unstable idle ('97 civic d16y7 SOHC engine)

[g4i8y0t]

Hi guys,

Lately, my engine is having unstable idle problem. The rpm goes up and down between 1000 and 1500.
I don't have time to send it to my mech yet. As far as I know, it could be contributed by dirty throttle body or a vacuum pipe got loose. I've already check the pipes, no prob so far. If I clean the TB, would the problem be solved? Is it possible that unstable idle be caused by any other things? BTW, this problem only showed up after i remove the battery recently to clean the battery holder due to rust.

If you have encountered this problem before (and managed to solve it), please feel free to share.

 

[testpower]

if u never clean up ur throttle body, i suggested u to do that. then check ur iacv ..

 

[shiroitenshi]

good answer. :thumbs:

Additionally, check tps voltage.

 

[g4i8y0t]

thanks a lot guys! one more question, how to check the TPS voltage using multimeter? What voltage range is considered normal?

 

[camp]

if u never clean up ur throttle body, i suggested u to do that. then check ur iacv ..

Bro, what u saying that clean up the trottle body by using throttle body cleaner ie. cleaner in spray can or by dismantle the throttle body and clean it?

 

[shiroitenshi]

tps use multimeter. 800ohm. 2nd choice, Use jumper harness and get real voltage readings better, but sometimes gotta use what you have.

 

[g4i8y0t]

thanks shiro! i've got to study the repair manual first :hmmmm:. dunno where to put the +ve multimeter probe..

 

[shiroitenshi]

Unplug tps got three pins. One is ground, and it's probably an obvious colour. The other is the 5v power, last is output to ecu. Set multimeter to 10v. Turn on ignition, look for power and ground on connector. The remaining is the output/signal wire. Remember the location of pins and match to tps male connector. Turn off ignition, set to ohm, check resistance from signal and ground on tps connector. Make a tps harness if you're a mechanic, it's faster and easier that way. No need to remember wire colour codes.

 

[g4i8y0t]

thanks again shiro. you're really2 helpful.

 

[g4i8y0t]

Update:

Went to my mech yesterday, told him about the problem. He checked the grounding first, no problem detected. Then he confirmed the problem is most problably caused by bad throttle body (TB) and maybe some of the sensors attached to it. He gave me 2 options:
1. Clean the TB. This may solve the problem but there's no guarantee.
2. Replace the TB with a good conditioned half-cut unit (with some 120,000km mileage done). The TB will be replaced at no cost if there's a problem later.

I chose the 2nd option, so far so good except for some very minor leaky gasket at the bottom of the TB where the coolant hoses are attached. He opened up the TB again, put some new gasket, problem solved.

Bill:
1. Half-cut throttle body = 250
2. Workmanship = 10
TOTAL = 260