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Ping Fortch

Discussion in 'The Lounge - Off Topic' started by ffreeloader, Jun 28, 2006.

  1. ffreeloader

    ffreeloader Terabyte Poster

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    Fortch,

    I need to pick your brain on a car problem. I'm good with the old V-8's, point ignition, carburators, and the like, but I don't have the tools to troubleshoot the new technology.

    I have a 99 Honda Accord with the 4 cylinder Vtech engine and 5 speed tranny. This thing really stumbles when forced to lug at low rpms. It will bascially almost completely die before it catches again. This doesn't happen in 1st gear, but in 2nd through 5th when attempting to accelerate sharply at anything under 2000 rpm this thing will stumble badly.

    It gets great mileage, idles smoothly, and burns no oil whatsoever. It does have almost 200,000 miles on it though. I just bought it 3 months ago so I'm not aware of the history of the car although it's in basically new car condition in all other respects. Other than the stumbling it purrs like a kitten and drives very nicely. It's basically like driving a brand new car.
     
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  2. fortch

    fortch Kilobyte Poster

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    Hmmm.... foreign cars aren't my specialty, but they all basically run the same, so I can offer some suggestions. To clarify, it probably doesn't happen in 1st gear because you can't accelerate from a stop sharply without revving past 2000rpm. That said, and taking into consideration the engine's miles, I would be suspect of maintenance items first. On an OBDII-equipped system (engine/emissions management system), most failures in the electronics will be indicative of a warning lamp. However, that doesn't exclude a sensor on the verge of failure -- enough to cause a driveability issue, but not enough to flag the control module. Still, that type of problem normally stems from an incomplete combustion.

    Right off the bat, I'd look for the basics --- when you say stumble, does it actually misfire? Poor secondary ignition (plugs, wires, and even a coilpack --secondary side) would be something to look at -- particularly along the wires for cracking or carbon arcing near bends that are close to metal (around heads and valve covers) or even between each other. On the coil(s), carbon arcs and discoloration are clues as well, as it is with spark plugs (cracked porcelin insulators are common).

    Obvious things like air flow restrictions (aftermarket filters) and such can affect the sharp acceleration -- the engine needs that air ASAP for combustion, and anything that impedes induction is a candidate. Something a bit tougher to examine is the fuel system -- partially-clogged injectors can flow fuel fine until you romp on it, and the injector may not be able to meet the demand of full pulse-width. Also, poor spray patterns (huge problem with GM cars in the early 90's) can cause this, too -- the spray is there, but it's not perfectly conical, or finely atomized, or directionally on target. Problem is, testing for this, depending on the type of system, is not the easiest thing. An injector flush, using manufacturer-approved methods can sometimes solve this. Using decent products, like BG, can help disolve the varnish and crud that collects on injector dispersion plates, as well as the backside of intake valves.

    I'm not too knowledgeable on VTechs, but I know many foreign cars have a problem with Mass Air Flow sensors (MAF). Most are hot-wire sensors, that determine the mass of air flowing by monitoring the amperage flowing through the wire as it is constantly being cooled by the airflow. As the resistance changes to reflect this, the mass is calculated, and is part of the algorithm for the car's fuel curve. Now, if the wire is covered in dirt (sometimes hard to tell), the accuracy of the sensor is altered, and driveability problems arise (another problem in GM FI engines). Simply cleaning the wire with a very soft, fine bristled brush (think toothbrush), with either water, or a light cleaner (NOT carb cleaner) will sometimes fix it. However, they are very fragile, and usually expensive, so be careful.

    I'd be remiss if I didn't bring up the timing belt -- 200,000 miles on it, and this symptom is very indicative of a loose or worn one. Most foreign cars are suggested to change it every 60k or so. Even new belts, put on a tooth off, can idle smooth, yet stumble on acceleration (been there, done that -- that was a no-pay day :blink ). However, that is a rare case indeed.

    Rarely, in fuel-injected cars, does a rich condition cause a driveability symptom. With carbs, as you know, if the float was set wrong, or the metering rods weren't adjusted, or the MC solenoid was off, or the purge vavle was leaking, the engine would stumble and almost die. Contributing to that was the relative weak output of yesterday's ignition systems. Today, there's no way (mostly) a rich condition can cause a driveability problem, without the ignition system burning it up, or the PCM knowing it and flagging a hard failure. So, I'd look for things contributing to a lean condition. O2 sensors are culprits also, but since most of today's vehicles have multiple sensors in strategic areas, the problem can generally be isolated. Similarly, a Throttle Position Sensor (TPS) with a rough spot on the carbon/graphite track (resistive element) can be flakey at times, as well.

    Vacuum leaks can cause something like this - although they generally show a higher than normal idle - because they throw the entire fuel management system out of whack. A clogged fuel filter, or weak fuel pump can also cause this. Techs often forget that a fuel pump needs to deliver fuel volume, in addition to the proper PSI. Often, even a fuel pressure test (suggested also) doesn't reveal the true problem -- but rather than performing a flowtest, most techs just replace the filter. Addresses most problems, but doesn't pinpoint the occasional fuel pump or other item.

    I've checked for Technical Service Bulletins (TSBs) for your car at NHTSA , but nothing stands out as remotely related. Don't rule out fuel, too, especially if you tend to get fuel at the same station. Some tanks have water, some fuel is just old, and some older tanks contribute rust and varnish to your fuel system. Also, make sure it's not an issue with seasonal blends, which would cover the area that you're in, and not just a single station.

    Phew, sorry for the long post, but a symptom like that can cover several systems on a car. I've only mentioned maybe 25% of the possibilities, but I won't go any further (to save your boredom) until we can possibly narrow the problem down a bit. In truth, though, being in the car, with a proper scanner (to scan the realtime datastream), can take most of the guesswork out of this. Plus, most accomplished Honda factory techs (and those that repair Hondas daily) can, knowing the cars the way they do, go right to the problem. Whatever the case, good luck!
     
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  3. ffreeloader

    ffreeloader Terabyte Poster

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    Thanks Fortch. I already suspected timing belt, and sensors but don't really have a way to test them. Guess I'm going to have to buy a manual for this thing.

    I was just hoping you would come up with some magic pill and it would fix itself.... :D
     
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  4. AJ

    AJ Administrator Administrator

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    Wow not only computer/IT advice but automotive advice as well.

    :iluvcf
     
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  5. noelg24

    noelg24 Terabyte Poster

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    some of us do have some hidden talents indeed AJ...lol...:biggrin
     
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  6. AJ

    AJ Administrator Administrator

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    Must have missed yours somewhere mate 8)

    Anyway, I always pay a mechanic to look after my car. I can change brake pads and oil and the like but after that it goes to the garage.
     
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  7. The_Geek

    The_Geek Megabyte Poster

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    I don't know about the 99 Accords, but if I lose the belt on my 95 Civic, I just lost the engine as the pistons will hit the valves and it'll be "a big 'ol mess".
     
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  8. Bluerinse
    Honorary Member

    Bluerinse Exabyte Poster

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    You have got to love Honda's for that! My wife has a Civic and I drive a CRV. Both cars are over 6 years old now and both still look as good as new. The paintwork, interior and performance hasn't diminished one iota, since we bought them when we first arrived in Oz.

    I have owned numerous cars in the past and none of the others, including BMWs had the same longevity.

    Interesting thread. Have you changed the spark plugs Freddy? :rolleyes:
     
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  9. fortch

    fortch Kilobyte Poster

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    LOL. Yeah, computers were a hobby of mine for the 14 years, while I was the foreman for a multi-franchise dealership. That basically just means I was a troubleshooter, getting all the headaches that have been worked on time and again. Then, for a year, I was coerced into teaching automotive technology to professionals for ACDelco (GM). No wonder about a career change, eh?

    Anyways, Freddy, normal routine is to make sure the basics are sound. Such things like worn timing belts, secondary ignition, filters and such can cause issues like this, and possibly aggravate other subtle problems. Narrowing the concern is the key here, and that *always* starts with communication, which is why I needed clarification of the stumble. For example, in a 'carb' engine, a stumble on sharp acceleration was a smooth, yet rapid, reduction in rpm (this is where I make seemingly-accurate mouth sounds to my customers :biggrin ). Incomplete Combustion, in the form of a misfire, is a reduction in rpm, but in an increased load (such as acceleration below 2000) it is the misfire of an individual cylinder, and can be felt rythmically. Often feeling like a stutter, it can be pinpointed to one (or two --buddy cylinder -- 1 coilpack feeding 2 cylinders) cylinder(s).

    During the misfire, and particularly on an older car with a weak catalytic converter, there might be black smoke (indicative of a rich condition -- misfire) coming out of the tailpipe. Normally, you can trace that type of failure to a out-of-spec coilpack, an arcing plug wire (or high resistance), or faulty plug. Most times, its a wire or a coil, since plugs are pretty bulletproof (factory -- not crap like splitfires) if installed correctly.

    You can usually rule out a lean condition (in this case) -- a lean engine will run rough and hot, and usually doesn't run long before component failure.

    Like I said, check the basics first. Myself, test driving is key, since I'm able to mentally check off all the things it can and can't be --- for the most part. Here, I can only go by what you say, and the accuracy is not very good. My advice would be to do the service work with *factory* components (if needed), and then possibly driving by the local Honda dealer (or other Honda repair specialists), and grab a foreman (or tech -- it might cost you a trip through the drive through :) ) for a quick testdrive. Let it be known that any repair decent shop will want the basics out of the way first.

    T_G -- yeah, those no-tolerance engines are nice -- good power, generally low maintenance, easy to work on -- but they carry a high price when the timing belt goes. Don't think the belt can't loosen and cause problems without piston-to-valve contact -- low tolerances mean that a loose belt is that much more susceptible to erratic timing in engine management.
     
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