Weird Popping
Weird Popping Car: 1999 Transam 137k miles
Relevant mods: Cam/Stock suspension
Problem: Popping sound coming from what sounds like under the dash almost. Sounds EXACTLY like those collapsible
straws that make a popping noise when you extend them. Started yesterday in stop and go traffic.
Conditions for it to occur: At idle when rpms drop below 500(sometimes[AC on with decent cam, idle drops when pushing
in clutch and bounces around for a while until it gets up to temp with AC on.]) Also happens when I brake, but only
around >10mph(RPMS are probably dropping.) I have also heard a really loud bang that was very different yesterday
when braking after hurry through a light and turn at an intersection. Again Note the car doesn't need to be moving, I
can do it at a stand still when the rpms drop to about 300 and the car surges/vibrates a lot(obviously) then recover and
repeat until it warms up and idles about 1000. I haven't tried driving without the AC as I am in dress clothes for work
and trying to keep em nice(started my internship this week). The car doesn't have these idle problems with AC off.
I don't think it is the engine, I don't know why... but it sounds like it is coming from behind the gauges/under the dash.
Also when trying to "feel" it I could barely feel a pulse through the clutch pedal... I think. This noise isn't VERY loud,
conversation loud.
At first I thought it was the brakes b/c I started noticing it when braking, then I thought turns(idle drops with power
steering/clutch in) but it doing it at a stop eliminated both of these.
Any ideas?
The straw:
This would make the noise too:
Relevant mods: Cam/Stock suspension
Problem: Popping sound coming from what sounds like under the dash almost. Sounds EXACTLY like those collapsible
straws that make a popping noise when you extend them. Started yesterday in stop and go traffic.
Conditions for it to occur: At idle when rpms drop below 500(sometimes[AC on with decent cam, idle drops when pushing
in clutch and bounces around for a while until it gets up to temp with AC on.]) Also happens when I brake, but only
around >10mph(RPMS are probably dropping.) I have also heard a really loud bang that was very different yesterday
when braking after hurry through a light and turn at an intersection. Again Note the car doesn't need to be moving, I
can do it at a stand still when the rpms drop to about 300 and the car surges/vibrates a lot(obviously) then recover and
repeat until it warms up and idles about 1000. I haven't tried driving without the AC as I am in dress clothes for work
and trying to keep em nice(started my internship this week). The car doesn't have these idle problems with AC off.
I don't think it is the engine, I don't know why... but it sounds like it is coming from behind the gauges/under the dash.
Also when trying to "feel" it I could barely feel a pulse through the clutch pedal... I think. This noise isn't VERY loud,
conversation loud.
At first I thought it was the brakes b/c I started noticing it when braking, then I thought turns(idle drops with power
steering/clutch in) but it doing it at a stop eliminated both of these.
Any ideas?
The straw:
This would make the noise too:
Yep - Check to make sure you didn't brake your clutch pedal return spring. Its a 2 coil spring that hooks in to the pedal mechasim at three points. They last around 50K miles and when they go, you get a big bang, the spring splits in two, and some of the parts usually hang in the mechanism. The leftovers sometimes rattle. (When you brake at low speed, you are probably on the clutch pedal, right?)
Well it would make the noise with the car in neutral in a parking lot as well, but I will check the spring. I also think that wouldn't make the straw noise, but we will see.
