By on March 14, 2012


Chris writes:

Hey Sajeev,

Long time lurker here.  Since you asked so nice, here’s a problem that I haven’t managed to troubleshoot myself, and so far my own searches & forum postings haven’t nailed an answer. My girlfriend drives a 99 Mazda Protégé.  If driven for an extremely short distance (like from the street into the garage), it will not start the next morning.  It turns over just fine, but doesn’t catch.

I’ve found that I can eventually get it to start by holding the gas pedal to the floor & cranking, followed by easing up on the pedal slightly (maybe 1/2 or 3/4 of the way down) & continuing to crank.  This process takes 5 – 10 minutes, so there’s lots of breaks in there as well.

Almost everything on the spark side has been replaced for different reasons (I was chasing engine codes the wrong way).  So I’m pretty sure it’s not battery, spark plug/wire, or coil pack related.  Simiarly, I’ve changed the MAF, O2 sensors, cat, & the acordian hose that feeds from the intake to the throttle body (the hose being what was actually causing the codes, BTW).  None of these changes seemed to affect this particular problem.

This lead me to believe the problem must be fuel delivery in some way, but now I’m second guessing myself.  The problem seems to happen most often when it’s cold & damp outside (by Georgia standards).

Normally I’d have changed the fuel filter by now, but it’s not a separate unit.  It’s attached to the pump & sits in the tank.  That’s probably going to be my next step.  Before I do that I wanted to run this by you.  Any ideas?  Someone suggested the the charcoal canister could be trapping water vapor (since the engine is never hot), and then forcing that vapor into engine when I try to start it the next morning.  I’ve never played with that before, but if that’s right then shouldn’t there be a hose I could disconnect & see if the car starts?

Anyway, if you have any suggestions, I’d love to hear them.  This isn’t an urgent problem, but it’s one I’d like to be able to solve.



PS, here’s another write up of the problem, just in case I missed something.  Mine’s the 3rd post.

Sajeev answers:

Thanks for your letter. I like the post on the Mazda Forum, especially since you did my homework for me. And by your own admission, you threw parts at a problem instead of finding the proper diagnostic for the engine codes generated.  Are the codes still present?

Your problem sounds like a lack of fuel, and I seriously doubt that’s a stretch for me to armchair analyze that from my remote vantage point. Check the fuel pressure with the key on, engine off.  Compare the reading on the gauge to what your EFI system needs to run properly.  If you are at the lower end of acceptable (or worse) you have found your problem.

Maybe a bottle of fuel system cleaner in the tank is all you need.  Or maybe a fuel filter.  Or maybe the fuel pump itself. Or maybe the fuel injector’s resistance is out of spec. Or maybe the fuel pressure regulator, or its associated vacuum plumbing. My point is, this is hard to guess from my laptop.

My advice is to start with a fuel pressure tester and buy a filter, maybe a pump after that. Also make sure the vacuum lines to the regulator aren’t fossilized, gooey or cracked. If they aren’t as soft/pliable as the rubber on your shoes, replace them.

Good luck on your hunt, I am sure your girlfriend appreciates your hard work…provided you never, ever throw parts at a problem again.  Never again, son!

Send your queries to [email protected] . Spare no details and ask for a speedy resolution if you’re in a hurry.

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22 Comments on “Piston Slap: Throwing (Ignition) Parts at a (Fuel) Problem?...”

  • avatar

    What brand name parts were the spark/ignition components replaced with? I ask as anything Autozone is JUNK. It has skewed many a diagnosis for me and I will never buy parts from them again. Not ranting just giving you another angle before you spend more money. I have learned the hard way to never trust a new part 100 percent. HTH

  • avatar

    I’ve had an issue with AutoZone ignition parts as well.

    Too bad, my local store has a really good staff and they never question when I have to return something.

    But I went with NAPA Echlin stuff last time I needed a coil and ignition module. The AutoZone modules didn’t last.

    That said, many modern vehicles – in lieu of a choke – simply count on the extra-high pressure of today’s fuel systems to deliver the goods to make the engine start when cold.

    My son’s ’95 Blazer had an issue with hard starting when cold. It was fine – or so it seemed – when warm but cold starting was always an issue. Turned out the fuel pressure was only around 40 PSI, instead of the factory-recommended 56-60.

    I didn’t think it would run at all if the pressure was off that much but I was wrong. Changed the fuel pump, problem solved.

    EVEN THOUGH new ignition parts don’t always equal “my ignition problem is fixed”…IOW check the obvious first…I’d run a fuel pressure/component check and make sure it’s good.

  • avatar

    At this point, take it to a dealer or a good mechanic, because you obviously haven’t located the problem and have thrown already a bunch of your time and money at it with no resolution. In cases like this, it’s time to take it somewhere where they have the equipment to accurately diagnose the problem(s) and fix the car.

    • 0 avatar

      Assuming he is lucky enough to have a mechanic who is competent enough to resolve the problem and he trusts not to rip him off.

    • 0 avatar
      Mr Nosy

      I’ll have to concur w/Zackman.You’ve already eliminated seven issues,and posters below have offered up five more.I’d say you’ve more than earned your “My boyfriend can fix it/He cares about me” badge,but it’s now time to work smart,not hard.Have you checked out or AutoMD,to find a local repair shop? As for worrying about finding an honest mechanic,you probably have enough knowledge to know.Repair shops need repeat customers to stay in business.Yelp and AngiesList only need a supply of investors,as neither one has yet to turn a profit.Oh BTW,repairpal had three more possibilities listed.
      for your problem.Bon chance.

  • avatar

    Doesn’t the Mazda RX-8 have a similar issue? Something about re-priming the fuel system and it’s a big no-no to start it and immediately shut it off?

    • 0 avatar

      Rotaries flood their engines in that scenario.

    • 0 avatar

      I used to own an RX7, and would have a similar issue that the OP is having. My issue was that the car would flood. The only way that I could get it to start the next day would be to pull the fuel pump relay, crank the engine for 10-15 seconds to burn off any fuel in the engine, then replace the relay and start the car. You can try what I just described to see if that takes care of your issue, or you can do my cheap fix to prevent it. Right before I turned the car off, I would rev the engine to 3-4k rpms, then turn the car off before it made it down to idle. Doing that would burn off any extra fuel pressure after the pump lost power, preventing it from flooding. The real issue with the car was that the fuel injectors were gummed up, and letting fuel leak out after the car was shut off. My test is free and easy- see if that takes care of your issue.

  • avatar

    In the days of carbureted cars, the solution to a flooded engine was to mash the gas pedal to the floor and crank the engine. The increased airflow through the engine would cause the fuel in the cylinders to evaporate and be expelled through the exhaust, until you achieved an air/fuel ratio that would combust and the engine would start.

    I recall reading that EFI systems provide the same functionality, in case your engine gets flooded for some reason. If you hold the pedal to the floor while cranking, the EFI shuts off fuel flow to the injectors.

    Chris says that cranking with the gas pedal fully depressed eventually gets the car going. Possibly the problem is not fuel starvation but flooding?

    • 0 avatar

      I concur with your recollection.

      My friend has an older Ford truck which had similar symptoms to the subject vehicle of today’s Piston Slap. We tested his spark and compression which were fine. Trusty Google tells us that when flooring the gas pedal with the key engaged actually recalibrates the TPS and, as you stated, stops fuel flow with maximum air flow. It started right up…any time it starts giving him trouble he follows the same procedure and it starts for his 8 minute round trip to the transfer station and back home.

    • 0 avatar

      You are correct that full throttle in a FI will shut off the fuel injectors while cranking. To the OP, while the car is having the no start condition, I would pull a plug or two and see if they are soaked in fuel. I would also check spark at this time to make sure you don’t have a failed component.

    • 0 avatar

      Carburetors were designed to behave exactly that way; the linkage implementing this was called the “choke pull-off.” (It had a name because it needed adjustment.) Holding the accelerator to the floor would 1) open the main butterflies, and 2) engage the “choke pull-off” to crack open the choke plate. (This presumes you’re starting a cold engine.)

      Cranking the engine with everything open this way would eliminate any vacuum in the intake, eliminating any fuel delivery. The flooded engine would dry out.

      As noted by another post, modern FI systems were designed to mimic this behavior because it’s useful. In practice, it’s forgotten, because FI systems seem to be less prone to flooding. :-)


    • 0 avatar

      I agree…I tended to thing flooding first. When the car does start, does she blow blackish smoke at startup?

  • avatar
    Educator(of teachers)Dan

    And another argument for buying a code reader for your vehicle if you plan on doing any of your own wrenching.

    • 0 avatar

      No joke, you can buy a cheapie from Harbor Freight for around $30 if you catch it on sale IIRC. Mine’s pushing 3 years old so they don’t seem to have reliability issues.

  • avatar

    I’d suspect carbon deposits in the combustion chambers if the car is up there in mileage. Have seen Hondas do the exact same thing.

  • avatar

    Try this before you spend money on a mechanic. The next time you move the car and then turn off the engine, pull one of the plugs.

    Is it wet and covered with gasoline? I bet that it is. Most cars of that era ran pretty rich when they were cold. This situation is much worse when it is cold/wet outside like in our Michigan winter months (my dad likes to move his car like you describe, and it is always harder to start the next time).

    My suggestion is that when you move the car like you said, put it in park, then rev the motor one or two times, and shut it down without letting it idle again. This will keep your plugs drier and make it easier to restart the car next time.

  • avatar

    My solution my sound sarcastic, but will cause fewer trips to the parts store and will cost less money…

    We’re in a situation similar to this: PATIENT: “Doctor, it hurts when I do this.” DOCTOR: “Then don’t do that.”

    If it only happens when the car is driven for an extremely short distance… then drive it around the block before parking it in the garage… problem solved.

  • avatar

    A friend of mine moved her 2002 Toyota Echo from outside her garage to inside with a cold engine. Much later that day it refused to start. I tried and failed. Next day she called the Auto club. I wasn’t there when he came and ‘kept the starter turning for about a minute’ until the engine started. The claim was that there is a sensor that prevents starting until it is mechanically safe to do so. I could get no more meaningful info unfortunately, but you may be throwing money at a feature.

  • avatar

    Sounds like the charcoal canister purge solenoid is stuck/dirty/bad. On most cars it opens for a minute or so when the engine first starts then closes. If it goes bad and sticks, it leans out the engine and causes a vacuum leak. Once warm it works fine.

    Replace it and see. They are usually pretty cheap. Also check the hoses to it and to the canister.

  • avatar

    It’s most likely the fuel pump or the pressure regulator. The fuel pressure should have been checked before throwing all of those new parts on it.

  • avatar

    My car has done this a couple of times and I think the problem is caused by petrol flooding. There were no ill effects afterwards so the comments about faulty parts didn’t apply in my case. The best cure is, as someone has already said above, to avoid driving it a very short distance.

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