302 (306) Tuning - spark plug diagnosis.

[john42]

Am I running rich? This plug is brand new and run for 200 miles.

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The black carbon is soft and easily removed by just rubbing it with my finger.

[Railroad]

Short answer, yes, or it has been rich and is burning the soot off.
Any info on what you are dealing with?
Are you getting any black or blue/white smoke?

[john42]

No smoke. The investigation started when 1 cylinder stopped firing. I pulled the plug and it was caked up bad. I put in all new plugs and have been "observing" for the last week. The previous set of plugs were 1 year old.

Some of my thoughts... My driving is 90% side roads. I almost never take the freeway. Most my speeds are below 45mph. I do however do a few autocrosses a year (call it 6). That is 2nd gear driving at high rpm for very short bursts of time. My driving habits don't get the engine revving for long duration's of time. I'm going to force myself to change my habits! However, while I'm sure that's a contributing factor it doesn't explain that sparkplug of this last week as I made it a point to get out on the highway and drive 70mph in 4th gear (sustained 3500rpm) for an hour before pulling and checking the plugs. I've also been especially attentive to watching for smoke and I haven't seen any.

[Hoooper]

How often do you need to add oil?

[john42]

The other thing I've been searching for is a good how-to video on tuning a 1990's era fuel injected 302. There are hundreds of videos on modifying everything but a straight forward rich/lean, timing advance, video is totally lost somewhere in the weeds and I've yet to stumble across it.

[john42]

How often do you need to add oil?

Maybe 1/2 quart in 1000 miles. Not much since I fixed the leaking rear main seal!

[Railroad]

You might check the easy stuff first. Exhaust leaks, mess up O2 readings, 302 intakes are notorious for needing re torquing.
It sounded like, you found 1 spark plug fouled, prior to putting in a new set. You could be oil fouling. Where does you pcv pick up its vacuum? If you are plumbed on an intake runner, your pcv valve may be letting oil get pulled on that cylinder,,,should be the one with the fouled plug.

[MB750]

The other thing I've been searching for is a good how-to video on tuning a 1990's era fuel injected 302. There are hundreds of videos on modifying everything but a straight forward rich/lean, timing advance, video is totally lost somewhere in the weeds and I've yet to stumble across it.

What FI system are you running? Is it the standard OEM Mustang parts from a Fox Body?

Since you said 90's, I'm guessing it's Mass Air based? (If there's a Mass Air Flow meter in the intake between the filter and the throttle body, it is). The other style of tuning is speed-density, and doesn't have the MAF in the intake. That ended in 1988.

Most people shy away from tuning because they don't understand the cause and effect relationship between changing something on a computer (or a jet in a carb) and the resulting effects on the car. If you're really interested in tuning fuel injection, be ready to learn a lot. If you're not, find a tuner. You're not finding straight forward videos on it because it's never straight forward.

I've lost count how many engines I've tuned. Personally, reading a spark plug will only tell you "rich" or "not rich" so I start with a wideband oxygen sensor in the exhaust. That will tell me the AFR (rich or lean, and how much) under every possible engine condition. Then knowing what to change based on RPM and throttle position is where tuning comes in. For example, low RPM low speed cruise is the idle mixture screws and needle height in a carb, or high vacuum low throttle percentage in tuning software.

[i.e.427]

If you're running a stock Ford ECCIV or similar, you're going to be limited on making adjustments fuel-wise. You could try playing with the timing or you could try adjusting fuel pressure. This usually happens when injector size in increased and a "matched" MAF is installed. If you are running an aftermarket ECU you have much more to work with, including fuel injector pulse width and fuel enrichment tables.

[MB750]

If you're running a stock Ford ECCIV or similar, you're going to be limited on making adjustments fuel-wise. You could try playing with the timing or you could try adjusting fuel pressure. This usually happens when injector size in increased and a "matched" MAF is installed. If you are running an aftermarket ECU you have much more to work with, including fuel injector pulse width and fuel enrichment tables.

Yup, agreed. I couldn't find those plug-in tuning chips anywhere. Megasquirt makes an ECU that literally plugs into the Ford harness and even comes preloaded with an initial program to get running so you don't have to fumble through tables to get it to start.

https://lmr.com/item/MSPNP2-EEC4A8/mustang-megasquirt-stand-alone-ecu-pnp-1986-1993?utm_source=Youtube&utm_medium=ProductLinks&utm_term=Megasquirt

Here's a great video on the install and intro to tuning:

https://www.youtube.com/watch?v=x5F2khhzMZo


https://www.youtube.com/watch?v=x5F2khhzMZo

[john42]

Wonderful info! I was questioning if the custom ECU road was where I was heading. It seems every vid I find is along these lines when it comes to tuning. My engine setup (from what I understand) is a very typical Challenge car setup. Trick Flow intake upper and lower, Trick Flow heads, Trick Flow cam, 24# injectors and a Summit Racing MAF. It also has a cold air intake box built into the right side of the car that is shielded from the exhaust and uses a pair of brake vent pickups to feed air into the box and the side louver as an exit/suction effect. It has a stock Ford computer which my guess just isn't able to tune right for this setup. The interesting bit is it runs and idles great, if it wasn't for the spark plug fouling I'd never know anything was amiss. Throttle response is very good and it revs happily over 5k rpm. I recently drove a friends Cobra with a 427 stroker with 460hp and I have to admit that I couldn't tell the difference between his car and mine in acceleration and throttle response. He drove mine as well and had the same comment. I know that's antidotal but it was surprising to both of us. His motor is brand new from Forte. Also to a point above, I've put in new O2 sensors in the exhaust at the same time I put in new plugs. I been trying to get a good read on the timing and thus far I've spent more hours then I thought I ever would cleaning and chalking the balancer and my old crappy eyes still can't read the flashing numbers.

Anyway... seems like getting a better ECU is the route to go at this point.

[David Williamson]

From your description it sounds like it is running well so maybe not a tune issue? as an old race car that was likely run very hard it sounds to me like an oil burning problem. I had a hard time seeing the timing marks so I put a dab of white paint on the balancer at the point I wanted the timing set to. I just went round the fouled plugs that looked like yours on a new engine and in my case it started to smoke badly after a few thousand miles, turned out to be badly machined valve guides.

[john42]

From your description it sounds like it is running well so maybe not a tune issue? as an old race car that was likely run very hard it sounds to me like an oil burning problem.

That's possible. However this is engine #3 in the car. As the last engine in it only has a few last races on it. The first 2 went BOOM. :-)

[MB750]

An engine runs great... at 12:1 AFR. How's your mileage?

Also, did this issue manifest itself after the plug and o2 sensor change? Or did it develop over time and the plug and O2 swaps were an effort to fix it? Since this is the 3rd engine, were the other two using the same EFI system, and did they have similar issues?

Another weird thing, these OEM style injection systems are pretty reliable. It seems odd you've got a rich condition on your hands since that's what the OEM systems are designed to avoid at almost all costs. Typically if there's an air leak you'd be lean, but not many things deteriorate and cause a rich condition. O2 sensors fail rich, but yours are new. Too large of an MAF sensor will make the ECM think your engine is larger than it is, dumping more fuel.

[john42]

An engine runs great... at 12:1 AFR. How's your mileage?

Also, did this issue manifest itself after the plug and o2 sensor change? Or did it develop over time and the plug and O2 swaps were an effort to fix it? Since this is the 3rd engine, were the other two using the same EFI system, and did they have similar issues?

Another weird thing, these OEM style injection systems are pretty reliable. It seems odd you've got a rich condition on your hands since that's what the OEM systems are designed to avoid at almost all costs. Typically if there's an air leak you'd be lean, but not many things deteriorate and cause a rich condition. O2 sensors fail rich, but yours are new. Too large of an MAF sensor will make the ECM think your engine is larger than it is, dumping more fuel.



The issue manifested itself after I cleaned and ummm oiled the K&N air filter. The O2 swap was after the plug was fouled and I started trouble shooting. I've now replaced the Air Filter with a non-K&N style and also replaced the PVC valve as the rubber bushing was very dried out. After those 2 things I went for a 2 hour highway drive, got home and pulled the plugs and low and behold they are clean and look great! I think I'm a victim of my own bad job on the K&N filter. It was the first time I've ever cleaned and re-oiled one. I have a feeling that is my root cause of all my troubles. So at this point I'm calling it good! Wednesday I hit the road for the London Cobra Show. I'm driving from New Hampshire. Should be fun. I'm taking a healthy set of tools with me and will again pull a spark plug when we reach London, Ohio and see how it looks.

[MB750]

The issue manifested itself after I cleaned and ummm oiled the K&N air filter. The O2 swap was after the plug was fouled and I started trouble shooting. I've now replaced the Air Filter with a non-K&N style and also replaced the PVC valve as the rubber bushing was very dried out. After those 2 things I went for a 2 hour highway drive, got home and pulled the plugs and low and behold they are clean and look great! I think I'm a victim of my own bad job on the K&N filter. It was the first time I've ever cleaned and re-oiled one. I have a feeling that is my root cause of all my troubles. So at this point I'm calling it good! Wednesday I hit the road for the London Cobra Show. I'm driving from New Hampshire. Should be fun. I'm taking a healthy set of tools with me and will again pull a spark plug when we reach London, Ohio and see how it looks.

It's ok, I've been here before with many a K&N filter. You can oil them, but immediately after oiling get a nozzle your air compressor hose and blow air through the filter with max psi to get the extra oil out of the filter.

Or, never oil it. ;)