Hey guys...suppose I'm in 3rd or higher gear and the RPMs are under 3,000......when I attempt to accelerate the car seems to buck pretty violently.......almost like the fuel shuts off or half the cylinders don't fire. Once it gets around 3k this stops. I check my secondaries, they're working just fine.
I'm not getting a check engine light unless I do this on purpose for an extended period of time.
I have new spark plugs, FMS wires that are 1 year old, a 1 year old coil pack, all new underhood wiring <1 year old, new Delta Pressure switch............
Any ideas??? The car seems to run fine in the upper rev range.
Originally posted by Art Hazebrook:
Fuel filter?
This is where I would start. Also 
the cheapest.
I've replaced that already.........oh...I forgot to mention that I have 163,000 miles!!!
Possible a loose or broken mount, maybe engine or tranny, somewhere along the line.
Nope....I replaced those as well. The issue is related directly to the rpms and cylinders not firing or fuel delivery or a combination of the two. Above 3k the engine is perfectly fine. It's when I'm at low speed in a high gear.....high load on engine.
Originally posted by MystiqueSVT:
I've replaced that already.........oh...I forgot to mention that I have 163,000 miles!!!
When did you replace it??? Needs to be replaced at the minimum every 30k...
I replaced the fuel filter approxiamately 10 months ago. Once again, if it were the fuel filter I'd think that it would affect fuel delivery more at high rpms as opposed to low rpms.
How do you know if the fuel pump is going? What about the charcoal filter that resides under the spare tire well.
Do you have the TH fix? My car bucked when I had a really small hole in the TH fix. Opened up the hole and the bucking was gone.
Are your injectors clean? That could cause them to not deliver fuel proporly at low RPM.
I used some good fuel injector cleaner and it hasn't gotten any better. I haven't touched a thing in relation to the TH fix. I have the BAT pipe with the aluminum flex tube. It's been on there for a year.
WHat kind of fuel injector cleaner are we talking about?
If its the kind you dump in the tank, that won't cut it. You need the pressurized stuff that you hook up a tool to the fuel rail with. That's what hte pros use...
When it gets dark out go lift your hood and look at your spark plug wires with the car on. If you see big blue archs then you need to replace the wires. If they're new, a little bit of water or a small scuff of anything could damage the wires.
Originally posted by J-Lab:
WHat kind of fuel injector cleaner are we talking about?
If its the kind you dump in the tank, that won't cut it. You need the pressurized stuff that you hook up a tool to the fuel rail with. That's what hte pros use...
Jeff...dude...wusup!!!!
The pressurized stuff...eh? Where do I get it?
What I don't understand is why the car runs poorly under 3k but shows no noticeable loss in performance about 3k. Wouldn't some sort of fuel delivery or spark problem be multiplied when the revs climb higher?
This is what I don't get. When I creep up on the revs under 3k...I'm fine...but if I push it just a little...it will buck. I wonder if the Sho high flow cat is busting it's ceramics? I already had to remove the smaller honeycomb in the rear of the cat....I wonder if the front one...the main one is now the problem. Maybe at higher speeds the pressure keeps it straight...but at lower velocities the sudden pressure change causes it to tilt.
Hmmm............
Originally posted by MystiqueSVT:
I'm not getting a check engine light unless I do this on purpose for an extended period of time.
So then what code do you get ???
What do you mean by Delta Pressure switch ???
Pressurized fuel system cleaning is a service. You don't want to buy the machine.
Things to try:
Check plug gap.
Reset PCM.
Clean the MAF.
Check for vacuum leaks. Check the PCV valve and hoses carefully.
Make sure the secondaries work properly, or just unhook them and tie them closed for test purposes.
Unhook and plug the vacuum hose to the EGR valve for test purposes.
Test the TPS with a meter or get a new one.
Put a fuel pressure guage on it where you can see it while you drive around.
Hey! Long time no speak, Ryan! How have you been?(besides the obvious promlem, lol)
I've seen several cases where a car misfires at low RPMs but revs o.k. at higher rpms...hey, any chance you have oil or water contamination in your spark plug hole passages? I've seen valve cover gaskets seep oil there and it accumulates at the plug boots and can cause a misfire. Have a look.
I've been doing well Jeff. By the way..did you see the SZ02 video...you and I are on there chanting "We're number 5!"
Thanks for the suggestions guys. I have to go repair an exhaust leak now (ok, the SVT exhaust separated from the SHO y-pipe).
I'll check some of these areas while I'm out there...thanks!
Money is on plugs and wires. I've been through 3 sets of wires in 130k.
Have you tried checking your vaccum lines or checked to see if there was any build up around the TB area? When the bucking occurs, do the RPMs change on the tach?
Does it buck with car in neutral? If it does, then grab a bottle of carb cleaner, rev it like you mentioned and spray the carb cleaner around the hoses and around the seals of the UIM.
If it does not do it while in neutral, then maybe we are talking more along the lines of a possible clutch or contact surface issue.
Just trying to throw around some ideas that might not have been mentioned before.
Originally posted by eagle98:
What's the TH fix???
Throttle Hang fix. Normally, when you push the clutch in to shift, the RPM's hang or slightly inscrease. The fix allows the RPM's to drop, like a normal car.
hey man your not the only one that has the problem, my car does the same exact thing, i changed sparkplugs, wires, coil. cats, precats. and i still have the problem, i have no idea as to what it can be but its a major pain in the ass, the car is almost undrive able in low rpms, because it bucks so much, and some times its relaly dangerous when it ry to pull out of places.
It looks like i get to join the club of bucking tours because mine started this yesterday and is realy sucks. I dunno what to do. I know that for a fact i need to change my mounts but i cant get the off
. And i dont see why all of a sudden it just started doing it and not shown signs before.
I had that same problem....... but mine was a fuel pump going bad...... when I was a 1/4 of a tank of less the car would hesitate at higher RPM's..... But no matter how much gas I had in the car the idle what jump by itself.... it would "hang" and then drop back to normal... I took out the fuel pump..." another bad design by FORD" and the screen for the pump on the bottom of the pump was sitting on the bottom of the gas tank.... I tried to put it back on it wouldn't go back on.... So, I bought a new pump and installed it and the hesitation went away... the throttle hang went away...
I figure the reason that the rpm's where reving up by themselves is that the computer was trying to compensate for the lack of fuel.... I took apart the pump and there was a lot of dirt and such in it... So, I guess the best way you can figure out your problem would be for you to get a fuel pressure check..... I don't see how jamming a copper pipe cap into a hose would fix the problem?????? I think it just masks the problem........ It may not be the fuel pump.... but maybe something else... anyway you loose power with that copper cap....