Very confusing engine problem need help

onebadace01gt · Aug 13, 2010

Alright heres the problem. i have an 01 gt with a custom built engine but basis of a 4.6 stock fuel and ignition.. well starting 2 days ago my car had a slight vibration at speeds above 45 mph. so today we were going to check the balance of the tires knowing that sometimes thats a problem. well today on the way out to the shop my car pushed out a spark plug which caused the car to spit and studder to death. well after i removed the boot and the plug i noticed that the plug has been mechanically damaged. talking gap space smashed closed, looking in the plug there is obvious oil on the piston. well we blew the oil out replaced the plug and a new coil. well now the car will crank healthy and will spudder and die as if its not getting fuel. there is some white smoke which makes us believe we are not getting any fire at all. but for the most part we are stumped. any info or advice would be awesome cause we have ran out of ideas,

Saleen#498 · Aug 13, 2010

sounds like you have a major problem, with the gap "smashed" shut, chances are your piston hit and you could either have a cracked piston, or damaged head, either way coolant is getting into your cylinder and burning off

onebadace01gt · Aug 13, 2010

see i had a problem with my last motor with a cracked piston skirt and it made a ton of oil bypass and i had a hard knock. but with this one the spark plug doesnt make alot of sense the way it happened. i heard tonight from a guy i race with that his thoughts are the crank sensor sending info thats throwing off my timing... possible?

wmburns · Aug 13, 2010

onebadace01gt said:
there is some white smoke which makes us believe we are not getting any fire at all. but for the most part we are stumped. any info or advice would be awesome cause we have ran out of ideas,

Ok, lets work through this.

Let's assume for a moment that the white smoke is gas/air mixture. If the crank shaft sensor were bad, the PCM would not fire the fuel injectors nor fire the spark. Therefore, no fuel vapors out the exhaust.

If the timing were just plain off, the spark would still occur at some point. The result-back fires.

My vote is a blown fuse. Test fuse F1.26 in the BJB and fuse F2.8 and F2.2 in the Central Junction Box (CJB). Not a bad idea to test all of the fuses.

If the IAC is bad, this could cause a no-start. Try cracking the throttle half way open. Does this improve starting?

If the white smoke is anti-freeze, the there has to be a break in the water jacket.

If you really want to know if the motor is hurt, perform a compression test.

Good luck.

onebadace01gt · Aug 13, 2010

ok well tomorrow morning we will check all the fuses u recommended and we are going to pull the iac and swap it to see if that makes a difference. as far as the smoke it only happened at full throttle on a choke and die. but we are willing to try anything we can. im going to pull codes tomorrow to see if anything is showing up and see what else i might be able to ask. thanks for the help and any other ideas are greatly appreciated

joshjwc9 · Aug 14, 2010

Did the spark plug come off in your hand without unscrewing it from the head?

If that is the case then you have spark plug blowout.

I am just suggesting this as I may have misread your first post, and I've had too many drinks this evening

Three50won · Aug 14, 2010

wmburns said:
Ok, lets work through this.

Let's assume for a moment that the white smoke is gas/air mixture. If the crank shaft sensor were bad, the PCM would not fire the fuel injectors nor fire the spark. Therefore, no fuel vapors out the exhaust.

If the timing were just plain off, the spark would still occur at some point. The result-back fires.

My vote is a blown fuse. Test fuse F1.26 in the BJB and fuse F2.8 and F2.2 in the Central Junction Box (CJB). Not a bad idea to test all of the fuses.

If the IAC is bad, this could cause a no-start. Try cracking the throttle half way open. Does this improve starting?

If the white smoke is anti-freeze, the there has to be a break in the water jacket.

If you really want to know if the motor is hurt, perform a compression test.

Good luck.

Good advice here...

Also, maybe there was too much timing, or it went way too lean, or there was too much heat in that cylinder or on that side of the engine or a combo of all three scenarios. Was the car tuned properly...?? Is there any way to get a scan tool on and monitor the fuel and spark trims throughout the operating range...??

Can you give more details about this custom built engine...?? Compression ratio, piston dish, heads, cams, injector size, MAF. This info will help a lot...

onebadace01gt · Aug 14, 2010

ok lets see. first off the spark plug was completely loose that made us think about the blowout but none of the threads seemed to show any damage and another spark plug did thread easily. but whatever force was used like i said did damage both the spark plug and the boot itself. it actually broke the plastic mount. As far as the engine it is a base 347 block running a 8 bolt with flat tops, stage 2 cams and the aftermarket pullys.

Three50won · Aug 14, 2010

onebadace01gt said:
ok lets see. first off the spark plug was completely loose that made us think about the blowout but none of the threads seemed to show any damage and another spark plug did thread easily. but whatever force was used like i said did damage both the spark plug and the boot itself. it actually broke the plastic mount. As far as the engine it is a base 347 block running a 8 bolt with flat tops, stage 2 cams and the aftermarket pullys.

huh...?? Wait, your first post said you had a 01 gt with a custom built engine and a 4.6 stock fuel and ignition set up...and now you say it's a base 347. Did you convert to a pushrod engine...?? Even if you did, a stock 4.6 fuel and ignition set-up won't work with that type of engine...

If it is actually a 4.6 with flat tops and stock heads then your compression is probably around 11.5:1 or maybe a little higher depending on head gasket thickness. That much compression on a stock head with stock springs and stage 2 cams will definitely cause the valve to hit the pistons. You might have damaged your pistons...also, if you jacked up the timing then you probably had soo much pressure and detonation in that cylinder that the spark plug gap was forced closed and you might have blown a piston ring or the piston itself. If you kept the stock 19lb injectors in there then you probably also went lean which isn't good either.

onebadace01gt · Aug 15, 2010

The motor was originally out of a 02 saleen. it was tore down and built by outback motorsports here locally. and eveything is still running stock ignition and fuel system.

Three50won · Aug 15, 2010

Ok, so it's a 4.6 SOHC with flat top pistons, stock PI heads, stage 2 cams, and 19lb injectors. Was the car tuned...?? Did you get any check engine lights or lean codes...?? That combination will have piston to valve issues if those heads have the stock springs. Also, a high compression 2V engine with cams needs at least 24 lb injectors, a MAF calibrated for the injectors, high octane gas, a good tune to adjust the timing and AFR, and maybe even a colder plug. You can't just throw an engine like that into a Mustang with the stock fuel system and stock computer tune. You might have had some detonation or the piston hit the valve and got damaged or damaged the head. Did your shop tell you or warn you of any of this...??

Very confusing engine problem need help

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