View Full Version : Poor idle with Lights, Fan etc

05-10-2008, 01:53 PM
Simply, the more power I draw, the more the idle drops. I've had to set it at 1500rpm warm just to keep it idling with my fan and lights on. There's no distinct item that's drawing these down. I can simply start the car, turn the heater on, and have a terrible idle. Here's what I've tried for fixes so far. With everything on, the battery reads 13.89 volts.

- Completely rebuilt alternator
- 2 added engine grounds
- Cleaned current grounds completely to bare metal
- Cleaned MAF
- Cleaned Cold Air Idle Valve (IACV or whatever it's called)

One night I unplugged the igniter chip, cold air idle valve thing and engine temp sensor. When I put it back together and drove it, it appeared to be running in top shape with great idle (I think. Maybe it sucked less and I just didn't notice). It could be a bad IACV, but god knows how to check that thing. When I unplugged it, the idle dropped to 500rpm.

Ideas? So far no one has been able to help out with this. I've tried other places too.

05-15-2008, 08:59 PM
How about battery? If you have an intercooler, chances are you are running a small battery, which is a POS i don't care what brand.... Those mini miata batteries last like 1-2 years max...

05-15-2008, 09:17 PM
It had a tiny battery, and the alternator drained it (at least that's what I think happened.) So I had the alternator rebuilt and put a big battery in the trunk.

The only ECU code was knock sensor. It looked fine to me, so I don't know why it was saying that one. Someone said when they had bad motor mounts they had the same problem and the same code. When they replaced the mounts, the problem was solved. These are just windoweld-filled mounts. I may order nismo mounts next friday.

05-16-2008, 11:35 AM
THat is stupid, motor mounts? Yah tiny batteries are junk.... I am going to move mine to the trunk... Idle sucks and inconsistent when the battery sucks.

05-19-2008, 03:25 PM
Your ECU knows better than your eye. If it says the knock sensor is bad replace it, or if you are so sure its fine, check your harness for shorts. Make sure all your factory grounds are grounded, make sure you have a 800cc battery, and go get the alternator that you had "rebuilt" tested.

05-19-2008, 03:36 PM
How do you have your Electric fans Setup? What are you drawing power from?

I personally got with my local battery shop and he suggested a selenoid to run all my accessories. It will only draw like .4 amps. Basically all you need is a wire stright from the battery to one side and a remote wire/ (trigger) and the accessories hooked the the other side and your putting out alot of amps and not drawing too many.

I have, 2 electric fans, Line Lock, SAFC, Gizzmo Launch Control and shift light, Wideband 02, Boost contoller, Oil temp gauge, Water temp Gauge, Oil pressure gauge, Boost gauge. All hooked up on my selenoid. It also makes wiring nice not having to hack into other power wires and will keep your fuse box and relays from frying.

I also suggest hooking your fans into a relay.