Surging at low RPM

[JOEZ33]

Just an observation I noted tonight while experimenting with my Hydrogen Generator install. I had a loose vacuum line connection at the PCV valve and the engine was surging about 200 RPM every 3 seconds. The leak wasn't very loud so most people wouldn't even realize there was a vacuum leak. I only knew it because I caused the leak on purpose trying to prevent too much vacuum inside my hydrogen canister.

 

[Lazzman]

Repalced the fuel filter and threw in a can of Lucas Injector cleaner this weekend, also re-did the wires to the TPS sensor. Sensor is functioning normally when monitored through my X-cal livelink software.

Though surging has improved it is still present and not knowing what is causing it is driving me mad. I have checked thoroughly for a Vacuum leak with no luck.

The surge is at any RPM below 2k and feels like a slight bucking, as if I am hitting many small bumps in the road.

Any idea's? Wonder if it would be worth it to Smoke the intake with Seafoam? I run a PCV bypass so there should not be any stray oil getting in the intake.

 

[aldive]

Though surging has improved it is still present and not knowing what is causing it is driving me mad.

Did you ever restore the PCM to stock?

Wonder if it would be worth it to Smoke the intake with Seafoam?

Not sure what these means????

I run a PCV bypass .

Just curious, but why?

 

[Lazzman]

I run the bypass to limit the amount of oil that goes back into the intake. My truck sufers from a lot of blow by. No more excess oil in the intake and on the plugs.

Al, I notice you run the PCV bypass also- why? Don't you see a need for it also?

Seafoaming the intake through the IAC valve.

 

[aldive]

Al, I notice you run the PCV bypass also- why? Don't you see a need for it also?

I do not and have never bypassed my PCV.

I think you must be confusing using a filter with bypassing. http://www.explorerforum.com/forums/showthread.php?t=148135&highlight=crankcase+filter

 

[Lazzman]

My mistake AL, I guess I ment the crankcase breather Mod.

 

[jmock1010]

maybe some light

Hey lazzman,

Had the same problem you are having at one time. It was driving me crazy
becuase I was sure it was vacum leak somewhere or my IAC. Well long story
short it was nothing more than a bad spark plug wire!!!!! GO FIGURE! Hope this is your problem as well. Like I said I had the same bucking or pot-hole as
you call it problem as you did. Hope this works for you, sounds like you done
everything else possible. Peace Out!
Jason

 

[Lazzman]

Thanks Jason I was thinking the same thing, spark plug or coil.

I have the screamin deamon coil and it already crapped out on me once and was replaced. I am running Magnecore wires that are about 2yrs old, they seem to be in good shape. I am going to swap out the coil and see what happens.

Thanks again- Great tip.

 

[Jakee]

It's all in the IAC valve.

 

[JOEZ33]

I've been delayed in the past over a simple spark plug wire several times. The symptoms were never what I expected for a bad spark plug lead. It would backfire through the intake instead of just being one dead cylinder, and it would only drop out at high rpm's, but not while bogged down under a load. -Usually on past cars I would find bad spark plug wires when putting the engine under a load, even by power braking. Also on rainy days it makes the problem worse due to condensation/water etc. On this truck the problem has always been the ignition lead that runs across the back of the engine, between the firewall and the engine block. I've since rerouted the wire and secured it away from hitting anything, no problems anymore.

 

[Lazzman]

Swapped the coil out and it made no difference. I do not believe the plug wires or plugs are bad since they are both less than a year old.

Joe what exactly is the ignition lead? What is it connected to an what does it look like?

I would like to check that out next.

Thanks

 

[millerman23]

i got the fuel filter from walmart. the filter number is G8018 it is the fram one not the motocraft one

 

[burtonbrd138]

i have this same surging problem while in overdrive around 35 mph when the rpms are bellow 2000k. I changed the plugs made the problem less noticable but still there. Even when i press on the gas the surging gets faster until i have to stomp on the pedal for it to downshift and pick up the rpm's. I have a feeling that my problem is in the transmission. Maybe a loose band or wrong tranny pressure?

 

[jamester_a]

Lazzmon,

How old are your upstream O2 sensors? Are you able to verify their good behavior with your scanner?

How about your EGR? How is it reading on your scanner? Normal? How about condition of DPFE sensor? Disconnect DPFE and plug lines and go for a drive.

- James

 

[Jimmy4765]

Having the same issue and was wondering if anyone ever came up with a solution. I have replaced my plugs, wires, coil, 02s, tps, maf, ect but it still does it. Was suspecting the IAC but was looking for a result before throwing any more money at it. It has a little over 100k and I have cleared the codes via an SCT, disconnected the battery and let it sit overnight. Ive tried the stock programs, turning off the egr, ect and nothing seems to fix it. Its an 02 XLS with a 4.0 that is meticulously maintained and its making me crazy! Thanks for any help.

 

[Jimmy4765]

Went out at night and looked for any spark leaks from the coil, plugs and wires and found none. Decided to try Jakee's advice and swapped out the IAC and viola! Problem solved! No more surging, starts easier, idles better and has a lot better throttle response, too!

 

[16vcabman]

Recently my truck has been surging at lower RPM's, most often just below 2000rpm when in overdrive. Also the idle has been very low lately with a lot of shudder in it.

I did get a check engine light a week after this started and the code said that the TPS sensor was not working properly. I changed it out with a new one but the problem is still persisting. I checked all around for Vacuum leaks and did not find any.

Is there anything else I can check? My next step is to smoke the intake with Seafoam to see if that does anything.

It does not happen at rpm's over 2000. When cruising below 2000 rpm it almost feels as if I am hitting many small potholes as I drive, the surging is faint but it is there.

Any ideas or suggestions?

How many miles? Try transmission fluid change

 

[C420sailor]

11 year thread resurrection. Not bad!