Bad Throttle Hang

[Rustee]

Hai guise, I'm new here Recently picked up a '93 turbo.

I just finished putting in a new clutch (removed engine & tranny) today, all went well, started right up etc. But heres my problem; after revving it up a little bit it will stay at that RPM. It does this at basically any RPM and at the lower rpms it will slowly start to return to normal idle speed after about 15 seconds. It did have a hang before the engine was pulled, but now its worse.

I tried finding any vacuum leaks with brake cleaner but couldn't find or hear anything. Went over all hoses and everything looks like its connected and in the right spot.

Any ideas?

[brweber352]

Have you tried snapping the throttle under the hood to make sure it's returning to the closed position? It could be hitting something, keeping it from closing all the way. If you have a top mount intercooler it could be hanging up on it, I had this problem with my TMIC.

You may have some carbon built up in the throttle body housing, maybe try cleaning it.

You may want to try cleaning the Idle Air Control Valve, they have a tendency to start sticking. They're a pain to remove, you have to pull the turbo to take it off. Most people just pour a lil' seafoam down the black hose that runs from the airbox to the IAC.

Warm the car up, shut it off, pull the IAC hose from the airbox and pour a lil' seafoam down it so it get's to the IAC and let it soak for a few minutes. Crank it up and let it idle, the fumes will be extreme so do this in a well ventilated area. You may want to reset the ECU after this so the ECU can learn the new idle.

Have you checked for any CEL's. My only other thought might be trying to adjust the idle stop switch on the TPS.

Hope this helps some and good luck. maybe someone else will chime in.

Brian

[brweber352]

here's a thread that might help some.
http://bbs.legacycentral.org/viewtopic. ... adjustment

Here's how to adjust the idle stop switch.
http://www.main.experiencetherave.com/s ... sting3.jpg

More on testing the TPS
http://www.main.experiencetherave.com/s ... sting1.jpg
http://www.main.experiencetherave.com/s ... sting2.jpg

Here's a good page with info on checking CELs and resetting the ECU, also more infor about the TPS closer to the bottom of the page.
http://www.surrealmirage.com/subaru/engine.html

[Rustee]

Thanks for the input Brian. First thing I checked was to see if it was closing all the way, and it is. Right now I have the intake all apart and throttle body off and cleaned, also that little check valve right above the IAC in the manifold seemed a bit sticky so I cleaned it.

If it still does it after I reseal everything I'll probably try to find some seafoam around here to dump in the IAC seeing as it's a PITA to remove.

[brweber352]

Check valve? Your talking about the threaded valve in the manifold? that's the pcv, there not real expensive, like $2-$3, may just want to replace it.

[Rustee]

After putting everything back together the CEL came on with a code 22. I got a can of seafoam and poured it down the IAC pipe, let it sit for a few mins, ran the engine. I did that multiple times using more and more, and it hasn't changed a thing.

So I did the resistance tests described in AllData and got some interesting results.

IAC valve
Terminal: / Resistance:
1-2 / 9.9 (spec 9 Ohms)
2-3 / 9.9 (spec 9 Ohms)

TPS
Terminal: / Resistance:
2-3 / 9.45K (spec 12K)
2-4 / 8.20K fully closed (spec 1K)
1.37K fully open (spec 4.3K)

Knock sensor
258K (spec 560K)


Not sure if any of this is really usefull.

[Rustee]

Some more findings, if I pinch off the hose to the IAC valve while its "stuck" at any given rpm, it will return to normal idle and doesn't hang when revving.

Now my question is, could this be a sticky IAC or a bad TPS? Would a TPS giving off a bad signal cause the IAC to open more? Does it even work like that?

[Rustee]

Adjusted the TPS as it was out of spec (no continuity at fully closed and 0.7mm open). Readings are now 8.92K closed, 2.05K open.

Won't know if this does anything until tomorrow now. One of the hose nipples broke off the coolant tank spraying hot coolant everywhere

EDIT: I think it just hit me. When I lifted the engine and trans out I only had one chain from front of the engine to the back. The chain ended up sliding through the hook on the crane and bent the engine cover bracket pushing it into the TPS. (What was I thinking ) That must of turned it more out of spec than it already was, causing the throttle hang to get worse. Seems possible to me.

[brweber352]

All that should help alot. Now that you set the TPS idle stop switch your specs seem alot better and you probably fixed your problem. I would highly recommend resetting the ECU and clearing the codes.

Code 22 is the knock sensor. The original knock sensors were prone to cracking and had a grey connector. Subaru has updated the sensor to be more crack resistant, the updated version has a white connector.

Your knock sensor is probably in need of replacement. I would check all your connections and reset the ECU, if the code comes back I would replace it with a OE sensor. This is probably non-related to your other problem, but this is a very important safety feature that should be working properly, for piece of mind anyway, IMHO. With all the engine/tranny removal, there is a possibility you may have damaged the KS wiring, it tends to get brittle and weaken over time. I'm optimistic and think it's an eronious code or just a bad sensor though.

Brian

[Rustee]

Yeah, I was looking at the knock sensor when I had the intake off again and noticed it has 2 cracks in it. I'd say its time for a new one. That's how I broke the hose off the tank, trying to get the KS connector plug off the bracket, must of hit it with my arm. Also disconnected the battery and leaving it overnight.

Would you happen to know the torque spec for the knock sensor bolt? It's hard to find stuff in AllData sometimes.


EDIT: A TSB in AllData says 17.4 +/- 2.1 ft-lb. sound right?

[Rustee]

Problem solved, it was the TPS out of adjustment the whole time. Derp.

The CEL turned off after a bunch of driving breaking the clutch in, but the code is still there. Time for a new knock sensor.

[brweber352]

I feel you on the coolant tank issue, mine just broke at 166k miles after swapping turbos. I just replaced it with a stock one, cost $120 but figure if it last another 166k miles it worth it.

Don't know the KS torque specs off the top of my head, but that sounds close(15-17ft lbs). I just snugged mine down with a 3/8 ratchet, I cleaned the block before I installed it, not sure it's needed but doesn't hurt. I check the bolt every once in a while to make sure it's still snug, and it is after 70k miles.

I've never had luck resetting the ECU and clearing stored codes by disconnecting the battery. I've only ever had luck by doing the connector and driving procedure or pulling fuse 14 for about an hour. Pulling fuse 14 and disconnecting the battery are supposed to be essentially the same thing, but never works for me, don't know why.

Here's some links on fuse 14, if you click on the images it will zoom in.
http://www.main.experiencetherave.com/s ... ns/118.jpg
http://www.main.experiencetherave.com/s ... ns/119.jpg

Brian

[Rustee]

I might just have to buy a new coolant tank as well, I tried all the local wreckers with no luck. Attempting a more solid fix using a brass hose nipple, some plastic pipe and lots of super glue haha.

I'll keep that info in mind when I try to clear codes next time. When doing the connector and driving procedure, once you start moving can you stop, go, stop, etc. until you get a full 1min of driving over 7mph? I'm guessing thats how it works but not 100% clear.

[Legacy777]

How did you adjust the TPS? The actual resistance of the TPS isn't as important as the idle switch. The ECU adjusts things based on the TPS resistance on startup. The newer cars did away with the idle switch and based things on the resistance at startup.

Here's the third scan out of the two that Brian previously posted. It talks about the idle switch and how to adjust it.

http://www.main.experiencetherave.com/s ... sting3.jpg

[Rustee]

Yeah, I followed the alldata procedure which are the same as those. Using a feeler gauge and multimeter to check for continuity with the different sizes. No more hang

[brweber352]

Josh, LOL it's no biggie, but if you look at the 3rd post, the 2nd link I posted was about the idle stop switch. I posted it out of order because I recently found out about the resistance not being as important as the idle stop switch itself, LOL.

Rustee, I think we established you got the hang/idle problem under control,right?

I might just have to buy a new coolant tank as well, I tried all the local wreckers with no luck. Attempting a more solid fix using a brass hose nipple, some plastic pipe and lots of super glue haha.

I am gonna keep my old tank and fix it in a similiar fashion in case of emergency. I was thinking about using a tap and die to make some threads in the tank for a fitting, and maybe use some liquid teflon, high temp RTV, epoxy, or something similar that can handle the heat. Maybe use some epoxy on the outside of where the fitting meets the tank. Probably not needed, unless 13psi is enough to blow the fitting out?
To each his own, this is how I'll probably fix mine. Your's maybe broken completely different than mine.

I'll keep that info in mind when I try to clear codes next time. When doing the connector and driving procedure, once you start moving can you stop, go, stop, etc. until you get a full 1min of driving over 7mph? I'm guessing thats how it works but not 100% clear.

If you have an automatic you should be able to do the connector/throttle procedure and just drive untill the CEL starts flashing the all clear, including stop and go. I have done the procedure and driven for like 30 miles in traffic before I disconnected them, you should probably drive easy though. If it's a manual, I think you have to at least upshift into 3rd gear or something.

This is how I normally do mine, it's Automatic Transmission.
Warm engine to operating temp, I usually wait till I get home after work. Turn key to off position, connect both sets of connectors. Turn KOEO(key on engine off), slowly depress throttle all the way down and hold for like 2 secs, slowly return throttle to half way and hold for like 2 secs, slowly return throttle to top. Start engine and idle for like 10 secs, put in reverse and back out of parking spot, put in drive and after 30-50ft(sometimes alot less) the CEL is already flashing the all clear. Re-park car and shut off, unplug both sets of connectors, restart vehicle and let idle for like 10-15 secs, then turn car off. I then usually connect the black connectors just to make sure all the codes are gone.

After I reset the ECU I normally drive easy(no boosting, WOT) for 50-100 miles, so the ECU can relearn a lil'. If I go WOT right after I reset the ECU, I normally get knock and the ECU sets boost to wastegate pressure(which is like 5-6psi), and retards ignition timing.

All this is just stuff I do and some of it may not be needed. This works for me, it may not work for you.

Good Luck,
Brian

[Rustee]

Rustee, I think we established you got the hang/idle problem under control,right?

Yep, thanks for your help figuring out the problem, which turned out to be a simple mis adjustment

I am gonna keep my old tank and fix it in a similiar fashion in case of emergency. I was thinking about using a tap and die to make some threads in the tank for a fitting, and maybe use some liquid teflon, high temp RTV, epoxy, or something similar that can handle the heat. Maybe use some epoxy on the outside of where the fitting meets the tank. Probably not needed, unless 13psi is enough to blow the fitting out?
To each his own, this is how I'll probably fix mine. Your's maybe broken completely different than mine.

Yeah, I was actually going to do something very similar to this. But I don't have the right tap for any of the fittings I have around. So far the brass/plastic/super glue ghetto fix is holding up great.

This is how I normally do mine, it's Automatic Transmission.
Warm engine to operating temp, I usually wait till I get home after work. Turn key to off position, connect both sets of connectors. Turn KOEO(key on engine off), slowly depress throttle all the way down and hold for like 2 secs, slowly return throttle to half way and hold for like 2 secs, slowly return throttle to top. Start engine and idle for like 10 secs, put in reverse and back out of parking spot, put in drive and after 30-50ft(sometimes alot less) the CEL is already flashing the all clear. Re-park car and shut off, unplug both sets of connectors, restart vehicle and let idle for like 10-15 secs, then turn car off. I then usually connect the black connectors just to make sure all the codes are gone.

After I reset the ECU I normally drive easy(no boosting, WOT) for 50-100 miles, so the ECU can relearn a lil'. If I go WOT right after I reset the ECU, I normally get knock and the ECU sets boost to wastegate pressure(which is like 5-6psi), and retards ignition timing.

All this is just stuff I do and some of it may not be needed. This works for me, it may not work for you.

Good Luck,
Brian

Thanks. I have a manual. I believe you have to take it up to at least 4th and drive for a minute or so. No biggie either way. I know all about relearning ecu's, usually takes about a tank of gas for my chipped Volvo 240 to relearn before getting into boost, or else you get pinging and such.

[Legacy777]

Josh, LOL it's no biggie, but if you look at the 3rd post, the 2nd link I posted was about the idle stop switch. I posted it out of order because I recently found out about the resistance not being as important as the idle stop switch itself, LOL.

Brian,

Sorry, I missed that you posted it out of order