Hi all. Long read, but trying to share all details and hoping someone can help. 2001 Maxima that we’ve built for 24 Hours of Lemons. In our current build we’re one of the better platforms of cars we see. But this last race we had major power issues. Cold start up and through the night time racing (50’s ambient temp) the car ran good. As soon as ambient heated up we had zero power. Anything more than 1/4 throttle bogged down and the car wanted to die. Not the kind of power that makes you unhappy, the kind that you slow down at even the slightest incline. Not good for racing. Sometimes 2nd gear runs fine but 3rd is bad. Other time after heat up 2nd also shows the issues.

Rough start up in general.

Checked vacuum lines and all are good. All routes correctly and most are new. Spraying engine starter doesn’t effect any rpms.

Has a new MAF sensor (hitachi) but we also tried the old one.

No codes are showing in the engine.

Injectors were recently removed and sent out for cleaning and mapping.

larger intake.

New coil packs - hitachi.

Stock internals - we’ve never cracked the case.

spark plugs show white so running lean. Relatively new.

Stock fuel pump with bottom of return ‘holding tank’ cut out for Holley mat added to the bottom.

Custom headers and side exhaust mostly heat wrapped.

car runs around 210.

aero at front of car and underneath so limits air flow - we have seen hot temps on exhaust hump and metal behind driver seat above gas tank. Best bet is hot fuel so vaporizing, but that seems excessive.

Night time cooler temps and it ran ok. Not great, but we had power.


Not sure if the heat is symptom caused by running lean making engine run hot, or cause.

And great items that were missing?

 

Do you have an AFR gauge? I would start there and chase your lean condition, even if not the cause of all of your troubles, it sounds like your best starting point.

Did you scan for codes, or are you trusting the SES light? A faulty knock sensor will pull timing, but not turn on the light.

 

We do not have an AFR. I agree with chasing the lean condition. Not sure of the heat is causing the lean (vaporizing) or if the lean is causing the heat.

We scanned for codes with a standard reader and nothing shows. Kept the scanner plugged in and verified it recognized MAF and O2 sensors by unplugging and getting error.

Faulty knock sensor has come up, but would it pull timing enough to literally have zero power? Anything more than 1/8 throttle and it bogs and wants to die. Idle is ok. 1/8 throttle is ok, but that’s not enough to accelerate on 2nd much less 3rd gear.

 

Yes a Faulty Knock Can, I have verified this my self. It can check good, but be cracked. Pull it and check it. Which Engine BTW..?

I'de, suggest using the live data function with the scan tool you are using and Drive the car. Get it Hott and check your values. Check to see what the fuel pressure drops to under load with a gauge. This is Something You really need to diag right as it is happening. Typical Signs of a Bad Maf though tend to Over Fuel.

 

2001 with the VQ30dek. We plan to change the knock sensor as that one should be easy enough. We’ll add fuel pressure monitor to the list. Tough to get repeat conditions as the car isn’t registered so we don’t want to drive it on the street. And...it kind attracts attention the way it looks.

Outside the headers and intake we made though, engine is stock. When it’s running right, it runs great. Only clocks the scales at about 2,450lbs so not as much weight to move around.

 

Any relation?

 

Funny you should ask...That was actually a very key influencer for our theme.

 

Love it!