engine knocks when under load

[dixie01]

hey everyone i have a 94 explorer xlt 4.0 im losing my mind trying to figure out what is causing this engine knock it only does it when the engine is under a load i have already cleaned the maf and the throttle body i have replaced radiator(thought it was over heating) and i have replaced the fuel pump the check engine light will come on after a few hundred miles of steady interstate driving when i start going up a hill as soon as i top the hill it goes off does anyone have any ideas?????

 

[westfield]

Could be anything from timing, carbon build up and or winter blend gas. Mine does it to and I can't figure it out.

 

[cflecknell]

I had replaced the sparkplugs in and messed up the gap on two, and it casued this... Once I fixed the gap it went away.

 

[Gadget X]

I had a similar issue, and mine was the oil I was using. Are you using 10W30 or 40 motor oil? If so, then a switch to 5W30 may help you. There are other causes, I'm sure, but that may help! Good luck!

 

[Slowlyvverot]

are you sure its knocking and not your lifters? that's what it sounds like to me.

 

[laserstun]

Thanks for this post (and the answers). Mine does the same thing. Doesn't seem to have an affect on performance, and I just passed emissions on Friday. Still, annoying when climbing hills.

 

[ShadyGrady]

HI, just an opinion, but anyone check all basics first...vacuum leak comes to mind here first(stuff gets brittle and a vacuum line can crack before it breaks all the way, it can act intermittent for awhile till it DEVELOPS into the real deal) Vacuum leaks can be found with a spray of carb cleaner around the vacuum lines and intake manifold gasket area...do this while the engine is running...listen for rpm change. a small hole in the air ducting between the MAF and intake manifold can be just small enough to contribute, spray it also...anyplace airflow and vacuum is sealed off. Gasket areas and lines.

Dirty fuel/air filter, Ignition wires, bad-wrong-dirty PCV valve, dirty injectors (cause lean mixture and over correction by computer). could be a combo of stuff going on here. Maybe the wrong type plugs...maybe too hot for extended highway driving?? If the wrong plugs were used they will cause ping and knock just like too low octane gas and bad timing.


If the engine is knocking due to worn/bad parts...try a lifter chemical fix ( I like one quart of red tranny fluid in place of one QT of oil at oil change time...can be done with the dirty oil too...but it is best used with clean...hi-detergent oil...the cheap stuff...recycled oil comes to mind...do a 2000 mile change out to the stuff you should be using...5w30 of the recommended API service...any brand...and monitor...don't beat it...just drive normal and see how she sounds. this and other stuff helps with worn lifters.

If it is a tapping at double engine speed...it is a lifter...if it is in time with engine speed or picks up speed as you decelerate...it is rod...get help fast!!


This is backyard but you can get lucky

If it is determined to be a rod...and you catch it early...you may be able to just replace the bad rod bearing (I would do the whole set w/oil pump to be safer that just the one bearing) and the crank looks OK (not all scratched and scoured)...see a Chilton's manual for what it looks like, and the guidance for doing this job...I bailed myself out a few time doing it this way. I drove a car a 100K with the rod bearings replaced at home...it is all in what or who you know sometimes! If you can get help from a friend mechanic...it can be just what you are in need of...I wish you the best of luck...and I hope it is not the latter!

 

[Anime]

My X had some hard engine knock under load, much different sound from the clatter of worn lifters/pushrods. Turned out the injectors were dirty from using cheap gas, switched over to using top tier gas 100% of the time and the injectors cleared up and no more knock since. Still has the lifter clatter.

You might also try replacing the air filter, and the spark plug wires and plugs, especially if they are old or worn. New wires solved a hesitation issue on the 4.0L for me.

 

[arco777]

Mine has this issue, only occurred after lots of highway driving and then climbing hills at high throttle. Mid-grade gas alleviated the problem somewhat, premium stopped the problem for good.

 

[westfield]

Lots of gret opinions here but I think we need to isolate the problem - lifters or pre-ignition...Lifters have a distinct sound - engine knock could be something different and pre-ignition could sound like a can filled with bee bees under load.

 

[MrShorty]

Under load is usually pre-ignition. It seems that lifter noise is more often associated with a clatter at idle or initial start up on these engines.

Have you tried tightening the lower intake manifold gasket? See the "useful threads forum" but that is a common, and commonly overlooked, source of a vacuum leak that leads to pinging.

 

[Anime]

The valve clatter can happen under load as well, which mine still does actually, especially in 5th/overdrive when hitting the gas, or at higher RPM in other gears. I've heard some valvetrain/lifter noise at startup since using some thin 5W-30 oil, which just sounds like some muffled rotating sound, at first I thought it was the fan blade hitting the shroud.

The "knock" under load, whether from pre-ignition or other cause, is very different. Mine was a rather violent noise that sounded like a sledge hammer was being pounded against the block, sometimes more than 1 time each second. The shake from the engine each time it happened is quite noticable. There is no mistaking it for valve clatter.


Since knocking damages engines in many ways, a quick fix by throwing new replacement parts at it isn't too bad of an idea. New plugs (Motorcraft) and wires for sure, maybe a new fuel filter too. If it's throwing a check engine light, get a code reader and see what it says, or have the codes read for free at an auto parts store. Could be anything from a Throttle Position Sensor to a Fuel Pressure Regulator. Pricey parts, but better than engine damage.

Definitely switch to some top-end brand name detergent gas in the meantime too, something like Chevron or Shell if you can get it.

 

[Guido0136]

My X had some hard engine knock under load, much different sound from the clatter of worn lifters/pushrods. Turned out the injectors were dirty from using cheap gas, switched over to using top tier gas 100% of the time and the injectors cleared up and no more knock since. Still has the lifter clatter.

You might also try replacing the air filter, and the spark plug wires and plugs, especially if they are old or worn. New wires solved a hesitation issue on the 4.0L for me.

Same here, I noticed the knock lessen with 94 gas. If I use 89 octane gas the ping/knock is terrible, with 94 it's hardly there.

Good luck

 

[westfield]

Same here, I noticed the knock lessen with 94 gas. If I use 89 octane gas the ping/knock is terrible, with 94 it's hardly there.

Good luck

I seem to remember reading something about it not being a good idea to use a higher grade gas to solve the pinging problem...Anyone remember that???

 

[Anime]

Higher octane gas is a band-aid fix, that can quickly, but temporarily, solve knock from pre-ignition, carbon buildup, etc. It's not a *bad* idea, but it is an expensive one at 30 to 40 cents more per gallon. It also doesn't do anything to fix the problem, although you could make an argument that 93 octane gas like Shell Premium (which supposedly has 5 times as much detergent/additive, compared to their 87 and 89 grades that have 3 times as much additive) might help if it cleans your valves and injectors, and if they are the problem.

Using higher grade octane in an engine designed for 87 also has the effect of "masking" the problem to the all-important knock sensor. I'd say the only reason to use higher octane gas is if your engine is designed for it, or you're running a custom ECU tune or some kind of high compression/modified engine which needs it to run correctly.

 

[ShadyGrady]

I can't say I remember the notice about the Higher Octane fuel as a band-aid fix...BUT I DO AGREE that it is a band-aid FO SHO!! I say it a lot, I may not mention all the parts and stuff but the vroom vroom needs all the basics checked and confirmed to be good.

BAD Knock Sensor is a BAD thang. It will not allow the ECU to adjust the timing so our vroom vrooms can act right while we are driving! The knock sensor tell the ECU that there is a party in the stomach...if the ECU gets the message in time, AND does it's J-O-B correctly then we never hear a peep...not narry a peep about spark knock or ping.

Now we X owners need to remember that lack of proper maintenance may prevent the ECU from ever working at all...remember that stage of operation for da vroom vroom called closed loop(say it with a deep southern drawl...LOL)?

Well it starts with the coolant temp sensor. If it is old & crusty or bad wiring/connectors, it may operate slow if at all, failing to report the proper temp to the ECU. This will prevent closed loop mode! We can't have that going on...never ever. All those nice automated adjustments that occur from the read-act operations of the ECU & vroom vroom sensor relationship never happen. The ECU and them sensors is dating, and the ECU is spoiled rotten. IT MUST GET da info it needs, dat info must be right, and it can't be late fer da date. ALL ECU are players...they love to date a lot of sensor! If the ECU is out of the picture when closed loop operation should occur, then it is usually the cause of one of 3 thangs (hopefully your problem is NONE or just one)! The coolant temp sensor is faulty, wiring problem, bad ECU. Yes your vehicle CAN RUN on the ignition module unless it is incorporated into the ECU, if it is external...then she can run on the parameters inside the IGN. MODULE, just not good, no good gas mileage, higher than normal idle, maybe some knock /ping, even some seemingly engine noises. If it has been in this condition foe a good while...it will have some carbon build up on the intake valves, and the exahust valves may get burned.

It is worth a meantion about the IAC. This lil gem can be cleaned if your are carefule on some vehicles, if it is acting up...it will effect idle, and spark knock/ping. It can contribute to a carbon build up inside the vroom vroom. if there are a few systems needing attantion, the ECU and the sensors can not go out an a proper date, The Vroom vroom can have all the high quality top shelf beer it can get...but it will become USED to it and won't want to go back to the X Beer it was supposed to drink. Good old boys don't want the top shelf beer...we is on a budget...pass da BUD!!

Sorry to say it folks...and if you already know then PLZ just consider it an ECHO! Sure high octane beer will help, but fixed...it ain't. imagine the pistons all black, carbon valves, vroom vroom all cus'ed up from all the years of band-aid fixes. soon it will time to replace da vroom vroom. help is EZ tho.
Tune up...yep tune your X up the right way...prep it first...with all the old parts on it...don't want to cus up da new stuff do we?
a lil water ah-la-home-injection. (I will rely on you to look this one up yourself...it is an advanced back yard trick. It will do the J-O-B...but you need to be REAL-CUS-CAREFUL!! you can slip on a banana peal real fast with this one...do it right, and you will have zero carbon you dat vroom vroom. then treat it right from here on out...and you is good hoomie!
If i got a real bad running vroom vroom, i just got...i drive it and get an impression of the situation.
1 i want to see if it is transitioning to closed loop operation...if not...it is time to investigate and create a list. you want to see if it is a senser or a wire, maybe it is time to re-conduit everything. I put the stuff on my spark plug wires too...the new ones that is...i am not looking to be spending that same cash again for a few years...fo sho!
basic tune up stuff is a no brainer...but all them sensors need to function properly and on time...slow O2 sensor will give da wrong readings to da ECU and cus it all up on the very next vroom vroom cycle. how to test a O2 senser is anybodies best guess...i just replace the son-of-a-cus...if the wiring is good that is. making sure the wiring will pass the bend test. yep ther is such a thang...I Invented it too!(joke)
Chilton's manual will show how to inspect a spark plug wire , one of them there test is a bend test. well that same test will tell you if your other wires are in "alright" shape. if it will bend and not snap...it might just be good..if it has colors, stripes, and you can tell what them colors and stripes is...chances are they be "ok". if you savy e-nuff fer a DVOM Digital-Volt-Ohm-Meter check...go fer it...all the better. you want to be sure all them "basics" is covered tight and right...clean up your X while you is at it, if it needs it dat is...sure you need to plan a day(maybe 2) work fer all dis cus...but it will help you find da problem...WE ALL IS JUST GUESS'IN at it.
If we ain't there...it be a hard thing to get you the right info...time to do some work on the vromm vroom boy! and a lil good beer never hurt nutt'in but yer wallet...mines is all cus'ed up fo sho...dat why i get deep-break'in it off into my X...like it was da only ** left and I had to compete wit an army fer it...dat army jus died...you better believe it son!

on the serious note...vacuum, knock sensor, coolant temp sensor, IAC, air leaks, and O2...after all the basics has been covered and all is well...look at those for good operation and condition. O2 is needing to be i cus good condition so it don't report bad on all the other sensors...causing the ECU to be upset fer nutt'ing. low output coil can cause low power operation also...and wiring to it can cause it to have low output...think of how it might act if a coil was only gett'in 10 volts? it ain't going to put out like it should. if the POS+ wire feeding it id in bad shape, it can get a low voltage feed. Your coil can only produce from what is feed to it...give it some high quality 12+ volts(13.5+ more like it)...anyone ever hear of HOBO DAN? he has a good copy of my favorite auto repair manual...it is a share affair...think creatively plz on that one and happy hunting.

Clogged/partially clogged Catalytic converter can cause poor operation, cause vroom vroom to run hot, ping and knock, use more gas than it should, and if it has been on the vroom vroom act'in up fer a while, it has contributed to a good carbon build up...and contrary to some belief...they can not be cleaned. there are a lot of rumors on how to "clean" a cat. DON"T YOU BELIEVE IT!!

So far...ain't no body...told any thang wrong dat I can C! I hope you find out exactly what is wrong. I still lean on vacuum leak...and I do like the knock sensor going bad idea.

 

[brandon1]

Egr Valve

Anyone here know of a way to clean or fix an egr valve? i know that i can do with out it but then my mpg would decrease quite a bit and i really dont need that and why would my front wheels lock in sometimes and others not and when they dont lock in my actuator makes a weird noise. :exp:

 

[ShadyGrady]

EGR not worth cleaning...just replace it with new...you will be way happier in the long run! Your other problem is a vacuum leak IMO!! a lil carb cleaner while it is running might help. BE CAREFUL and have a friend near by with some safety equipment. you R in need of safety when attempting to do this for diagnostic aid. It will make the engine run a very lil bit faster. so go slow and listen for subtle engine speed changes. a leak in a vacuum line will cause a few different symptoms depending an where the vacuum leak is. go slow and use short spray burst...if there is a vacuum leak you will find it fast this way...just go slow with it.

safety protection is a must...safety EYE gear, fire retardant mechanix (or any leather work glove), and be outside, wheels blocked/chocked/e-brake ON/and a buddy who also knows about safety. no kids around just in case...and PLZ go slow cover an inch at a time...ZERO saturation...fog it from 4 to 6 inches...zoom in after you establish an area of suspicion...then use even shorter spray burst...is long as the carb cleaner can raise engine speed from outside the intake manifold...then you got a leak. I hope this helps.

 

[KobeJ05]

i found useing this actually works really good when you fill it up on 87.

made it went away.

 

[ShadyGrady]

well...at least you found something that works for you!! How is it at freeway speeds?