I have been experiencing a good amount of surging below 2000RPM in my pickup when I’m 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 isn’t the best ~300 miles per tank roughly (not what it used to be it doesn’t seem)
• Idle isn’t 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 haven’t put it in yet) (I don’t 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. It’s almost like a slight surge or a miss possibly. When I hit 2k RPM it’s almost like it stops immediately, it’s really weird. Has anyone had this happen to them, or do you guys have any ideas where to check or test next? I’m slightly baffled at this point….

 

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.

 

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

 

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?

 

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

 

Did you ever figure it out? Mine's doing the same thing.

 

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.

 

Try replacing the Synchronizer on the back of the engine block including the cap. Change these simple fix things and it can help. Thats what ive done to my 02 ranger 3.0.
camshaft sensor, crankshaft sensor, purge valve on the driver side engine bay under ABS module, change the fuel pump, mass air flow sensor, Air-Idle control valve, throttle position sensor, temperature switch, temperature sensor, oxygen sensors, put in a higher grade of gas, change the water pump, fan and clutch, alternator, battery, check for corrosion, check to see the tiny vacuum lines that go across the top of the block that go to the black vacuum ball under the coolant reservoir, air filter, check the coolant hoses upper and lower for any tiny leaks, pull the bed off and check the fuel pump fuel lines and vapor lines for leaks or corroded hoses, gas cap could be bad, check the charcoal canister line or the Y tee that connects the fuel pump because that Y tee could have broke. Completely cover all wire connectors and clean the engine bay from caked on layers of blowby debree. Check spark plug gap, the right spark plugs, clean the throttle plate with air intake cleaner, buy a compression tester for 20 to 30 bucks at autozone, let the truck warm up and do a compression test. Not very 100%accurate but does give an idea if any pistons are misfiring. While the truck is running, pull the positive cable off...truck should still be running. If it cuts off, its the alternator. Check the voltage regulator sitting on and behind the alternator. Radiator could have a small leak somewhere.

 

Jeremyd4, I'm sure after 5 years, this problem has been taken care of one way or the other.

NEVER disconnect the battery while the truck is running, especially on vehicles that have electronic controls, PCM, ECU, Internal voltage regulators in the alternator.
You risk a power surge and can burn out anything electronic.

 

Delete the IMRC flaps that is always the issue with these, the lever on the back of the IMRC controller pops off it's plastic and easy to miss I'll snap a pic but delete imrc as a whole it makes no difference to how the truck runs and you don't lose any hp and tq as proven by chassis Dyno

 

Was wondering how one would delete the imrc,I'm thinking about doing mine tomorrow but was wondering what to do with the vacuum lines and what to cap off and such.thanks in advance for the help

 

What i did what break off the flaps and left the metal rod, didn't pose a threat to performance at all, you can leave all the connections hooked up and never get a cell, or anything and never worry about it, and also always pass emissions if you have to it's that simple

 

I have my intake off right now to replace the valve cover gasket (2003 2.3L). I replaced the intake in 2012 when the front plug fell out and caused a lean condition. The IMRC seems to be in great condition this time (8 years on this intake). I had considered deleting the IMRC but wasn't sure of the best method. I saw one guy remove the flaps and the metal rod, but that leaves the holes where between each runner where the metal rod passed through. I'm not sure if those small holes between the runners would cause any issues or not. Of course the actuator is left in place so that the computer is happy.

But I had never thought of leaving the metal rod in. I had heard that the metal rod is what can break and get sucked into the engine and cause major damage, that would be the only concern I would have, but otherwise leaving the rod in is a much cleaner solution. I think either way I plan on using some epoxy on the front where that plug tends to fall out.

 

I havent had any issues and the rod stayed in place, currently its the same intake on my 2.7 stroker duratec still no issues even when under boost