Question about 1999 Dodge Dakota

16 Answers

Iac is opening full causing vacuum and power loss

Switcted crank,air temp,iac,map,fuel positoining,sensors and main computer with known good parts no change. the motor just had a valve job to repair compression issue.there are no codes when scanned and symptoms seem to be more when warming upbut it will also loss vacuum and power when shut off and let sit for awhile then started and run while hot.

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  • 10 more comments 
  • theconfers Dec 15, 2008

    My brother is a mechanic and we know there is a vacuum loss because we hooked up a vacuum gauge to the intake hose and also when hooked up to the scanner it shows the vacuum loss. You can watch the iac piston open all the way up. No parts were replaced. It only had a valve job done. The bottom part of the motor didn't have anything done to it, it only had a 3 point valve job and the heads ground and cleaned because it had "sticky" valves. We have tried everything we can think of and are at our wits end.

  • theconfers Dec 15, 2008

    Forgot to answer about the compression test...yes did a compression test after the valve job and the compression is fine now.

  • theconfers Dec 16, 2008

    I haven't gotten any response after adding additional info does any one have any ideas?

  • theconfers Dec 16, 2008

    The last answer we got does not seem to be an answer to our question...might be for someone else? Anyway I would appreciate another idea.

  • theconfers Dec 18, 2008

    This model does not have EGR

  • theconfers Dec 18, 2008

    All of the vacuum loss is through the IAC that is open all the way, the solution I need is what is telling the IAC to stay open all the way?

  • theconfers Dec 18, 2008

    Engine is 5.2L V8. Vacuum reading with engine idling is 5-7 lbs. "Does it rev to high?" The Map sensor and fuel position sensor correct the motor (we have watched this happen on the scanner) and it revs high and then levels off, but then it starts all over again with the IAC opening up and then it starts to run "rough" again.
    With the air cleaner off you can see in the throttle body that the IAC piston moves smoothly key on motor off. There is no restriction in the throttle body (we tore apart and cleaned it)and IAC Piston was cleaned. The timing was checked (the distributor didn't need to be removed for the valve job).Hope this answers all the questions.

  • theconfers Dec 19, 2008

    TPS is steady at idle. vacuum gauge stays steady at 7 after it drops from 18.yes the vacuum issue was there before valve job. no EGRon this motor.we,ve been over every vacuum line and check all connections

  • theconfers Dec 19, 2008

    checked timing its good

  • theconfers Dec 19, 2008

    motor doesnt have egr

  • theconfers Dec 19, 2008

    PCV valve is new also hose to PCV

  • theconfers Dec 22, 2008

    did vacum test on map sensor. fuel pressure good

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Welcome-

i have read over everything that was ;posted and the only thing that i can suggest is that you might have some bad wiring. im not sure where it would be with out having the vehicle in front of me.

thanks

tom

Posted on Dec 22, 2008

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Two things you can check and that is the vacuum canister thats the can that holds the supply of vacuum like an air tank it has to have one i just don't know where at. then you can check the one way valve thats on the power brake booster. Also check the fuel cap and see if its working properly.

Posted on Dec 19, 2008

  • Greg Wilkins
    Greg Wilkins Dec 22, 2008

    The pcm or ecu controls the IAC .
    Also during the course of an IAC motor's life, it is opened and closed
    against the throttle body housing so much that it eventually developes
    spot where it unevenly seats. The Idle motor is basically a cylinder
    with a piston that moves in and out in a straight line. At the end of
    it is a pointed tip. This tip pushes in to a hole to close off air
    flow. If the tip does not seat properly, then the computer will
    continue to open and close the motor trying to find a position that
    will maintain the idle it thinks is necessary for a closed throttle
    plate. This is called "Hunting" when the idle surges up and down trying
    to find the right RPM.
    The IAC does not present codes all the time
    The throttle body and intake often get very dirty. This is caused by a
    number of things which include small dirt particals that the air filter
    cannot filter out, oil residue and crank-case fumes from the PCV
    system, carbon from the EGR system and many other contaminants. As the
    car is driven more and more the intake and throttle body begin to build
    up deposits on their surfaces. In the intake the problem is not
    noticeable accept on highly tuned vehicles and flow bench readings.
    However, the build-up in the throttle body can be very obvious.
    Basically, this build-up will coat the walls of the TB where the plate
    meets the housing and also in the IAC bypass and on the IAC motor and
    tip itself.



    This build-up will eventually start to strangle the engine. It's not
    noticeable at first for many reasons. The build up is only minimal. Air
    flow is restricted at the throttle plate opening and at the IAC path.
    The PCM/ECU sees that there's less air flow and so it commands the IAC
    motor to open a bit more. Everything's fine now for many more miles.
    Then again, the build up is too much and the IAC motor is commanded to
    open further. This continues on and on until the IAC motor can no
    longer open far enough to maintain enough air flow to the engine and it
    basically is strangled until it stalls.


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  • 48 Answers

Check the PCV valve. these things can sometimes cause those symptoms.

Posted on Dec 19, 2008

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  • 327 Answers

Sounds like mass air sensor is out. is it burnung exsess fuel? if so sensor is bad. Also check knock sensor on side of block. for some reason the threads losen and will back out on it's own. This will cause rough and high idle and bad shift points

Posted on Dec 19, 2008

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Sounds like the EGR valve might be blocked by something

Posted on Dec 19, 2008

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Check your timing.

Posted on Dec 19, 2008

  • Jerry Parmanand Dec 22, 2008



    Your engine designed to operate with a prescribed amount of vacuum. If vacuum is allowed to leak it can cause a high idle condition. Check for broken or dilapidated vacuum hoses on and around the engine. Your car's engine is designed to run on a system that can hold vacuum. Vacuum hose are typically connected to the engine intake manifold or throttle body and will supply engine vacuum to various accessories like power brakes and cruise control. Some manufactures like Ford are designed with a larger vacuum transfer hose that connects the intake manifold to the IAC (idle air control) motor. If a broken or dilapidated these vacuum lines can cause the engine to lose vacuum which will allow the engine to idle high. Inspect all engine and accessory vacuum lines to look for missing, torn or dilapidated lines and replace as needed. Also start the engine running and check the engine when it is running to listen for any whistling noise coming from the engine that is not usually present. Follow the noise and inspect vacuum lines in that area. When the engine is running it will pull a broken piece of the hose inward to create a larger vacuum leak. Check the integrity of all vacuum hoses at each end of the hose, typically this is where a vacuum hose fails. If all vacuum hoses check "ok" proceed to the next step.











    - The sensors that monitor your car's engine are delicate. If a sensor is malfunctioning intermitted it might not set a trouble code and this is why. Let's say the senor is failing intermitted about every 2 seconds. The PCM program is not designed to set a trouble code unless the sensor fails at .5 milliseconds or shorter. Now the PCM is collecting data that is false and adjusting accordingly. This false data convinces the ECM to raise the engine idle. Unfortunately it takes a little more detective work to detect these type of sensor problems. Using a multi meter with a zero bode rate (real time) connect the leads to the sensing wire of the sensor and ground. You will need a car repair manual to perform this test. I can tell you this, the oxygen sensor (02), MAF or MAP and coolant sensors are prone to this type of sensor failure. good luck buddy happy holiday



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  • 92 Answers

What about wiring?

Posted on Dec 18, 2008

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The relay that tells the it to stay open will need replaced!

Posted on Dec 18, 2008

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If there is a vacuum leak you should be able to hear it. sounds to me as tho a vacuum hose has not been hooked up properly or you have a vacuum leak from a head or intake gasket.

Robert

Posted on Dec 16, 2008

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Sir,

check this link for more information sir

thanks
good luck

Posted on Dec 16, 2008

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Did you check your gas cap by chance?

As mentioned above it could very well be your gas cap. If not take to the dealer where they can peroform a smoke test to determine where the gasoline fumes are coming from.

Posted on Dec 16, 2008

  • taran_2005
    taran_2005 Dec 16, 2008

    clean the IAC motor(idle air control). it's oon the back of the throttle body. check out www.speedtweaks.com Tricks & Tips, How to clean the IAC.



    Don't forget about that O2 sensor that's located in the exhaust, especially for the vehicle over 50,000 miles. It can cause your truck to run ruff, to rich, and loss of power.

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WHAT is your vacuum reading with engine idling?does it rev to high? if iac counts show it opening all the way and it is not idling too high then we have a restriction. with key on engine off iac valve will open all way.could be a timing issue this would explain low vacuum

Posted on Dec 16, 2008

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  • TripleTauto
    TripleTauto Dec 16, 2008

    what size engine?

  • TripleTauto
    TripleTauto Dec 16, 2008

    NEED MORE INFO

  • TripleTauto
    TripleTauto Dec 18, 2008

    I assume you mean throttle position sensor? If so you should not see data change on tps at idle if it is giving readings that change then this could be your problem.Computer would think throttle is opening when it is not and change the iac position.Does you engine even have a egr valve?some do some dont. vacuum reading is way to low.should be around 15-20inches at idle. did you have this problem before valve job? does the vacuum gauge flop around or is it pretty steady?with key on engine off check data on tps sensor and be sure it gives clean readings while opening throttle.Are you sure all lines are hooked up correctly?

  • TripleTauto
    TripleTauto Dec 19, 2008

    HOW CAN THE GAS CAP CAUSE A POOR VACUUM CONDITION AT ENGINE??????



    try installing a vacuum pump on map sensor and see if it holds vacuum. if it is bad it would think engine is revving up and try and compensate. is fuel pressure good?

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Hi and welcome to FixYa,

Initially, a few ideas to explore and/or discuss with your mech:

  • re-check compression both when hot and cold engine;
  • check vacuum leak at manifold to head by spraying with injector cleaner. If idle changes, then leak at that point is confirmed;
  • do the same at every mechanical junction;
  • you may have to do a reset on the ECM by removing the - terminal of the battery for about 5 minutes. Thereafter, the ECM has to re-learn everything and would need at least 30 mins to 1 hour of driving around (though a bit rough) till everything stabilizes;
  • In all instances, IAC could be electrically and mechanically checked;
  • In most instances, IAC could be adjusted.
Good luck and Thank you for using FixYa. Happy Holidays.

Posted on Dec 14, 2008

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Hi,, Well EGR closed voltage higher than expected, which means either the EGR isn't closing all the way or the sensor isn't positioned right giving the computer a higher reading than expected. If the computer thinks the EGR is stuck open it will remove vacuum from it to try to close it.The timing of the valve opening and closing in relation to piston movement is critical to the performance and efficiency of the engine. Dyno testing has shown that 2 degrees movement ( equivalent to approximately 1/8 of a tooth on the timing gear) can change power output by up to 10 hp. The timing specification supplied with Crow Cams list a checking figure for "lobe lift at Top Dead Centre on the overlap" which is a simple method of ensuring valve timing is correct. This check is particularly important on Holden V8 engines as the original timing gears came in several different timings. NOTE. Make sure you are using an dial indicator calibrated in inches or convert readings to metric before checking. Hint. If the engine runs better with a big increase in ignition advance, there is a good chance the valve timing is retarded.Or maybe a faulty torque converter (failed stator) can cause a severe loss of power. its a transmission problem, regards JAN_yuanjia hope it will guide you for the problem  

Posted on Dec 14, 2008

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Hi, first, how do you know that there is a vacuum loss ?
Did the mechanic do compression test on the engine after the valve job ? Did he change any engine parts like piston/cylinders ?

Posted on Dec 14, 2008

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Here are a few tests I want you to do, but 1st let me explain about the IAC, it opens all the way because it is attempting to keep the engine from stalling, this causes a loss of power and low vacuum, but on to the test, after the engine starts and runs a minute spray the EGR valve with water and see if it boils right off, u can also touch the body of the valve and see if it is hot, this will indicate that a peice of carbon is stuck in the valve and it is being held open, let me know the results of this quick little test.

Posted on Dec 16, 2008

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When the outside temp is below 30 degrees my 1994 jeep grand cherokee 4.0 will not start


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Here are some tests you can try. The list is generic and you may have tried some of these already. It sounds like a vacuum line issue to me. For other info try this website:

Repair Guides Symptom Diagnosis no Codes What To Do When There Are No...

Preliminary Checks
Prior to starting this symptom test routine, inspect these underhood items:
  1. All related vacuum lines for proper routing and integrity.
  2. All related electrical connectors and wiring harnesses for faults (Wiggle Test).
  3. Check the throttle linkage for a sticking or binding condition.
  4. Air Intake system for restrictions (air inlet tubes, dirty air filter, etc.).
  5. Search for any technical service bulletins related to this symptom.
  6. Turn the key to off. Unplug the MAP sensor connection and restart the engine to recheck for the idle concern. If the condition is gone, replace the MAP sensor.

Test 2: Rough, Low or High Idle Speed Condition (Continued)
Test 2 Chart
Step Action Yes No 1 Step Description: Verify the rough idle or stall Does the engine have a warm engine rough idle, low idle or high idle condition in P or N- Go to Step 2. Fault is intermittent. Return to the Symptom List and select another fault. 2 Step Description: Verify idle speed & timing Verify the base timing is within specifications Verify that the base idle speed is set properly Are the timing and idle speed set properly- Go to Step 3. Set the base idle speed and timing to the specifications and then retest for the symptom. 3 Step Description: Check AIS / IAC Operation Check the AIS or IAC motor operation Inspect the AIS/IAC housing in throttle body for restricted passages. Clean as needed. Set the parking brake, block the drive wheels and turn the A/C off. Install the Scan Tool. IAC Motor Tester - Turn the key off and then connect the IAC tester to the IAC valve. Start the engine and use the IAC tester to extend and retract the IAC valve. ATM Test - Start the engine. Use the tool to change the speed from min-idle to 1500 rpm. Did the idle speed change as commanded- Install an Aftermarket Noid light and check the operation of the PCM and AIS or IAC motor circuits. Check the motor for signs of open or shorted circuits. Replace the IAC motor or PCM as needed or make repairs to the IAC motor wiring. If all are okay, go to Step 4. If the AIS/IAC motor passages are clean and engine speed did not change as described when the AIS/IAC motor was extended and retracted, replace the AIS/IAC motor. Then retest for the condition. 4 Step Description: Check/compare PID values Connect Scan Tool & turn off all accessories. Start the engine and allow it to fully warmup. Monitor all related PIDs on the Scan Tool. Verify the P/N switch input in gear and Park. Check the O2S operation with a Lab Scope. Are all PIDs within normal range- Go to Step 5. Note: An IAC motor count of over 80 indicates the pintle is extended and an IAC count of (0) indicates the pintle is retracted. One or more of the PIDs are out of range when compared to "known good" values. Make repairs to the system that is out of range, then retest for the symptom. 5 Step Description: Check the Ignition System Inspect the coils for signs of spark leakage at coil towers or primary connections. Check the spark output with a spark tester. Test Ignition system with an engine analyzer. Were any faults found in the Ignition system- Make repairs as needed Go to Step 6. 6 Step Description: Check the Fuel System Inspect the Fuel delivery system for leaks. Test the fuel pressure, quality and volume. Test the operation of the pressure regulator. Were any faults found in the Fuel system- Make repairs as needed Go to Step 7. 7 Step Description: Check the Exhaust System Check Exhaust system for leaks or damage. Check the Exhaust system for a restriction using the Vacuum or Pressure Gauge Test (e.g., exhaust backpressure reading should not exceed 1.5 psi at cruise speeds). Were any faults found in Exhaust System- Make repairs to the Exhaust system. Then retest the symptom. Go to Step 8. Repair Guides Symptom Diagnosis no Codes What To Do When There Are No...

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I would check the IAC motor or idle air control motor, heres a little info.about the part.Stratus Sedan, 1999-2005 Idle Air Control Motor

Print


Description & Operation

Not for Dodge Stratus Sedan
The idle air control motor (IAC) attaches to the throttle body. It is an electric stepper motor. The PCM adjusts engine idle speed through the idle air control motor to compensate for engine load, coolant temperature or barometric pressure changes. The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. The idle air control motor pintle protrudes into the air bypass passage and regulates airflow through it.
The PCM adjusts engine idle speed by moving the IAC motor pintle in and out of the bypass passage. The adjustments are based on inputs the PCM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, MAP sensor, vehicle speed sensor and various switch operations (brake, park/neutral, air conditioning).

0996b43f8020234f.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig.

Not for Dodge Stratus Sedan
When engine rpm is above idle speed, the IAC is used for the following functions:


Off-idle dashpot Deceleration air flow control A/C compressor load control (also opens the passage slightly before the compressor is engaged so that the engine rpm does not dip down when the compressor engages)
The idle air control motor (IAC) attaches to the throttle body. It is an electric stepper motor. The PCM adjusts engine idle speed through the idle air control motor to compensate for engine load, coolant temperature or barometric pressure changes. The throttle body has an air bypass passage that provides air for the engine during closed throttle idle. The idle air control motor pintle protrudes into the air bypass passage and regulates airflow through it.
The PCM adjusts engine idle speed by moving the IAC motor pintle in and out of the bypass passage. The adjustments are based on inputs the PCM receives. The inputs are from the throttle position sensor, crankshaft position sensor, coolant temperature sensor, MAP sensor, vehicle speed sensor and various switch operations (brake, park/neutral, air conditioning).

21180_cdia_g257.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig.

When engine rpm is above idle speed, the IAC is used for the following functions:


Off-idle dashpot Deceleration air flow control A/C compressor load control (also opens the passage slightly before the compressor is engaged so that the engine rpm does not dip down when the compressor engages)
Target Idle
Target idle is determined by the following inputs:


Gear position ECT Sensor Battery voltage Ambient/Battery Temperature Sensor VSS TPS MAP Sensor
Target idle is determined by the following inputs:


Gear position ECT Sensor Battery voltage Ambient/Battery Temperature Sensor VSS TPS MAP Sensor


Removal & Installation

  1. Disconnect the negative battery cable.
  2. Disconnect the IAC electrical connector.
  3. Remove the IAC mounting screws.
  4. Remove the IAC.

To Install:
  1. Install the IAC to the throttle body.
  2. Tighten mounting screws to 5.1 Nm (45 inch lbs.) torque.
  3. Attach electrical connector to the IAC.
  4. Connect the negative battery cable.

    0996b43f80202350.jpg enlarge_icon.gifenlarge_tooltip.gif

    Fig.


  1. Disconnect the negative battery cable.
  2. Disconnect the IAC electrical connector.
  3. Remove the IAC mounting screws.
  4. Remove the IAC.

To Install:
  1. Install the IAC to the throttle body.
  2. Tighten mounting screws to 5.1 Nm (45 inch lbs.) torque.
  3. Attach electrical connector to the IAC.
  4. Connect the negative battery cable.

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Have an 02 liberty. Cut out on me. turns over but wont start


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Every engine needs fuel air and spark in order to start and run Air is pretty much a "given" unless there is a big fat woodchuck stuck in the air filter box. Air flow is regulated by the throttle body which simply opens and closes when you press down on the gas pedal.
(which should really be called the air pedal)
The computer sensors see the internal conditions: TPS "watches" how far you have depressed the pedal. Computer sees that info and changes fuel delivery ans timing according to info from there after comparing info from other sensors, MAP measures the difference in external (ambient) air pressure and compares it with manifold vacuum.Map sensor info translates to proper shift points, engine timing changes and fuel delivery etc. Manifold air temp, measures exactly that.
Coolant temp sensor monitors the engine temp by measuring coolant temp Crank position sensor sends a signal telling the computer exactly where (what position the crankshaft is in) And cam position sensor tells the computer what the position of the camshaft is.Usually an engine will run with a bad sensor except for the tps, cam sensor, and sometimes map sensor. Your asd relay needs a signal from the crank sensor (through the computer) or it will not permit fuel to reach the injectors and will also prevent spark. The cam sensor does much the same thing. Crank Position sensors have a relatively high failure rate so I'd look at that first.
O2 sensor(s) measure the amount of O2 present in the exhaust and send that info to the computer which alters fuel delivery to attempt to keep exhaust "in range" of pre-set parameters.
The IAC (Idle air control) is not a sensor. It responds to what the computer tells it to do in regards to keeping the air in "balance" with fuel flow at idle.
Carburetors remained relatively clean because the fuel and air was mixed there and sent down to the combustion chambers. With injection, only air goes through the throttle body and that leads to "crud" deposits that can obstruct the valve or keep the plunger off the seat and alter the air/fuel mixture. Passageways need to be cleaned and the plunger end as well...but, never turn the plunger while doing that.
The computer takes all the information and uses it to maintain proper spark control and fuel delivery for every load condition.
The computer needs a good connection to all sensors, a good power supply and good ground.
Always check those things before testing. A bad connection in the ignition switch can cause a low or no current condition at the computer. Your engine has two main grounds (battery to block and block to firewall) but also has several smaller ground connections on the fenders and block, all of which need to be clean and secure. Always test with a known good fully charged battery or no test info is valid. All fuses need to be tested before running any other tests.

Bottom line: A shop needs to do the same testing I mentioned that is in the manual. A shop also has a hand held or larger scanner that helps them run tests faster.
Find out whats missing (spark or fuel) and work first on items that make that happen.
Most common failure is the CPS. Fuel pump is second in line, but if you hear it running likely it's good (but make sure the fuel is reaching the injectors...a dirty fuel filter can prevent that)
Guessing gets expensive and the manual will come in handy for many repairs later (never a bad thing to have)
If you have any questions along the way just ask and I or someone else will give you an answer.
Most times running a full diagnostics can be both annoying and frustrating. Keep away from sledge hammers the urge to use them may overcome you but if you stay with it, you can find your problem.

May 25, 2010 | 2002 Jeep Liberty

1 Answer

05 hemi 1500 first start of the day truck will fire rite up, every start after that it cranks for atleasst 30 seconds before it fires,and when it does start it smells like its flooded..........any...


check the iac motor(idle air control) this valve controls the air and fuel going into the throttle body during the truck idles aslso look at the vacuum going to map sensor for pin holes. iac valve is located to the rear of throttle body. map sensor is located in front under breather on throttle body. hope this will help!!!

Apr 09, 2010 | 2005 Dodge Ram 2500 Truck

1 Answer

Long Crank Time When Hot


Timing belt/chain may have been put it slightly off time, when motor rebuild

Jan 13, 2010 | 1993 Dodge Spirit

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