vnt boost problems `again`

[GLHSHELBY]

I had posted this a few months ago and had a couple good responses but I forgot to print them. The thread must have been deleted. I`m getting abount 6 lbs of boost before it cuts-out.I`m almost positive my vacuum lines are right. Someone had said something was near the battery that I maybe needing to look for. I`m gonna try a little harder this time to work on it,I was working every weekend then. If I have to success I may try and just put a t2 on it.

[Will Martin]

I just thought of something while reading your message that 'may' help you out. While changing out ALL and I mean EVERY FREAKIN LINE in my S60 VNT, I noticed that while all the lines were hooked up, some connected incorrectly, a couple were just tee'd off into no where and some of the plastic lines had hairline cracks in them. Meaning that they would barely show when the car was idling, but under boost they probably leaked a lot.

Are there any codes? Exhaust leak? Are the VNT solenoids connected correctly? Wow man, I'm really stumped on this one. If it were me, I'd just start with redoing every vac line and then every connection (intercooler lines, etc) until everything was checked. BTW, are you using the stock airbox?

[GLHSHELBY]

I had an extra set of solenoids.I switched them out and it got worse.I then switched back,and replaced some of the lines that had hairline cracks with the ones in good shape. I`m getting no codes .It run`s good on the hwy besides this problem.I just drove it to Charlotte for the autofair[1st time driving it longer than a mile in 6 months].

[Will Martin]

Well if you don't have any codes and you switched everything back, maybe it's something mechanical. Sounds like you have a boost leak somewhere. What about the intercooler hoses? Exhaust manifold and turbo bolted up alright? What about the donut on the exhaust? Mine looks as if it's about to fall apart. I'm sure I'll have to replace it soon.

[sdac_guy]

Quote:

I`m getting about 6 lbs of boost before it cuts-out.

What do you mean by cuts out? Boost stops, engine dies, goes into overboost control (stutters like a consistent misfire)?

Trying to narrow the problem here. Is it that not enough boost is being made, or that while target boost is being attempted, overboost control is coming in.

Generally, if the vacuum lines on the boost side of the vane actuator leak, boost will be uncontrollably high, not a low boost condition.

If overboost control is coming in early, then the MAP sensor could be suspect.

Has the car ever run right for you? Is this a problem that just started happening one day, or has it always had problems?

Do you know the history of the car? Did it ever have the TSB regarding overboost control applied at the dealer? That TSB, while well intentioned, really screwed up the system. I do not have any exact details on it, but it used another solenoid and a replacement SBEC.

Barry

[Turbozcs2003]

what condition is the turbo in? Dont some have issues where the vanes get carboned up and the turbo does wierd things?

Also if your cat is clogged, could cause issues.

Do you have the vacuum diagram? I believe the vacuum harness has one way check valves/orifices in it(all Turbo harnesses do) and if you ditch the hose and check valve and simply sweap in new line it can cause issues, probably more so in a VNT.

As Barry mentioned, are you hitting cut out at 6PSI?? should be higher than that and should trigger code 53 if so.

Mike

[GLHSHELBY]

Quote:

Originally Posted by sdac_guy What do you mean by cuts out? Boost stops, engine dies, goes into overboost control (stutters like a consistent misfire)?

The boost stops,engine doesn`t die ,it didn`t stutter much,fells like hitting overboost slightly .I went to change the wheels and tires today and when I cranked it up it smelled like gas really bad.This is the 1st time of it doing that. Well I tracked it to behind the gas tank. The hoses were severely cracked so I replaced them for $1.18. I drove it around the block and it drove perfect,no problems like a new vnt car. About 2 miles later it cut -out again just a little bit and boost actually feels like it`s getting power and pulling the car.I drove it again about an hour later and it drove pretty good but it didn`t seem to pull any harder after 9lbs or so but the boost needle still climbed to around 12. So I`m not sure what was happening but that it`s gotten a lot better part of the time. So I believe I`m gonna try and fix the problem now instead of switching to t2 status. I do feel as of right now it maybe reliable so I`m gonna be driving it some now so I may run into some problems. I did get a new oil leak somewhere under the intake manifold that I got to track down.

[GLHSHELBY]

I can`t find anything out of place now.Anyone else with ideas on what could be happening?

[GLHSHELBY]

Barry,the car has never run good.I bought it in this condition.I just couldn`t let the csx-vnt slide past me w/o grabbing it. I actually thought the turbo was bad when I bought the car because it sounded like a vw bug.It ended up just being a really bad exhaust leak because some bolts had come loose on the exhaust manifold. I replaced the turbo and turbo lines.

[GLHSHELBY]

Quote:

Originally Posted by Turbozcs2003 what condition is the turbo in? Dont some have issues where the vanes get carboned up and the turbo does wierd things? Also if your cat is clogged, could cause issues. Do you have the vacuum diagram? I believe the vacuum harness has one way check valves/orifices in it(all Turbo harnesses do) and if you ditch the hose and check valve and simply sweap in new line it can cause issues, probably more so in a VNT. As Barry mentioned, are you hitting cut out at 6PSI?? should be higher than that and should trigger code 53 if so. Mike

I don`t believe the cat is clogged,but is there a way to check it?I`d say if I take off at 10 different redlights the car will run normal 2 or 3 times in 1 gear only. So the problem isn`t 100% of the time which in my opinion rules out the cat.

[GLHSHELBY]

I`m almost happy with the performance of the car when it`s running normal which aggravates me more that I can`t find the problem out with this car. Once I finally figure out the problems I want to put a 14-15 lb cal in to really wake it up but until then I have to drive the car and get this problem fixed.

[sdac_guy]

Nearly all faults on a VNT system will cause too much or uncontrollable boost. It is rare for too little boost, almost as if the actuator is stuck in one position, not letting the vanes move to where they need to be for upper rpm boost range. But then it is not a consistent fault since it runs fine sometimes ... why?

hmmm .... still thinking.

One thing to try, with the engine off and cold (so you don't burn your arm), reach behind the intake and grab the actuator rod. Then have someone start the car, the rod should move from the vacuum applied. That just proves the actuator/vanes are not frozen in place.

You should have vacuum on the line to the top actuator nipple at idle. The larger bottom line should (and most likely does) have boost pressure under boost.

Barry

[90DodgeVNT]

Here is my spin...


Took me a good 2-3 times to get all the vac lines right with the check valves in place. This was even after I had silicone lines that did not leak, however, the 4-5 point junction off the intake did. Get a few brass fittings, vacuum block, and about 5-6 brass nipples to connect the lines to.


Were it me and I had to do it all over again, I would just replace the whole mess with some really good silicone and not try one line here, one line there



Good luck.

[rachaelabel]

I had the exact same problem with my VNT lebaron. It was a vacuum leak directly off the turbo from the main vane. It didn't even look like the line was off, but once I carefully put the line back on, I was back to 12 lbs. of constant boost with overshoots to 15 psi.

[GLHSHELBY]

Quote:

Originally Posted by rachaelabel I had the exact same problem with my VNT lebaron. It was a vacuum leak directly off the turbo from the main vane. It didn't even look like the line was off, but once I carefully put the line back on, I was back to 12 lbs. of constant boost with overshoots to 15 psi.

The factory turbo had 1 vacuum line hooked to it,the new turbo I have has 2 on it.I connected it to the same one. I doubt this would make any difference since the factory turbo just has a plug instead of a vacuum line barb. I plugged it off real good.