It's a 2004 Fabia 1.4 with the BBY engine. It runs and idles perfectly with one exception. Any attempt to drive it at 1500RPM results in really severe engine judder. A tad different RPMs and the problem is gone. If I insist on driving it at 1500RPM I eventually get P1553 Barometric/Manifold pressure signals: Implausible Correlation. 

 

Since under normal driving conditions I rarely end up driving at 1500RPM for any significant amount of time, i.e. I either accelerate or decelerate via 1500RPM the problem does not manifest itself and the error goes away after a couple of trips.

 

Now I'd blame it on a faulty MAP sensor but it's a fairly weird way for it to fail. Is there something else that might cause this?

Could be the engine mounts.

The CEL cannot be caused by this though.

"implausible correlation" - could be a shaky connection caused by the engine's excessive movement.

1500 rpm is too low, the judder is caused by the ECU trying to prevent the engine from stalling, peak torque is at 4500 rpm, peak power is at 6200 rpm, there simply isn't enough useful torque available at 1500 rpm, it's not a diesel!

12 hours ago, tyy990 said:

It's a 2004 Fabia 1.4 with the BBY engine. It runs and idles perfectly with one exception. Any attempt to drive it at 1500RPM results in really severe engine judder. A tad different RPMs and the problem is gone. If I insist on driving it at 1500RPM I eventually get P1553 Barometric/Manifold pressure signals: Implausible Correlation. 

 

Since under normal driving conditions I rarely end up driving at 1500RPM for any significant amount of time, i.e. I either accelerate or decelerate via 1500RPM the problem does not manifest itself and the error goes away after a couple of trips.

 

Now I'd blame it on a faulty MAP sensor but it's a fairly weird way for it to fail. Is there something else that might cause this?

 

Sounds interesting.

Don't suppose you've got access to VCDS to do some logging? (MAP reading, EGR activity, misfire counters, that kinda thing). I could run mine at same engine speed and compare.

I'd check the usual suspects like brake servo vacuum line for leaks, and the EGR feed pipe into the inlet manifold for blockage, along with a throttle body clean.

I vaguely remember that EGR action starts to happen at this rpm, on this engine.

Manual or automatic gearbox?

 

 

It's manual. 

 

I tried another MAP sensor from a scrapyard today. No change whatsoever. Cleaned the throttle body, too. Again no change.

 

@Wino I will definitely do the readings with VCDS. EGR has been replaced recently so the chances are low it's bad. Having ruled out EGR and MAP I am thinking along the line of timing belt tensioner. What else could be the root cause?

 

Played with it some more today. On higher gears the RPM range where the problem happens grows. On 5th gear it's there between 1500 an 2200rpm. It is more noticeable when trying to drive in this interval or decelerating through it. When accelerating it's less noticeable. No more CELs, too. Now that is really weird.

Sounds similar to the symptoms my car experienced not too long ago. First it started as a P1553/17961 with some judder. Changed both timing belts (unrelated to the problem) and nothing changed. Changed MAP sensor and again, nothing. Kept driving like that and it "evolved" to a faulty #4 coil. Changed the coil, and that was it. Runs like new. 

Could also be an intake or exhaust leak. Potentially messing up short fuel trim causing the judder.

Edited 6 October, 20205 yr by Xsr

There are too many of these topics with no solution given. I'll try to make a difference.

 

The EGR was the problem. Judder started when EGR opened. It disappeared at higher revs but I think the problem remained it just couldn't be felt at higher revs.

 

The EGR was brand new but non-OEM. I got an OEM one and that solved the problem. 

Did you adapt the ECU to the new EGR (either time)?

Yep both times. It was saying Adaptation Status OK or something both times and lower and upper voltage limit slightly changed.

Glad you got there in the end. And good on you for closing out the thread with the relevant info.