Why's that guy's car revving up and down while idling?

[alm4rr]

the guy has a pos honda with a huge, noisy exhaust pipe. my apartment building is a half block from a traffic light. even when the car is a half block away at the light, the car is incredibly loud.

the car's engine probably goes from 1000rpm to 4000 rpm and back down to 1000rpm every 2-3 seconds. it is so perfectly consistent that he can't be doing it by foot. this lasts for the entire time of the light (the light is longer than average) and the guy is always driving around. [the locality has an anti-cruising ordinance (b/c of car shows and gearheads that frequent the place).]

any leads/info on any chip or method by which he has his engine intermittently racing while idling at the light?

Any info is appreciated!
Cheers

Moved from Off Topic
moderator allisolm

 

[BlahBlahYouToo]

vacuum leak.

 

[Goosemaster]

never underestimate the lengths to which posers will go to in an attempt to become the best faux rally drivers they can be.

 

[Goosemaster]

Originally posted by: BlahBlahYouToo
vacuum leak.

+5hp

 

[EarthwormJim]

You sure about the rpm ranges?

He could possibly have a bad idle control valve (or whatever a honda uses), a vacuum leak, a really lightweight flywheel or really aggressive cams.

 

[AgaBoogaBoo]

Originally posted by: BlahBlahYouToo
vacuum leak.

Yeah, my first guess too, that stuff sucks.

 

[ViviTheMage]

misfires, or a leak...

 

[alm4rr]

Originally posted by: EarthwormJim
You sure about the rpm ranges?

He could possibly have a bad idle control valve (or whatever a honda uses), a vacuum leak, a really lightweight flywheel or really aggressive cams.

thx for the info.

would all this result in perfectly symmetrical sounds? they are always completely the same, during the same stop, each day, and each week. exact same timing and symmetry, exact same rpm ranges.

i was just guessing at the rpm ranges. but the bottom range goes down to idle, and the upper range goes to about 3/4 of the rpm where'd you'd shift outta first. (if that helps make it bit more objective )

thx!

 

[EarthwormJim]

Originally posted by: alm4rr

Originally posted by: EarthwormJim
You sure about the rpm ranges?

He could possibly have a bad idle control valve (or whatever a honda uses), a vacuum leak, a really lightweight flywheel or really aggressive cams.

thx for the info.

would all this result in perfectly symmetrical sounds? they are always completely the same, during the same stop, each day, and each week. exact same timing and symmetry, exact same rpm ranges.

i was just guessing at the rpm ranges. but the bottom range goes down to idle, and the upper range goes to about 3/4 of the rpm where'd you'd shift outta first. (if that helps make it bit more objective )

thx!

Vacuum leak then.

 

[alm4rr]

great, thx!

 

[Lithium381]

Originally posted by: alm4rr

Originally posted by: EarthwormJim
You sure about the rpm ranges?

He could possibly have a bad idle control valve (or whatever a honda uses), a vacuum leak, a really lightweight flywheel or really aggressive cams.

thx for the info.

would all this result in perfectly symmetrical sounds? they are always completely the same, during the same stop, each day, and each week. exact same timing and symmetry, exact same rpm ranges.

i was just guessing at the rpm ranges. but the bottom range goes down to idle, and the upper range goes to about 3/4 of the rpm where'd you'd shift outta first. (if that helps make it bit more objective )

thx!

Nope, that's where YOU would shift out of first.....you know this guy is HARDCORE, so he must take it past redline with frequency....heck, he probably pegs the tach EVERY SHIFT!!!!!

 

[SparkyJJO]

Ricers don't make sense. He probably thinks it is "cool" :roll:

 

[iamwiz82]

vacuum leaks are the ones that cause significant idle loping in my experience. Bad IACs usually bounce, but not so obviously.

 

[Black88GTA]

This is a very common thing on late 80s - early 90s Hondas. My 89 Prelude did this for a while, until I finally found the vacuum leak and fixed it. Mine was actually caused by a leaking intake manifold - although, more often than not, this is caused by the fast idle valve becoming loose and allowing too much air past. If this is the problem, it's a 5 minute free fix - remove cover, tighten plastic valve, replace.