Major HP Dropoff above 2500 RPM in 5th...

Status
Not open for further replies.

alluneedizshagbaby

Active member
Joined
Aug 3, 2002
Location
Denver
'96 NA Passat TDI (112,000 miles)

When I cruise along flat freeway at 87MPH (140KPH) at 3000 RPM and then hit even a slight uphill incline (1-2 degree gradient) speed drops to 80MPH (along with RPM) with pedal floored. Have instances of dropping to 65 or 70MPH with steeper uphill gradient with pedal floored. Notice related problem when driving in mountains. Had to down shift to 4th and sometimes 3rd!

This is a recent problem in the past 20,000 - 30,000 miies (currently has 112,000). Timing Belt replaced at 55,000 miles. I can remember 1- 2 years ago I could fly through the mountains with no compromise in Speed/RPM at 80MPH/2750RPM. Also no problem with HP on Freeway driving in past.

What could cause seemingly gradual drop in HP performance?

I know Air Filter is fine, not relevant. Compression problem? Could Timing be off? Brainstormers welcome!
 

alluneedizshagbaby

Active member
Joined
Aug 3, 2002
Location
Denver
I can rule out Air Filter because I removed it for a Test Run and same HP performance.

Please spell out MAF and can you help identify where it is located under the hood?
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
Not MAF, either. Not on that car. (By the way, that is a Mass Air Flow sensor - but it's only a problem on the later models - the older ones almost never break).

I can almost guarantee that the problem involves the hose from the intake manifold to the ECU. The ECU is not seeing the proper boost pressure, and is going into "limp mode". Read the TDIFAQ troubleshooting section.
 

alluneedizshagbaby

Active member
Joined
Aug 3, 2002
Location
Denver
Thanks GoFaster...I checked out TDiFAQ Section 8.e.1 2nd paragraph: Manifold pressure sensor problems.

I'll replace the hose and give it a test run. Might take me a week or 2 (got Holiday obligations around now), but I'll post the results ASAP!
 

alluneedizshagbaby

Active member
Joined
Aug 3, 2002
Location
Denver
GoFaster...you're a TDI BIG BRAIN!!! I checked out that hose. The outside of the hose is a black, cloth kind of sheath. The inside of the hose is a black rubber hose. The reason I know that is because I followed the path of the hose to the Intake Manifold and found that the hose has been rubbing against another engine component (electrical). The other component was cutting into the hose. I could see it cut far enough into the hose to expose a hole in the air pressure passage. I let you know the results after I replace. Hopefully tonight!
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
One other thing, check the intake manifold for possible clogging. (If you have OK acceleration in the lower gears then this isn't the MAIN problem, although it could be a contributing factor.) TDIFAQ has a description of how to fix the problem and how to prevent it from happening again.
 
Status
Not open for further replies.
Top