legacycentral bbs

I know you guys are sick of these threads (as it seems to be the most commonly asked question).

Basically, I have a bone stock '93 Turbo Sedan. I suspect my car is victim to the known "Hesitation at full throttle due to the Boost Control Solenoid" issue that I read about in the Turbo FAQ. Basically the car is peppy, but at full throttle I get a slight hint of jumpiness... it's not smooth at all.

Now, I feel my needs are particular because I won't really be modding this car. I don't plan on getting an intercooler, I dont plan on getting exhaust, so I don't really plan on upping the boost.

Ideally, I would just buy another boost control solenoid to replace what I think might be a faulty one. I was reading, however, that a boost controller could be a cheaper solution, and it would allow for upgrades in the future. I don't have a boost gauge installed... so tuning one might be difficult.

What are your guys opinions? Should I just get a new stock BCS or go with some form of MBC or EBC?

Without a boost gauge, the only reasonable option is a new stock boost control solenoid.

But a simple ball-and-spring boost controller and boost gauge would probably cost less combined than a new solenoid, and should serve your needs pretty well. Drawbacks are that you won't get altitude-compensated boost and that some MBCs can be sensitive to changes in temperature.

Have you tried cleaning the solenoid?

How would I effectively clean it? just externally?

We discussed it a little here:

http://bbs.legacycentral.org/viewtopic.php?p=46201

I cleaned mine how I described and it seemed to smooth out boost buildup a little, but it might have just been the placebo effect.

Mine ran a lot better when I replaced all the vacuum and boost pipes. I say this as its been hesitating a bit recently and 1 of the pipes was a bit loose, hey presto no hesitation (or fookin massive bunny hops when coming off the throttle).

Before you do ANYTHING else: lose the old knock sensor and get the updated version. Even if it doesn't fix this problem, you've just fixed a problem that you're almost guaranteed to have down the line.

-mike

Hmm, didnt really help mine m8, just put a new one in mine after wrecking the last 1 trying to get it to work properly (at 93 pounds im still feeling ill!) and its only as good as it was before sadly .

Sir Yach-o, I am curious about your comment on replacing with an updated knock sensor. I have a 94 Turbo sedan. What is up with knock sensor problems?

Did you sand the mating surface on the block and sensor before installation?

FWIW:
I also am experiencing the "hesitation" problem. I took out my BCS and sprayed it down with carb cleaner last week. I was expecting a bunch of gunk to come out but the fluid ran clean. I stood it on it's end for about 40 minutes and waited for it to dry out. I blew into it and it seemed pretty dry so it put it all back together. I haven't had an opportunity to get on the highway and check to see if hard acceleration will trigger hesitation now. I will report with any news.

One thing that happened to me is when I was prying the solenoid off the bolts/strut-towers, I banged into the MAP solenoid and broke the little plastic piece end off. It's the one on the left side that looks like a cylinder - black colored, not where the tube hooks up but next to it. I epoxy'd it back on (I made sure I didn't glue up the hole in the center). Should I get another solenoid instead? What does that bit do?

-Brian

Hesitation doesn't always have to do with the boost control solenoid; non-turbo Subarus suffer from it sometimes too.

You cleaned the solenoid off the car? I don't know if it really matters or not, but I cleaned mine with it still connected to the car's wiring harness and with the ECU in test mode. This cycled the solenoid on and off, so I felt confident the cleaner got into all the little crevices inside the solenoid. A noticeable amount of grease came out.

By "MAP solenoid" do you mean the pressure exchange solenoid? The little brown cylinder? That solenoid switches the pressure sensor input between atmospheric and the manifold. Did you break off the little black cylindrical filter that goes over the atmospheric nipple? If so, you could probably just get rid of it and put a little piece of cloth over the opening. Secure the cloth with a ziptie or something, and it should work fine.

I cleaned the BCS off the car because I didn't know you could do it on the car. Thanks for the tip. How do you put the ECU in "test mode" anyway?

You got it right vrg3! I broke *that* piece off. I think I glued it back in place though. What does that whole solenoid thing do anyway?

BTW: I went and checked everything again and I found a vacuum tube unhooked. I don't know if it was because I hooked it back up or the cleaning but the hesitation on hard accel seemed to go away. It was the tube that branches off the air intake to something underneath the throttle body.

-Brian

To enter test mode, hook up the green connectors under the dash. When you turn the ignition on with the engine not running, the ECU cycles the solenoids repeatedly. I sprayed carb cleaner into each of the ports while this was happening, rotated it around to let as much dirt drip out as much as possible, and then hooked it back up and went for a drive to let boost pressure blow out all the remaining carb cleaner.

That solenoid lets the same pressure sensor measure two different pressures. There's a little more explanation on this web page: http://www.graphics.cornell.edu/~v/chrysler_map/

The tube that branches off the air intake to tsomething underneath the throttle body... Sounds like you're talking about the blowoff valve. Was it a big 19mm hose? If it was, I wouldn't imagine your car would even run, so it was probably the small vacuum hose that feeds the blowoff valve actuator. That would be a small vacuum leak which would screw up fueling slightly and also allow the compressor to surge whenever you let off the throttle. Here's a diagram of all the small vacuum lines on the car: http://www.graphics.cornell.edu/~v/vacuum/

Thanks for the ECU test mode info vrg.

Yes, it was a big hose. Does the blow off value also have another hose that goes back to the air inlet ductwork? It connects to the big elbow after the resonator box (I hope I'm naming it right).
Is this the blow off value?
http://www.legacycentral.org/images/mem ... e_side.jpg
The piece on the middle right with the red/silver badge on it and connects to the elbow? The hose connected to that thing.

-Brian

Yes, that's the blowoff valve. One hose goes to the intake duct right behind the throttle body and the other goes to the elbow at the turbo's compressor inlet.

So your engine was able to idle with one of those hoses disconnected? Wow.

Well in the end there, it wasn't very happy about idling, but it did. It definately wasn't happy about accelerating.

-Brian