2.9l Fuel Fouling Number 3 Cylinder

88 XLT Ranger · Jan 18, 2017

JerryC said:
Put an old plug in the boot and and ground the body of the the plug to check the spark. It should spark evenly.
Something that may contribute to the problems but wouldn't be the cause may be the coolant level. If you don't have enough or have air trapped in the system it might make the ECT read erratically causing fueling issues.

Jerry

I did some of what Ron said cleaned the PVC valve and put the Fram filter in line. It works great I feel the vaccum and feel the check valve opening and closing real quick as it running. Its still popping misfiring it don't want to clear up like it use to. I pulled number 3 plug it was black wet I put a fresh plug in still popping missing I put a plug in the boot grounded it its firing perfect. I pulled number 6 plug dark black I changed it still popping. I put a plug in the boot of number 6 its firing perfect. The engine started running smooth I get in it get on the road popping bogging

I got home pulled number 3 plug looks good pulled number 6 plug looks good. I checked the rest of the plugs they where perfect. I fired it up misfire tick off and on give it a quick throttle pop. The only thing I can think of is the computer mixing the cylinders up. I did pull number 4 wire from the cap I didn't notice a change in the engine I did notice the arch on the dist cap terminal was running down around it. I checked the plug looks real good the engine was misfiring on first start up motor ice cold. It cant be a ignition module issue this leads me to think main brain computer issue

RonD · Jan 18, 2017

"Computer mixing up the cylinders"

You don't have sequential fuel injection on a 2.9l engine, they all used Batch Fire, basically same as a carb, well one step up from carb, keeps intake full of air/fuel mix and the next opening intake valve sucks it in.

If you look at the colors on the fuel injectors wires you will see each has a Red wire, that wire has 12volts when key is on.
Then 3 injectors will have a Tan wire and the 3 others a Light Green wire, those 2 wires go back to the computer, computer Grounds one of the wires and 3 injectors open, next time it ground the other wire and the other 3 open.

2.9l also uses distributor so no computer involvement in firing order, just spark advance and retard based on throttle position

JerryC · Jan 18, 2017

Have you double, triple, quadzipple checked your firing order? I'd guess if there was an out of order wire it would run worse than you say, but it can't hurt to check.
If there's any doubt of cross firing at the distributor cap, you can try dielectric grease in the boots, same at the plug end.

JerryC · Jan 18, 2017

This is where you could use one of those old Sun analyzer machines that most shops threw out a decade ago.

88 XLT Ranger · Jan 19, 2017

JerryC said:
Have you double, triple, quadzipple checked your firing order? I'd guess if there was an out of order wire it would run worse than you say, but it can't hurt to check.
If there's any doubt of cross firing at the distributor cap, you can try dielectric grease in the boots, same at the plug end.

Thanks Ron and Jerry

Now I know its not a computer issue and great to know more about that. I will take the Dist cap off look it over see if I can see anything that might cause a misfire or crossfire. I will put dielectric silicone compound for Dist and plug boots that I have see if its better. I checked and triple checked firing order its all correct. My Dist cap and rotor is a new BWD Borg Warner Division I got from 0reilly Auto Parts they say there better quality

RonD · Jan 19, 2017

I had an older chevy motor that had a bad distributor bushing, shaft and rotor wasn't tuning true, it had a wobble, which caused misfires but not steady it was intermittent.
Check rotor/shaft for wobble.

Popping can be misfired air/fuel mix being ignited in the exhaust manifold(back fire).

It can also be very lean mix igniting when it enters a hot cylinder when intake valve opens, intake popping, engine needs to be fully warmed up for this to happen.
So cold engine popping is not this.

2.9l needs to have spark timed manually, you need to use a timing light and disconnect computer from distributor.
There is a SPOUT connector that is there to disconnect computer from distributor.

Google: Ford ranger 2.9l SPOUT images

So you know what to look for
10-12deg Before TDC is suggested base spark timing

2.9l Fuel Fouling Number 3 Cylinder

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