Hey all, have had a long standing problem with my EF and just cant figure it out.....its a 1996 Ford Falcon EF 4.0l inline 6 misfiring and stumble whilst in idle.

Occurs frequently all the time, either in park, neutral or drive.

When driving under load, has heaps of power, no hesitation and is completetly smooth.

Only problem is idle misfire and stumble when in N, P or D.

Engine mostly cranks and turns the starter over for a about 5 seconds until it ignites, in both either warm or cold conditions. Sometimes starts first time, but mostly not straight away.

Compression test conducted and all cylinders within spec. No vacuum leaks to master brake cylinder either and carbon cannister is not faulty.Timing chain has correct tension.

The following have been replaced as NEW items;

-Brand new cylinder head (with valves and springs) + gasket
-New harmonic balancer
-New Cam Angle Sensor
-New Crank Angle Sensor
-New Alternator
-New Coilpack
-New Knock Sensor
-New Map sensor
-New Spark plugs (correct gap)
-New high quality Leads (not earthed by touching any metal)
-New Fuel Pump+filter
-New Fuel pressure regulator
-Cleaned Air intake Sensor
-New intake and exhaust gaskets (no leaks)
-New air filter
-New Idle Speed Control Motor
-New Throttle Position Sensor (set to correct voltage within specs)
-New Serpentine Belt
-New Waterpump and thermostat
-New Battery
-New Air Filter
-New O2 Sensor (Ford geniune)
-No power steering leaks
-New coolant + Oil (not dirty as is replaced every 7000km)
-temperature sensor ok
-No vacuum leaks

-NO ENGINE PROBLEM CODES.

As the new head and headgasket was replaced last year, alot of water had passed through the exhaust creating a small hole at end muffler, hence a noisey exhaust.
Possible damaged Catalytic converter??? (although power band through acceleration is great!) , collapsed exhaust causing back pressure or something?
faulty ECU?? (although no codes have registered to indicate this)
Not sure how to test for correct earth. I have read somewhere that the ECU ground may need attention, but havent investigated yet but not sure how to.... Doubt its the BEM either, as interior light works fine and smartlock operates normally.

Theres a youtube link below;

http://www.youtube.com/watch?v=HxYU8zqyJAM

Comments would be appreciated for any suggestions.

Cheers!!!

Is there a particular time you can relate this problem to? (as in a repair) or has it gradually just gotten worse to this point?

The problem just started to arise around a few weeks before the head and gasket needed replacing.

At that time, I replaced the fuel injectors for new ones, as i had hesitation and poor fuel economy. New injectors and an o2 sensor had fixed it, but problem came back a few days later.

The water jackets near the cylinder bore were cracked. (2 places)

Head was replaced around 7 months ago, and the problem hasnt got worse or better, but still persistant.

Back 7 months ago, I replaced with a brand new head with valves/springs including all necessary gaskets. Cylinder bores were cross hatched an no sign of carbon fouled damage to rings.

Hoping the brand new head, including injectors (*note* aftermarket replacements from Ebay...so could be a dodgey injector as most of these components are chinese manufactured) and the list of other replacement parts as stated in OP would have fixed it, but to dissapointingly discover that the problem is still persisting with poor idle fluctuations.

Scotty Kilmer (youtube mechanic) had suggested that it I have it put on a high level scan tool that reads live data and check mode 6 data stream, where often weak injectors would show up as the culprit.

Could be that i need to inspect the functioning of injectors and test them out....although buying new injectors wouldnt necessarily mean i did in fact get perhaps 1 dodgey injector that was prone to failure. So much for quality control....

The car aint worth more than $1000, so understandably dont wanna invest more $$, but the unsoved problem is really annoying me.

Theres also another member on this forum which has the same identical problem. Havent heard back that he has fixed his issue either.

May have to save up a bit for an FG Falcon, theyre getting quite cheap now

Check that connection to power steering pressure switch is clean and tight.You say it shows no diagnostic fault codes,but idle speed is clearly out of spec and jumps around a fair bit(should be 700+ or - 100rpm)This indicates that base idle speed may not be set correctly(this must be set in diagnostic mode,you cannot just adjust throttle stop screw with engine running),or that ecu may be faulty as it should give you code 411 and 412 when idle speed is out of spec.Another possibility is that the idle circuit in the ecu is fried(this is a mid nineties ecu and uses paper capacitors which can blow,easily spotted by a bulge on the top of capacitor).Ef falcon ecus are very cheap at wreckers and are very easy to remove/ fit,just make sure you get one with the same catch code which is the four digit code printed in bold letters on the sticker on ecu connector(Ef Falcon codes start with 4).Ecu is located behind front passenger side kick panel,and the ecu earth is the small wire which is screwed onto the ecu mounting bracket.Make sure this is clean and tight.
As you say head gasket has recently been replaced,remove all spark plugs and check to see if any of them are clean and shiny as this indicates coolant leaking into combustion chamber which may also cause intermittent idle fluctuations.

Hey Zabatron, thanks for the reply mate. A few things, I have checked the power steering switch and it seems fine as when I turn the steering wheel there is pressure in the system and ups the idle to compensate.
I had set the idle to around 700 rpm a few weeks ago by warming up the car, disconnecting the ISC, turning the car back on and adjusted the set screw to the 700 rpm mark. Turned off the engine, reconnected the ISC and also checked the voltage to TPS is just under 1.0v ( as indicated by a post on here)

I'm thinking it may in fact be the idle circuit in the ECU is fried, as those capacitors are troublesome and alot of members have reported this as a common problem.

I'll take it out on the weekend and investigate. I may even try to solder in new ones from jaycar if they are stuffed.

I'll post back with findings.

Cheers mate!

The idle, as zabatron said, needs to be adjusted while in diagnostic mode. (KOER) It cannot be set simply be disconnecting the ICU. It also needs a 0.75mm feeler guage set between the screw and the stop.

1) start engine, warm up to operating temp, and put into KOER diagnostic mode (Key On Engine Running) this mode will be held for about 2 mins.

2) Check base timing, should be on zero.

3) disconnect ICU

4) Put feeler gauge between idle screw stop and screw,

5) adjust.

6) Stop engine, remove feeler gauge, take out of diagnostic mode, and replace ICU.

7) restart and see if now good

From reading a post on tis forum regarding setting the idle, I was convinced that my method was correct, but reading your post not only makes sense, but is the correct method!!

I will follow your advice and set the idle using your method soon.

Just one question, I dont have a timing light and was wondering if its important to check the base timing, confirming that it needs to be on 0. If i get a timing light and its not on 0, can it be adjusted?? ..... I was under the impression that since the EF runs a coil pack and no dizzy, there's no way to adjust the timing as the cam phase sensor is non-adjustable?

Also, whilst the engine is running in diagnostic mode KOER, I unplug the ICU and then i wait a while until the revs drop significantly and straight after I get my 2 mins to stick the feeler guage between the screw and screw stop and make adjustments to tune it down/up to the 680-720rpm mark?

Your instructions are clear to follow, but just unsure about the systematic approach to unplugging the ICU whilst the engine is running in its diagnostic mode.

Thanks for some great advice here, will report back once complete.

Cheers mate!!

With engine in diagnostic mode,wait for revs to drop,then if you have a timing light check that timing is at 0 degrees,insert .75mm feeler gauge between throttle lever stop tab and throttle stop adjusting screw,then unplug the idle speed control solenoid and check that base idle is between 680 and 720rpm(this is best done by connecting an accurate tachometer as the one in the dash is not accurate enough).If base idle is out of spec,adjust using throttle stop screw before timing returns to normal and revs increase(ecu will maintain base timing of 0 degrees for approximately 2 minutes).
Timing is not adjustable on EF as it is controlled by the ecu.I would not bother replacing capacitors as EF Falcon ecus are dirt cheap and very easy to get for automatic models.

What he said

Too easy!! I'll retune tonight. Appreciate the effort with prompt replies!

Cheers!

After retuning as per instruction, my base idle was down a notch, so adjusted it to sit just above 700-710. Disconnected from diag mode, plugged ICU in and started it up. It does idle somewhat smoother, but is still cutting out at same intervals as before.
Must note that during diag mode with engine running, it seemed to be idle hunting during the first minute until crankshaft pulley aligned to 0.
Could this be that the idle circuit in the ecu is fried good?..
Everything is pointing now toward the ECU.
I'll take it out on the weekend to visually inspect the internals...i guess swelled capacitors may be a giveaway??..anyway ill probably chase another ECU.

Cheers for the help guys!

In relation to my idle problem, I had noticed the small condenser attached to the coilpack is just hanging in the air without being bolted in...does this condenser need to be bolted down and earthed?..could it be responsible for erratic idle?

Cheers!

In relation to my idle problem, I had noticed the small condenser attached to the coilpack is just hanging in the air without being bolted in...does this condenser need to be bolted down and earthed?..could it be responsible for erratic idle?

Cheers!

That is for noise supression. Stops the static on the radio.

Won't effect your idle.

Make sure you check for vacuum leaks around the injectors or intake manifold too.