Need Help Fast!! 98 OHV Running Terrible!!

[faron021]

But I don't know if running lean is the problem. I'll check the vac lines and make sure the intake gaskets are tightened to specs. It shouldn't be bad, its fairly new. I'm sure it could use a tourqing I'll hit that stuff tomorrow and see what happens. Worse comes to worse I pay the buck for the diagnostic and fix whatever this "phantom" problem is.

make sure you check the intake gaskets, not sure when you switched blocks that you replaced this, im talking about the o-rings/gaskets under the black plastic intake where is sets on the metal part of the motor. my mom had a 99 that had this problem, and it never run bad other then bad mpg then when the check engine light came on, running to lean. i knew that was the problem. we also had a problem with a water temp sensor, not going complately bad but off enough to throw the running of it off. making the motor still think it was cold, but the sensor was still in the range of the pcm thinking is was still good so it never threw a cel.

i have run into that problem with alot of stuff before. remember this when working with any sensor, speaking form my exp that is, i have had alot of sensors give a bad reading for nothing, basically to sum it up, the sensor is going bad enough to effect the running, but not bad enough to tell the computer the sensor is 100% bad.

also i have brought alot of "new" parts and there bad, its possible for you to have got a bad MAF, those are very touchy parts and if there not mistreated they can brake.

oh i do agree with these other guys bosch plugs are to me the worst plug i have ever brought. to answer about the NGK vs autolite. autolite makes motorcraft to a ford spec. i have been running NGK v-power in the 01 sohc with no problems.

to me it sounds like a sensor or a vac leak, with it running bad at idle. sorry i couldnt be more help

 

[ranger7ltr]

I did the same thing on my truck too...

Anyways, before I got the new block and head I went to replace the fuel pump and noticed a flaky substance, almost like rust but crumbles easier, all inside and on the walls of the tank (moisture I think was the culprit!) And the gas inside didn't really smell like gas. It smelt like gas that went bad 100 years ago! Cleaned it out as best we could, pretty damn good, put in a new pump/ whole tank drop in assembly, new filter and new lines. Just thought everyone should know that

Thought since I cleaned the tank out at a radiator shop that it was all good...When I pulled the fuel filter the inlet side looked like coffee grounds and rusty water/fuel...To fix that I finally bought a new tank since I could not drive it for more than 200 miles without the fuel filter clogging up...That is why I suggested the fuel filter even if it was brand new...

 

[xploder98]

when I changed my filter the inlet side looked like it had "coffee grounds" in it to. I'll replace the tank, pump and filter again soon. My CEL never came on. But then again I unplugged my maf and got 6 codes and engine light was never on. Those codes were only because of the maf being unplugged but shouldn't my CEL light come on, kinda besides the point. Whatever the problem is it happened within a matter of hours.

 

[faron021]

when I changed my filter the inlet side looked like it had "coffee grounds" in it to. I'll replace the tank, pump and filter again soon. My CEL never came on. But then again I unplugged my maf and got 6 codes and engine light was never on. Those codes were only because of the maf being unplugged but shouldn't my CEL light come on, kinda besides the point. Whatever the problem is it happened within a matter of hours.

whenever you unpluged the MAF the computer put the running into a safe mode, which is way it runs fine. fords are sometimes very slow to catch somethings, if it is something small it could take even longer. my 01 f150 i have a vac leak for almost a year before then cel ever come on and after a reset it it would take almost 700miles for it to come back. as mentioned also the computer has a set range to check for sensors, if they are out of range the light will pop on quick. but if the sensor(s) has some kind of short circut, ect the computer for some odd reason might still read the sensor as fine, but yet its enough off the effect the running.

with my exp. fords will hardly ever report a misfire, unless its extremely bad, say you have a plug thats half firing, it will effect the running, but the computer still seen it as a fire and went on.

just going to throw this one out there, it hasnt been mentioned and i highly doubt it is, but what about the exhaust system, is the o2's in working order, the front ones tell the computer how to run. just throwing that out there, i have never actually heard of one of these failing. but i thout i might throw that out there.

good luck ill post back if i thank of anything else.

 

[xploder98]

Actually shortly after the new engine I noticed my passenger side front o2 sensor somewhat melted to the header. The truck had always ran fine tho, kinda bad gas mileage for a new engine but I just figured it was from having bigger tires and a manual trans I just moved it out of the way and left it alone. Its melted pretty bad, one side/ corner of the o2 sensor plug and the harness it plugs into. Maybe I'll try replacing that and checkin vacuum and go from there. Its kinda weird that it would happen out of no where but who knows

 

[xploder98]

Well, got called in this morning so wasn't able to work on the ex at all. Pop is comin down tomorrow mornin and we'll throw in new o2's, new intake plenum o rings, and check vaccum and check wiring on the maf harness. If we can't figure it out by the end of the day I'm unpluggin the maf and drivin it to meineke for a diagnostic. Will let ya guys know wut happens.

 

[xploder98]

I think, and PLEASE correct me if I'm wrong, that it has to be some kind of sensor issue. Because when I unplug the maf the truck idles GREAT which means good fuel pressure, good spark, intake, etc. Basically the basic necessities needed for the engine to run without the maf must be ok if the engine runs good without using the sensors and being in open-loop mode. Am I right? It makes sense to me. If I'm not explaining something right or leaving something out don't hesitate to let me know. Btw it idles smoother than it ever has with the new plugs, wires, and maf unplugged so I'm guessin I needed a plug and wire change

 

[faron021]

I think, and PLEASE correct me if I'm wrong, that it has to be some kind of sensor issue. Because when I unplug the maf the truck idles GREAT which means good fuel pressure, good spark, intake, etc. Basically the basic necessities needed for the engine to run without the maf must be ok if the engine runs good without using the sensors and being in open-loop mode. Am I right? It makes sense to me. If I'm not explaining something right or leaving something out don't hesitate to let me know. Btw it idles smoother than it ever has with the new plugs, wires, and maf unplugged so I'm guessin I needed a plug and wire change

im not going to say for sure 100% but it does make since what your saying. basically the motors is running regraudless of the sensor readings.

have you tired unplugging other things to see if you have the same effect as with you do with the MAF? make sure you plug the MAF back in, and find another sensor (that want kill the motor as soon as you unplug it) and see if it has the same effect as with unplugging the MAF?

if it does i would say form there take it to a shop. if it doesnt it really doesnt change much but you then know its something related to the MAF somehow.

when you take it to the shop, get a est first and go to a few more shops get the best price and go with it, some charge by hour, and the goof of and will still charge you for it, others will give you a flat rate. take your pick. biggest thing make sure they will give you a warranty incase something happens down the road it will be on them and you want have to pay for it.

i wish i could tell you exctaly what it was, but now im very curious as to find out what it is, so if you find out please post it.

 

[faron021]

just thought of another sensor that could possible be bad, not sure if you replaced it. how about the knock sensor?

 

[xploder98]

Sorry I didn't post yesterday, got caught up in the madness. Problem Solved!! Anyone care to guess? Anyone? I'll give u a hint, it wasn't my maf and it wasn't fuel or firing/timing issue. mthe infamous 02 sensor! I replaced the right upstream o2 sensor and not the left and sure enough, I took it to the diag and sat with the master mechanic and we went over everything and finally we looked at running voltages on everything we could and the o2 sensor was reading 0 and at a few times it was actually giving negative readings telling the computer to give less gas to my left bank causing me to run lean. Thanks for all the help and suggestions guys. And remember the o2's play a big role on how your engine runs so keep an eye on em. I thought they only helped with smog. I was way wrong!

 

[faron021]

Sorry I didn't post yesterday, got caught up in the madness. Problem Solved!! Anyone care to guess? Anyone? I'll give u a hint, it wasn't my maf and it wasn't fuel or firing/timing issue. mthe infamous 02 sensor! I replaced the right upstream o2 sensor and not the left and sure enough, I took it to the diag and sat with the master mechanic and we went over everything and finally we looked at running voltages on everything we could and the o2 sensor was reading 0 and at a few times it was actually giving negative readings telling the computer to give less gas to my left bank causing me to run lean. Thanks for all the help and suggestions guys. And remember the o2's play a big role on how your engine runs so keep an eye on em. I thought they only helped with smog. I was way wrong!

thanks for posting, wow to thank i was very close to guessing the o2 but i said it prolly wasnt, haha, thats what i get for thanking. glad you got it fixed, anyone say anything about why the cel never triggered?

that would also explain why unplugging the MAF worked, you sent the computer into the lean safe mode, which if the o2 was already sending a low voltage, is was already lean, which basically you equaled the air out to the fuel. hmmmm. never wouldve have guessed it. well i was close but im not taking credit for anything your the one who fixed it not me.

 

[xploder98]

I THOUGHT the same thing. Then when someone else chimed in with the same thoughts I figured it wasn't. After sitting with the master mechanic he explained exactly how it controls the engine (which I already knew ) and why it wasn't comin up with a CEL. The o2 sensors should be reading anywhere from 12 to 47 with the engine running. My driver side o2 sensor was reading 0 then to -4 then to -12, which is takning fuel away from that bank, BUT it was still sending a signal to the computer so the computer thought it was fine. The computer can decifer wether a not a signal is on/ functioning, however it cannot tell when the sensor is malfunctioning or giving bad signals. Catch my drift?

 

[faron021]

I THOUGHT the same thing. Then when someone else chimed in with the same thoughts I figured it wasn't. After sitting with the master mechanic he explained exactly how it controls the engine (which I already knew ) and why it wasn't comin up with a CEL. The o2 sensors should be reading anywhere from 12 to 47 with the engine running. My driver side o2 sensor was reading 0 then to -4 then to -12, which is takning fuel away from that bank, BUT it was still sending a signal to the computer so the computer thought it was fine. The computer can decifer wether a not a signal is on/ functioning, however it cannot tell when the sensor is malfunctioning or giving bad signals. Catch my drift?

i got ya, thats what i been saying in the past reply, just didnt know how to sum it up. alot of people dont relize that either, that they could have a bad sensor(s) and not even know it. the computer simply checks for a loop, sends/receives, could be good or bad, but unless it see's a short of some kind the light stays off.

i have a small shake at idle in my 4.0 and when i unplug the iac nothing changes, wonder if the front o2's are bad in that, i got some credit at autozone, we will soon find out. no vac leaks already changed the both set of the intake gaskets. funny thing is i was pretty close at what was wrong with yours but cant firgure out whats wrong with mine, could be too its not causing no problems and i have yet to look father into it. lol. well again glad you got it fixed and maybe learned something i know i did, when you think its not the o2 it is. lol. take care

 

[Dono]

nice!
I wish all fixes turned out like that.