1999 Explorer -Intermittent rough idle, 4.0 L SOHC

30

Asked by Feb 02, 2016 at 09:28 AM about the 1999 Ford Explorer 4 Dr XL 4WD SUV

Question type: Maintenance & Repair

I have no Check Engine light or codes. During idle it
will every few minutes start to stumble as if it is
going to stall. I am unfamiliar with this Ford 4.0L
SOHC engine (not to be confused with the 4.0L
OHV engine) and the common issues that it may
have. It accelerates well and seems to have the
power it should have. I ran a live Elm327 scan and
it appears that an injector was being stuck open at
times but i do not have enhanced DTC's for this
vehicle to see anything more in depth. However, I
am also thinking that a possible cause may be a
vacuum leak coming from the intake manifold. I
am not quite sure why there is no code that is
being set in the PCM. Hence why I am leaning
towards a possible intake manifold leak. Are there
any mechanics that are experienced with this
engine that can give me some input? Thanks in
advance.

8 Answers

have you checked: - Vacuum leaks - Fuel filter - Spark plugs and Wires (to check wires, just spray mist over top of wires if see any sparks, change them) _ Fuel injectors (clogged (needs replacement)/dirty) - IAC Valve/PCV Valve - MAF or MAP sensor - EGR Valve - Oxygen sensors (upstream and downstream, you might have 2 or 4 O2 sensors)

Best Answer Mark helpful
30

-Vacuum leaks, Not checked -Fuel Filter, Checked (fuel pressure good) -Wires and plugs new -Injectors, Cyl 5 sticky -IAC, EGR and Map, untested -MAF cleaned but untested -o2 sensors, voltage output good on each -TPS, not tested Any common weak spots for vacuum leaks on these engines?

30

As far as the sticky injector goes, I will just clean, change filters, and test spray patterns and replace as needed.

i use a smoke machine to find vacuum leaks..

30

I cleaned the IAC which basically was already very clean, as is everything under the hood, fortunately. Judging from the various internet search results and posts, it appears to be a very common issue to have a vacuum leak at the intake manifold upper plenum. The other being faulty/clogged fuel injectors. Both of which I will repair soon. I will post my results which I hope will help others if they have a similar problem.

30

Update: I replaced the upper and lower intake manifold gaskets. I am still having the goofy idle. I checked the fuel pressure, which was at a stable 63psi. I changed the fuel filter and now I am running at 64psi fuel pressure. I was listening to the engine idle and I heard an injector stick and the engine stumble. The issue is only getting worse as the vehicle sometimes has hard start issues. I checked the fuel pressure leak down and it immediately dropped from 64psi to 0 after about 15 seconds. The fuel pressure regulator is not losing any fuel to the vacuum line. I will be cleaning or replacing injectors soon.

Fuel line on frame near exhaust at rear left side of engine and fuel line on front of engine going to injectors causing vapor lock I moved the line at both places and have not had anymore trouble got the idea from old ford and Chevy

30

It's been over a year now. I went through everything imaginable. I will perhaps give that a try. Currently, the 5R55E transmission gave up (second tranamission in 5 years). I'm not quite sure if I will be repairing this again unless I swap a GM drivetrain in place. That, or the scrap yard.

Your Answer

Explorer

Looking for a Used Explorer in your area?

CarGurus has 69,233 nationwide Explorer listings starting at $1,495.

ZIP:

Ford Explorer Experts

  • #1
    OJ
    Reputation
    11,060
  • #2
    Tom Demyan
    Reputation
    4,400
  • #3
    tennisshoes
    Reputation
    2,560
View All

Related Models For Sale

Used Jeep Grand Cherokee
841 Great Deals out of 70,041 listings starting at $700
Used Ford Expedition
359 Great Deals out of 18,210 listings starting at $1,989
Used Chevrolet Tahoe
713 Great Deals out of 41,427 listings starting at $1,995
Used Ford F-150
2,557 Great Deals out of 198,440 listings starting at $1,500
Used Dodge Durango
262 Great Deals out of 22,802 listings starting at $895
Used Toyota 4Runner
276 Great Deals out of 23,268 listings starting at $2,300
Used Nissan Pathfinder
365 Great Deals out of 26,658 listings starting at $1,500
Used GMC Yukon
457 Great Deals out of 22,162 listings starting at $1,995

Used Cars For Sale

2018 Ford Explorer For Sale
548 listings starting at $32,363
2017 Ford Explorer For Sale
90 Great Deals out of 42,023 listings starting at $19,650
2016 Ford Explorer For Sale
96 Great Deals out of 3,917 listings starting at $14,989
2015 Ford Explorer For Sale
286 Great Deals out of 6,764 listings starting at $11,199
2014 Ford Explorer For Sale
221 Great Deals out of 4,934 listings starting at $8,979

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.