Hi guys, I know this issue has been covered and I've read every possible thread I could find, but nothing seems to quite match the symptoms I have, so here we go - hopefully one of you knowledgable people can help!

• Car appears to run fine in every other way (idles fine etc)
• The problem is noticably worse when the engine is warm
• Under load (typically 1500-3000rpm), the car will jerk and run terribly. I can avoid it if I change down a gear or back off the throttle
• No fault codes registered
• No Check Engine Light
• Have already replaced/cleaned MAF sensor
• Have already replaced crankcase breather hose
• Visually inspected ribbed hose from airbox to throttle body and can't see any splits (although the seal to the airbox doesn't look all that great)

My next step is likely to be replacing the spark plugs, but before I do, has anyone had the same symptoms as me and managed to solve?


It does seem as though I may have a vacuum leak somewhere after the MAF sensor, but wouldn't this cause an error code to be recorded?


I will get hold of some starting fluid this weekend and try to find a leak (if there is one), but could someone help identify the likely culprit?



Many thanks


Ioan


['04 2.5 V6 manual]

 

By "run terribly", do you mean like misfiring? How's your fuel consumption? Also, if you "blip" the throttle while warm, does the tacho needle settle quickly but gently, or drop fast and undershoot normal idle revs slightly, before settling?

 

Hi jimgoose, thanks for that. I'm not sure whether or not it's misfiring, but I don't think it is. Is there an easy way to find that out in this case? Fuel consumption is fine, I am getting just under 30MPG on average. Good question, I'll have a look later. What are the implications for both scenarios please?!

 

Dropping-and-undershooting of the needle back to idle would generally indicate over-richness, possibly caused by a problem with the coolant temp sender, possibly a couple of other things. I would expect any sort of misfire to flash the MIL and log some DTCs, whether due to leanness or richness, but I've been surprised before.

 

It just happen to me as well. I changed the 1,3,5 cat converter and it fixed the problem....But i had a list of codes a mile long. But after fixing all the codes the car did what yours is doing. Bought a after market cat for 130. bucks and had a guy at a local shop weld it up for 50 bucks cash. Hope this helps

 

Hi Dr dome, thanks for your help. Is there anything I can do to help diagnose a faulty catalytic converter? That being said I have only ever had one fault code which is a pending P1111 code (either successful system check or IAT sensor). Am I right in thinking the IAT sensor is part of the MAF sensor, or are they separate?

 

OK, I've checked this and revs return properly. Also, I only have the one P1111 code as mentioned above.

 

I have a very similar problem with my 02' 3.0L 5spd. I have a idle that dithers 50rpm back and forth and I can feel a misfire. NO DTC's or MIL at all. Car stumbles when under acceleration but not every time. I just ran bottle of Chevron Techron in a 1/2 full tank of gas and also had a new fuel pump (it failed) and a new fuel filter installed. I am leaning towards a fuel injector but I would think that would log a DTC. MPG is ~26-28. Still have yet to figure this out. The ECM was scanned for any codes when it was in for the fuel pump replacement and none were found.

 

I am chasing the same problem you guys are.

Hesitation between ~ 1500 - 2000 RPM.

Replaced the IMT seals, brake booster line, brake booster and other manifold vacuum hose bushings, new PCV valve, new spark plugs and fuel filter. I just ordered a new PCV hose although mine is the new style and likely isn't the cause. But I am running out of the easy options.

These changes made a big improvement but it is still there from time to time. I am hoping the PCV line is it. No obvious damage or leaks but maybe there is one when it is hot and under pressure.

It runs great when pushing it hard but in that zone with lite throttle it hesitates.

 

You might also consider checking the 02 lambda sensors..

They could be failing but not throw and codes, yet still impact on performance / fuel economy etc

If you've got some miles on your car and these are original, it may be worth at least checking them if you can, to rule them out.

 

Dear Ioan, i know your thread is older now, but searching this forum for my problem which was yours....did you finally fix the problem? was it the cat converter?
I have just taken delivery of a 2002 Xtype sport auto and hoping i can fix this problem as the car is superb in every way even for 12 yo. rides beautifully on highway at high speed and holds road well, great to drive around town. BUT the judder is taking the joy away...grateful for any hints....n o warning lights, no rpm needle alerts, just this intermittent judder, sometimes i can go so lightly on the accelerator that it doesn't happen, other times it will happen under load going up a slight incline, after running well beforehand. did you finally solve the problem?

 

I wanted to follow up on what my problem was. I had a weak #6 ignition coil. I ended up causing the engine to studder and misfire to the point of generating a DTC.

 

thanks Chas. I have it booked in for diagnostics this week and another person mentioned ignition coil so it is good to get your experience. I will see how it goes and promise to report back!

 

I have a few posts out there pertaining to the same thing and I've been chasing it for awhile. Most recently I've been updating the Thread "I've got codes". I've been chasing this issue since just before May 2014. I had the plugs replaced during my 90K Tune Up and it seemed to have gotten worse to the point that going up inclines I would literally bog down or the car would buck and it was often in 4th. Down shifting to 3rd seemed to help, but even at that it still would occur.

I don't have a for sure solution, but I am interested to see what the feedback is that comes back. You all might be on to something with the Coils being the root of the issue. These cars seemed to be very sensitive.

I recently started getting codes, finally after 3 months, indicating a misfire. First on Cylinder #5. So i went down and had the Coils replaced. Then Friday I got codes again, but they were indicating a misfire on Cylinder #2 as well as an Open Circuit issue and a bad coil on #2. So yesterday I broke down the top end (i.e. took off manifold) pulled all the new plugs, bought replacements (NGK) and gaped them at .052, put them back in. I also kept my old coils when I replaced them and I swapped the apparent bad new one with an old one. There feels like there is that subtle stutter still, but the car does run better at the moment. No codes yet either.

I'll be keeping an eye on this thread in case someone can crack the mystery. With as many similar comments on here it seems to be a common thing to occur.

 

I did the 60k maintenance (plugs, IMT valve gaskets, Intake Gaskets T&B, fuel filter, PCV valve and PCV tube-new style). The car ran perfect before hand, although I started to notice a slight rough idle when parked or when stationary, which I'm contributing to the original plugs. Since I changed everything listed the car has started to give the symptoms mentioned in this thread when my speed is from 30 to 35mph.
The hesitation is now happening more frequently as I'm doing more local city driving as that's about the extent of the speed limit for my drive to and from work. When I take it on the highway it runs flawlessly. I have no MIL or Messages on the display.
Side note; I used Bosch Double Platinum plugs that were pre-gapped. I also noticed a few of the ignition coils springs were slightly bent to one side of the inside of the coil. I didnt want to pull on them for fear of pulling the spring from the base so I reinstalled them thinking that it wasn't a problem prior. There was two different types of PCV valves for sale (from rock auto) with VIN numbers designated for each valve. I chose the match for my VIN. I also know that I put a lot of stress on the break booster vacuum line when I flipped the upper intake manifold to get at the rear plugs. I tried removing it, but couldn't figure out how to pull it out from the manifold or at the break booster so I just tried to be as gentle as I could.

I'm a little apprehensive on doing the Starter Fluid/Carb Cleaner trick to test for vacuum leaks. Will this corrode the rubber or damage any sensor it comes into contact with?
I was going to start replacing coils but wanted to see what others thought first.

Thanks everyone.
-G

 

Bad coil(s) would most likely throw a MIL code. I would clean the throttle body. It is probably sticking when near closed. There are several threads that describe how in this forum.

 

X, I'm still experiencing these symptoms of hesitation or stuttering around 30-35mph and it's been just about a year. 90% of my driving is in the city too. It happens when I'm cruising at 35-40mph, it happens if I'm going uphill and it happens when I put cruise control on. I haven't figured out what it is. Maybe it's the nature of the transmission and gearbox around that specific speed. I don't know, but I'd really like to. I agree, it kinda takes the joy out of driving around town.

I've replaced all 6 coils and plugs twice with brand new ones. I've replaced the MAP sensor, MAF sensor, Breather vent hose, IMT gaskets, Upper Plenum gaskets a couple times, Crankcase sensor, Fuel Filter, Air Filter, no reported vacuum leaks, checked the brake booster hose and replaced Throttle body (twice). The last code I got was throttle related, but we discovered the pins in the plug were loose and a wire was slightly damaged. That was fixed and since then I haven't had a code, but I still get the stutter. It just feels like air bubbles popping. So maybe it's injectors. Mine were apparently fine, but how do you even test injectors.

What I haven't done: I haven't replaced the transmission or gearbox fluid - 1) I don't have a garage and personal space to do it. 2) I'm not confident I won't screw it up. I haven't tested or replaced the injectors. I haven't replaced the 02 sensors. I haven't replaced the cat converters.

I put 92 in my fuel tank and I go to the same place to refuel. I tried different gas stations when I was noticing it, but couldn't see a noticeable difference. I never noticed it prior to doing my 90K tune up (April 2013). So..........I'm still hoping for a solution. When i can afford what I haven't done I'll pick away and report back. That might take some time so fingers crossed someone knows exactly what is happening.

 

I have had the exact same problem for the past 2 years. I wish we could fifure out what causes this, it is very iritating and embarrassing when others are in the car with me. I replaced plugs twice, coils, and checked all the ignition wiring. I don't know what it is!!!!! I love the car other than this problem. It seems like there are a lot of us out here. I haven't found any vacuum leaks with carb cleaner spray. I wouldn't use starting fluid, it is pure ether and could ignite very easily on a warm engine or a spark from wiring. Someone, please help us figure this out.

 

It makes sense to check codes ( not sure if you have? )


Failing or out of spec 02 Lambda sensors will not necessarily throw codes, so no help there


My son's old Vauxhall Astra suffered from hesitation under load, sometimes it would want to go, then hesssitate / stutter etc
Mpg was really poor too, another symptom


We replaced the 02 sensors and all was fine, big difference.


I'm guessing on an 02 plate I think it is?
You must generally be in the higher mileage category, say 90k or thereabouts?


Its certainly something to think about, but obviously check as far as you can first


Good luck

 

Dumb suggestion: My automatic tranny shifts from 3rd to 4th gear at ~40 MPH. Perhaps your tranny is shifting prematurely to 4th gear at only 30-35 MPH, causing the engine to lug at low RPM. Below 30 MPH the tranny stays in 3rd gear. Above 40 MPH the engine has sufficient RPM and power in 4th gear. So you'd experience the problem at only at 30-35 MPH if the tranny shifts into 4th gear too soon.

I could be all wet (won't be the first time, nor the last!), but the idea is easily tested: Drive at 30-35 MPH with the J-gate in 3rd gear. If the hesitation and shuddering stops, shift the J-gate from 3rd gear to Drive (still at 30-35 MPH) and see if the hesitation and shuddering resumes.