Question about 1998 Chevrolet Tahoe

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Hesitation under load ,creating a misfire code that clears in three drive cycles

Engine runs great except when regaining speed after a downshift to pass or go uphill. hesitation and loss of power triggers a misfire code that clears in three drive cycles. have changed plugs ,wires, cap, rotor, entire sfi, fuel and air filters.

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  • Anonymous Nov 18, 2008

    I have the exact same problem on my '03 Focus and before I spend a lot of money on a bunch of parts, I'd appreciate if someone can help me out

  • joecyr Dec 02, 2008

    I have the same or similar problem without a check engine light. The car ('98 Pontiac Bonneville, 3800 MFI V6) will misfire and buck at low RPM (1200-2000) under load until the transmission downshifts. Adding more throttle, but not enough to downshift, aggrivates the problem. I ran hightest gas on one trip to the mountains and reduced, but not eliminated, the problem. I've had this problem for 2 years now. The only solution is to quickly punch the gas pedal and force a downshift or manually downshift the car on hills.

  • 1pur1ty1 Jan 07, 2009

    2001 Tahoe. idols fine, level ground accelerates fine. Changed plugs & wires and fuel filter. Fuel filter was especially dirty so I changed it again 6 weeks later and that one was even dirtier. For the most part it drives fine with a slight hesitation when engine is cold but can not go up steep inclines. I guess it's time to take it to the shop and let them figure it for me. Any ideas?


  • rodney850 Mar 19, 2009

    My 97 Lasabre problem is similar (P0300 Random Misfire), runs perfect until I get to 55-60 and slowly accelerate or go up a hill. It stumbles and will not accelerate until I punch it putting into passing gear. Fuel pressure OK, new plugs, wires, fuel filter.



    I am starting to think my problem might be a Ignition Control Modual or EGR. ???

  • yadayada
    yadayada May 11, 2010

    Have you tested the fuel pump for proper pressure? How about the crank shaft position sensor? Is it a random misfire, or is the code always for the same cylinders? All this info is very important to get to the root cause. The Chevy dealer has electronic test equip. that can be taken along on the road test to record the problem, then the tech can download it and decide the problem area to work on, you are wasting allot of money on parts that are not causing the problem.

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Problem is almost always plugs, wires, or coils/ICM. I have seen all three, they all act exactly the same with the symptoms you all describe. Sometimes CEL and code are present, other times not. Start with cheapest solution and work your way up (plugs & wires, coils, then ICM) The coils can be tested with a spark indicator individually, plugs visually inspected. Most auto shops can test the ICM.

Good luck!

Posted on Dec 16, 2009

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I belive the dealers have a T.S.B. ( tech service bulletin) on a issue close to this. I belive they re flash the ecm as the repair. Just thought you might check into it. Hope this helpes.

Posted on Jan 25, 2009

  • man gone Jan 25, 2009

    You might also want to check the egr system. It could be leaning out one cylinder causing the missfire. just a after thought.

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Egr valve port hole have to remove the intake to clean but that's my problem rite now on a 4.3 vortec the port hole gets cloged with carben not slowing it to work properly.

Posted on Jun 07, 2011

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You either have a bad catalytic converter causing too much back pressure or you are running rich. I think cylinder 3 and 6 are on the same side of the engine (except opposite banks) right? Locate the fuel pressure regulator. Is it on the same side? I've seen those go bad and allow fuel to be sucked into the vacuum line causing a rich condition/ misfire on two or three cylinders on that side of the engine.

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I have a 1997 lumina with 3.1L. the problem started with loss of power under load and p0300 code. check coils and vacuum leaks both OK.change spark plugs and wires.[same problem] check compression OK.


Since you changed the sensor we will assume it is working. When you disconnect it you put the computer in limp mode which stops it from using sensor values. If code 300 is the only code we will assume the coolant temp sensor and others are ok.
I would check fuel pressure with a gauge next.

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I have a 2005 Ford Focus ZX4 ST. I have less than 73k miles on it. Have never had any issues with it. Perform all the regular maintenance at required intervals. About a month ago the check engine light...


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Mar 25, 2011 | 2000 Ford Focus

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My 2000 Saturn did not pass inspection due to evap. and O2 sensors "Not Ready". How can I fix the problem or how can the problem be fixed?


What is the EVAP code?

The O2 are not ready because it takes some time for them to complete there self check after clearing trouble codes. This will involve a few drive cycles. Once the evap problem has been resoled, the check engine light cleared, you'll have to drive it for a couple of days to get everything in the "ready" status.

Sep 27, 2010 | 2000 Saturn SL

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At times or most of the time the fuel data keeps cycling through all its functions including the change engine oil lamp.


There can be a misfire too from the cylinders.

An engine that hesitates, stumbles or misfires when accelerating or when it is under load is an engine that is either sucking too much air, not getting enough fuel or misfiring. If the Check Engine Light comes on, you may find any of the following codes:

• P0171, P0174 Lean fuel condition codes
• P0120 to P0124 Throttle position sensor codes
• P0222 to P0229 Throttle position sensor codes
• P0400 to P0409 EGR related codes

If there are no misfire codes, a common cause of acceleration stumble is a bad throttle position sensor (TPS). The TPS tells the computer how far the throttle is open. The computer uses this information to determine how much fuel is needed to maintain the correct air/fuel mixture and when extra fuel is needed if the throttle suddenly opens wide.

Another common cause is dirty fuel injectors. If varnish deposits have built up in the tips of the injectors, they won’t spray as much fuel as they normally do, or will “dribble” fuel instead of spraying a fine mist. This creates a lean fuel mixture and conditions that are ripe for stumble and hesitation (also misfire). Look at short term fuel trim (STFT) and long term fuel trim (LTFT) with your scantool. If the numbers are high, it tells you the engine is running lean and the injectors need cleaning. Treat mild cases with a high quality fuel-injector cleaner additive. Severe cases require professional cleaning equipment.

Also if this sensors apply to your vehicle, camshaft sensor or crankshaft sensor if sensors bad you don't get any spark. Also run a scan on the car.

Good luck and rate this solution, please.

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  5. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 20 mph (32km/hr). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
  6. Accelerate. Accelerate at 3/4 throttle until 55-60mph (88-96 km/hr). This will perform the same diagnostics as in step 3.
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