Intermittent problems after new engine - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 05-01-2016
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Icon4 Intermittent problems after new engine

Greetings! I hope someone has ideas. The vehicle is a 204 Ranger, 4.0, manual trans, 4X4.

I put a new engine in and I have driveability problems. The truck will run fine for about 30 seconds, then stumble and have little power. After 1-2 minutes, it will be fine for another half minute or so.

Things I have done:
New crank sensor, cam sensor, injectors, upstream O2 sensors. I did these just because I was putting in the new engine.

Things I have observed:
Error codes (and check engine light) don't always happen. I can drive for perhaps 15 minutes before the light comes on-even with these fairly severe problems. Error codes are P2196, P2197, P2198. Yup, it's reading the O2 sensors as being stuck both rich and lean.

The short term fuel readings are way out of wack; they vary from -28 to +66. I notice as bank 1 (passenger) goes lean, bank 2 goes rich.

Cleaned the MAP sensor. Just a whim.

Can't find a vacuum leak---doesn't mean there isn't one!

I need ideas! I have to leave on a trip in about a week and need this fixed.

Thanks for ideas!

Chris
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Old 05-01-2016
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Welcome to the forum.

2004 Ranger with factory 4.0l SOHC and you pulled that out and put in another 4.0l SOHC engine.

So same engines, right?

I would get or rent a fuel pressure gauge.
60-70psi is what you should see when engine is idling
Raise engine RPMs to about 2,500 and hold it there watch if fuel pressure starts to drop, if it does then fuel pump is most like starting to fail.

If fuel pressure is jumping around then you will get lean/rich codes and fuel trims, computer is trying to keep O2 sensors showing good burn but as pressure drops it opens injectors longer and longer to stop lean burn and then a jump in pressure causes it to go rich suddenly.

Video on finding schrader valve here: www.youtube.com/watch?v=F7mYC9JwMLg

Also back by the schrader valve there should be the Pulse damper, end of the fuel rail, it will have a vacuum hose attached, check this hose for fuel, shouldn't be any sign/smell of fuel in that hose, if damper leaks then fuel is sucked into engine, causing same symptoms.

Another test is for leaking fuel injectors, they are new which means never tested, not they work.
After engine is warmed up shut it off
Turn on the key
Press gas pedal to the floor and hold it down all the way
Crank engine
It should NOT start, or fire at all

All fuel injection computers have a "Clear Flooded engine" routine
With key on, computer on, engine off, if computer sees WOT(wide open throttle), gas pedal to the floor, it will enter clear flooded engine mode, it will shut off fuel injectors but leave spark on.
So when you crank the engine there should be no fuel in intake so no starting or firing at all.
As soon as you release gas pedal injectors will start, or if engine does fire enough and RPMs show above 400 then computer will restart injectors.
If engine does fire then you have fuel getting in to intake.

If you disable coil and do the same above test you could ID the leaking injector.
After cranking pull all the spark plugs, the wet one has the leaking injector


I would also buy a Fuel Pump Relay, just a standard car relay, under $8, while it is unusual for these to fail they do.
It is in the engine fuse box.

Last edited by RonD; 05-01-2016 at 01:57 PM.
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Old 05-01-2016
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Thanks, Ron, I'll work on it today or tomorrow. The fuel pump is about two years old. Yes, they are the same engines. I forgot to mention that when I changed O2 sensors (after the new engine was in and running) bank 2 (drivers) had lots of carbon soot on it. Bank 1 was pretty clean.
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Old 05-01-2016
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Did you install a used engine? or a rebuilt engine?

If it is a used engine. did you swap over all your injectors, fuel rail etc?
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Old 05-01-2016
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Rebuilt engine from S&J in Spokane. I put in new injectors-old engine with original injectors had 260,000 miles. Time for new, as long as you have them out.
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Old 05-01-2016
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Well if I were in your shoes, I would start by double checking all your work.

Look for any wiring harness that could be pinched or laying against a hot exhaust manifold.

When you installed the the long block did you use any RTV - sealant that is not compatible to O2 sensors?

looking at the Pin Point test for these codes one of the basic things to look for as you know is vacuum leaks.

Get a hand held propane torch remove the tip and install a 3 or 4 foot vacuum line, use the regulator to adjust the flow of propane near any suspected sources of leaks while the engine is running.

if you replaced the pcv valve pull it from the engine but leave it connected to the vacuum line. block off the valve to see if the symptoms improve.

I am guessing the engine did not have this particular problem with the old engine and appeared after installing the new engine.

If this is the case I wouldn't have a reason to suspect a part failure.

If you double check your work and still do not find any problems from anything listed above, I would suggest getting a subscription to Alldata diy and follow the pin point test for each code you have.

My gut feeling is something was missed during the install of the engine.

BTW you didn't mention what happened to cause you to replace the engine, did it overheat? or something catastrophic happen?
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Old 05-01-2016
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Just checked; don't have a pulse dampener on my engine.
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Old 05-01-2016
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I replaced the engine at 260,000 miles because it was getting tired and I pull a 4,000 lb trailer with it. We're leaving on a 10,000 mile trip once I get this figured out. I agree I may have missed something.
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Old 05-01-2016
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Have to have a pulse damper, not optional with 70psi fuel pressure.

Look on opposite side of engine end of the fuel rail near firewall, check vacuum hose


With that much pressure each time an injector opens and closes there will be a pulse wave formed, if there was no damper then they would build up, and as an injector opened if wave was passing by then less fuel or more fuel would flow into the engine depending on what part of the wave was there.

Older 30-40psi fuel systems could have the same issue but they used a Fuel Pressure Regulator which was a rubber diaphragm so acted as a pulse damper does, adsorbing pressure waves so they can't increase

Last edited by RonD; 05-01-2016 at 04:40 PM.
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Old 05-01-2016
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Thanks, Ron. I'll keep looking. I just ohm'd the lines to the O2 bank 2 sensor and found shorts in three of the wires. The ground wire (obviously) which is tan on my Bosch sensor and BOTH white wires-which are heater. Guess I'll start by pulling the intake manifold to get to the wires.
When I get the intake manifold off, I'll look for the pulse damper.
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Old 05-02-2016
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Just moved the coil and disconnected the harness both at the PCM and the O2 sensor. Now I'm getting normal resistance in all 4 wires. I'll check the plug next. I have 3 wiring diagrams, none of which are correct according to my particular vehicle. They also disagree with each other. However they are a clue, which is better than nothing. Back to the drawing board!
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Old 05-02-2016
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On 2004 Ranger with 4.0l SOHC I am showing Light Blue/Orange stripe wire as the common Power for the O2 heaters, coming from fuse #41 15amp in engine fuse box.

Then each will have Grey/red stripe wire for O2 signal ground

So Light blue and Grey/red wires will be on all O2s, Light blues are spliced together and Grey/red are spliced together

The heated circuit Ground wire on each will be a different color, which goes to Computer so it can monitor heater voltage.

And then each will have a different color O2 signal wire going to computer for the O2 voltage, .1 to .9 volts, generated by the O2 sensor from chemical reaction with oxygen in exhaust.

So wouldn't make sense to have 2 white wires at 1 O2 sensor
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Old 05-03-2016
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FOUND IT! It was a wiring glitch. Seems a wire was pinched. Took off coil pack, PCV, straightened wires,, etc. While I was at it, checked all wires to O2 sensors; they did not match either wiring diagram I had.

One from Chilton's and the other from a college auto repair program which said it was specifically for my truck. Tracing/find wire terminals is fun........

I was able to drive the truck for 45 minutes without an error code. YIPEE!

The truck drove well, with some VERY minor hesitation and stumbling issues. It felt like slightly rough pavement once in a while. Software from my computer (OBDwiz) indicated heating element on opposite bank upper O2 sensor not working properly all of the time---but did not show up on the check engine light.

I'll check all of the wiring and take it for a longer ride today.

Thanks for all of the help!

Chris
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Old 05-03-2016
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Good work

Thanks for the update
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Old 05-03-2016
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That is good news I am glad your making progress.
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  #16  
Old 05-03-2016
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Drove it 200 miles today to complete the break on for the first oil; change. Achieved 21.3 MPG--better than it was new! Gave a lean cycle error code once on the opposite bank that was the problem before, but I turned it off and it hasn't returned. I'll continue to monitor it, but the way it runs and the fuel economy indicate it can't be too far off.

Thursday I will take toe core back to Spokane. It's about a 700 mile round trip. This should almost complete the break in.

Thanks for everyone's support!

Chris
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Old 05-03-2016
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Ranger 4x4 with 4.0l SOHC can push to almost 19MPG on a long highway trip, with a tail wind most of the way, lol.

At 21mpg you are running too Lean, or you have smaller tires and ODO is off.

But glad that it is back to running well
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Old 05-04-2016
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I have gotten over 20 mpg on a long highway trip but only a couple times. It takes driving no more than 65 mph and being light on the accelerator pedal. If I drive normally and around 70 mph it drops to around 18 mpg. At 75 I am lucky to get 17 mpg.
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