please help, engine skipping, running out of ideas.

Klockworc · Oct 6, 2009

I have a 2002 gt with about 80k on it. recently I sprung a coolant leak but had it taken care of. the culprit was a cracked intake manifold, which I had replaced, although before the repair, a decent amount of fluid got into some of the spark plug holes on the driver's side of the engine, before and after the repair, the engine has been having misses under load. it runs fine if you drive it lightly, but under hard acceleration, it skips and doesn't have as much power as it should, no pops or strange noises. the worse is driving in 5th, and giving a decent amount of gas, the car will shutter forward and back.

I had all the spark plugs switched out with new motorcrafts, and changed two of the COPS (coil packs) on cylinders 5 and 6.
fyi,

Rear
4 8
3 7
2 6
1 5
Front

Still the same skipping, could it be the injectors, fuel pump maybe? spark plug wires, (which I doubt)? please, anyone who might have experienced the same thing? any help is appreciated.

Twista · Oct 6, 2009

I had the same problem.......

changed my sparkplugs and my old stock wires and the problem went away/./

do your wires ..

tonytaylor85 · Oct 6, 2009

What prompted you to change the coil packs? Mine had identical symptoms when the intake cracked. I blew the coolant out with compressed air (spark plug still installed) and it ran fine. Are the boots wet? Are any of the springs (wires) rusty? Did you check all of the cylinders? It sounds like you still have some coolant somewhere.

Klockworc · Oct 6, 2009

I've been reading up on teh problem almost every night, a lot of people have been saying coil packs, and thats what my machanic said when I finally went back to him, obviously easier to do that one myself. Sadly, no result... when I changed the packs today there was still some coolant in all 4 cylinders on the driver's side, most in 5 and 6, so I swabbed those out, 7 and 8 had some but it seemed minimal, that and they're a bit harder to reach... how much fluid would it take to foul the plugs? I will clean them out again tomorrow, and perhaps look into new wires...

boots were a little moist,
none of the wires are rusty,
checked all the cylinders on the drivers side and #1 on passenger side (which was bone dry)
hope swabbing them out further gets me somewhere, thanks for the sugguestions so far!

wmburns · Oct 6, 2009

clean out the gunk

I bought a 97 with a leaky intake manifold. The prior owner allowed the leak to continue for a long while. What I found was the repeated wetting/drying cycles cause the dirt/dust to form almost concrete in the bottom of the spark plug hole. The sludge retained moisture which grounded out the spark plugs.

The sludge was hard to clean out. I used a combination of break clean and compressed air. Used an old feed tube from a spay bottle to direct the air all the way to the bottom of the hole.

It seams to me that untill the spark plugs holes are completely dry, you are spinning your wheels. Besides, when clean then the gunk can't fall back inside the combustion chamber when the plugs are ever removed.

Klockworc · Oct 6, 2009

thanx for the tips wmburns, I'll be doing some heavy cleaning tomorrow.

Klockworc · Oct 6, 2009

On a side note however, if spark plugs are being grounded or had bad wires, wouldn't the engine skip all the time instead of just under load?

tonytaylor85 · Oct 6, 2009

I haven't experienced any trouble with my ignition system other than the coolant leaking in so I can't say. Get em clean and let us know how it goes.

20th turbo · Oct 6, 2009

swap out the coilpacks, it sucks but you may have a few bad ones

GDawg · Oct 6, 2009

Geeze... is this the year of AC ripple or what? If your plugs are clean now and no grounding, is it possible that your alternator got sprayed too? Alternator AC ripple will cause this after all that. Have a skilled tech test your alternator for AC ripple. It's a simple test that none of the backyard techs seem to know about. Don't let them charge you a massive amount of money for the test either... it's a simple one minute test. PM me if you want to test it yourself.

rconaway · Oct 7, 2009

You could actually have a few problems. I'm It may take a while to work out your issues though. I"m assuming you checked your codes and eliminated what they are saying. If they don't have anything, then move on.

Don't assume the problem is with the electrical system. Start with the basic mechanical stuff and make sure you didn't damage the engine. Do a quick compression test. Make sure your cats aren't clogged either. I have seen both problems cause the symptoms you are discussing.

From there move over to electrical. Grab a meter and check all your plug cables and coils. I would also have them put it in a dyno and then monitor the plugs. That may be the only way to find out.

sneaky98gt · Oct 7, 2009

When my plastic intake bit the dust, a little bit, and I mean not much, water got into the 5 and 6 spark plug holes. And it was enough to make them not work anymore. I took the old plugs out, blew out the holes with compressed air, let it sit overnight just for good measure, and replaced all 8 plugs. Haven't had a problem since. I don't know how many miles your car has, but it's probably a good idea to change the plugs and wires anyway. I know mine needed em.

-Will

wmburns · Oct 7, 2009

Klockworc said:
On a side note however, if spark plugs are being grounded or had bad wires, wouldn't the engine skip all the time instead of just under load?

While I did not say it specifically, the gunk actually caused spark leakage which sometimes caused a misfire. The grounding was not absolute but the reduction of spark was enough to cause misfire and rough running (esp at higher RPM's).

What I was trying to point out was a way that apparently dry spark plugs holes could in fact harbor moisture thus causing weak spark. In my case, the motor ran fine once the COP boot/spark plug/hole were clean and dry.

However, it is possible that the boot has been damaged from the spark escaping out of the boot (damaged insulation). Visually inspect the boot of any suspected COP's looking for any signs of arching damage. Some silcone dielectric grease on the plug is not a bad idea either.

Another suggestion is to run the car at night with all of the lights out. See if you can see the blue spark escaping (this may not work for COP applications as the spark would not be visable deep inside the hole).

Bottom line is that for the home hobbyist, testing the high voltage side of a COP is not easily done. This leaves some of the old methods of swapping parts until the bad part can be isolated.

Klockworc · Oct 7, 2009

the boots on the rest of the COPs are fine.

Please note that the engine misses are anywhere on the RPM band but only occur under load its just a certain point on the throttle, thresh hold, that I pass when giving it gas does it start to knock around... I think it might be a fuel problem or exaust, something other than electrical. Wouldn't it skip all the time if it were the Cops, plugs, wires, etc?

GDawg · Oct 7, 2009

rconaway said:
You could actually have a few problems. I'm It may take a while to work out your issues though. I"m assuming you checked your codes and eliminated what they are saying. If they don't have anything, then move on.

Don't assume the problem is with the electrical system. Start with the basic mechanical stuff and make sure you didn't damage the engine. Do a quick compression test. Make sure your cats aren't clogged either. I have seen both problems cause the symptoms you are discussing.

From there move over to electrical. Grab a meter and check all your plug cables and coils. I would also have them put it in a dyno and then monitor the plugs. That may be the only way to find out.

Sorry to dis you brother but electrical tests should be done first. They cost nothing and bad electrical AC ripple will cause your computer to give false readings... meaning that mechanical parts may not work right...

Don't start switching out parts... that's stupid.

2002SN95MUSTANG · Oct 8, 2009

I have the same issues. I sprung a coolant leak. Fixed leak. Cleaned out spark plug tubes. reinstalled everything as normal. Cranked car up adn revved a bit just to make sure everything was still in order. Threw a P0316 code- Crankshaft Position sensor. I deleted code at shop where I work, and drove home. On the way home it seemed a little sluggish at WOT. It felt like it was surging as if it was running on 7 or even 6 cylinders and then the other 1 or 2 would kick back in. It drives fine in all gears and rpm ranges unless its at WOT. Any help appreciated!!!!!!!! I also noticed that I have an exhaust leak on drivers side where exhaust manifold connects to piping. Can a bad enough exhaust leak cause this problem?

2002SN95MUSTANG · Oct 10, 2009

some added info on the engine skipping situation

Through trial and error of having the same problem with my car I hooked it up to a scanner at work one day and did some testing. My check engine light was not on, but it had a code in there. It was something like a P0202 or something. It had to do with the fuel injector on cylinder 2 being bad or having a short or something of that nature. I checked out the wiring and connector and sure enough there was some moisture inside the connector. If you have recently washed out your engine bay from your coolant leak or even just from your coolant leak. I would HIGHLY recommend checking all of the connectors going to your fuel injectors. Maybe take some electrical connector cleaner and clean them. Hope this helps and I definitely hope this works for you and fixes your problem. It seems to have cleared up my issues.

usiskin99 · Oct 10, 2009

hey man, i had exactly the same problem. apparently the coolant or whatever got in my stuff busted some cops and i ended up replacing all of them and problem went away. how to know which ones are bad? ok. open hood and start your car. unplug and plug back cops one by one. if the cop is good, you will notice a slight engine decelaration. if its bad, nothing will happen. before i did that, i thought it was only 2 cops that were bad, but after doing that, i found 4 that were busted. give it a try. might help. good luck.

usiskin99 · Oct 10, 2009

hey gdawg, im having electrical issues... where can i get an electrical check (for nothing)?

Klockworc · Oct 10, 2009

UPDATE

I was testing wire by wire under the hood today, fuel injector and spark plug wires, to see if disconecting would result in any changes to find a faulty one.

I then discovered a colapsed vaccum hose that feeds FROM the passenger side engine bank INTO the block that the air intake is connected to (says 4.6) I think thats the throttle body? could be wrong on names, w/e. Does this make sense as to being the culprit for my loss of power? I'm obviously going to switch it as soon as I can get my hands on a new short piece of hose, but imput until then would be great, thanks guys.

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