I have a rough idle. Feels like a misfire, but I am left scratching by head. PLEASE HELP.

Here is the data and work done so far:

2003 Ford Ranger Edge 3.0l FFV 2WD with 5 speed AUTO.

1. Recent compression check numbers:

cyl1 161
cyl2 156
cyl3 160
cyl4 160
cyl5 146
cyl6 165

2. Vacuum check:

18" and steady

3. Fuel Pressure check:

a. ~40psi withe key on engine off

b. 60psi with engine running

c. Leak down test:
- Fuel psi drops from 60 to 50 when engine is shut off and holds steady
- Pressure drops ~12 psi in 30 minutes

4. Checked the PIDs with my scanner and all are within factory limits. Specifically checked the following:

ALL CHECKED WITH THE ENGINE AT OPERATING TEMP

a. TPS% = 17.8
b. LOAD = 21
c. All Fuel trims = within specs
d. MAF = ~4.9
e. Spark Advance = 18 deg
f. CTS = 193 deg
g. O2 sensors = within specs

I have changed or had the dealer change the following:

1. Coil Pack
2. Plug wires = Autolite premium
3. Plugs = Autolite Extreme Performance XP104 gapped to .045"
4. Upper Intake Gaskets
5. Heads and Head Gaskets due to an overheated engine.
6. TPS (throttle position sensor)
7. IAC (idle air control) valve
8. Fuel Filter

I have performed the following recent maintenance:

1. Oil and filter = Valvoline Maxlife 5W-30 w/ motorcraft filter
2. Seafoam through the brake booster hose twice in the last month
3. 3 tanks of Shell 87 with Techron or Gumout w/ Regain fuel system cleaner
4. Winns fuel system service = same as seafoaming in reality
5. Cleaned MAF with CRC MAF cleaner
6. Sent oil sample from last oil change to Blackstone for analysis. Awaiting report.

Ford Dealer performed Power Balance check and found nothing. Mode 6 data revealed a misfire on cyl 5 & 2 but never threw a code or CEL. Mechanic found no reason for the misfires.

 

I've had a clogged fuel injector cause a missfire. It was at approx 100,000 miles. I removed all 6, had them professionally cleaned, the reinstalled them.

One thing that stuck out with this is when it idled. After a couple of minutes the check engine light came on and i could smell fuel.

i don;t have much faith in cleaners you dump into the gas tank to remedy this.

Hope that helps. good luck.

 

I am thinking that the fuel system may need further exploring. If these pressures are satisfactory or not.

The truck has been to the dealership twice and nothing was found. They said that on the outside chance it was something internal, there was not near enough cause to tear the engine apart to investigate.

 

Interesting note. I am very **** about engine cleanliness so I went out to do the spring engine cleaning. After rinsing the engine off I noticed the engine seems to run much better.

Now the only place on this engine where water can pool in on the horizontal surfaces, and the only surfaces that have seems with seals on these surfaces are around the injectors.

Is it possible that there is a vacuum leak around the injector O-Rings? I will have to wait for the motor to completely dry and see if the idle issue returns.

 

it sprays straight into the intake air stream, so yes, a cracked o-ring could be sucking in air.

Also, the rubber hose that goes to the PCV valve. The pcv valve is on the rear side of the drivers side valve cover. I've had to replace the hose from cracking/disentegration.

what is the mieage on truck?

 

It has 59000 miles on it. I think I am going to get a vacuum pump and one by one, test all the vacuum lines individually. I don't know what else it could be.

 

It could be a leaky EGR valve.

 

Yeah, I had to bring back my Grand Marquis the day I picked it up. It felt like it wasn't running on all cylinders. Check under the plug wires caps at the coil pack for moisture. They steamed the engine bay the night before I picked it up cause they didn't have time to go thru it for a detail when the previous owner dropped it off. I cover what I can when I get busy under the hood, so check for water on all those terminals.

Good Luck,

 

2003 does not have an EGR system.

Odd thing is that it ran better after rinsing it down. The whole engine except the alternator, was soaked. Go figure. Nothing happens in a logical progression for me.

 

Does it idle better when first started cold? This would be "open loop" mode, instead of "closed loop" mode.

 

That is actually very hard to answer. Since the idle is 400 RPMs higher when it is cold it seems smoother. The idle settles out to about 800 when warmed and the "miss" seems more noticable. The one thing I guess I can say is that the "miss" is more noticable at the lower RPMs.

 

I know you said fuel trims where within spec but if i where you i would spray some brake clean around the lower intake while watching fuel trims . It sound to me like you have a intake leak even thought you say the trims are in spec if you spray the brake clean around and see the trims drop then you will know that you do have a leak.

 

I have done the whole carb cleaner on the mating surfaces thing and found nothing. Since you can only spray one side of the manifold, I took it in and had a smoke check done and nothing was found. That does not mean a leak does not exist, just that we could not find one.