The engine will not idle properly, it just hunts like crazy on idle

NO ENGINE TOLD AND IS AN ENGINE + EFI PROBLEM.
4.6 or 5.4L v8
sure 50 causes and up to 20 tests to find it.
GUe$$ing is super expensive and labor max.

if engine is good ,22 years latter, and passes compression tests.?
why not t scan he PCM FIRST and see DTC ERROR CODES.
LIKE (AND MORE)
P03XX CODES,. FOR ANY KINDS OF MISFIRE????????
new spark plugs and new COP boots < they do not lat 22 years. sorrry
boots are $2 each at rockauto.com

IF SPARK IS GOOD THEN CHECK FUEL PRESSURE

THE FPR IS PROBABLY BAD, OR INJECTORS CLOGGED OR LEAKLING
THE PCM IS CAUSING THE SURGE, ON A HOT ENGNE
THE PCM JOB OF MANY IS TO CONTROL IDLE, AND SINCE IT CAN NOT GAIN CONTROL OF IDLE IT HUNTS IT OVER AND OVER TO ATTAIN IT.
see seems crazy but that is how \it works. fix the engine power loss first

Yes EGR must not stick open ever at idle or it will hunt or stall.



THIS IS NORM\AL, FOR ENGINES GROSSLY MISFIRING OR OVER OR UNDER INJECTED GROSSLY'

BAD MPG IS mISFIRING AND OR DUE TO GROSS OVER FUEL PRESSURE
THE SERVICE MANUAL COVERS ALL FUEL PRESSURE TESTS.

Why skip the OBD2 scans/ ???????
what it it told you what is wrong, and you miss all that.
like P0303 error and injector 3 is clogged or leaking.
and the like.

we can rent, barrow,. buy or get the car scanned.
No reason to skip it.
even if no codes show up that MEANS SOMETHING.
top something is fuel pressure wrong, or injectors messed up.

HOT ENGINE? (ill guess hot)
idle surges.(hunts) (very simple reasons or very hard to find.
the car has 2 engines. G16A and G16B
they work totally opposite, (8valve and 16v)
the vin number tells you the engine type ,digit 8 is engine code
6= G16B 16v
U= G16A 8v
i have factory book. its in chapter 0 these facts.
the cause of idle surge and hunt are:
1: ISC failures. the ISC can stick partially open and then hunts.
clean it and test it . see videos of how.
2: engine running so bad the ISC can nOT regulate idle speeds.

#2 is caused by up to 50 reasons.
8v , air leaks, cause racing idle and iSC goes nuts.
16v , all air leaks cause lean and if too lean the ISC goes nuts.

by nuts , i mean it hunts or gives up.

the list is endless, but the tests are basic,
i cant help you because no engine stated.

http://www.fixkick.com/IDLE-AIR/idle-index-home.html


ISC = IDLES SPEED CONTROLER (a system not just a PART)

no engine type stated, there are 6 engines used.
but bad idle is caused by 2 things.

• misfire.
• or lean AFR, lean fuel mix.. causes HUNTING

the ECU can also cause the hunt if it can not hold hot idle to spec.
most cars is 800rpm.

hunting or surging ilde. name the 2 RPMS, low and high , is it hot or cold engine this issue.? 400rpm or 1000 or 2000 all are diff.causes.
no year, stated. so cant help.
but ill answer in the generic,
1: the ECU (got a carb,? )
the ecu controls idle speed at all times.
if not , there is a problem (you)
A: air leaks in the induction will make motor race at some point the ECU/ISC loses control. and hunts. trying hard to correct it.
b: egr stuck open idle too low, iSC cant correct it,, bad EGR.
c: engine EFI running way too leak starving for fuel so it hunts for 2 reasons < ISC hunting, and lean does that.
lean is gross power loss and opening throttle bogs the engine.
so is double bad. ISC makes it worse,

all this breaks down to 2 reasons.
1: ISC bad. in some way (gummed up. or restricted inside)
2: bad fueling or air leaks. vacuum leaks.

try answers , the hot cold question and the 2 speeds, of the hunt.
lowest rpm and highest of the hunted range of RPM.

I A C motor small part on throttle body ,controls idle mixture when they fail at idle the engine "hunts" for proper air/fuel mixture . when defective it causes o2 sensors and TPS to compete to set an idle thus the up n down effect.. auto wreckers if your broke new from your local parts store....dealer to much 1 plug in two bolts for most applications

Hi.it sound a lot like a ignition coil coils tend to do that if its got a crack it Swell when the temperature rises

vacumn leak

If the RPM's fluxuates at an idle at all times you have a bad spark plug or a bad spark plug wire

Have the fuel pressure checked. Could be an erratic pump or pressure regulator.

Poppascott

does throttle sensor check out correctly???