Need Help Fast!! 98 OHV Running Terrible!!

[xploder98]

Hey everyone, i'm in desperate need of some help. my 98 sport ohv is runnin terrible. everything was fine yesterday, took my buddy to work around 5, came home, went to get girlfriend and it started stumbling/hesitating mostly during acceleration and felt a stumble at idle. it progressively got worse throughout the night. started harshly stumbling during acceleration. got new plug wires and bosch platinum +4 plugs last night, put em on and seemed great right away, a min or so later started stumbling again during idle and again during acceleration. this morning i cleaned air filter (cone filter), removed ac (compressor, lines, and accumulator) and checked the vac lines. after i was done i pulled the pos off the batt for 15 min or so and started and was great for a sec or two, then it started stumbling even worse then before, did that for a min then started running and idling great for 7-8 min then even worse with the stumbling and missing and now it barely wants to run. engine sounds a lil different. I need to fix ASAP. If anyones got any ideas please let me know asap. thanks.

 

[moogvo]

First thing is ditch those Bosch plugs! Put in Motorcraft or Autolite. Bosch has been known to cause more problems than it fixes. I have seen MANY cars come into the shop with a check engine light or running ragged. Change out the Bosch parts and BANG! Good to go! I am not sure about the ignition setup on those, but my Bronco II had similar issues and it turned out to be 2 things. First, the ignition control module was bad. The other thing was the ECM relay. I could tap on the relay with a screwdriver handle and make it stumble and almost stall out.

If you have a map sensor, check that. It will NOT be an idle air control valve since it is not ONLY doing it at idle. Once you press the accelerator, the IAC does NOTHING.

When you say "New Plug Wires"... are you talking Motorcraft or Duralast? Cheap plug wires fail a LOT too... even straight out of the box!

 

[rjcooperss396]

Unplug the MAF sensor and see how it runs. I had mine run like that when the MAF went out. By unplugging it the ECU will use set parameters bypassing the MAF. If it runs good without the MAF plugged in the MAF is bad.

 

[xploder98]

I hooked on a timing light and started the engine and cylinder 1 and 2 were firing fine but the rest were speratic, at on point cylinder 4 and 5 only blank once or twice in a second (one missisippi), after a min or two they were all firing speratic. Coil Maybe? I'll go ahead and switch in different plugs, NGK or Autolite better? Also the truck will run if i keep on the gas pedal a lil but if i let it try to idle on its own it sputters shakes and dies. I have a manual trans by the way (dk if u needed to know that). Thanks

 

[xploder98]

Just unplugged the maf and it idles great! thanks rjcooper and everyone else for chimmin in on this one. Gonna go get a new maf right now!

 

[colintrax]

Check your coolant, could be leaking head gasket. You can check for spark at each cylinder if you have time (pull out plug, start engine and hold the electrode to the engine block. If it sparks its good, if not, theres a problem)
Check for intake gasket leaks

 

[rjcooperss396]

Check your coolant, could be leaking head gasket. You can check for spark at each cylinder if you have time (pull out plug, start engine and hold the electrode to the engine block. If it sparks its good, if not, theres a problem)
Check for intake gasket leaks

DO NOT HOLD THE PLUG!!! You will shock the S@%& out of yourself. If you want to test a spark plug that way, use a pair of vice grips to clamp it to a ground and do not touch it until you turn off the engine.

 

[xploder98]

just put on the new maf, same ****ty idle. 112.00 for nothin. It is wat it is. The truck runs terrible but great as soon as i unplug the maf. I'm thinking MAF Relay? Anybody agree? im leavin to autozone in a lil while.

 

[rjcooperss396]

Sorry that wasn't the issue but you can always return the MAF. For me that was the cause.

 

[joe doe]

is your check engine light on?surely it must be .if it is get the codes read and report back ,then we can help more

 

[SoNic67]

Bosch 4+ plugs are great on faster engines (like the 3.0L Ford DOHC Duratec).
They are bad for older generation, slower, OHV engines (or even on SOHC ones), because the combustion chamber architecture that is sensitive to flame shielding (by the ground electrodes).
Autolite Iridium XP103 are recommended for your engine. Catalog.

 

[xploder98]

You would think i'd have a CEL Light on but strange enough, I don't. I've even plugged in the code reader and nothin. I honestly have no clue at this point. All I can think is the maf wiring and or harness, maf relay, or somethin along those lines. I would think that it has something to do with the maf seeing how it runs smooth with it unplugged and unable to idle with it plugged in, but I've also heard that whatever my problem is and the maf aren't necessarily tied together. When I unplug the maf its putting the engine on closed-loop mode stopping whatever could be wrong (bad sensor, vac leak, etc.), if not the maf. Correct?

 

[SoNic67]

Open-loop without the MAF. Fuel goes by rpm's and tables in the memory - usually means a rich condition.

 

[xploder98]

So your saying my problem is a running rich condition? Or is that when I inuplug the maf? I just wanna know why it runs fine withit unplugged but bad/ not at all with it plugged in. Is there a list of things that i can check that it would have to be (certain sensors, vac lines, etc?)? I just want at least a starting point. Rebuilt engine and valvetrain by the way 6k miles and 137k on everything else (vac lines and actuators, I think that's what there called, sensors, etc.)

 

[xploder98]

Just got an idea.. if even when i unplug the maf & tps and get no codes, wouldnt that mean the pcm is bad? i only let the truck run for 7-8 min or so with the maf off, is that too short of time to make it throw a code? I wana just get a diagnostic (if that will pinpoint my problem) but i dont know if i can since the engine wont stay running with the maf plugged in, unless your givin it some pedal and even then rpm fluctuates and the engine rumbles and stumbles like crazy. Can a diagnostic be done? this is my daily driver and i just got hired at UPS so I need it running indefinitely by monday. Any and all help is greatly appreciated. Thanks guys

 

[ranger7ltr]

How did it drive withe the MAF unplugged?

Just unplugged the maf and it idles great! thanks rjcooper and everyone else for chimmin in on this one. Gonna go get a new maf right now!

Have you checked your fuel pressure yet? I am betting that the fuel filter is clogged and the drop in fuel pressure is causing the crappy running conditions... Especially since the engine was running before and it didn't overheat or get run out of oil or anything damaging before the problem started...

While I use Autolite plugs I haven't had the same issues with Bosch plugs in my Explorer engine... I have run them for 20-30k and only replaced them since I change plugs every 20-30 k miles anyway...

 

[colintrax]

DO NOT HOLD THE PLUG!!! You will shock the S@%& out of yourself. If you want to test a spark plug that way, use a pair of vice grips to clamp it to a ground and do not touch it until you turn off the engine.

SORRY. Hold the boot or put on gloves.

Honestly I'd still say to check for vacuum leaks or intake gasket leaks. If you run richer with the maf unplugged (right?) then its running lean

 

[xploder98]

To be honest I haven't checked it yet, the only reason being is when I unplug the maf it idles smooth and fine. I didn't see why if I do have a fuel pressure problem, it would get better by unplugging the maf sensor. I figured if there's a fuel problem, it would be there wether the maf is plugged in or not. Correct? I never really gave a backround for the truck, it sat for about 4 of the last 5 years in my driveway because of an oil problem. About a year ago iit was givin to me, I got a completely new/rebuilt block and valvetrain (the old piston #4 I think had a scar down the side of it about a half inch deep, as if you ran a plasma cutter down the side of the piston real slowly! Crazy huh!) 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

 

[xploder98]

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.

 

[xploder98]

BTW I just replaced the fuel filter a week ago