engine does not rev past 4200 rpm

I have a 2004 jetta tdi. with the unit injectors. I love the car but beginning to hate the engine. I put VAG-COM on the car to see what codes it had if any. The Mass Air Flow sending unit was bad, replaced it. The intake manifold was clogged, got it cleaned out. The EGR cooler was replaced under warranty. But real problem is that the motor will not rev past 4200 rpm. When the motor is cold the sound from the exhaust is smooth sounding but at operating temp that is a different story. The exhaust sound is sort of like tha, tha, tha, tha,tha. VAG-COM shows no problems whether under load or sitting idle. I had the valve cover off thinking it might be an exhaust lifter dying, but thats not it. The only thing I haven't done yet is injectors but, at almost a grand apiece I'm not that anxious to do them yet.

Help me please

With a TDI, theres no real reason to rev past 4000 RPM. Acceleration is minimal over 4k. It's not like a Ricer.
The rev limiter kicks in around 4300-4400 rpm because the combustion just simply can't keep up. Remember-- it is compression-driven, and not a spark-driven engine.
I'd say you're normal.

Rev limiter hits at 5100. Stock tdi should still be giving a little power at 4200. Over 4500, a rev should be possible, but minimal power. With no rev over 4200, something is wrong. I can't help with a PD, however, but someone should be able to provide some guidance. Good luck.

May be something wrong, but the fact remains that torque drops like a rock above 4,000 rpm, so there really is no need, and certainly no advantage to reving it up there.

go hard said:

I have a 2004 jetta tdi. with the unit injectors. I love the car but beginning to hate the engine. I put VAG-COM on the car to see what codes it had if any. The Mass Air Flow sending unit was bad, replaced it. The intake manifold was clogged, got it cleaned out. The EGR cooler was replaced under warranty. But real problem is that the motor will not rev past 4200 rpm. When the motor is cold the sound from the exhaust is smooth sounding but at operating temp that is a different story. The exhaust sound is sort of like tha, tha, tha, tha,tha. VAG-COM shows no problems whether under load or sitting idle. I had the valve cover off thinking it might be an exhaust lifter dying, but thats not it. The only thing I haven't done yet is injectors but, at almost a grand apiece I'm not that anxious to do them yet.

Help me please

Click to expand...

Where did you hear that the injectors are a grand a piece? Go to www.kermatdi.com or www.pdrdiesel.com and check their prices.

rdkern said:

With no rev over 4200, something is wrong. I can't help with a PD

Click to expand...

I agree, then something is wrong. Does not matter that there is no advantage of going above 4200 or not, it still should be fixed. But I can not help with a PD either. And I doubt that it would be injectors. Sounds like a MAF problem.

itsmejerry said:

With a TDI, theres no real reason to rev past 4000 RPM. Acceleration is minimal over 4k. It's not like a Ricer.
The rev limiter kicks in around 4300-4400 rpm because the combustion just simply can't keep up. Remember-- it is compression-driven, and not a spark-driven engine.
I'd say you're normal.

Click to expand...

NO, i have 2001 Jetta TDI and did little cut off engine test .

It happens just little bit over 5000 rpm.

Unless it veries from engine to engine. Go to this 'area' ones in 2 weeks to

exercise turbo vanes and clean intake pipes. Engine takes it without problem, running smooth/strong with 240 000km.

rdkern said:

Rev limiter hits at 5100. Stock tdi should still be giving a little power at 4200. Over 4500, a rev should be possible, but minimal power. With no rev over 4200, something is wrong.

Click to expand...

Chipped perhaps-- but are you sure that the rev limiter on a STOCK MK4 Jetta hits over the redline of 4800? Althought I've chipped mine, so it goes past 5000, I seem to remember before doing so, it would rev limit at 4800.

In gear or out of gear did yours stop at 4800?

In gear.

itsmejerry said:

Chipped perhaps-- but are you sure that the rev limiter on a STOCK MK4 Jetta hits over the redline of 4800? Althought I've chipped mine, so it goes past 5000, I seem to remember before doing so, it would rev limit at 4800.

Click to expand...

If it was limited to 4800, the MAF was bad. This is one test for a bad MAF. 5100 is what I've seen around here reported, and that's where my B4 goes and stops.

That's normal under load, gear depending.

In 1st I can hit 5100, in 2nd not quite, in 3rd...nope.

Out of gear it should rev to 5100 RPM.

What Bob said.

If you cannot rev a warmed-up engine to 5,100 RPM in neutral, there is something wrong. MAF is the first thing to look at, but you already replaced that. The second thing would be the fuel filter, in my opinion.

To clear things up, a VE or PD pumped TDI should be able to rev to 5,100 RPM in neutral. In gear, you might not be able to get there... especially in higher gears (as Bob_Fout mentioned).

Back on topic... You had a clogged intake already in a 2004? How many miles? What kind of fuel, driving, oil? The 2004 and early 2005 Jettas are "mules" -- A4 chassis with a US-emissions PD engine. There are some peculiar things about it... like the fuel pumps and EGR coolers. Of the six TDIs in our stable, only one is a 2004 Jetta. We've had both the in-tank fuel pump problem (loose wire), and the leaking EGR cooler. We also had a bad MAF on that car. After all that, it was bucking a little under full "throttle". It turned out to be a clogging fuel filter.

I had a bad fuel filter, changed it this week and it zings the RPM's now. Same model - I was thinking the transmixer was going out! It would not pull past 4,200 - how old is your fuel filter?

The PD will easily rev up to 5000 RPM, they have a much broader linear power curve than the VE cars, which DO lay down and die at about 4500 RPM.

Check the boost sensor while driving, measuring block group 011 I think. 3rd box, should very closely match the 2nd box. Also check the obvious like the air filter, etc.