Shudder While Cruising?

[ax0n]

I've noticed this before, but it seems to be getting more severe...

When I'm cruising at a constant speed, Say 45 MPH in 4th gear, 80 in 5th gear, 30 in 2nd gear. doesn't matter.

If I'm cruising, i get a shudder. like as if I'm taking quick, short jabs at the go pedal.

It will continue this way for as long as I'm staying at the same speed. If I lay on the gas, the takes bite and goes. If I let off, she slows down like normal.

Idle is smooth, purrs like a kitten.

Breakdown of my car:

2000 ZX3
5 Speed
A/C is about the only option, this takes place regardless of A/C being on, but A/C makes it more prevalent.
FocusSport 8mm spark plug wires
Intake Resonator Removed
No Speed Control or anything like that...

Otherwise, all stock, engine wise.

I know others have had similar problems. It almost feels like it's got intermittent power, but she tears it up if I mash the gas... and doesn't have that problem. Power in the low end is not intermittent if I shift at low RPM's Either... just if I cruise at the same speed.


Any Ideas what's causing this? was this a symptom of the ECU recall? I know it supposedly fixed the stumbling idle, but maybe it fixed something else?

[ZX34me]

I have the same thing, acts like it is surging or a gusty wind is blowing. Don't know what it is, but it is very annoying.

[spankenstein]

From what I heard on cf there is a technical service bulletin about this. Something to do with the ECU needing reporogrammed.

You can apparently testing this by plugging the vacuum line running the the EGR valve. I have this problem too but haven't had time to really check it out.

[ax0n]

yes - I knew I was part of a "club". My right foot is usually binary though (flooring it, or getting ready to stop )

So I don't notice it too much. When I do notice it, I just floor it.

[doogie78]

Yep I noticed it too. I think it's getting worse the more I modify, but that could be me. Could it possibly be the timing? I heard that Ford was so quick to get them off the assembly line that the mistimed most motors.

[niklasfocus]

Hey I get the same thing! I'm glad I'm not the only one. I just cleaned my MAF w/ rubbing alcohol and I'm going to change my spark plugs. But it looks like my efforts will probably not help the situation at all. I remember always having it a little bit, but it seems like it's getting worse.

[blurr]

Welcome to the Infamous Stumble/Hesitation Club, this one is even more irritating than the Noisy trans club. Ford seems clueless based on my experiences with them. It feels like a vacuum leak to me.

[rwgreenberg]

Had what I believe to be the same symptoms. My CEL went on after a couple of days living with the stumble. Brought it in and they replaced the DPFE sensor. Seems to have almost completely solved the problem. I say almost, because every now and then I think I feel it a bit, but the replaced sensor deffinitely had an almost 100 percent positive effect on this problem.

[vad]

I think that the malfunctioning DPFE sensor just makes the problem more prominent.
BTW, anybody tried to reset the computer?
I've done that several times. It "cures" the stumble, but just for a short while. Then it comes back.

[noresull]

The stumble you are feeling is what's called a lean misfire. It is caused by the EGR opening up and allowing exhaust gases into the intake.

The one fix I have found for this is to get a chip which cancels the EGR out of the system.

One way to check if it's the EGR, unplug the vacuum hose, plug the hose, then drive it, if the stumble goes away.... But if you drive around like that for awhile, the CEL will come on.

Vad, the reason resetting makes it go away, is the car is re-learning it's strategy and doesn't allow for full EGR until it relearns everything.

------------------
John
Puny little soldier of the 'Minnesota Mafia!'
2000 silver Focus ZX3 DiabloSport performance chip, MBRP exhaust, K&N Drop in or Ractive,(Depending on how I feel!) Esslinger Underdrive Crankshaft Pulley
This place rocks!

[njbongo]

Noresull, I have a dumb question. I have this problem to. Yesterday I had the AC on, which exaggerated the problem even more. I was on empty, so I said 'the hell with it' and filled her up with 91 octane.

Today, I've had the AC on all day, and guess what...the stumble is gone. Based on what your saying about the 'lean burn' problem, does this make sense?

I'm figuring since higher octane has more resistance to ignite, maybe that's the fix?

I have used NOTHING but 87 since I got the car in April. 2000 miles so far, and I've had the problem from day 3 or so. It only happens if I'm cruising at a steady speed for more than a minute or two. And ONLY if the RPMs are under 2500 or so. I tried cruising along at 3000 RPM, JUST TO SEE if it would happen...it didn't.

Does this make any sense to you about the higher octane rating. I'm going to finish off this tank of gas and see if it happens again after filling it with 87 next time.

Thanks............

[blurr]

I took a $67 gamble on the DFPE thingie, while the car felt better initially things eventually went back to the "El Crappo" mode. What Noresull says about the computer going back to it's default mode after resetting the ECU explains why this is happening.

My next mode of attack will be to find a vacuum restrictor and put it inline just ahead of the EGR valve, to see if I can get the EGR to open more slowly. Any thoughts on that Noresull?

Also you mentioned that some people are getting chips that eliminate the EGR function, what other areas should a chip tuner focus on to address this problem. I recall someone saying the stumble was related to the ignition timing advancing and retarding very suddenly. Thanks.

[Sartre]

I also have had this problem. It started out not very noticable, and only once in a while. Now, it has gotten worse, and I definitely find it irritating. Feels like the engine gets clogged up until I press the pedal further down, and it clears up. In a dyno I recently did, the hp and torque line dropped around 3000 rpm and came back up. I think this is a graphic illustration of my problem, and that this problem is definitely causing us to lose power.

About the chip, is this something we can have Cajun program for us? Thanks for this great topic, Sartre

[covert1]

Noresull, is this "Lean Misfire" saved in memory by the ECU? I have a friend with a code reader, and it says "Misfire Event Monitor Maximum Complete is 2051 counts with maximum limit of 2000 has FAILED" on my car.

Another failure it mentions is "Evaporative initial tank vacuum Phase 0 is 28910 counts with minimum limit of 29082 and maximum limit of 29184 has FAILED"

Are these 2 things interrelated?

[doogie78]

EGR? CEL?

------------------
injen cai,b&m shifter,borla exhaust,superchip,ford udp, don't underestimate a sleeper

[ax0n]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by doogie78:
EGR? CEL?
<HR></BLOCKQUOTE>

EGR: Exhaust Gas Recirculation - Hot exhaust gasses get brought back into the air intake so that fumes can be further reburned. It's an EPA thing. Damn Them. Damn them all to hell.

CEL: Check Engine Light. Hopefully I don't have to explain this one to you.


Someone's getting a hose kinker from the beater aisle of the auto-parts store tomorrow. (you know, the orange plastic "pliers" that you're supposed to use to keep brake fluid in your brake lines when changing calipers or something... )

[noresull]

ax0n, just get a Golf tee. It works very well.

NJ, I don't think octane has anything to do woth it because no matter what, the EGR will make it run a bit leaner.

Blurr, the restrictor probably won't work, because it will still eventually get the EGR open all the way

Blurr & Sartre, Diablo has the programming for sure for the JFA8 code, but you would have to ask Cajun if the other codes have it removed. I think a higher RPM stumble is the one related to the timing.


Covert, I have no clue what those codes are, they are not descriptions that I am used to seeing. However, this misfire is not the type that can throw a code. A misfire code is when the cylinder just plain misses.

[blurr]

John thanks for the reply,
you wrote....
"Blurr, the restrictor probably won't work, because it will still eventually get the EGR open all the way"

True, but my thinking is that perhaps the EGR is opening and closing rather rapidly at specific RPM's, like it's right on the verge of being full open, but is fluttering on the cusp. I saw this not knowing how rapidly the valve does open once vacuum is applied.


Then you wrote...
"However, this misfire is not the type that can throw a code. A misfire code is when the cylinder just plain misses."

Is this you speaking or Ford? By that I mean does Ford know this is an issue, or is this from your knowledge and insite? Reason I ask is I'm thinking of leaving the car with the service dept for as long as it takes for them to correct the problem. Will they be able to do anything?

[ax0n]

John - The Golf Tee will also keep me from getting a CEL, right? since the system can sense a vaccuum pressure is being made?

I can see it now: "I have the golf tee mod!"

[blurr]

axOn- sorry buddy, you will still get a CEL, it reads the vacuun differential, meaning it knows if vacuum is being applied. I'd thought that if you got some other vacuum pot, ie another EGR valve or a vacuum advance unit off an old distributor you could trick the computer. Just mount the new vacuum unit out of sight, run a hose and...voila!

Maybe.

[ax0n]

Okay - so what If I block the flow of recirculated exhaust gasses?

let it open the f***ing EGR, but bolt a metal plate in-line with where the gasses go back in, so they don't go through? Would that get a CEL? Would that fix the problem? DOES THE ENGINE REALLY NEED RECIRCULATED GASSES TO FUNCTION PROPERLY, or is it just some EPA bullcrap?

[vad]

And does the Diablo chip COMPLETELY eliminate the stumble?

[noresull]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by blurr:
Is this you speaking or Ford? By that I mean does Ford know this is an issue, or is this from your knowledge and insite? Reason I ask is I'm thinking of leaving the car with the service dept for as long as it takes for them to correct the problem. Will they be able to do anything?

<HR></BLOCKQUOTE>

The misfire codes are completely related to a dead misfire. The stumble we are feeling is what a very mild lean misfire feels like.

The dealer probably won't be able to do anything unless they are convinced it is not right, however, if they drive another Focus, it will probably do the same thing, so they will be harder to convince there's a problem.

[noresull]

ax0n, what is tripping the CEL light for the EGR is the DPFE sensor. It detects flow in the EGR tube. Eliminating this flow, will still cause the CEL to come on.

The Diablo doesn't program out the stumble, rather the most common thing that causes the stumble, the check for the EGR flow through the DPFE sensor.

[Sartre]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by noresull:
The stumble you are feeling is what's called a lean misfire. It is caused by the EGR opening up and allowing exhaust gases into the intake.

The one fix I have found for this is to get a chip which cancels the EGR out of the system.

One way to check if it's the EGR, unplug the vacuum hose, plug the hose, then drive it, if the stumble goes away.... But if you drive around like that for awhile, the CEL will come on.

Vad, the reason resetting makes it go away, is the car is re-learning it's strategy and doesn't allow for full EGR until it relearns everything.<HR></BLOCKQUOTE>

Norsull,

I am attempting this test you suggest, but I am not sure which hose I am supposed to plug with a tee. On the DPFE sensor, there are two hoses that connect to it. Am I supposed to plug the one on the left or right side, and should I leave the other alone where it is? THanks, Sartre