Question about Cars & Trucks
The idle is surging up to 1600 RPM regardless in neutral or transmission engaged. Need advise PLEASE!
WOW no car stated, model or year, what a challenge.....!!!!!
or engine option, (gee )?
In pure generic answer mode. I say.....
Do you want us to take a wild guess , or show the tests.
there are only 2 paths one with tools and one with out.
without is hopeless.
for sure there are free tests... but we cant do that yet./
surging is a complex topic. !
it is caused by 100 of things (mostly air leaks)
but can be reduced to 2, (ASE rules)
1: ISC system has lost control of idle !! (lots of way, air leaks #1)
2; lean AFR.
AFR is air fuel ratio, if for any reason, any Otto cycle engine goes
lean, it will in fact surge like a mad dog.
even your lawn mower. (try it 1 time) some calif models do it out of the box, (long story) avoid PR of CAL.
1: let me explain, lean?, say the 02 (oxy)goes nuts and ECU goes lean.
the ISC system tries (it's a servo system. "magic")
ISC is the idle speed control system ( i major system )
the ECU tells ISC opens the valve, to raise idle. (too low RPM) and it fails.
so the ISC hunts the failure. over and over, and makes a lean surge even worst. ( really, it only has 2 choices, try again or give up)
if the air leak causes, lean (ADS) or races(SDS) the ISC
sees both of these errors, (RPM sensor)
it tries to correct it and if i can not , it may surge.
some just give up, others rail and freeze and some surge
all this depends on ECU software how it works in a failed stated.
so here is my useless list of common failures, its not a guess list.
1: air leaks to the plenum (that is the air space from the intake vavles all the way to the MAF if in fact you have a MAF.
ADS = Air density systems.
SDS= speed density system. no car started, i must assume you have 2 engines, (LOL)
that is my answer. give better inputs and answer go to max. better.
Posted on Oct 20, 2013
Testimonial: "You are very helpful, but I don't know some jargon you use.(ASE rules, ECU, OTTO cycle engine? Thank You V M. IMRE ZAGORA"
What is the year make and model of your vehicle?
Posted on Oct 20, 2013
Testimonial: "1991 Mercedes 190 E 4Cyl"
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Posted on Jan 02, 2017
SOURCE: S80 engine surge at idle
You could have a bad or contaminated Mass Air Flow (MAF) sensor. You can get a used one online for less then 100. You can also purchase a can of MAF sensor cleaner at a local auto supplies store and clean it. It located right at the air filter housing.
Posted on Aug 11, 2009
Check for air leaks in the vacuum pipes in and around the inlet manifold, they have a habit if going brittle and splitting.
Another possibility is the temp sender , if the ecu thinks the engine is too cold it will compensate causing the engine to " hunt". This can be something as simple as a worn radiator cap seal letting air into the cooling system and tricking the sensor.
Hope this helps, Marshall
Posted on Apr 29, 2010
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