Misfire Hesitation And Popping Sounds

mark32

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Nov 15, 2015
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Hey, so I have a 2003 mustang gt and I seem to have problems with it starting up and running. So first off the car runs but it hesitates and misfires. So I'll have the car in 2nd gear and I'm cruising at say 2200rpm and then I floor it and it just starts to spit a chug and pop sometimes. Also it shows fuel injector codes but I did resistance checks and cleaned them so now they don't show any codes. Also the car has intermediate trouble starting up sometimes it just cranks and cranks but won't fire until I let go of the ignition key . so I'll have the key pushed forward and it will keep turning the engine but won't fire and as soon as I let go of the key to stop turning it, and the starter stops spinning the car all of a sudden trys to fire up but fails. But if I try again the 2nd time it will start right up. Is this a alternator problem I replaced battery 3 times . also I did a resistance test on the coils and they checked out good.
Any help is appreciated, thanks
 
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wmburns

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Sounds like to me that you have three problems (or maybe 2.5). One of which centers around the ignition switch.

I'm puzzled as why you have replaced the battery three times but not once has the alternator been tested. Especially since almost all auto parts stores will test an alternator for free.

Bottom line. Today's cars simply will NOT run right without a strong battery AND alternator. OBTW, what about the battery terminals? Are they clean and tight? Cut corners here at your own risk.

Check the fuel pressure sensor vacuum intake reference line. Is it connected and leak free? Inspect the line for evidence of raw gas.

Since the hesitation and popping "could" be related to an alternator problem, let's skip for now. Focus on the ignition switch.

Turn the key on /run but do NOT crank. Do you hear the fuel pump run for 3 seconds at EVERY key on cycle? If not, STOP and find out why.

Turn the key on/run but do NOT crank. Does the theft light go on and then off after a 3 second "prove out"? If not, STOP and find out why.

Get yourself an "add a fuse" and a Volt-Ohm meter (VOM). Using the "add a fuse" monitor fuse F2.34 and F2.2. Using a KNOWN good ground confirm there is NO POWER in each fuse with the key off. Turn the key on and confirm that each have power. Monitor the power in the fuse as the key is turned from run to crank. The power should stay on the entire time. IF the power drops as the ignition switch is moved, yell "bingo".

Post the results as this will give focus where to look next.

Note, IF the ignition switch is bad it can be replaced by a DIY'er. Replacing the ignition switch does NOT require PATS to be reprogrammed. Nor does it need a lock smith. The key cylinder is unchanged.

1996+ Crank with no start check list
http://www.allfordmustangs.com/forums/4-6l-tech/336452-1997-mustang-wont-ignite.html#2984838

1999-2004 BJB CJB fuse panel layout:
http://www.allfordmustangs.com/forums/4-6l-tech/305933-1999-mustang-gt-2001-motor-swap-wont-fire-please-help.html#post2669271
 
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mark32

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Hey I'm not getting any voltage to either of the fuses on or off even when i start. I used a needle stuck into the inlet of the fuse and overtop I wedged it in so it makes contact and I grounded the black lead off the VOM. everything else on the check list works.
 

wmburns

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Turn the head lights on. Do they work and are they bright? IF not, STOP and find out why. Likely the problem is:
  • bad battery positive
  • bad battery negative
  • loose grounds around the radiator core support
  • bad fusible link.
  • loose or bad connection inside the battery junction box (F1).
IF there's no key on power in fuse F2.34 AND there's power inside the BJB box (F1), then:
  • Blown F1.3 fuse.
  • Bad ignition switch
  • wiring harness fault.
  • bad/incorrect test results for example not using a good ground (warning. Wild Goose chase alert).
Be careful about jamming the VOM lead to deep inside the fuse socket such that the connector terminals are spread apart.

Basically if power is confirmed in and out of fuse F1.3 and no key on power at F2.34, then think "bad ignition switch".
 
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mark32

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Okay so the bjb fuse f1.3 is good and I still have no power coming to the cjb fuses f2.34. Is it really a bad ignition switch? Would a ignition switch cause misfire and hesistation at low rpms?
 

mark32

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Okay so the bjb fuse f1.3 is good and I still have no power coming to the cjb fuses f2.34. Is it really a bad ignition switch? Would a ignition switch cause misfire and hesistation at low rpms?
 

wmburns

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Okay so the bjb fuse f1.3 is good and I still have no power coming to the cjb fuses f2.34. Is it really a bad ignition switch? Would a ignition switch cause misfire and hesistation at low rpms?
Go back and carefully re-read my original post in this thread. It's possible that a bad alternator diode can cause cam sensor issues. Also incorrect system voltage can "cause" ignition problems. Has the alternator been tested?

IF there's no key on power in/out of fuse F2.34 AND this motor runs, THEN your tests results are faulty. Why? Because fuse F2.34 is the CCRM relay pilot duty PCM power circuit. With no power out of fuse F2.34 the CCRM will not pull up and the PCM wouldn't have power.
 
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mark32

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Okay so the alternator turned out to be bad I put a new remanufactured one in and it solved the starting problem but the car still hesitates a little bit at very low rpm around 2200rpm when I floor it in 2nd gear I'm thinking its maybe the sparkplugs and also when the cars idling it vibrates a bit and out of the exhaust you can hear like puffs of air idk how to explain it but its like its missing or something
 

wmburns

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when the cars idling it vibrates a bit and out of the exhaust you can hear like puffs of air idk how to explain it but its like its missing or something
Puffs of air? Maybe like a lawn mower? Think spark plug(s) backing out. Re-torque to factory specs. Don't delay as the spark plug could blow out. Once the plug blows out a thread repair is needed.

If the leaks are coming from the exhaust manifolds this can cause "issues" with un-metered air entering the exhaust. This will cause the O2 sensors to read LEAN when in fact the motor may be running fine or rich. This results in the PCM adding fuel will will make the motor rich.

What's one symptom of a rich fuel mixture? Popping in the exhaust.
 
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mark32

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The spark plugs were torqued down I also did take the injectors out and found that on some of the injectors the pintle caps are cracked and on some they have broken off.I'm not sure if this would be the cause of the problems I'm having? I'm going to go ahead and give the injectors another back flush clean. Also the whole starting problem is back even after I replaced the alternator.
 

wmburns

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I also did take the injectors out and found that on some of the injectors the pintle caps are cracked and on some they have broken off.I'm not sure if this would be the cause of the problems I'm having
IMO you should strongly consider an injector cleaning and flow test service such as InjectorRX.com. Once cleaned and tested they are as good as new. Much cheaper than new. This will take all of the guess work out of this.
Also the whole starting problem is back even after I replaced the alternator.
NO where in any of this copious amount of information provided did I ever hint that the alternator is likely responsible for the starting problem.
Also the car has intermediate trouble starting up sometimes it just cranks and cranks but won't fire until I let go of the ignition key . so I'll have the key pushed forward and it will keep turning the engine but won't fire and as soon as I let go of the key to stop turning it, and the starter stops spinning the car all of a sudden trys to fire up but fails. But if I try again the 2nd time it will start right up.
What I keyed on is the report that the motor's condition changed depending upon what was done with the ignition switch.

I have given a ton of tests that if done WILL narrow down where the starting problem is. Without these detailed results, everything else is just guessing.

IF on the other hand this is really just a "long crank" problem, then the injectors could be the cause. The injectors could also be part of the hesitation problem.

Try this. Cycle the key on/pause/off several times but do NOT crank. Listen for the fuel pump to run each time. Does this reduce cranking time? IF so suspect fuel pressure leak down as a possible problem source. Possible sources of fuel pressure leak down, injectors, fuel pressure sensor, fuel pump check valve.
 
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mark32

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Okay so I figured out the problem it was all in the sparkplugs right after I put new ones in the power was restored and starting problem fixed. Thanks for your help man really appreciate all the input I got from you.