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Discussion Starter #1
Ive replaced plugs,wires,cap,and rotor. Now Im thinking maybe 2 bad injectors? What else should I look for? Thanks
 

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Discussion Starter #2
Sorry, meant for this to be in 5.0 engine tech room. Any help or suggestions here though?
 

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Discussion Starter #6
The rest of the plugs look good, even brownish tint. I'll check for a vacuum leak, and try the 10 pin connector fix. I appreciate the ideas and will let you know what I come up with. I have posted a more in depth post on the subject in the 5.0 forum. I replaced the 2 injectors today and still have a studder around 1500-2000 at part throttle. If my timing is at 10 degrees the studder seems to go away put I havent heard any pinging. Thanks
 

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What do the lean plugs look like? Could you please elaborate on your idea of lean plugs; if you want help?....James
 

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Discussion Starter #8
the grounding strap( i guess thats what its called) was completly white from end to end, one plug had specks of metal on it. The other 6 looked almost new in color.
 

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It is not uncommon for several cylinders to be leaner than the rest due to the airflow characteristics of the intake and/or head.
Which plugs were lean/detonated? were they adjacent to one another? The other plugs porceline, were they tanish or white.
What is your combination, fuel injectors and fuel pressure?
James
 

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Is the car losing antifreeze? I have never seen a white ground strap before. Should be the normal metal color if running lean; no black carbon on the base ring either. White makes me think it is burning antifreeze.....James
 

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Discussion Starter #11
Im not losing antifreeze, at least that I know of. I'll check the level tomorrow and see where its at. I havent checked because its been running at 180(with 180 degree T-Stat)
Porceline was white on all of them. The number 3 plug,third one back on passenger side was the really lean one,number4,at firewall on pass. side was the one with metal flakes on it.
Ive tried timing everwhere from 8-20 with the only change is the part throttle studder gets worse as I increase timing. Fuel pressure has been around 45psi and Ive tried between 35-55 but it pauses on acceleration on with 35 and bogs at 55. 19 Lb injectors. Fresh engine,bored .030,Je pistons, crank turned 10-10,stock rods all rotating assembly has been balanced. Stock E7s ported and polished,milled .050, 3 angle valve job,new stock springs. Stock cam with 1.7 roller rockers. Im using 75mm bullitt and 70mm TB and stock intake. Thanks for your help
 

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I can only think of lack of heat transfer/exhaust release in that cyl.

could it be a collapsed lifter on the exhaust valve?
 

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My car seems to have the same problem. I pulled all the plugs and #3 and #6 looked rich. My fuel pressure right know is 41psi with vacuum off and plugged. I tried less pressure and the car pull strong but when I pulled the plugs they had specs that look like white flakes.My timing is set at 14* and I've been tempted to try more but this stumble between 1,000 and 2,000rpm's is pissing me off!! Any other ideas? cb93Lx and I will greatly appreciate your help.
 

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The porceline is used to look for detonation. The base ring is what you look at for rich or lean condition (a/f ratio). The ground strap shows timing. There should be a change of color on the strap and should generally be at the area where the strap bends. If the change of color is closer to the base ring, too much timing. (one may need to change the heat range of the plug if changing the timing has little effect on the change of color on the strap) If the change of color is closer to the end of the strap, too little timing.
The base ring of the plug should have a slight greyish/black color approximately 3/4 -7/8 around the base ring. If it is black sooty irregardless of the porceline being completely white, you are running too rich. Too lean would be no change of color to the base ring (normal blue/black metallic color)
Certain things can make an engine detonate: fuel contaminated with oil. Sharp edges on the piston/combustion chamber, too much timing, not enough fuel, wrong heat range for the spark plugs.
If the rest of the plugs were close to lean, I'd say you need more fuel; but I'm not reading your plugs. You have to shut the motor down immediately after a full throttle pass to read the plugs correctly. Are your timing marks accurate on the harmonic balancer? Do a compression check and tell me what you get.....James
 

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My cap and rotor is a new accel unit. I don't know about the plug wire since I bought the car with them and they look new. I know looks can be deceiving so I will check them. Thanks
 

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Discussion Starter #17
New cap and rotor. Tried new wires and just changed the plugs to autolite 24s and they still show the same symptoms.
 

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Discussion Starter #18
#1 150 #5 140
#2 150 #6 145
#3 150 #7 140
#4 140 #8 140

I also checked for a vacuum leak and found nothing. I bumped the timing to get the highest vacuum reading I could get and sprayed starting fluid in the area and checked all vacuum lines. Highest vacuum reading I could get was 16psi. That sound low?

With my plugs out and right here in front of me, all of the base rings are black all the way around. All the grounding straps are a tan color with no color change at all(on these autolite 24s and on the old motorcraft stock heat range plugs) All the porceline are very bright white except for number 5 and 4 which are a very light tan. The metal tip on top of the porceline has a tan bottom which fades into regular metal color.
 

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Discussion Starter #20
Yes I checked them after a W.O.T run. They dont look anything like any of those pics.

Checked firing order a few times and its correct. I mean I still drive the car and it feels strong. Only thing is the studdering at part throttle and those 2 plugs. thanks
 
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