Fouled plugs?

boy83 · 12-31-2007, 05:05 PM

I have a 1983 3.2 short stroke 10.2:1 , 120/104 cams, tec3, magnecore wires, ssi, wide band o2 sensor, carrera intake, BPR7ES spark plugs.

Would fouled plugs cause the AFR to go leaner? Should I use hotter plugs? It's a street driver.

It feels like it's running on 5 cylinders.

I

Eagledriver · 01-01-2008, 10:39 AM

I think that fouled plugs would cause it to be rich (unburned fuel going through engine). The question is are your plugs fouled? Pull them out and look at them. There are numerous guides that show pictures of what the plugs should look like. The look of the plugs will tell you if you have the proper heat range.

-Andy

911pcars · 01-01-2008, 11:45 AM

"Would fouled plugs cause the AFR to go leaner? Should I use hotter plugs? It's a street driver."

Insufficient fuel or too much air will create a leaner mixture. I assume you're monitoring the A/F with the wide band sensor and an appropriate gauge. Isolate the weak cylinder by shorting out its plug wire (temporarily disconnect wire). The cylinder that produces the least rpm drop is the weak one. Visually inspect the spark plug, confirm proper injector operation - whatever contributes to the fuel supply for a specific cylinder.

Sherwood

boy83 · 01-03-2008, 07:39 AM

I took the car to the shop. Mechanic found the spark plugs to be fouled, too much unburnt fuel. Changed all 12 plugs to BPR7ES plugs, same type of plugs. Car has its power back.
My question is should I have used hotter plugs? This last set of plugs lasted me about 6 months, 3000 miles before fouling up.
I know the car is running on the rich side. However, it was tuned on the dyno and I don't want to mess with the tec3.

Steve@Rennsport · 01-03-2008, 09:32 AM

I would be using BPR6ES plugs, for sure since you are using the car on the street.

Electromotive ignitions are not well known for keeping plugs clear as they do not develop sufficient voltage & current to keep the plugs clear in a rich-running environment (idling).

I would run the hotter plugs and adjust your idle (cold & hot) fuel mixtures as lean as you can without misfire. Unless you correct this on the Tec3, you will become very proficient at changing plugs,...

boy83 · 01-03-2008, 08:49 PM

Thanks for the advice Steve. Much appreciated.
Idling has been leaned a bit.
I would also switch to the hotter plugs.

beepbeep · 01-04-2008, 03:42 AM

WBO2 measures unburned O2. If cylinder is not firing (due to fouled plug), the oxygen drown to cylinder will be passed further down the drain and sensor will beleive that engine runs lean. (Trivia: This is usually thhe problem when doing a automap-run when raw fuel maps are not "between the margins". Esentially, if your fuel map is so rich from the beggining that engine starts misfiring, WBO2 believes that it runs lean and automap injects even more fuel to correct that. It soaks the engine in fuel even further which can in some cases damage the engine due to hydro-lock.)

I recomend fitting hotter plugs and re-doing a WBO2 logging run to be sure that AFR's are in check.