2 replies to this topic

[855T]

Rich said somewhere that bad O2 sensors will switch the ECU into low boost mode? If so, is there anyway to override that on my '95 855 to help in the troubleshooting process? I'm only making 5 psi of boost, so I'm constantly in danger of losing to V6 Mustangs.

I did replace my cracked throttle body hose with a Samco one, and am in the process of replacing the rest (although they all look fine as they may have been replaced recently) this weekend. What bothers me is that it's intermittent. A few months ago, after getting back in the car from Home Depot, I was making full boost. After the car sat for a weekend, it went away. It's done this a few times, with compeltely arbitrary stop and start times for full boost, although it only declines or increases after the car's been off.

All of the vac lines look good and the rubber elbows are all okay. I've been thinking it might be the BCS since the problem is internittent in the way only electronics can be. Would disconnecting the wire to the BCS allow me to, if the BCS is the problem, to make boost to check? Is it possible to lose the BCS completely and just use an MBC? I have a calibrated boost gauge, although blowing up my car would be bad.

I just started getting O2 codes but have $0 to replace them, so unless I can convince my parents to drop another $350 on my car, it seems unlikely that they'll be replaced anytime soon.

I suppose, if it were really necessary, that I could replace all of the vac hoses, but it seems like an awful lot of time and money and frustration to go through when the hoses all look really good. I'm not even sure how I would go about getting to some of the ones near the turbo.

Any help appreciated. Thanks.

[Gregg]

The vacuum hoses are really simple, and should be the first thing that anyone checks/replaces when he/she is having boost problems. The only one that requires some effort to get to is the one that's under the air inlet hose on the turbo. Just remove that plastic tube that goes from the turbo to the airbox, and look down and to the left of the turbo inlet. Check all the elbows again too, as sometimes they develop small cracks that can't easily be seen without closely inspecting them.

I had an MBC hooked up bypassing the BCS (my BCS was definitely still good) and I didn't really like it. It caused me to run super rich as I turned up the boost. If you want to run an MBC to increase boost or spool-up a little, hook it up between the bcs and the wastegate actuator.

P.S. the rest of the turbo hoses may look okay, but they are more than likely worn out and susceptible to expansion while under boost. The best time to check them is right after some hard driving. Then pull over, and just feel the hoses. Most likely they will feel kind of mushy. This is bad. If they feel like this, they probably could use replacing. But unless one of the hoses is cracked, you shouldn't have any problem making stock boost.

EDIT: Pop your hood, stand at the front of the car, and look at the bottom left of the underside of the hood. There should be a vacuum hose diagram sticker there

Edited by gmischenko, 11 May 2005 - 01:28 PM.

[JHEIII874T5M]

an o2 code will send your car into limp mode. Thus, you will be limited to 5 PSI when that code is set.

This can be overcome, however, by simply disconnecting all 3 vacuum lines from the BCS while leaving the BCS electronically plugged into that connector. Take the vacuum line that leads to your air intake, remove it, and then plug the hole left on your air intake. Then, take the other 2 vacuum lines (off the turbo) and run them to a MBC. Be sure not to go over 12 PSI with this setup. It will work just fine. You may run a bit rich (due to the o2 codes and the bad o2's) but you will be fine.

Edited by JHEIII850Turbo, 11 May 2005 - 01:04 PM.