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Engine surging idle

The idle is surging up to 1600 RPM regardless in neutral or transmission engaged. Need advise PLEASE!

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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)

air leaks.
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"

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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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SOURCE: rough idle / engine surges until power is applied

Sounds like a possible vaccume hose leak?

Posted on Feb 07, 2009

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SOURCE: idle surging

Consider replacing the rotary idle air control valve, and clean your throttle body.

Posted on Feb 28, 2009

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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

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SOURCE: Engine surging at low idle speed

IAC motor

Posted on Nov 22, 2009

Delage guy
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SOURCE: 1998 camry 5sfe engine, surging at idle

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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What should my timing be set at for a 1989 nissan truck with the z24 motor

Ignition Timing 10 Degrees
With manual transmission

Note :
Before top dead center
*Warm idle speed 800 RPM
*Transmission in neutral (Parking brake engaged)
special procedures are required when making
refer to service manual Ignition Timing 10 Degrees
With automatic transmission

Note :
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refer to service manual.

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Car surging

Is the car equipped with the Automatic Transmission?
If so, read on.
Otherwise skip to the end and answer some questions.

I have observed a condition where my car surges slightly when the torque-converter clutch (TCC) cycles between lock and unlock when driving on an uphill grade.
First some basics and history that will explain why the TCC is used.

Engine, Torque Converter, TCC, and Transmission relationship--
The TCC allows for a solid connection between the engine and transmission which allows the input to the transmission to rotate at the same speed as the engine.
Without a TCC, there is slippage between the engine and automatic transmission. The slippage is greatest at low engine RPM. That is what allows the engine to run with the automatic transmission in gear, like when you first shift into gear or stop at a stop sign. When the throttle pedal is depressed, the engine RPM begins to increase and the torque converter begins to slip less and less the more the engine RPM increases. The car moves. But even at cruising speeds the torque converter slips slightly. Engine RPM is greater than transmission input RPM, which is realized as slight decrease in fuel efficiency.
When acceleration is complete and a constant speed is being maintained, the engine power output is reduced to the point where the TCC can engage and eliminate any slippage between the engine and transmission. If the car has a tachometer the engagement of the TCC can be verified when a slight reduction in engine RPM observed without a corresponding change in vehicle speed.
One method used to test the operation of the TCC is as follows:
Find a flat section of road where it is safe to perform the test.
Reach a steady speed and keep the gas pedal depressed with one foot. While observing the tachometer (or listening for an increase in engine RPM), with the other foot depress the brake pedal enough to activate the break light switch but not enough to engage the brakes. When the brake light switch activates, the TCC receives a signal to disengage. With the gas pedal being held steady, release the brake pedal and the engine RPM should decrease when the TCC engages.
Old cars with Automatic Transmissions did not use a TCC. I believe the TCC was put in use in an attempt to increase fuel economy.

The condition that causes that issue on my car is this:
- A slight uphill grade increases the load on the engine.
The car tends to gradually slow and it is necessary to depress the gas pedal to maintain speed.
- Depressing the throttle pedal (manually, or automatically with cruise control engaged) signals the torque converter clutch to unlock when the load increases slightly. (A more drastic load increase would signal the Transmission to downshift to a lower gear.) The corresponding increase in engine RPM and output is enough to compensate for the reduction in speed. When the vehicle speed, engine RPM, and throttle position stabilize to the point that the TCC will engage and the engine RPM will reduce in correspondence with TCC engagement. Now, if the road conditions have not changed, power output is not enough to maintain vehicle speed. With the increased load caused by full engagement between engine and transmission, and the cycle (surging) repeats itself until the road conditions change.

Does that help?
If not:

Please define the symptoms.
What are the road conditions when the surge occurs? (A slight uphill grade?)
What is the frequency of the surge?
Does the engine power output have a noticeable surge?
Is there a speed change related to the surge?
Does the tachometer move up and down with little or no change in vehicle speed?
Are all instrument indication in the normal range?
What else has changed?

Good luck!

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well i dont have much to go by but the transmission may have a toque convertor lock up solenoid,that may have to change so i would say try going to a transmission man to check that out ok

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