HELP 6MT - Hesitation when cold

[tollboothwilley]

My friends 2003 350Z Touring 6MT is having some hesitation issues while driving. The only mod he has is a AFE short ram intake w/ heat shield.

During the first 20 mins of driving the car hesistates under HARD ACCELERATION.

When you hit about 3000 RPMs the engine feels like its getting no gas/spark because it feels like you are getting half the power you should be.

This problem happens sporadically. It has no gear preference. Sometimes 1st, 2nd, and 3rd gears pull hard, and then you go into 4th and BAM, instant lag like you hit a wall. Sometimes it happens in 1st, sometimes in 2nd....

If the ambient temperature is above 40-45* then the problems are nonexistant.

We just changed out the spark plugs, so that is not the problem. There have been no CEL codes. No issues with idle. Swapped TB, that's working just fine.

TIA.

[ldstang50]

is the car warmed up when he's doing this?

[MySXisSlowerThanUrs]

is the car warmed up when he's doing this?

The question should be.. Was the car warmed up before he started getting on it hardcore?

maybe its so fast that he's spinning the tires and the TCS is kicking on haha i dont know.

It could be alot of things

[tollboothwilley]

Ya, the engine is fully warm. Its not the SLIP light coming on.

Sometimes this lasts for 20 minutes, and after that it drives as if there never was a problem.

I know that its not the clutch/flywheel. They engage strong, no slipping.

[aris_unlimited]

Check all the air intake hoses, if one of those isn't on all the way it could cause all these problems.

[ldstang50]

Hmm interesting indeed......waits for C-Kwik to jump inYou say it only happens when the temp is below 40 or degrees and the first 20min of driving, an driving HARD.I wonder if it has something to do with the engine still be cold. It sounds like the car is running too lean and the ECU is pulling timing. Cold air will make it run lean because its much denser than warmer air.How long has he had the air filter on? Has he allowed the ECU to 'learn' with the new filter? The combination of more air coming in and cold could be throwing the MAF off and making the ECU pull timing.

[tollboothwilley]

I have checked and double checked multiple things for him. I tried to get the clutch to slip. Nope, they work great.

I rechecked all connections from filter to throttle body. No problems.

Additionally...he hasn't been able to use cruise control. I'm not sure if the problems are related or not.

We're gonna take a look at the MAF tonight. See if there are visual problems. Possible try CRC MAF cleaner.

[tollboothwilley]

Intake has been on for over a year now.

[mec011]

I had issues when it got hot this summer with hesitation and idle issues, but the car had ran fine (great even!) in reasonable weather.

I know it was the heat that did it for me, but a couple things helped greatly, first doing the full ecu reset, TB position relearn, and vacume Idle relearn.

AND! changing the spark plugs. Mine were seriously toast (just beyond a 100k+ miles) so they could have been done much sooner than recommended. Maybe that would help? It's easy enough to do that yourself in less than a day.

Car runs even better than it seemed to when I bought it.

But try the resets, it's free!

[tollboothwilley]

All of those ideas were tried before I even started a post.

GOOD NEWS THOUGH!

You'll never guess what the problem was.........AFTERMARKET LED Tail Lights. Cause an irregular voltage to the ECU

It treats it as if the brakes are depressed, which also affects the cruise control function and acceleration

[ldstang50]

wow! now thats freakin weirdnice job diagnosing and fixing

[bmike818]

thanks for the update!

....LOL who would have guessed...Tail Lights

[rmezz13]

....LOL who would have guessed...Tail Lights

probably richie and we would have flamed him for it....

[bmccann101]

Hey I just sent you an email about this... please get back to me... i am experienceing the same crap... just want some more idea as to how you found all this out. .thanks!.

[tollboothwilley]

email replied..