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Engine feels like it's "chugging" under load at low rpm.

22K views 24 replies 9 participants last post by  Resinears 
#1 ·
MY 2000 has 98,000km (61,000 miles±)...
I haven't driven the car much in the last year, but was using it daily in the last couple of weeks, and I've noticed that the engine "chugs" or "shudders" when I put a slight load on it at low rpm (1500 - 2200±), but more pronounced at the 1500 rpm range. This is not road speed related, so the guibo (new) is not the issue. The behaviour is in the described rpm range, no matter what gear or speed I'm driving.

I'm not talking about lots of throttle at low revs (which does make it worse), but even really gentle amounts. The engine really feels like it's being "lugged" if I'm not driving over 2500 rpm with traffic flow. My city traffic drive to work is now mostly in 3rd gear instead of 4th to smooth it out.

Tranny and diff fluid, plugs, mafs, and fuel filter have less than 10k on them, and there are no stored codes or cel. I did a muffler delete in the last year, and didn't notice any "chugging" then...

Any suggestions? CPS?
 
#2 ·
I usually try to avoid loading the engine below 2K rpms anyway just to make sure the parts are getting enough oil delivered to them so I'd recommend against that driving style to begin with. But on to your issue, have you checked for any codes? Your description sounds a bit like the symptoms I was getting when my throttle position sensors started to go bad however it was in a different rpm range and eventually started to spread to other ranges until I replaced them. I started to notice it when cruising between 2500-3000 rpms. I'd get a slight hesitation or shutter now and then. Checked for codes and got none so didn't think much of it. As it started to occur more often but still didn't produce codes I'd try staying in a higher rpm range to avoid it and it worked for awhile but then would randomly happen around 3500-4000 rpms as well. Eventually it finally set a code for throttle potentiometer so I changed them both out. Smooth as a stipper's hoo-ha since.
 
#3 ·
Thanks Strike,
I absolutely agree with you with respect to not usually driving below 2000 rpm. I'm talking about the sedate cruise in traffic (like if there was a police car behind you), and VERY gentle load that doesn't warrant an upshift. It's only under these conditions that the issue is apparent when going from off throttle to barely on throttle.

The only other thing I've done prior to having the car sit for the last months, was the thermostat and a plenum and throttle body intake clean (which I did, preferring to remove the plenum while doing the t-stat). I used a clamp on the linkage to keep the throttle bodies open, and cleaned the bore seats with towels soaked in solvent. I didn't make any adjustments, not wanting to disturb the sync between the throttle bodies. Come to think of it, the behaviour feels somewhat similar to a multi cylinder motorcycle whose carbs are perfectly sync'd. I doubt that that's the issue though...
 
#4 ·
Thanks Strike,
I absolutely agree with you with respect to not usually driving below 2000 rpm. I'm talking about the sedate cruise in traffic (like if there was a police car behind you), and VERY gentle load that doesn't warrant an upshift. It's only under these conditions that the issue is apparent when going from off throttle to barely on throttle.
Not sure if I can help, but 2 things that won't always throw a code are MAF's going bad and CPS starting to go bad. If you drive with MAF's unplugged, any difference?

Regards,
Jerry
 
#6 ·
Unfortunately, I don't have a way to check the fuel trims. I hate vacuum leaks! I've paid for smoke tests on my 540 after doing the intake manifold gaskets, with no leaks found, but was convinced it still wasn't right...

It actually seemed much better today (after I posted the problem), until I gave the car some high throttle/rpm time while getting into a tight opening in traffic. The low rpm shudder was back after that. Maybe a clue? I'm tempted to change the camshaft position sensors...
 
#7 ·
Mine does the same but not all the time. Yesterday morning driving to work, I noticed it was more 'chuggy', and it felt happier in a lower gear, raising the revs to smooth it out. This isn't always necessary though, usually it will pull around at low revs quite happily. Perhaps the intermittent nature of the issue points to a failing sensor of some kind.

I have done the MAF disconnect, and found little difference so despite my first strange conclusions that they were OK (clearly a bad day for me...), I think these are bad, I just need to get up to RichardP's to try his known good items, but this would back up Jerry's diagnosis above. :)

I haven't yet touched TPS or CPS in any way.
 
#8 ·
Mine does the same but not all the time. Yesterday morning driving to work, I noticed it was more 'chuggy', and it felt happier in a lower gear, raising the revs to smooth it out. This isn't always necessary though, usually it will pull around at low revs quite happily. Perhaps the intermittent nature of the issue points to a failing sensor of some kind.

I have done the MAF disconnect, and found little difference so despite my first strange conclusions that they were OK (clearly a bad day for me...), I think these are bad, I just need to get up to RichardP's to try his known good items, but this would back up Jerry's diagnosis above. :)

I haven't yet touched TPS or CPS in any way.
Thanks for chiming in - it's good to know I'm not alone. I've taken it for granted that mine are fine, given that I bought them from "neighbour" whom I found through the board, less than 10,000 km ago. I'll disconnect them and see if there is any dramatic change. Please let me know if you have any luck on your end.
 
#9 ·
When I bought my 5, part of the ad was they were recent new Bosch items, and having removed the element part last weekend to inspect them, I've no reason to think they weren't. But when I disconnected them both, I didn't notice much of a difference, where I should've, so suspect they are no working as intended. Perhaps they are the VW ones that some have had issues with, guess I'll never know.
 
#10 ·
Not seeing much difference would make me suspect MAF's. When I disconnected my good MAF's, the car drove OK but lost a significant amount of its "snap".
Are you getting any oil leaking from the plenum back to the air filters?
Have you tried the bouncing-of-the-limiter MAF test?

OP, can you describe the ticking sound?
 
#12 ·
That's a bit awkward, I have any number of quiet areas (quiet in terms of other traffic, and zero pedestrians) where I can wind third gear up.

The problem is, it's tests like that that begin to narrow it down to a particular problem, without being able to do this, it's harder to find what the problem is, but I can understand the issue you face.
 
#13 ·
I was getting a similar chugging/power surge when driving on the highway at constant speed and fairly low rev's (say 120 km/h at 3000 rpm) this past weekend. I scanned with my Peake and got code 78 - throttle position cross check. It goes away after restarting the car but came back the next day. It's fine if I keep the throttle variable, which makes me look like I'm driving like a ricer :p

Searching around on this board, I found that it was the TPS at the back of the throttle bodies under the plenum, about $75 USD each. I'm going to tackle that when the part gets in.
 
#14 ·
Order hex head bolts to replace the screws that hold them in. Trust me on this one.
 
#16 ·
My advice... Downshift.
I tried that. I just put $78 for 62 litres of fuel (almost empty, but not dry), to go a whopping 372 km (232 miles). I prefer to drive in traffic at a more relaxed rpm. My travel to work rarely has me going faster than 65 km/hr as 50 is the limit. Being on someones bumper in 2nd gear at 3000 rpm is a little too juvenile for me. I suspect that something is off.
 
#17 ·
Just thought, no proof, but if you unplug your MAFs you should feel almost no difference. If you feel a difference then you would be feeling the unmetered air being allowed for, would you not? Unmetered air through the plenum and crankcase are negated when you unplug the MAFs. I can't pass my vacuum test nor can I shut it down by blocking the intake, but I am pretty sure my only leak is my rear main seal. I feel almost no difference now but did feel a huge difference a month ago before I started sealing the crankcase.
 
#18 ·
I didn't feel much of a difference when I unplugged my MAF's. Does this point to good or bad MAFs then. I originally thought it didn't mean they were shot for some reason, then it was pointed out that if they were good, I would feel a difference. Confused.com. If I had the time, I have the offer of some swap outs to test.

Having said that, I'm hoping to be able to Alpha-N next month anyway...
 
#20 ·
Mentioned in post 13 above. Do TPS's generally throw a light or a code?
 
#22 ·
I was exaggerating. I actually mentioned them already on page one. lol. No they don't always. I was having the identical symptoms for awhile with no codes being set at all and I would dodge the problem by staying in a different rpm range. Then it started to occur more frequently at other rpms and finally set a code for throttle potentiometer. Replaced them both. Perfect.
 
#21 ·
When one of my cam sensors started to go bad I had some strange behaviour at the lower revs. Put in a new one (exh, bank 1 iirc) and it went away, behaving nicely at low revs again.

Get the car scanned, it will probably have a stored code but the engine light will not come on, unless it happens more than a certain number of times.

Hth.
 
#23 ·
Update

Just an update to make the thread a little more useful for future searchers...

The car finally threw a code (I forget what actual Peake code it was), for the exhaust cam position sensor on bank 2. I replaced that last night, and all is well. No more chugging at low rpm/load. It also seems that the exhaust has less over-run burble when coming off the throttle and listening to the rpms come down. I think it pulls better throughout the rev range as well.
 
#24 ·
How long in miles did this go on before it finally thru a code? Just food for thought, even though the other three are not throwing codes don't you think they could be downhill too. There is a reason some of us replace the originals at some point with the updated ones.
 
#25 ·
My car has less than 100,000 km. I paid $180 for the sensor from the dealer so I could install it riight away, so I was reluctant to order up 4 as a "just in case". Had the sensor been on the intake side of bank 2, I probably would suggest doing both, but I was thankful that I didn't have to. Access to the exhaust sensor was bad enough for me. As far as your "there is a reason some of us replace the originals at some point with updated ones" statement, I've read differing opinions, and it seems the bank 2 exhaust sensor is more prone to failure than the others. It's not like I replaced one of two MAFs.
 
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