So the on my truck surges slightly, fluctuating aprox 50-60rpms and vibrates a little and it clears up anything above idle. . it did before and after new injectors. ebpv is good and open fuel filter is good, about to put a new one in any way. air filter is good, oil is good. idk about the ipr, is there a check for that? would fuel pressure mess with idle like this? any ideas on things to check to diagnose the issue. Thanks.

 

Automatic or manual transmission?

 

manual transmission

 

How old is your CPS and which color is it? A torn Injector O ring can cause fluctuations in Idle and sometimes between 2500-3000 rpm.

 

i tried a new cps, no difference. and idle is surges at idle. i.m really hoping its not an injector o-ring!!

 

injector orings are not hard to replace and is under $75 including shipping in most cases.


Do you have a scanner to look at IPR % duty?

 

Going to bump this thread because mine does this too and I'm curious to flesh out the issue a bit more. To the original post, I don't mean to hijack the thread, so if I describe anything that's different from yours feel free to clarify or redirect. To everybody else, thanks for any feedback.

Similar issue here, manual trans, minor fluctuation of idle speed, about 50 RPMs, accompanied by minor vibration. Does not appear to be any major issue, just kind of unnerving. Clears up at anything above idle. Does not do it cold at startup, only at operating temp.

Regarding the first round of questions...for my truck:

1) Manual trans, DMF swapped to solid flywheel and conventional clutch by original owner.

2) No new CPS here, but OP said no change with new CPS.

3) Fresh injector o-rings here too, and I assume all are okay since install (no oil in fuel, no smoke, idles and runs fine except this small issue, MPG is good, passes all diagnostic tests, hold-down bolts torqued to spec and re-checked since install).

4) Revs okay 2500-3000 RPM. Minor vibration at some engine speeds, but I assume it is clutch/flywheel balance or accessories because engine revs freely, no miss or stutter.

5) Regarding scanner and duty cycle. I have an Aeroforce gauge on mine. IPR duty cycle fluctuates a bit while the idle RPM is fluctuating, roughly +/- 0.4%. I video'd it at operating temp idle one time, it was 11.3-11.7. Pulse width moves a bit too, maybe 0.1 (roughly 1.0 to 0.9). Not sure if the movement in PW or DC are as much reactionary to some kind of intermittent load, or are causing the issue.

Other items I have considered as possible culprits, want to offer these as suggestions and seek feedback from folks here.

1) Could IPR O-rings lead to this in early stages of failing? No hot restart issues here, so haven't considered this much.

2) Intermittent load caused by some accessory, such as a failing bearing in a tensioner, PS pump, vacuum pump, alternator, etc? Mine does it with AC on or off, so AC compressor is not the culprit. I have done one test running it briefly (15-30 seconds) with belt off. Issue did not occur, need to try this again a time or too to see if I just got lucky once. Curious how to isolate any one accessory. My tensioner and idler pulleys and accessories seem to spin freely by hand without belt, no noises.

3) Some kid of resonance in clutch/flywheel.

Thanks for any responses. Again, don't think it's a major issue for me, just find it kind of annoying and was intrigued to see someone else post about it.

 

THANKYOU!! so i'm not the only one. good lol. so everything is exactly the same for me except the a/c cause i haven't fixed it yet. i recently replaced the tensioner and idler due to wear but it didnt affect the under laying issue.

 

so i heard if you have a slightly worn mechanical fuel pump plus horse power mods equals more fluctuation is fuel pressure because its a piston pump. i plan to replace the fuel pump plus add an electric lift pump that's low pressure but high flow to supply the mechanical fuel pump to only pressurize.

 

mine used to romp at idle


I replaced the fuel pump since fuel was dripping off of it
FPR screen on mine was clogged up
My Injector orings were shot, dark filter


Mine only romps at idle now if stopping hard on the highway with engine hot


I am looking forward to my oil change to see if it helps at all and to check my armature clearances when I change my glow plugs out.

 

im waiting on riffraff to send parts and im going to rebuild the fuel bowl and do the whole works bewtween the fuel bowl and fuel pump. i'll have to wait for $$$ to add electric fuel pump.

 

if doing that work to fuel bowl, get new rubber fuel lines, IPR orings and get a new FPR spring from the link in this https://www.ford-trucks.com/forums/1...sel-truck.html


maybe a new fuel pump too?, they are cheap

 

i have the new fuel pump already and the whole hpop was replaced by the last owner in 2008 by ford. he gave me all the receipts since he owned the truck.

 

I have had this for a long time. Not all the time but when it does it is very rhythmic . It can change from red light to red light no rhyme or reason. e- fuel constant new cps and other things like ipr. Still does it. lol I think the Russians are doing it, or the tuner added it in to drive us crazy . Drives good so IDK.

 

Seems like I remember some guys installing an HPX line to help with idle fluctuations...