Low rpm while coasting/coming to a stop
#1
Low rpm while coasting/coming to a stop
When I'm coming to a stop or slowing down to turn my rpm drops to +/-500. the car hasn't stalled on me yet but it seems like it's going to.
I know I have a small vacuum leak and I'm having an issue with the transmission also but i don't think it's related.
The car is an 86 regal with a mild cam 5.3 and a 4l60e.
Any ideas?
I know I have a small vacuum leak and I'm having an issue with the transmission also but i don't think it's related.
The car is an 86 regal with a mild cam 5.3 and a 4l60e.
Any ideas?
#2
LS1Tech Administrator
iTrader: (3)
Join Date: Nov 2001
Location: Schiller Park, IL Member: #317
Posts: 32,362
Likes: 0
Received 1,794 Likes
on
1,278 Posts
How small is the vacuum leak? I would fix this first, then see how the issue is, before spending time trying to find other possibile causes.
#5
I noticed a couple of other things too, the vacuum hose coming off of the back of the intake going to the brake booster is squeezing in on itself.
Also if I put the car in drive and give it no throttle and let it pull itself forward at idle the rpm drop steadily and the car acts like it's going to stall.
Also if I put the car in drive and give it no throttle and let it pull itself forward at idle the rpm drop steadily and the car acts like it's going to stall.
#7
Launching!
iTrader: (2)
Join Date: Dec 2011
Location: Cincinnati, Ohio
Posts: 241
Likes: 0
Received 0 Likes
on
0 Posts
My car has the same problem. The last time this happened to me it was a gunked up idle air control valve located on the throttle body. Going to try that first. If i remember, they are about $15-$20. It is what controls the amount of air is fed into the idle circuit. When they get cruddy they dont adjust quick enough and can cause that low idle on decel and it straightens out after a second.
Trending Topics
#11
TECH Senior Member
iTrader: (39)
When I'm coming to a stop or slowing down to turn my rpm drops to +/-500. the car hasn't stalled on me yet but it seems like it's going to.
I know I have a small vacuum leak and I'm having an issue with the transmission also but i don't think it's related.
The car is an 86 regal with a mild cam 5.3 and a 4l60e.
Any ideas?
I know I have a small vacuum leak and I'm having an issue with the transmission also but i don't think it's related.
The car is an 86 regal with a mild cam 5.3 and a 4l60e.
Any ideas?
Also, are you running a stock PCM or has it been tuned by HP tuners or something similar? If it has been tuned that might be the problem or at least part of it.
There are several things in the tune that will control how fast/slow the idle drops off when you get off the gas.
The only way I could see it being a torque convertor issue is if its not unlocking and is pulling the engine speed down.
#15
Don't rule out bad O2 sensors! Experienced this first hand while knowing for a fact that it was my O2 sensors being fowled. In addition to the RPM dipping when coming to stop, there was also rough idling when hot operating temp was reached (not sure why not when cold (random misfires P0300--not actually misfires, but rather imbalanced firing as confirmed by a Snap-On scanner)). But my sensors were severed fowled, so a mildly bad sensor might just give the low RPM you're experiencing.
Keep in mind also that, if it is/was your sensors, unplugging other sensors around the intake might make it appear as if it fixed the problem when, in reality, you've only bypassed it.
Keep in mind also that, if it is/was your sensors, unplugging other sensors around the intake might make it appear as if it fixed the problem when, in reality, you've only bypassed it.