99 Sport OHV - intermitent hesitation when warm

[manousos]

1999 Explorer Sport OHV....the engine hesitates. Symptoms are:
- Hesitation while accelerating, especially under load (uphill)
- Hesitation is very sudden and jerky, and appears only when engine is hot and has been running for at least 30-45mins on a warm day, longer (2-3 hours) at night or with cooler temperature

No CEL at any time since this problem first appeared in early March

To date I have done:
- changed the fuel filter
- changed the spark plugs (motorcraft gapped at .054)
- changed the spark plug wires (motorcraft)
- changed the coil pack
- changed PCV
- cleaned the MAF with electrical contact cleaner

When I changed the sparkplug wires I found one severely frayed. Problem persists even with new wires, plugs, coil pack, etc..

My mechanic can't figure out what the problem is, primarily because he can't recreate it (the weather has been fairly cool lately and he can't take it on a long distance drive just to troubleshoot).

He has recommended that it might be an O2 sensor problem - does this sound plausible without the CEL lighting up? Any direction would be greatly appreciated, I need the truck for a long distance trip next weekend!

 

[Runnin'OnEmpty]

Check the MAFS connector for loose terminals
or wires. Ford has had trouble with these in the
past.

 

[Scanner85]

I have the same problem every once in a while too. I have also experienced when cruising at highway speed. It's almost like something slipped and then catches back and there is a jerk when it "catches". I have also replaced plugs and wires and fuel filter. Have also had transmission rebuilt (separate issue) and new gears and carrier installed in the rear axle (upgraded to 4.10 and LSD from another exp).

 

[manousos]

I have the 4.10 and LSD on mine, and right now it feels like it's the only thing preventing me from selling the truck

I'm going to check wiring/connectors over the weekend on MAF and o2 sensors

 

[nugrapeman2]

I had an similar issue and it was the camshaft synchronizer. Along with the EGR valve.

 

[manousos]

UPDATE:

After a few months of tinkering and trial/error, the engine has developped a loud whine from the back (near the firewall). I'm assuming it's the synchronizer

I'll be replacing that this weekend *crosses fingers*

 

[JusTheUsual]

a lot of problems are fixed by...get ready for this...ask how I know lol ready? **** i'm not I forgot name of it, but if you have a return or non return fuel system(forgot which one) there is this circular lil round object on passenger side fuel rail. It holds pressure or fuel in fuel system. I've had it do many funny things, it in fact didn't work on my truck but worked on another persons, funny lil things they are..i cant believe I forgot name of it, 2:30am what you expect...hard starts, runs funny, does different funny things and after having everything from fuel tank, to pump to lines to filter to injectors, oh wahla, that's the problem... I never seen a thread mentioned about it, mine is acting up again. go to junk yard steal a couple I mean purchase one and try, watch the difference, good luck people

 

[manousos]

at my f*^ing wit's end with this problem(!)

Changed the synchronizer (seriously Ford, could you have made it any more difficult to access!!) The old synchronizer was actually toast, when trying to twist it by hand it kept jamming up and squeaking. Installed a ford re-manufactured unit (dealership wanted $400 for a new one) and drove it for two days to work and back without any issues.

Now my wife just called me from the side of the road after a 90 minute highway drive describing the same hesitation and jerkiness that we've been experiencing for the past 2 months

ugh, seriously frustrated with this...any additional advice/help would be appreciated

 

[JusTheUsual]

at my f*^ing wit's end with this problem(!)

Changed the synchronizer (seriously Ford, could you have made it any more difficult to access!!) The old synchronizer was actually toast, when trying to twist it by hand it kept jamming up and squeaking. Installed a ford re-manufactured unit (dealership wanted $400 for a new one) and drove it for two days to work and back without any issues.

Now my wife just called me from the side of the road after a 90 minute highway drive describing the same hesitation and jerkiness that we've been experiencing for the past 2 months

ugh, seriously frustrated with this...any additional advice/help would be appreciated

My truck is starting to do it again, but not as bad as before where it literally lost a lot of horsepower because it couldn't keep fuel pressure in fuel rail, you think the fuel pump would but it doesn't, That's why also its a hard start because it never kept fuel pressure or fuel up in the lines in fuel rail. So no fuel instantly available on start up. Those things are weird, wouldn't work in mine but worked on another exact same engine...weird. Also could be another thing whats wrong with your vehicle, but who knows. i'm just stating through my experience with these engines

 

[eazuaje]

Check the fuel rail pressure. I had a similar problem last month and turned out to be the fuel pump. anything less that 65psi is not good.

Also, a sync code came up because of a bad battery, it wouldn't give enough energy during startup and the ECU didn't undestood the signal, so that was flagged as a syncronizer not working. Replaced the battery and erased code, then it was running smooth again.

The other thing I did was to clean the EGR passages with carb cleaner, I think I have to replace the EGR valve because when driving arround 3000rpm it jumps up; I'm not sure, but I believe that the when the ECU receives a VSS signal different from 0 and also a RPM signal of 3000rpm or so, it tells the EGR Solenoid to apply vacuum to the EGR valve which opens the passage to the heated recirculation gases into the intake allowing to perform better, and also allowing the DPFE to sense pressure to achieve better performance and mileage. Please correct me if I'm wrong. I'm also very new in this matters, this is my second truck, I first owned a 1999 F-150 with a 4,2L V6, and I stupidly sold it because I had no knwoledge whatsoever, biggest mistake I had made, the good thing, I embraced Ford and bought a Explorer, and I love my truck!

By the way, I know it's weird, but check your battery. I had the exact same code, and the light is off ever since I replaced the battery. Not even remanent codes when I scan. My truck has 300.000kilometers on it and stills runs great.

Eiber.

 

[goalkeeper21986]

oh man...I feel your pain...ive been dealing with your issue for close to a year now. onky thing is mine doesnt need 30 mins to get warm to start issue
check out my thread, ive

cleaned mac
reolaced mac
cleaned iac
replaced iac
replaced throttle position sensor
new air filter
replaced o2 sensor
professionally checked for gasket leaks
plugs
wires
tested coil pack
replaced fuel filter
replaced fuel pump assembly

...

still get your symptoms...

btw 99 ohv sport

 

[JusTheUsual]

My truck is starting to do it again, but not as bad as before where it literally lost a lot of horsepower because it couldn't keep fuel pressure in fuel rail, you think the fuel pump would but it doesn't, That's why also its a hard start because it never kept fuel pressure or fuel up in the lines in fuel rail. So no fuel instantly available on start up. Those things are weird, wouldn't work in mine but worked on another exact same engine...weird. Also could be another thing whats wrong with your vehicle, but who knows. i'm just stating through my experience with these engines

I will repeat myself again, do i have to take a pic?

 

[JusTheUsual]

a lot of problems are fixed by...get ready for this...ask how I know lol ready? **** i'm not I forgot name of it, but if you have a return or non return fuel system(forgot which one) there is this circular lil round object on passenger side fuel rail. It holds pressure or fuel in fuel system. I've had it do many funny things, it in fact didn't work on my truck but worked on another persons, funny lil things they are..i cant believe I forgot name of it, 2:30am what you expect...hard starts, runs funny, does different funny things and after having everything from fuel tank, to pump to lines to filter to injectors, oh wahla, that's the problem... I never seen a thread mentioned about it, mine is acting up again. go to junk yard steal a couple I mean purchase one and try, watch the difference, good luck people

just adding again

 

[goalkeeper21986]

JusTheUsual...pic?

 

[JusTheUsual]

JusTheUsual...pic?

ok my bad, tomorrow I promise I will get you a pic of it online, its a round part 2 bolts and a top connector to fuel on passenger side fuel rail. I promise about 12hours or so from now I will take pic of it and post it

 

[JusTheUsual]

JusTheUsual...pic?

http://imgur.com/pz1CEA6

http://imgur.com/LdSYat0

http://imgur.com/ZvX9GMG

http://imgur.com/DrNaBlg

that part. it got so bad before where literally I only had half the horsepower.

 

[goalkeeper21986]

JusTheUsual, thanks for the pics! will investigate!

 

[Vic_Ferrari2002]

Fuel Pressure Regulator

 

[goalkeeper21986]

fuel modulator for a returnless system is my guess...am I right?

this totally sounds like what could be causing my issues. reading up on it now!

 

[goalkeeper21986]

symptoms of a bad fuel pressure damper explained

d https://www.google.com/url?q=http:/...cQFjAA&usg=AFQjCNENxp1JugYnYYL-wrc-yNtWJW74xw

ordering a replacement in the morning!