87 300d w124 was fast but now slow

[thayer]

We have a the above listed car. Recently rebuilt engine, all new lifters and a rebuilt tranny. 4000 miles ago it ran extremely fast (as compared to my 83sd and our 86sd). Now it has trouble keeping up with our 240. I've looked through the alda adjustment threads, the plugged cat threads, and the trap threads.

I haven't done anything to the car since it has lost its luster. We have checked air filter and fuel filter.

What is the sequence of testing the above items? Are there any specific symptoms we should look out for outside of slow acceleration?

Thanks

Kent

[winmutt]

See if you can blow air through the overboost valve on the sound wall.

[vstech]

"has trouble keeping up with a 240"
that's more in line with cat issues. is there any soot around the exhaust in the engine bay? if not, then pull the brass pipe plug out of the exhaust manifold and take it for a drive. if it's more responsive, your cat is plugged. (*it will be LOUD with the plug out!)

Bring the car saturday, and we'll give it a thorough once over.

[compu_85]

When My ALDA line was plugged the car was quite slow. It struggled to do 80 and would never make the 3-4 shift @ WOT.

An easy quick test is to nab a bit of vacuum line and connect the intake fitting right to the ALDA. Beware this can cause shifting issues as it takes the boost modulator out of the circuit.

-J

[thayer]

Will deleting the Alda remove the modulator from the circuit? I doubt it but I wanted to be sure. Many people remove the alda on their daily driver and I can't believe they would drive with no modulator.

[compu_85]

You could still leave the blue boost pressure based modulator hooked up with the ALDA deleted.

I deleted the modulator on my car (which makes it like an 84 or older, or 92 and newer).

-J

[thayer]

Originally Posted by vstech

"has trouble keeping up with a 240"
that's more in line with cat issues. is there any soot around the exhaust in the engine bay? if not, then pull the brass pipe plug out of the exhaust manifold and take it for a drive. if it's more responsive, your cat is plugged. (*it will be LOUD with the plug out!)

Bring the car saturday, and we'll give it a thorough once over.

That's a great idea. I'll see if the owner is cool with it.

[scottmcphee]

I've had an ALDA / seal fail in the night, only to find the car was a dog the next morning, couldn't make 60mph easily, and I noticed the turbo never spooling up past 6 psi.. (interior gauge). I figured it was a turbo / wastegate issue. Nope, removing the ALDA cured it.