Shunting in 4th & 5th gear at low RPMs

Rear end feels jerky in 4th & 5th gear at low RPMs

I changed out my gears to 4.10's the other week and I have not installed my speed cal yet. My car feels like it is missing out or shunting at 1500 -1800 RPS in 4th & 5th gears. I had someone describe a simular problem to me and they indicated that it may have be caused by the inacurate speedo signal and the ABS system. I pulled the ABS fuse for a test which resulted in no difference. I plan on installing the speedcal this weekend but I'm beginning to get a little paranoid that something else is going on. Has anyone else seen this after a gear change??

my car is 2003 GT
mods:
Borla Stingers
Magnaflow Stinger - replaced flows
FMS 4.10
B&K CAI - took off, back to stock
2003 cobra front end
Tri-axe shifter
DM Speed cal - still in the box

Anyone??
If I had titled this thread: Awesome Dyno!
I would have had more comments by now?? HAHA!

You are now officially by the Ford "hitching" plague!

This strange phenomenon has yet to be resolved... at least that I can find. It is weird how yours just started with a gear change though.

Try this: Disconnect your EGR hose going to the EGR valve, plug the vacuum end and see if this fixes the hitching drivability problem. You will eventually throw an SES code and the car will run slightly richer, but if the hitching problem goes away, you know that you are on the correct track. Because yours just started, you might have some hope. After diagnosing the problem, you can re-connect the EGR hose, disconnect the battery for a minute, reconnect it and the code will be gone.

I am still trying to figure out my own hitching problem. At this point it might even be a Kenne Bell problem. Ford has run every type of diagnostic possible and they came back clean. But they admit that there is a problem. Because I have a KB blower, they can not go any further. I have also replaced every EGR component, TB, IAC, MAF, DPFE, EGR Sensor, and performed a re-flash of the computer. A compression balance test was perfeormed and I and another mechanic independantly combed the car for exhaust and intake leaks. Every mechanic to work on the car has said that the chip from KB is the problem. KB has burned three chips so far. They are aware that I still have the problem and stated that they will work with me to resolve the issue. The part that is scary is the fact that neither I or any other mechanic can figure out for sure whose problem it "really" is. Ultimately I will probably have to get the car on a dyno and track it from there.

I have seen this problem posted on several boards and in each case there was never a resolution to the problem. The poster eventually "went away", never to be heard of again. I tried to contact those people to no avail. The problem is listed under several topics which include hitching, surging, missing, and bucking. My guess is that each person sold the car after giving up on the problem. There are several 03 GTs that posted with the problem, but there are some slightly older cars as well. One "key" common denominator may be the fact that all cars with this problem have "coil on plugs." I could be wrong about that, but most of these hitching issues have been with the newer Mustangs.

Good luck finding the problem. If you find the problem or give up on finding it, please post it here. It is very possible that your problem will be different since yours started with a gear change. My guess is that you had the probem right along and just noticed it because the gear ratio changed the rpm that you normally cruise at (during slower residential driving) and at that rpm the problem is more noticable. My problem becomes worse as the performance of my car goes up because (I think) the performance boost makes the car hitch more when it "recovers" from the miss.

I have also noted that mine hitches more at warmer temperatures. My guess for this is the fact that when the car is run in colder outdoor temperatures, it runs in open loop more. The EGR is not "supposed" to be active during open loop. However, I am not even convinced of that because I just fixed an EGR problem on my Chrysler Town and Country mini-van. On that car you can see the EGR pintle move in and out during throttle movement when it is first started at below freezing temperatures. That is how I diagnosed the EGR problem on that car; by pushing on the pintle at an idle. I sure wish my Mustang was that easy to fix.

I will also add that my Mustang pings a LOT more when it is colder outside. In other words, my pinging problem is inversely corelated with EGR hitching. Go figure.

I can not stress enough how bad a car can run with a bad EGR system. After I replaced the EGR valve on my Chrysler, it ran better than it has EVER run. It even shifts better. I almost traded the car in after trying unsuccesfully to get it fixed at the garage three times. I was fortunate to diagnose the problem myself and am VERY glad I kept the car. It now runs better than when it was new. I say this because I now know for a fact that a bad EGR system can wreck sever havoc. Because of this experience, I am guessing that either Ford or KB has not incorporated the EGR system well enough into the "total package."

These automotive computers are also STILL not sensitive enough to be able to tell us when a problem occurs. My minivan NEVER threw a code and that EGR was severely bad. And my Mustang is not throwing any codes as well. But I and the other mechanics know for a fact that there is a problem. Do not accept the common dealer comment "there is not a problem or there would be a code." Codes are only thrown for emmisssions and there has to be a "consistant" blatant problem for at least 40 miles SOLID before a code will be thrown. The computer does not throw codes for intermittant problems or non-emmision problems.

Let us know how you make out. It is very frustrating when people do not post how their problem ultimately got fixed. If I ever get mine fixed, I can assure everyone that I will post what the problem was, who found it, and who fixed it.

can one of you explain the problem more in depth? does the car buck when it is in a low RPM in a higher gear? if so, i have the same problem.

Thanks for the long post decribing the issue Red Dragon,

I did as you suggested: Disconnect your EGR hose going to the EGR valve, plug the vacuum end and see if this fixes the hitching drivability problem.

With the vacuum line disconnect the hitching sensation is gone. I'm going to drive it some more tomorrow with the line disconnected to completely verify that it is gone. I will take my car in to the Ford Dealership Friday to see if they will replace it?

Thanks again! By the way I'm envious about the KB SC and hope you get your problems resolved. Good luck!

For 1997 GT4.6,
The hitching sensation is described as the sensation of pulling a trailer hitched to your car. The rear end will feel like it is randomly surging or pulsing. This sensation felt more noticable to me at lower RPMS (1500-1950) while driving in 4th or 5th gear.

Ya know, I had this same problem but thought that it was normal. I guess not.

Bump.

Any news from your mechanic about the problem? Every time somebody posts about this problem, they never return. They go into the EGR hitching blackhole.

Went last Friday. They replace the EGR and the down stream controller (?? the one with the vacuum lines on it) and cleaned the fuel injectors. They also tried to tell me I really shouldn't be driving my car between 1500 - 2000 RPM's in 5th gear. to which i replied you got to be kidding me! They told me it was fixed and I went on my mary little way, with the same hitching problem needless to say! SOB's! I called the service gut back and he replies that we fixed it you probaby just feel it be cause you know where the EGR is opening and closing and that he would talk to the engineer (like they had a engineer ????? - get real) . I love nothing better than a shop monkey telling me that I dreaming this up. The hole event felt like they were trying to avoid this particular problem by planting ficticious resolutions for me to not reach this troubled RPM range for the EGR operation. I will have to take it back again next week when I get my next Friday off. Nothing like driving all the way across town to a mod friendly shop and waisting your day. I just put my CAI back on and cleaned the MAF meter this evening and had no results from that either. I haven't forgot about posting a fix when and if it happens.

I knew it! I really didn't think you would get it fixed. Ford is clueless. My guess is that the mechanics know about the problem and are trying to put you off and hope that you do not return. They do not like real problems because they do not make any money trying to fix them. I will also venture to guess that they have seen the3 problem before, could not fix it then, and will still not be able to figure it out when you return. But you must return! It is the only way we are going to figure this thing out. In the end, we may need to start a sticky for this problem so it can garner some attention. I am serious when I say that people withthis problem disappeat. It is the craziest thing!

That mechanic telling you to not drive at those RPMS! You better find a better mechanic because this Bozo sucks! And then to say that it is all in your head! Sounds like when my wife kept getting sick with a pain in her lower back. A Urologist said that she had a mental problem and prescribed Valum. A general practitioner later found a huge kindney stone. Don't let them convince you that you are nuts buddy. I have a feeling that we may have to gather round to do a survey to get any kind of action on this problem. I will probably start something in a few weeks to start it off. Good luck and keep at it until there is a fix.

In the mean-time, I would appreciate it if everyone would go out in their Mustangs, drive the car until at operating temp, find a long straight smooth road, and try to hold a constant speed somewhere in the40 - 50 MPH range in 5th gear. Pay close attention to how smooth the ride is. If you feel a slight jerking or hitching, then you have the problem. Sometimes the hitching feels just like a slight bump (or crack) in the road. If you experience this problem, then disconnect and plug the EGR hose from the EGR valve and try it again. If it feels smoother, then you are by the Ford Hitching plague. Several year Mustangs have it (I think only with Coil-on-plugs), but the 2003 cars seems most vulnerable. Let us know how you all make out. If the response is good, I will start a sticky to really get down on it.

I can drive mine @ 50 in 5th, but no less or it is really jerky. But it's always been that way & I don't think much of it; I usually just drive in 4th if I'm going less than 50. Most of the time I'm beating her anyway so she's in 2nd or 3rd @ 50.

When I go back to the shop I'm requesting that the hook up their computer and ride in the car. Hopefully they can better diagnose the problem while the car is operating in the troubled speeds and RPM's . We will see???

did you replace the screen when you put the stock air tube back on? along with idle issues, I had this problem with a BBK CAI and no screen. I also have a T/A. when I installed the screen, the problem went away. Maybe just lucky. You may also clean the MAF sensor.

I have this same problem. The slight hesitation when cruising in 5th at 45-50 mph....

I just ignore it... lol

Thinking back to when this started on mine. I changed several things at once an started having the problem. I cut the post from inside my MAF, installed CAI without screen and installed TA set to 15 deg. If I set the timing back to stock it didn't do it as bad. When I replace the screen( I cut a piece from scrap left over from porch project, It has larger holes than stock screen) the problem went away. I moved the timing back to 15 and no problem.

This is what I did and is for information only. There may be information out of this that may help or not.

I did take off my CAI kit and reinstalled the stock intake screen and all. I also cleaned the MAF with contact cleaner (non corrosive). No changes with going back to stock.

My last mod was 4.10's (500 miles ago) and a speed call after the problem started

When you remove the vacuum line to the EGR the car runs much smother with a slight hestiation at 2000 RPM's in 4th & 5th Gear.
The EGR was replaced and it still is hitching.

i think it runs smoother due to the rich condition, and i honestly doubt that the problem started with the gears, just doesnt make sense, but i think i may have the problem in my 96, ive noticed a slight bumping in 5th gear before, but now that i know its a problem ill pay attention to it and see what comes up

I already had 4.10s and speed cal. maybe it's because I have 31 spline axles and diff.

i just started getting this hitching problem immediately following the install of my C&L truflow inlet pipe, Accufab 75mm T.B. & C&L plenum. i had densecharger in but broke a couple of hours after install so went to stock box & stock paper filter. i will have the densecharger back in a few days.
it feels like car is just cutting out or like your slightly blipping throttle my kids even noticed it & thought i was doing it on purpose.......so i put the car on cruise & it still did it.

Having a similar problem for a few months now and had the exact same results taking it to my local Ford dealership - we even hooked a diagnostic machine up and took it for a ride looking for SOMETHING to show... nada... EXCEPT lately I've noticed it (cannot feel it but can hear it with the loud exhaust) is present anywheres under ~2300, only under light throttle or while cruising.

Hey, I've noticed this , too ! Generally, on one of the routes I take where there is a long stretch of road with no lights and a 35 mph limit (there's cops lurking, it's along the beach) , so I do 40 mph in 4th gear. I just think the engine is "lugging"(sort of like taking off from a stop in 3rd). The "hitching" goes away if I drop it down one gear ratio.