[infocusNW]

2001 ZX3 five speed power premium

66,000 miles

Issue: stumbles under light throttle, particularly during warm-up. No problem under heavy throttle and idle is silky smooth.

Tried so far:

-DPFE sensor
-MAF sensor
-coil pack pigtail
-plugs (Motorcraft OEM gapped at 50 thousandths)
-ECU firmware (OEM) update by dealer
-fuel pump replaced under recall


Any and all ideas/suggestions appreciated!

 

[Johnny_P]

if its idling fine and fine under WOT, I'd suspect an EGR-related problem. Might want to check your EGR valve. The zetec turns off EGR systems at WOT.

 

[infocusNW]

Thanks Johnny P.

 

[infocusNW]

bump

 

[boosted00focuszx3]

plug wires?

 

[MY20ZX3]

Are you running the A/C when it does this?

Mine stumbles a little bit too under light throttle with the A/C on....off it's not a problem.

Zetec's are gutless running that compressor.

 

[infocusNW]

The plug wires are original and it is worse with the A/C on.

However, I pulled and plugged the vacuum hose from the top of the EGR valve today, and voila, the stumble is gone.

I've done the DPFE already, so what's left?

-Oxygen sensor(s)?
-EGR valve?
-firewall mounted unit at the other end of the vacuum line?

Also, if I ran it this way (EGR disabled) indefinitely, other than higher emissions and an eventual CEL, is there a downside?

 

[deaconblue23]

Goto focus hacks and search for the egr work around......hold on here it is for you.......http://www.focushacks.com/index.php?modid=80
Or you can get a tune and disable the egr system all together. I did the workaround (#2 I think...) I got tired of replacing the EGR crap all the time. Hope this helps if nothing else it is good for a read.:thumbup:

 

[infocusNW]

Thanks, deaconblue23

 

[guitarseth]

Check your front O2 sensor. Sounds pretty characteristic.:dunno:

 

[infocusNW]

First, thanks to all jetters who've replied with ideas.

I've disabled the EGR system twice now by pulling and plugging the vacuum hose going into the top of the EGR valve and both times the stumble went away. Of course I eventually got a CEL but otherwise there are no obvious side effects.

I've so far;

-replaced DPFE sensor (again)
-replaced coil pack pigtail
-replaced MAF sensor (dealer tech said it was out of spec)
-replaced fuel pump/filter (some time ago under recall)
-replaced plugs and wires
-cleaned both O2 sensors with MAF sensor cleaner
-had latest firmware flashed to PCM

.......but it still stumbles, particularly during warm-up under light tip-in, with the EGR system enabled.


MY QUESTION:

--what would you replace next?

I'm tempted to replace the front O2 sensor, and I'm thinking if that doesn't work I'll go to the EGR valve.

What other components should I be suspecting? Also, other than the CEL and higher emissions what side-effects come with a disabled EGR system (fuel consumption, ect.)?


any ideas you can offer would be appreciated!

 

[deaconblue23]

You could always clean your egr valve, using alcohol, lighter fluid, etc, etc. I would try that before I bought one. Personally I would just do like I mentioned earlier and use the work around that will get rid of the pesky "CEL". Those are just my thoughts, but clean before you go and buy a new one.

There are no other side effects and If you use the #2 work around (see link I gave earlier), that is the one I used. There will be no "CEL". That will be the easiest and cheapest fix. :thumbup:

 

[infocusNW]

Thanks deaconblue23,

I replaced the front o2 sensor today. No change. In fact it's running worse, but I'm guessing the PCM is adjusting to it. Next stop, EGR valve.

 

[infocusNW]

OK. Three days of driving and no change.

'01 ZX3 5 speed, 67,000 miles.

-stumble/surge under light throttle, worst after driving a couple of minutes until
fully warmed up. Worsens with A/C on.

Replaced:

-fuel pump/filter
-plugs and wires
-DPFE sensor
-MAF sensor
-coil pack pigtail
-front 02 sensor
-PCM firmware updated by dealer

Question: What would you do next?

-lower 02 sensor?
-EGR valve?
-TPS?

 

[Slide]

Check out my thread. http://forums.focaljet.com/team-tech/559705-engine-stall-after-hard-stop.html
I would first locate the PCV valve and make sure your tube is not soft and collapsed at the turn into the intake.
My bet is the IACV.

 

[MEJ684]

Question: what mileage and how long ago was the fuel pump replaced? The light stumbling was common on my zx3 when the pump went. Im not leaning on vacuum (like pcv) related because you said under WOT its fine, usually anything vacuum will show up on a bad idle.

My bet is IACV. It sounds to me that if it stumbles in lite throttle then the valve maybe stuck open letting in air the ECU doesnt know about. Also if the IACV is bad ive read alot about hard starting in cold weather, but if its stuck open it might not matter.

Another idea is the EGR valve thats stuck open. Honestly Ive replaced 2 DPFE sensors, the valve and cleaned the input tube and there still was a problem with mine, I ended up just plugging the vacuum tube to valve and living with the constant CEL. Mine also would shudder under constant speed (around 30-40 mph) before I plugged the tube.

You can spray carb cleaner in the IACV port (little slit located inside the throttle body) or clean the EGR valve may help. Hope this helps.

 

[Mr. Zetec]

Change the second o2 also, Cannot hurt, I know from experiance it could be anything. Try the ground wire also see if any corosion

 

[infocusNW]

Thanks for the input!

I checked the vacuum hose from the PCV and it's solid. Also checked the ground and it's good. The lower O2 sensor is easy enough but I'm reluctant to part with the $$. How much will an IACV set me back?

Maybe from here it's the IACV but honestly, at this point I'm tired of pouring money into it and might just leave the EGR bypassed (tube plugged) and CEL bulb pulled.

I should probably try cleaning the IACV port. Can I get to it from the top of the TB?

 

[deaconblue23]

If you did one of the work arounds you will not get a CEL I have had my wifes car set up sometime like that and still no CEL. Not trying to sound like a broke record, but I am just trying to help. :dunno: But do what you like it is your car after all. :thumbup: Best of luck with it.

 

[Flofocus]

Thanks for the input!

I checked the vacuum hose from the PCV and it's solid. Also checked the ground and it's good. The lower O2 sensor is easy enough but I'm reluctant to part with the $$. How much will an IACV set me back?

Maybe from here it's the IACV but honestly, at this point I'm tired of pouring money into it and might just leave the EGR bypassed (tube plugged) and CEL bulb pulled.

I should probably try cleaning the IACV port. Can I get to it from the top of the TB?

Im just took mine out...PITA. Not sure why everything I read says it *super* easy...its def not. The bottom bolt is easy to get to from underneath, if you have sausauges for fingers...forget it. :lol:

The top bolt is what gave me a hard time, I had to remove my IC piping to make some room for my tools...I couldnt get your normal wrench in there, not enuff swing to undo the bolt...I had to use a key to losen it, then used my mastercraft ratched to undo the rest. This ratchet is awsome...its saved me a few times where space is tight...All you have to do with this ratchet is turn the handle, you dont have to 'swing'...just turn the handle and it undoes the bolt. This is what I had to do. Took me 2 hours to figure it out.

Got my new part, now I have to figure out how to tighten it back.