2002 2.3L surging below 2K rpm HELP!!! - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 04-24-2015
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2002 2.3L surging below 2K rpm HELP!!!

I have been experiencing a good amount of surging below 2000RPM in my pickup when Im at part throttle at a cruise. (Say 35-40mph on the freeway)

Symptoms: (in order of severity)
Surging up to about 2000RPM then it almost just stops at 2k and is fine above that (at least i cant feel it)
Hardish starting
Pinging (may or may not be related)
Seems like it has less power
Fuel mileage isnt the best ~300 miles per tank roughly (not what it used to be it doesnt seem)
Idle isnt bad, but every once in a great while it will drop low then recover quickly (like once a month frequency)
What I have done:
Replaced the fuel filter
Spark plugs
Plug wires
Coil pack
TPS
Thermostat (old one broke)
Going to clean the MAF this evening hopefully
I have a new engine temp sensor (just havent put it in yet) (I dont think this will effect anything but I have it)
Checked the vacuum fuel Reg. for any leaks (nothing)

I am starting to run out of ideas as to what could be causing this surging feeling I feel when I drive could be coming from. Its almost like a slight surge or a miss possibly. When I hit 2k RPM its almost like it stops immediately, its really weird. Has anyone had this happen to them, or do you guys have any ideas where to check or test next? Im slightly baffled at this point.
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Old 04-24-2015
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Assuming an automatic transmission?


Fuel injected engines can't use an "idle screw" because there are no jets to pull extra fuel from when you increase the air flow.
So they all use an IAC(idle air control) valve, computer operates this valve, it is what sets the idle at 1,100rpm when engine is cold and then at 700rpm when warmed up.
If opened all the way it can certainly reach 2,000rpm.

First do this test, warm up engine, unplug IAC Valve's wire connector, idle should drop down to 500rpms or engine may even stall, either is good, it means no vacuum leaks.
If idle stays high, above 700 then you do have a leak, you will need to find it, PCV valve hose is a common leak.

Remove EGR valve and clean it out if clogged up, check that is opens and closes when you put a hose on it and suck on it(simulate vacuum)


Remove it and see if valve is loose or dirty inside, just 2 bolts, you can reuse gasket if it looks OK.
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Old 04-25-2015
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Sorry guys, it's a manual.

I will do that test for the iac today, I cleaned the maf, but haven't had a chance to drive, the wires are definitely shinny now, where they were very dull gray before.

I'll check the pcv and egr hopefully today and see if those are good. Is carb, throttle body cleaner Ok to use on those parts if they are gummy? I might spray them down either way
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Old 04-25-2015
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I tested the IAC today, it seems to be working fine, the truck died immediately as soon as I unplugged it. one thing I did notice while slowly revving the truck was that as I slowly brought the RPM's up once I hit 2000 it immediately jumped 5 to 700 rpm. can you guys think of anything that would affect the throttle response or reaction of the engine at rpms below 2k?
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Old 04-25-2015
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Start engine with IAC Valve unplugged, then try the RPM test, see if it does the same thing.
Testing if computer is adjusting the IAC valve when it shouldn't be.

Check throttle plate and it's spring, see if it is loose.
Plate itself is attached to shaft, if it is loose on the shaft the air flow can change.

And check throttle cable as well, disconnect it and see if it slides in and out smoothly, lube it in any case.

Also disconnect cruise control cable if so equipped, and see if RPMs are stable, cruise control cable is vacuum controlled if it is malfunctioning then vacuum changes could cause throttle position changes without cruise control even being on.

Check TPS voltage, it could be a voltage issue not a TPS issue.
Top wire should have 5volts when key is on
Center wire is the return voltage that the computer uses for throttle position.
.9volts when throttle is closed
above 4.6volts when throttle is wide open

Key on, use a pin(sewing needle) to pierce top wire, use battery for ground and then engine, see if voltage changes, should be 4.8-5.0volts
Then check center wire, slowly open throttle and watch for stable voltage increase, not jumping around, also do it using battery and then engine as ground.

Computer supplies the 5 volts, but Ground is the ground, it should always be 0volts but if there is a loose or unstable ground, then 0volts, might float, +.1 to +.4, and since the TPS sends variable voltage as the control signal...........it would vary with the floating ground.

If you get a different voltage reading when using battery and engine as ground then make sure the Ground strap from the the head to the firewall is in good condition, and clean and tight at both ends
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Old 05-01-2015
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Did you ever figure it out? Mine's doing the same thing.
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  #7  
Old 09-29-2015
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Just an update guys, still experiencing this same problem.

New:
ERG
coil pack
plugs
wires
throttle pos
fuel filter

cleaned:
IAC
MAF


I had a mech pull some data from the computer and he said it looked like the readings on the MAF were low. I havent seen any codes yet, anyone have any experience with this. Those things are pretty darn spendy so im trying to do my HW before i buy.

What about the O2? No codes, just thinking maybe it could be reading off?

Thanks guys.
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