jumpy rpms

I have recently changed the transmission in my 1996 mark 8. I drive the car hard on occation, and when i do it sputters at high rpm... when the engine gets above 4000 rpms :while the gas pedal is down: it seems to loose and gain torque until it shifts. The car at say half throttle will accelerate and get to speed faster than if it were full throttle.... I was thinking the fuel filter, but we have already changed that...say 7000 miles ago. then i thought of the torque converter...hoefully i have explained this better than i think i have...if anyone has any thoeries they would be greatly appreciated...

Fuel filter won't cause a "sputter" like you're describing. Sounds to me like you have a bad spark plug wire. As you increase the load, the wire can't supply the demand for spark and it can't jump the "break" in the wire.

First off....you have a 96 so even though you probably DON'T have a check engine light on, you need to get your car "scanned" for codes. Most likely you'll have a "p0300 random misfire" code or a "misfire on cylinder number *" code and it'll point you in the right direction.

If you don't want to go the easy route(may cost 40 bucks to get the codes at an independant shop), than you can go the more expensive route and start throwing parts at it.

When was the last time you did a tune up, for example, spark plugs, spark plug wires, PCV valve, air/fuel filters.....stuff like that? If you want to just throw some parts at it, I recommend buying some BELDEN brand wires at Napa/Reibes and get some AutoLite 764 spark plugs and start there. Most likely this will cure your problem, but once again, this is the internet and we're all "guessing" from experience because we can't actually drive your car for you.

changed the plugs about 12000 miles ago. havent
changed the wires yet. I had it scanned and the only codes that came up was...lean bank 2, rev limit reached...the check engine light does come on about 50 miles after being reset. Would bad gas be an issue? i will change the plug wires tonight and see if that does anything. I have heard rumors of the 'throttle body plate' that spans the lower intake clogging up. Cant remember the name of it but could that be disrupting the air flow?...Oh and the car is 100% stock, no modifications.

You also might try putting a can of Seafoam thru it. It'll clean up the whole throttle body and insides. DO NOT put it in the oil.

You're only running lean on one bank, which pretty much rules out fuel issues, unless you have a couple three bad injectors. Highly unlikely though.

I don't think it's a matter of bad gas, since again, you're only leaning out one bank of the motor.

If you're talking about the IMRC (Individual Manifold runner Controller(s)), no opening, I would think you'd get a rich code, because at those higher rpm's the computer will inject more fuel, expecting more air. Reach your hand behind the heads and find the IMRC cams. Try to move each cam by hand, and see if it's relatively easy to move.

If you have Original wires on the car, I'd go with what's been suggested before. Try replacing the wires and change the plugs while you're at it.

Either way, it sounds like you're getting too much air, and not enough fuel...

Maybe the fuel pump is on its last leg?

Clean the MAF.

mikegadde425 said:

lean bank 2

Click to expand...

This is good info......I had one of my Nology wires fail on me with almost the same symptoms(mine did it at about 20% load vs. your higher WOT rpms). You gotta have a BAD wire on Bank #1 which is causing unburned fuel at higher rpms, which inturn is throwing a "lean" code on Bank #2. This is the exact same thing that happend to me, and I too was hoping for a "misfire code", but no dice, only a lean code on Bank #1. After swaping over my old MSD wires one by one, I found a bad wire and had to buy a new one.

Let us know how the wire change works out

SammyK said:

Either way, it sounds like you're getting too much air, and not enough fuel

Click to expand...

This theory doesn't work because if this was the case, he'd be having multiple codes concerning the Lean code, for example, "unmetered air codes(MAF voltage too low/high)", or "vacuum leaks(unable to reach base idle rpm, etc.)". He would also be having these symptoms at all rpms, not just at WOT or slightly less. And if it were the IMRC's being the problem, it would do it at ALL load %'s after 3250rpms, and he would have slight idle issues. Plus he'd have a code for an IMRC not opening.

Driller is also onto something.....these cars rely on the MAF(too much IMHO) and if there is the slightest amount of dirt, you're going to get all sorts of issues. None however that will cause a "sputter" like you describe that comes and goes depending on load. Its obvious to me that you have a failing wire under load.......or atleast based on your descriptions, but hell, your sputter could be someone elses rattle, haha.

how do you clean the MAF sensor? i will ohm the plug wires tonight and check the IMRC's i will comment back after im done checking this.

Sweeet, lets us know how things go!

To clean the MAF sensor, you remove the airbox lid completely from the car(the MAF is inside), unclip the outside of the airbox from the inside of it(small tabs around the flat portion, using a small screw driver just pry apart). Once you have access to the actual MAF sensor, you'll need to remove the tamperproof torx screws by either buying the appropriate tool, or using vise grips to clamp on to them and swist them off(the latter is better). Once you get the sensor off of the adapter than take a small Q-tip and dip it in rubbing alcohol and VERY VERY VERY gently rub the little element that is dangling from the sensor.

That is the "hard" way.

If you want to clean it with a little less effort, grab a can of brake parts cleaner(CRC green works great), and with the airbox removed, spray through the little "tube" inside the MAF housing. Spray it for about 10 seconds in both directions and than use compressed air to blow it out. This will dislodge any particles on it and also dry it thoroughly. If you can get in there with a q-tip you can do that too, but access is very limited.

I wouldn't recomment brake cleaner. Even "residue free" cleaners leave a residue. Go to Radio shack and buy a can of electronic component cleaner. That stuff IS residue free.

As far as the compressed air... Well... umm... Yeah. I wouldn't blow compressed air through my MAF, but to each his own.

Even better get the CRC mass air cleaner from your local auto parts store.