Positive Crankcase Ventilation (PCV) Hose Leaks

I skimmed first few posts but don't remember, where are you at on the MAF - touched it or no?
(if no, first would be clean with MAF cleaner)

vac leak would cause stumble and stumble worst at idle - so plays into what your thread title is...

where are we at on smoke test?

if you just can't pin it down to either of those, my next step would be forscan and a laptop, checking short term fuel trim and long term fuel trim.

 

[Brain75]

Oh something else to do - crank away for 10 seconds with the throttle all the way down (WOT), that should shut off the injectors, if it tries to fire at all during that crank you have a leaky injector (or a stretched out throttle cable and not achieving WOT) - if so time to figure out which injector.

 

[AK Ranger]

So much for a simple fix… LOL

Lots to look into when I get back to the truck in a few weeks.

Smoke Test - Isn’t anything I’ve ever done and would have to look into it.

MAF - I pulled it off and cleaned it with MAF Sensor Cleaner.

I sprayed both MAF Sensor Cleaner and Throttle Body Cleaner around the different intake connections and various gasket locations, there was no change in the idle condition. I can look into it more when I get home.

Thanks for all the points to look at!

 

[Brain75]

quick check, start the engine, and with it running disconnect the MAF, if the engine stalls entirely then the MAF passes to some degree - if the engine continues running the MAF is bad.

checking the MAF with multimeter - maybe mute cause the guy does that awful robo speak - just go off the on screen words...

what he says at 2:36 should be... the voltage needs to go UP as RPM goes up.


you can also check with forscan I think - for sure with $$$$ obd readers that can show sensor readings and fuel trim data.

 

[AK Ranger]

quick check, start the engine, and with it running disconnect the MAF, if the engine stalls entirely then the MAF passes to some degree - if the engine continues running the MAF is bad.

checking the MAF with multimeter - maybe mute cause the guy does that awful robo speak - just go off the on screen words...

what he says at 2:36 should be... the voltage needs to go UP as RPM goes up.


you can also check with forscan I think - for sure with $$$$ obd readers that can show sensor readings and fuel trim data.

Well, I was home for a bit and we did a little work on the Ranger, to include three new Bosch O2 Sensors and a new Coil, but it is still throwing the same P0305 Cylinder 5 Misfire Detected and P0175 Fuel Mixture Imbalance.

Here is a picture of fuel trims at the moment the light was triggered:

We did a smoke test on the exhaust system and there were no exhaust leaks at, up upstream of the O2 Sensors.
I will have to test the intake when I am back home again.

We had previously installed a new injector in the Cylinder 5 location. We have also replaced the spark plug again and we have swapped the spark plug wire with a different one on the truck and there was no change.

I am back at work, but we did unplug the MAF with the truck running. The idle dropped a little, but it idled smooth as could be. I almost ordered a MAF, but dug into it a little more and there are statements by others that say the engine should run with the MAF unplugged, as the ECU goes into a closed loop to protect the engine.

Getting pretty frustrated with all this. I am not use to chasing my tail this much. Generally I scan the vehicles, find the problem, fix the problem and go on my merry way...

 

[Brain75]

I'd clean the MAF before replacing it - 50/50 chance on junk "new" parts anymore, old one more likely to be better than new.
Did we eliminate air leak?
how bout the crank+ WOT, testing for a leaky injector?

 

[AK Ranger]

*I edited my above post with some more information.

The MAF was cleaned and no change.

I think I did the crank+ WOT test, but honestly cannot remember. Last time home was a crazy blurrrrr.
I will have my son try that when he gets home tonight and report back.

I am pretty sure the cable is stretched, as there is slack in it at the throttle body.

Air Leak - This one I am not sure of. I sprayed the MAF Cleaner around gasket and hose clamp areas and there was no change in the idle of the truck, but I still need to smoke the intake and see if there are any leaks noted.

 

[Brain75]

search here on TRS for "ziptie fix" for stretched throttle cable, I don't have the issue yet, but enough people here swear by it I would take it to the bank.

 

[Brain75]

what kind of RPMS do you see with it cold and hot... I have a little suspicion you tuned it down too low, 450 sounds awful low for any ranger especially the 3.0L... it is a higher RPM beast - it is just getting it's legs at the kinda RPMS where my flathead would start barfing up rods.

 

[Brain75]

TRS Magazine - Throttle Cable Mod

www.therangerstation.com