So about 3 hours into our second run after the brake leak (more on that later) we noticed a hesitation or a feeling of a misfire around the 6K mark (7AFE 5spd) as the driving session turned into a 4 and 5 hour run this feeling feel to the 5K mark and into the 4K mark. At the end of the race (call it 15 straight hours of driving) the car was limping around the track in 5th gear chewing up laps - nothing above 3K really without getting the hesitation.... we think its heat related and we think in between driver changes, it gets better briefly - so we think its something that does not retain heat like cast iron.... so.... what do you think it is?

7AFE isn't a race engine, you would do better with a S series engine like the 3SGE

It looks like spark plug overheating leading to detonation
try colder thermostat, hood air duct, insulate headers, colder grade spark plugs

uh just over 6000 is your fuel cut. like 6300-6500ish rpm?

I don't know about fuel cut, but redline is 5800.

it almost sounds like a worn out oxygen sensor or fuel pump. What is your stoichiometric reading during the hesitation. From what i can tell, it sounds like your engine is leaning out during full throttle when the engine begins to heat soak.






The hesitation would not be caused by spark plug detonation because it only happens after heat soak. Once the engine is warmed up the spark plugs will remain the same temperature.




red line is different on different year 7afe. It was higher in the older generation before obd2.

Plz see www.24hoursoflemons.com

some more information:

We thought it was plugs and we swapped out new-ish (under 500 miles at this point) champions for NKG's - plugs looked good after checking them.... some people felt they were running "hot" but they did not have the appearance of being run "Lean" i.e. white discoloration?

The oil did not look burnt - and we know we are running the wrong oil (5w-30) we should be running straight 30

The coolant is plain old H20

We have a craptastic CAI made up of a flexible exhaust pipe with a cone on the end right behind the headlighs

The hesitation would not be caused by spark plug detonation because it only happens after heat soak. Once the engine is warmed up the spark plugs will remain the same temperature.








Man if if gets better when he changes driver, this is a component overheating problem. Maybe I misunderstood and he meant that "long after drive change, it gets better"
By the way I have a great advice for you, unplug the Water temp sensor on the base of the radiator, the cooling fan should work permanently

Ah - more information is required:

We had both radiators running all the time - we actually didn't have one plugged in thinking we couldn't get the engine UP to temperature / by the end of the first few runs we had them both plugged in and running

also and keep in mind stock gauges: Temp Gauge never went over 1/2

we didn't visually notice any overheating with regards to water in the radiator (only allowed to run H20) and the oil didn't look/smell "burnt"

coil? or plug wires. i know if they heat up, they'll start to cause problems if the're bad

New Cap, Rotor, Plugs, and Wires Pre Race and new Plugs mid Race- but NOT new coil

i know for a fact that a hot coil/ignitor will cause misfires if they're on the way out.
But to be sure thats the issue, check your codes. if thats your problem a code 13 or 14 will probably also be there

do all codes throw a CEL? and will the code stay persistent between key cycles / battery removal like they do now-a-days?

awesome, a 6gc in the 24 lemans. i read about this in motortrend, but i cant bear the thought of a 6gc be destroyed randomly.

if changing your plugs did not help with anything and its not showing signs of being overly lean (blistered porcelain), then it would have to be something electronical. electrics parts usually are the most prone to decrease performance when they are exposed to heat. (ignition module)

Did you try spacing your hood hinges up so allow more air flow under the hood. See if that helps after some hard runs.