I have a 2002 Ford Ranger.
4.0L SOHC, 5R55E automatic, 4 wheel drive, extended cab.
127,500 on the dial.

Keep having this problem where Once the truck gets warmed up, I'll be driving down the road when all of a sudden the engine stops responding to the throttle. It can happen when I'm doing 45, 70, or just sitting at a stop light. The engine basically idles down to around 200 rpm, shake a little bit, and want to die. If I stab the gas pedal a time or two, it usually comes out of it and runs fine.

After about four or five drives where this occurs, I'll finally get a check engine light which gives me the codes P0171 and P0174 (system lean on banks 1 and 2). I came on here and researched several threads that have this problem. I've checked common areas such as the PCV hoses from the PCV valve to the front of the engine and found no cracks, or leaks. I've checked as many vacuum lines as I could trace down with no issues there. I even heard where some people have this issue because the oil cap isn't on tight. Yet my problem still remains.

I've removed every gasket up to actually pulling the intake manifold off the engine and visually inspected them and determined that none of cracked or shrunk to the point they don't seal off anymore. I have backed this up by spraying carb & choke cleaner at every seam on the intake manifold I could and heard no change in RPM. I have also cleaned the MAF sensor, using approved cleaner from NAPA, to no avail.

I've also read that one should do a complete tune up, clean/replace the O2 sensors, replace the fuel filter, monitor the fuel pressure coming off the rail, and so on and so forth. I'm not exactly sold on these, as the engine runs like a champ right before it acts up, and then runs like a champ after I stab the gas and get it worked out. If my understanding of the fuel system is correct...if either the filter was clogged or the pump was under performing, the engine wouldn't be noticeably missing at high rpm, which is not the case.

I have inspected the spark plugs and found them to be in good shape. The wires don't appear to be cracked or arcing in any way. Will have to get a gauge to measure fuel pressure and see what I can find there. Same is true with

I will continue on with tune up procedures and analyzing electrical signals to see if I have a bad sensor somewhere. My question however, is where do I look after this? I'm afraid I will have exhausted my options soon and still not have a cause.

Has anyone out there experienced a similar problem, and found something rather strange that has been the culprit? Say a sticking EGR valve or something?

I thank you in advance for your responses and guidance.

 

have you tried testing the fuel injectors to see if there functioning correctly?

 

I had a similar problem, twice. (It sure is annoying when it happens in rush hour traffic.) Interestingly, both times it happened in the dead of winter in freezing temperatures. The first time, a friend, who owned a similar truck, told me something solid was stuck in the fuel pump and said I should tap it with a hammer a few times. This solved the problem for a year until it happened again, and the hammer trick no longer worked. It turned out I needed a new fuel pump.

 

35l911, how would one check fuel injectors? Remove the fuel rail and crank the engine to see that all are spraying in the correct pattern?

Charlotte, you hit on something I failed to mention. My truck only seems to do this when the weather gets cooler. I noticed it when it started getting down into the 50s, and the colder it gets, the worse it gets. But what solid ends up in the pump?

If it's freezing cold, I could see the water in gas freezing into ice and messing up the system. But mine started before we cooled past the 32 degree mark.

 

Update:

Read somewhere online that PCM computers can be flashed with the latest program engine management. Contacted a nearby Ford dealership, and they confirmed this. Took the Ranger over and discovered that a PCM update (dated at the end of 2008) addressed 15 different TSB's that affected the 4.0L SOHC computer system.

We agreed that it may not fix the issue but flashed the computer with the update anyway. Will try to keep people apprised.

Keep the information flowing. Thanks!

 

Update:

Reprogramming computer helped the issue slightly, but has not cured it.

Went to NAPA for a NAPA Gold fuel filter. Found that was actually a lot easier to change than I expected it to be. Pretty convenient little setup they have down there. However that still wasn't the problem.

Bought a gauge to measure fuel pressure with but have yet the time to put it on the truck and test.

lol!

 

after reading your thread the fuel pressure test is what I would suggest you want to do a koeo and a koer test. from memory you want about 60.

 

Have you tried cleaning the MAP sensor? Also might want to check out the throttle position sensor.

 

Another Update:

Went to Harbor Freight and purchased ITEM 92699-3VGA (Fuel Injection Pump Tester) and roll of Teflon tape. Assembled gauge and was confident in setup.

KOEO - 60 PSI
KOER - Slowly varied between 65-69 PSI

 

I reread the thread. I forget the exact FP # but I think yours is ok. I wonder if you kept the tester around and when it acted up test it. I am kind of at my knoledge limit. Have you run injector cleaner.could it be that you have a bad maf. Can a bad or dirty iacv throw lean codes? Have you checked air filter? Let's see what some others say

 

Is coolant full? coolant temp sensor?intake manifold leak? I think you said you checked for leaks. I will mention it again a bad maf can throw a lotof stuff off

 

I've run several bottles of injector cleaner through the system. The last tank I filled up with, I also included a pint of Seafoam in the tank to clean injectors and absorb any water that might be in the fuel.

I have cleaned the MAF sensor, but it's been awhile so it's probably getting time to do it again. The last time it was cleaned, it didn't correct this problem. The problem went away when it got warm out, and recently returned when winter hit. So it has something to do with cold weather.

I sprayed choke / throttlebody cleaner around every gasket seal I could find out the intake, but couldn't detect a change in RPM. I hear that the OHV versions of the 4.0L have a problem with manifold gaskets. Do the SOHC versions have this problem as well?

Will check on the other stuff and report back.

 

Update! Finally!

While I was running my fuel pressure tests a couple weeks ago, I started wiggling various wires on the engine. When I wiggled the wiring close to the connector on the MAF sensor, the engine started running rough and surging until it finally died. Then when I started it back up, it ran okay and hasn't acted up since. The connector was tight in the MAF sensor, but I'm thinking one of the inside it was intermittently losing contact.

I bought some electrical contact cleaner from NAPA, and some grease for electrical contacts and applied both. We'll see now if this issue is resolved and I will report back.

 

I am glad you got it fixed. keep us posted if anything changes.