Idle stalling

Jwpierce said:

I’ve got a 94 with 38k miles. Occasionally it will stall at idle. Could a spark plug wire rubbing the header cause it to die? Or should I keep tracing down the issue? I did see the idle surging checklist and will follow that but the first thing I saw when getting started on the checklist is the plug wire rubbing the header. Pic attached.

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It might sound innocent but its pretty harsh on the coil and also the 02 sensor in many ways as the spark gets bypassed by the copper resistor sparkplug so if running anything but resistor plugs isnt recommended although others will say otherwise I use nothing but #24Autolites and #24R Autolites in ford engines w/ stock heads & exhaust manifolds and Autolite #255 shorty headder plugs for engines with headders


To give your 02 sensors a more honest reading you should wrap your headders and also put boot protectors on the ends of the wires..



The spark thats hitting the headder is being sensed by the O2 sensor ground on the sensor & pin #49 and the misfire is messing with the ECU in the form of alot of noise in the circuits..When the system gets way too noisy it shuts down...........

When you look at my wires I layer them in EMI resistant shrink wrap too........



When I had the sudden death issues the leaky wires werent the only culprit...

Another issue that created it was because I changed my 60mm maf out for a 70mm maf and the items affected by the maf transfer like IAC fuel and timing were affected until I finetuned the IAC , spark and air settings.. as the IAC was opening up way past 50% and wouldnt open and close quick enough..

Another time it was a bad EGR diaphragm that caused a vacuum leak and also a cracked vacuum line on the vacuum tree.

There was an issue when the MAF was dirty and the TPS both got a lil whacky..............

Then on one car the clutch switch was the issue and another the O2 sensor wires burning on the exhaust pipe............

Although most wont agree but I like to keep my IAC around 15% at idle instead of the recommended 54% Ford uses and it seems to help alot in all areas to where everytime I do a hard reset at oilchange time or base idle reset the engine doesnt surge and fluxuate wildly like it used to after changing the settings because what I do differently with my base idle reset is I only drop the idle 75 rpm's from the stock 672rpm's with IAC disconnected to get that 14% when reconnected which is less taxing on the IAC giving lesser fluxuations and quicker reaction to an idle drop..

Just think how low your idle is able to go when you set the base idle to just above stalling....Its only logical to not set the engine to just above stalling or the ECU will allow the engine to dip that low..............LOL

This was before I changed the settings plus I did the recommended base idle reset...It made my car sound like it was tuned on alcohol and had a radical camshaft meanwhile all I did was change the maf , and throttlebody plus changed out the 1.6 rocker arms to 1.7's..................

The 3 near the top are the MAF settings and the two greens in the middle are idle and IAC.

The choppy green is the idle and as you can see the IAC was so slow it didnt have time to correct so when you have a system in chaos its not good to add to the chaos already going on............



This is after finetuning the MAF transfer plus the IAC settings , spark settings and increasing the lowslope setting 15% for the fuel injectors giving them better control at idle ;-........This is what I got after a base idle reset setting the idle only 75rpm's under target rpm................

Th 3 top ones are the MAF and you see the grouping is almost dead on yellow is the idle , green is the IAC just doing what its supposed to do and the scrambled lines representing a radical camshaft are gone......

So what Im getting at is your car already has set parameters to correct some issues but extra issues noted above cause the problems to go beyond the capabilities of the ECU and the more dialed-in you make your car the less issues you'll experience.



The other thing that caused the sudden shutoff issues in other vehicles was the ECU relay as its the most dominant relay in the system that even powers the fuelpump relay and also the fuelpump relay could be giving intermittent issues.........

What I found out is the EEC-IV system is almost like a carburetor as to where a carb needs tweaks for the different seasons the EEC-IV needs to be tweaked for the altitude for where theyre sitting in and the MAF is flowing and then they act totally right and correct alot faster............

Ford just slapped in a 1 size fits all tune and that doesnt jive everywhere and the ECU is only capable of doing a 12% + - correction..I have mine set at 22% correct rate.

Its quite evident of the one size fits all when looking at the throttlebody setting where Ford uses 0.550 lbs/min for all throttle bodies regardless of make and model and engine size...

This is why the sparkplugs come out white unless theres an engine problem or regulator issue.






Heres what my stock 302 pulled on air at under 600 rpm's of idle setting and what the MAF is pulling and creating a certain voltage

When you look above and look next to the current settings are the stock generic A9L settings that cause that huge idle swing and when you look below notice the flow rate flowing through the meter.. After doing the math and calculating how much flow is being used by the IAC at 14% the number gets deducted to become the 1.0891 regardless of what it says above as the engine will run pig rich....

The voltage determines flow rate of the fuel to be sprayed...........At 588rpm's this engine was pulling 1.28615 lbs/min of air. Stock idle is 672rpm's and ECU is set to 0.550.........LOL



Heres what my MAF transfer looks like compared to a stock A9L computer setting....It only takes very small incriments of .002 at a time to change fuel rate of the injectors



This is stock lowslope fuel setting on the right compared to mine...........When you raise the number the duty cycle lowers and fuel at idle becomes way more manageable too...........

When you go by Fords recommendations it seems that the real math doesnt reflect the lowslope setting it should be....19.6417 x 1.33 is 26.123461....



What lots of people dont know is that one of the services a local Ford dealership was capable of doing for a fee under special requests was finetuning your vehicle to the altitude and MAF flow plus the other settings by actually changing the same settings I did with a tool that looks like this....




Most people would never know until aftter changing out the ECU and having the car run differently and if you dont know to tell the rebuilder youll never get the same parameters back either(food for thought)......LOL

For desert you should also know that with a special $10 adapter you can convert OBD1 into OBD2 and read whats going on with a scanner able to read both you can read live PID's for certain parameters as the engine is running............




Good Luck with your car..