headlight on, idle revs goes down? updated 16/11/2009!

[altong0840]

hi~i got a D15B4 twin carb EG, recently 2 problems on the car, seach nothing on the forum, so open this topic


problem1 : Fast idle not work, the idle up to 1400rpm after warm up in P gear
but drop to 900rpm in D gear, is it normal>???

problem2: idle 900rpm without headlight on is smooth~ but feel stall and drop to 700rpm after turn the headlight on/the fans/any electric stuffs...


it is twin carby engine but running a ecu to control the fuel/air mixture, but no iacv on it~ so is there anyway i can anything to fix the problem??cheez




[SIZE="6"]I just check the voltage by the mech shop and it shows that


P gear(0 rpm), no elec load, battery 12.5V
P gear(1400rpm), only start the car, no other elec load, battery 14.0V
P gear(1200-1300rpm) , start the car and and headlight, no other elec load, battery 13.8V


so the professional told it is not about the alternator, is about the carby setuP~


thanks everyone!

UPDATE :16/11/2009


thanks for everyone in here first, recently i had been replace my ground wires, the one relate to the headlight, low the idle to 1200-1250rpm when P gear

before replace the ground wire: 1300 RPM (P gear) drop about 300rpm when headlight on

after replace the ground wire: 1200rpm (P gear) drop about 100-200 rpm when headlight on, 950 RPM in D gear when healight off, 700-800 RPM in D gear when headlight on

so it seems like getting fix~ but the auto choke still need to be check~

will update ASAP i found the problem

[V73C]

Maybe battery or alternator ?

[riruiz_88]

when u start the engine when its cold, the revs under normal conditions should be roughly 1300RPM. then as the engine starts to get warmer, the revs drop down to 900RPM. this is normal.

your problem is the alternator. as you turn more electronics on, it puts too much load on the alternator. you need to replace or rebuild it. do this simple check.
-use a volt meter and measure the volage at the battery when the car is off. a good battery should indicate above 12V.
-start the engine and let the engine warm up to operating temperature. then rev the engine to 2000RPM and turn on the headlights (need 2 people).
-now check the voltage at the battery, should be roughly 13.9V to 15.1V.

let us know how you go with that.

[OMG.JAI xD]

Go fuel injected.

[altong0840]

but my rev normally 700-800when it is dead cold in D gear 1300-1400 rpm in P gear

the rev will back up to 900rom in D gear 1300-1400 rpm in P gearwhen it is warm...

i will check it asap and let u know~cheez!

[altong0840]

i thought there are something on the engine will detect the elec load and provide enough power~hahaha

so u means it is only 3 part relate to the elec provide

1. battery (start the car)
2. starter
3 alternator

i checked the battery it seems ok i bpught it band new 3 months ago
but don't have the meter things to check the alternator.

so do u think the problem will fix/better if i replace the alternator ?

thank you so much man!

[altong0840]

Go fuel injected.

i love to get a D15B7 vtec
but 1.5 EFI is not in australia.....

[ep3_ctr]

yeh sounds like the alternator, to double check inspect your battery's voltage and terminal connections while the engine is idling. use a multimetre and look for a reading between 13.8 and 15 volts. If the reading dips to 12.8 to 13 volts your alternator may be gone

[riruiz_88]

haha dude thats what i just said

[altong0840]

but my rev normally 700-800when it is dead cold in D gear 1300-1400 rpm in P gear

the rev will back up to 900rom in D gear 1300-1400 rpm in P gearwhen it is warm...

i will check it asap and let u know~cheez!

[OMG.JAI xD]

i love to get a D15B7 vtec
but 1.5 EFI is not in australia.....

Get a d15b7 with a d16y vtec head.
Or better. get a d16y1/8.


Most carby systems are mechanical. All about mixture adjustments.
As long as your engine doesnt stall. I see no problem.

[altong0840]

Get a d15b7 with a d16y vtec head.
Or better. get a d16y1/8.


Most carby systems are mechanical. All about mixture adjustments.
As long as your engine doesnt stall. I see no problem.

isn't that the D15B4 use the ECU to control the mixture?