Odd Misfire/Slip

[Nick388]

So I've been having an odd misfire-like symptom that seems to be getting worse over time and I can't seem to narrow it down. I have an 03 GT with just under 70,000 miles on it and I keep getting a hesitation/jump/misfire every time I seem to hit a small bit of uneven pavement while driving. As far as I can tell, it's not the clutch because my RPMs do not increase and my logic behind that is that if the clutch was slipping or missing, it would allow the RPMs to climb if I was on the gas, but they don't.

When I do get this miss, you feel it inside the car as if I just decided to floor it (although I don't get pushed back in my seat, but rather forward). Sometimes it just "cuts out" for a second, but you can hear that there's a break in the exhaust and other times it can be pretty violent and actually scare the crap out of me. If I just coast over a bump or something that I feel will cause a misfire with no acceleration, nothing happens, although whether or not this symptom would actually happen or not is obviously unknown, but I've tried multiple times.

This started happening after I read all the positive things about washing the engine and decided to give it a try for myself . However, the wash was a month ago and I only used shower mode on my hose (first and last time, I'm going to use my girlfriends toothbrush from now on) so I kind of feel like there shouldn't be any left over water. At that time I received a code for a misfire on a certain cylinder and it was picked up by the computer as a misfire (the CEL blinked and I was running on four cylinders). I found and pulled a dead coil, got a replacement (and even replaced another one I thought could be on its way out) and that fixed the code and got it running back on all 8. Checked the well for water, didn't see any, but stuck a rag down there anyways for any sort of wetness and even replaced the spark plug on that cylinder ($2 insurance, right?). All seemed fine for about a day and then these random misses started. I do not get any codes and I can't find any sort of issues going on. I haven't pulled all the plugs to check them, but I have pulled most of the coils. I've just been a little busy and I hate driving the car this way, but I have to get to work and back. I'm probably going to dive into it again tonight and wanted to know if anyone had suggestions on where to start with this.

Edit: I did not wash the engine hot. It sat overnight and I washed in the following day stone cold. I also let it sit for a few hours after the wash (I cleaned up and dried it off, obviously, just didn't immediately start it). I used Simple Green as well.

 

[trinity_gt]

This started happening after I read all the positive things about washing the engine and decided to give it a try for myself . ...

Yeah...I've never heard good things about washing engines. It almost invariably winds up causing electrical headaches...

...I'm probably going to dive into it again tonight and wanted to know if anyone had suggestions on where to start with this.

Since the problem seems to be related to bumps in the road I'd suggest taking a careful look at a mechanical issue in an electrical connection somewhere. For example, check your battery terminals. Remove the terminals from the battery and check the ends for looseness on the cables. Check the chassis grounds. Check for loose or improperly seated fuses in the fuse panels. Check your underhood connections to make sure all electrical connectors in the harness are seated and "clicked."

Check the wiring around the EGR valve vacuum solenoids and around the back of the engine near the firewall as far as you can. Look for signs of abrasion and wear-through. You may find insulation has been worn through and a bump is enough to cause a momentary short.

You may also want to crawl under the car (use jack stands...) to verify that the O2 sensor wiring has not been crushed or burned-thru.

 

[Nick388]

Yeah...I've never heard good things about washing engines. It almost invariably winds up causing electrical headaches...

Lesson learned, trust me

Okay, just a couple questions as this is a bit new to me. The "EGR valve vacuum solenoids" you mentioned, is that the UFO-looking device above the drivers side fuel line that has the one connector going into the roof of it? Since you mentioned that (and the part about the fuses), it made me remember something that I forgot to mention. I had blew a fuse out twice under the dash that was for Engines Controls (forget exactly which one it was, but I know it was for one of the Engine Controls, I think it was the F2.8). Also, I had unplugged with the device I mentioned above twice as well while checking for water, could I have blown the fuses simply by unplugging it with the battery connected or do you think that moisture may have gotten in?

Very good advice though, I didn't think too much about checking for shorts, but that does make sense. While I'm at it, I'll double check all the coils to ensure that they clicked and are not loose. I did have the battery unhooked for something around the same time, so it could very well be there... Man I'd feel like an *** if that was it .

Thanks!

 

[Maxpowers]

Most common issue after washing the motor is getting water in the spark plug wells and ruining the COP's. I would tell you to start there, however it only happening over a bump does not work out with that logic.

As trinity stated above, it is most likely an electrical problem. Do yourself a favor and don't wash the motor anymore.

 

[Nick388]

... getting water in the spark plug wells and ruining the COP's. I would tell you to start there, however it only happening over a bump does not work out with that logic.

Right, which is exactly what I was thinking. Although I had also thought maybe there's still just a tiny bit of water down there and bumps/rough pavement cause it to splash up and cause it to kind of "intercept" the spark. I'm not sure, but I'll definitely start with the easier stuff and inspect all my grounds and cables.

 

[trinity_gt]

Okay, just a couple questions as this is a bit new to me. The "EGR valve vacuum solenoids" you mentioned, is that the UFO-looking device above the drivers side fuel line that has the one connector going into the roof of it?

That's the EGR valve itself. The solenoids I mention are located back towards the firewall a the back of the intake manifold.

I mention this because a while ago Bullitt Mustangs suffered a problem not unlike what you describe:

"Some 2001 Mustang Bullitt may exhibit a hesitation or stumble over bumps condition.

This condition may be followed by the theft light flashing for a period of time, and diagnostic trouble codes (dtc's) C1284, U1147, U1262 may also be present. When diagnosing you may find no communication with the PCM. This condition may be caused by the DPFE wiring chaffing against the DPFE bracket shorting out VREF. Repair the wiring and re-route the DPFE wiring to run over the accelerator cable to prevent this condition from reoccurring. "

The top-most reference here:

TSB's and Special Messages

I know yours isn't a Bullitt but it may be a similar problem.

Since you mentioned that (and the part about the fuses), it made me remember something that I forgot to mention. I had blew a fuse out twice under the dash that was for Engines Controls (forget exactly which one it was, but I know it was for one of the Engine Controls, I think it was the F2.8). Also, I had unplugged with the device I mentioned above twice as well while checking for water, could I have blown the fuses simply by unplugging it with the battery connected or do you think that moisture may have gotten in?

F2.8 may blow if there's a short in the O2 sensor heater circuit and such a short may be momentary if it makes contact only during bumps etc.

 

[Nick388]

That's the EGR valve itself. The solenoids I mention are located back towards the firewall a the back of the intake manifold.

Okay, I will 100% look for that.

Also, as mine is not a Bullitt, it is a Steeda, so I'm not too sure if it along the same type of issue or not; but to be 100% truthful, I did get a theft light blinking on one occasion when it did what I described above back to back three times pretty violently. I didn't read the blinking though (someone mentioned to me that it blinks out a pattern that's like a code you can read/look-up or something along that line). I am unfamiliar with the wiring mentioned though, could you guide me in the right direction to check that as well? Sorry for the questions, but I am pretty unfamiliar with the electrical stuff.

 

[Nick388]

Okay, so here's an update.

I took a look at the wiring and everything for a good half an hour and can't find any discrepancies there. I found the EGR Solenoid you mentioned and the DPFE sensors (thanks Autozone for the pictures!) and their respective wiring but it all looks perfectly fine. Disconnected them, looked in and no sort of corrosion, condensation, or reasons for concern. Put them back on to a "click" and moved on. Battery had a bit of corrosion on the positive terminal and thanks to the plastic cover, it hid it from me. Took off the cable and took a rag to it and the connector on the battery. After that, I figured I'd check the new coils for giggles and they looked pretty much fine for being a couple weeks old. Little white/yellow mark on one of them, but it was on the rubber part the hangs outside of the well, so probably just some pollen mix. However, when I was taking off the second coil off, it "popped" off a bit and literally made a hallow pop sound. I haven't had that happen before and definitely thought that was worth mentioning. The new coil again, appeared fine and I figured I'd take the rubber boot off to inspect the coil, but when I did, the metal coil just came right off with it and I can't see how it winds back on, so I put one of the old coils back in (one of the replaced coils was still good, just looked like it was on it's way out). Started the car up and took it for a spin, but not even 2 minutes down the road, guess what happened? Yup, it did the hesitate/stutter. I won't have time to get underneath the car tonight to check the o2 sensor wiring, but I should have time this weekend.

Any other recommendations or suggestions?

Edit: I had the idea of getting a squirt bottle and misting some water over the engine to check for any sparking. Any input before I fry something?

 

[trinity_gt]

...Started the car up and took it for a spin, but not even 2 minutes down the road, guess what happened? Yup, it did the hesitate/stutter. ...

Was the stuttering/missing related to hitting a bumpy section of pavement again?

 

[Nick388]

Tbh, I just moved to California, so I'm still familiarizing myself with where I live; however, it did NOT seem like it was that much of a bump. The amount of hesitation I got was greater than I should have gotten. Also, just to make sure I'm clear and explaining as much as I can, it's not every single bump that makes this happen. I drive up the freeway everyday and there are certain places I "expect" it to happen, like a pattern, but it doesn't always happen. Sometimes I can hit a pretty bad section of road and nothing happen while other times it's like hitting a dog turd and I'm caught completely off guard. I truly cannot figure this out

 

[Maxpowers]

Tbh, I just moved to California, so I'm still familiarizing myself with where I live; however, it did NOT seem like it was that much of a bump. The amount of hesitation I got was greater than I should have gotten. Also, just to make sure I'm clear and explaining as much as I can, it's not every single bump that makes this happen. I drive up the freeway everyday and there are certain places I "expect" it to happen, like a pattern, but it doesn't always happen. Sometimes I can hit a pretty bad section of road and nothing happen while other times it's like hitting a dog turd and I'm caught completely off guard. I truly cannot figure this out

Are you 100% sure it has nothing to do with time?

AKA: The car gets warm about the same point on the same road on your way to work, and then starts to act up?

 

[Nick388]

Are you 100% sure it has nothing to do with time?

AKA: The car gets warm about the same point on the same road on your way to work, and then starts to act up?

I have no idea to be honest. I haven't ruled anything out, so it could very well be timing, although I do not know the symptoms -- I'm assuming I have some of them though.

I don't notice a particular spot where it acts up. Although, in the morning when I leave for work, it doesn't tend to act up until I get on the freeway (10 minute drive to get to the freeway). I can't remember it acting up before then. Kind of the same when I leave work, although maybe not as long (it's also a lot warmer at 4:00pm than 6:00am here in SoCal).

 

[Nick388]

Okay, so I have another update for you guys today that may help out (or may not ).

So I was on my way to work today and the hesitation happened twice back-to-back, wasn't too bad (4 out of 10 from what I have experienced) but the Theft light came on and I recorded the blinking of it. Now I doubt you guys need or want to watch a 2 minute video of a light blinking, but when it first came on it was just a constant blink, then gave me one slow blink followed by six slow ones (total of seven blinks before this pattern restarted). So I'm like okay, whatev, I'll look into at work but further down the freeway, about 15 minutes from work it happens again (and a couple times before then, but nothing notable) but this time, the speedometer went from ~70mph to ~35mph and back up. It was very quick and I did not notice if any other needles did it as I was making a lane change. This is the first time I've noticed this happening, so now I'm definitely leaning towards something electrical, I just don't know what. The car has yet to stall or cut off, but simply "jumps/giddy ups/hesitates, almost as if it was joking or playing with me (if only cars had a sense of humor, am I right?).

Any additional insight would be GREATLY appreciated, you guys have been a big help so far in what to check for. I'm going to, yet again, dive into when I get home from work and hope I can find something. Regarding the TSB that was mentioned, how do I go about checking for that? I found the DPFE sensor, but am not sure what wiring they're talking about and exactly how to change it if I need to. I had the idea about going home tonight, starting the car, and trying to shake it as much as I can to reproduce a "bump" to see if I can do it while it idles.

Thanks guys!

 

[04GTMustang]

Yeah...I've never heard good things about washing engines. It almost invariably winds up causing electrical headaches...



Since the problem seems to be related to bumps in the road I'd suggest taking a careful look at a mechanical issue in an electrical connection somewhere. For example, check your battery terminals. Remove the terminals from the battery and check the ends for looseness on the cables. Check the chassis grounds. Check for loose or improperly seated fuses in the fuse panels. Check your underhood connections to make sure all electrical connectors in the harness are seated and "clicked."

Check the wiring around the EGR valve vacuum solenoids and around the back of the engine near the firewall as far as you can. Look for signs of abrasion and wear-through. You may find insulation has been worn through and a bump is enough to cause a momentary short.

You may also want to crawl under the car (use jack stands...) to verify that the O2 sensor wiring has not been crushed or burned-thru.

I found that one of my connectors for my fuel injectors was bad on my stang and it was very lose to where i could just give it a slight tug and it would pop off. it didnt lock on like it is supposed to with the tabs on it. so maybe even check that. could be jiggling around when you go over a bump and causing misfire.

 

[trinity_gt]

I wonder if you've got a PATS pickup coil issue of some sort. You might try wiggling and "rapping" the steering column in the area of the key with it running to see if jarring it can generate a problem.

Problem is the needle behavior still suggests a power or ground issue somewhere...

 

[Maxpowers]

You might try wiggling and "rapping" the steering column in the area of the key with it running to see if jarring it can generate a problem.

I second that. Start the car, and attempt to create the problem sitting in your driveway with a friend.

 

[Nick388]

Okay, I tried banging all over the column while driving and sitting still and I could get anything. The column is quite sturdy and I'm sure I did more damage to my knuckles and fingertips, haha.

I keep referring back to the TSB you mentioned and looked more closely at it today. Mine is situated differently (probably due to the issue mentioned within the TSB) and there is no actual way for the wire to rub or chaff on anything. Although the problem seems similar, I traced the wires back and attempted to see if they were pinched by the tubes coming out of my CAI or any of the throttle stuff there. I cleaned there recently (around the time of the wash) and I noticed there were "imprints" of the wire that runs to the EGR valve and solenoid on a soft part of one of the tubes that goes to the passenger side valve cover, but the wire wasn't ran that way anymore, so I thought maybe I had it pinched or circuiting on something it wasn't supposed to be next to. I took it for a drive and it took about 10 minutes, so I'm not sure if I'm "making progress" with this or if it was sheer luck (again, this hesitations seems absolutely random).

This may be off-topic and unrelated, but my transmission has been howling (almost like a screech) in 3rd, 4th and 5th that changes pitch with speed and whether or not I'm on the gas, so I'm not sure if it just may be the transmission giving out by any chance? You can hear it coming from the shifter and out the window if your next to something that sound can bounce off of (larger car, cement wall, etc). I thought maybe the transmission could be loose or certain internals could be bouncing around causing this. I do notice that on the more "violent" hesitations, I can hear a sound that sounds similar to engaging the clutch. But again, RPMs don't see to move (or at least not much that I have noticed).

Edit: Found a strange wire that was cut under the dash and apparently soldered to another wire that has a different wire (unrelated to it) running over/across it. I'll see if I can get a picture after I finish eating and see what you guys think. I don't know too much about the connectors, so I can't tell you what it is, but I'll get some good pictures so you know exactly where it is.

 

[Nick388]

Wire 1
Wire 2
Wire 3
Wire 4

Okay, there are the images. I couldn't figure out how to resize the images, so I just linked to them. Yes, I know my fusebox cover is off, I was checking fuses too. The black wire running to the 30A fuse is just for my radar detector when I use it, it's been hooked up for years, so I know that's not it .

I know the pictures aren't the best but I'm sure you get the idea of where it's located. The brown/copper color is the exposed wiring of one wire, then there's an exposed silver wire and solder connecting the two. I wanted to short them on something just to check, but for obvious reasons I don't want to go grounding random wires. I can't find too much else for concern under the dash, but I'm going to head back out in a few minutes to see what I can find.

 

[Nick388]

Okay, so I have another update, but you're not going to expect this one, lol..

So I took the pictures of that wire and moved them slightly away from everything else. They've been that way for years (I assume, since I haven't done anything down there, especially soldering). So I decide, "Meh, lets take another look under the hood" so I do that. I remember finding a small, rubber square piece a few days ago while attempting to fix this problem. Right around cylinder 7-8 on the upper intake manifold. I thought nothing of it, actually put it on the battery, just figured it would blow away and wasn't any reason for concern. I still notice it's sitting on the battery, so I'm looking around at my connectors, making sure they're in and everything when I look in one and make the realization that's it's supposed to be inside one of the connectors. Thinking back to the TSB you posted above, I went for the DPFE and saw the EGR Solenoid connector, so I unplug it and guess what? It fits and there's no rubber in there (also, keep in mind, I found it basically right below this plug). I'm not sure if you can put it in backwards (there are a few ribs) but the hesitation cut down a lot and is only VERY little still there over some pretty serious bumps (drove around for a good 20 minutes).

Do you think this would work itself out? Does this even make sense in terms of fixing the ground/power issue? Should I clean the connector with some sort of solvent/solution? If I could get this 100% gone I would be MOST pleased!

 

[Nick388]

I officially have no idea. At this point, I'm willing to accept any guesses anyone might have. I wouldn't mind throwing money at a part, but I don't even know where to begin.

I cleaned every connector I could think of with no luck. Reinserted the rubber piece into the EGR Solenoid, but didn't make a difference. I feel like it may have been better last night because of how cool the nights are. It seems to do it more when the car is warm and it's warm outside, but I could be completely wrong.

Any ideas or suggestions? At this point, there are no wrong answers, lol.