I will try to keep this short.

99 c5 has been running awesome. Went to pick up a car with my son yesterday. Traveled about 120 miles. No known issues. Did drive through some heavy rain but did not notice an problem.

Went to leave and was accelerating. At about the 4000 rpm range it felt as if the fuel shut off just momentarily (just my description).

Pulled out on to the interstate, car seemed to be running fine, and began accelerating and the best way to describe it is the car just seemed to be down in power. Seemed almost like hitting rev limiter but nowhere near it.

I was in the competitive driving mode. Put it in traction control off mode and it seemed to run better.

After catching up on the interstate we did a roll on and the car got into the above 4000, range and just kind of gave a quick shudder from the front. All gages are reading correctly and everything seems to be where it should.

Continued home with no incidents.

Car just seems to be down in power. Usually it breaks the wheels loose in 1st and 2nd. Not happening now. (this is as it approaches boost and on thru to redline).

Exhaust note sounds normal. Gages normal. Vacuum normal. Boost reading normal. Just down in power.

It really seems as something is just grabbing hold of the power and just preventing it from spooling at full power. Kind of a reduced power sensation.

I did have suspension work done where I had to take off the front charge pipes to change the front spring. Everything to my knowledge went fine and couplings were properly tightened.

So, car is not running badly, I can just tell it is down in power. Probably more to post but don't know what info to give from here.

Never pulled codes but will search the forum to learn that and will get that done this morning.

thanks for any input

Any ideas?

 

have you pulled the plugs? my .02 your missing an electrode...or part of one...

 

It is not missing or running rough. Just does not seem to have full power.

 

My guess is a discharge tube has slipped off, look by the rear wheel wells first. Do you have a boost gauge?

 

I do have a boost gage. It seems to be reading normal, it goes to full boost 7.5 lbs.

 

just double check....no SES?

 

What is an SES Nick?

 

My guess is you're blowing out your spark.

What plugs are you running and what are they gapped at?

 

that is kind of what i said, if your missing some/all of the electrode it may still be able to ignite/arc during regular driving but under a load/boost your blowing it out...

happened many times in my slow 10.80 vortec mustang back in 92 and also happend on my fairly quick 9.0 turbo hayabusa.

 

I had this exact problem and Doug hit it right on the head in that exact area is where it came loose, mine was bad about blowing loose after spirited driving.

 

Sitting here thinking about this. Is the what sts calls the charge pipe, the pipes going from the turbo to the intercooler? That would make sense to me.

Sorry to be so dense.

Let me know if that is correct.

 

yes. charge pipe would anything after the turbo that sees boost.
you should REALLY do a boost leak test, with all the piping associated with that kit there has to be a ton of leaks.

 

I am sure you are correct. Although I have not had any issues til now. I did just install new springs and I know the front charge pipes had to be removed for the install.

I will get it on the hoist and check all fittings. I don't think this is a coincidence.

thanks

 

If you say the boost looked fine when you were watching the gauge, I don't think it is a problem with your charge piping?

You didn't mention what your wideband was reading. I would take it back to whomever tuned it for you and ask them to log your vitals during a test run...

 

Well there was a clamp that was totally loose. Not a pipe disconnected but clamp was just hanging on the pipe.

Raining here so will have to wait awhile for test.

I do think a boost leak test would be in order and will try to get that done.

Thanks for all the help everyone.

 

just because the gauge is reading the correct amount of boost doesn't mean there isn't a leak someplace.

in a proper setup your boost gauge is tapped off the intake manifold and the WG is usually referenced off the compressor housing.
a leak in the charge piping between the two won't always be seen on the gauge, unless its HUGE, because the turbo might still be able to move enough air to make the target amount of boost. however, because of the leak, the turbo could be WAY out of its effiency range and thats why there is loss of power... if that makes sense to anyone.

thats the reason why boost leak testing an FI car is sooooo important!

 

Rain stopped and got it out for a test run and it seems to be running strong again.

Thanks for all the help.

 

That makes a lot of sense, especially with the way our STS kits are ran. I haven't measured it, but from my boost gauge through to the vacuum/boost reference hose (brake booster hose) then back down to the wastegate in back next to the turbos is at least 15' feet of hose? It may or may not have a greater delay than front mount kits.

I can definitely see from your description if a leak was up near the intercooler for example, the turbos would be forcing 5psi of air past the wastegate and that would register back up on the boost gauge correctly but the pressure would be splitting off at the leak causing less pressure to enter the intake. Great description, I'll have to check all my lines now as well