Overboost Condition

[RobGT]

Yup. Thats me. P0234 Overboost.
My first CEL came on when using autostick.
This has NEVER happened in D.

FYI
Was at about 1/2 or 2/3 throttle.
I was letting the autostick change gears from 1 to 2.
Hit my DSBC switch/high boost at about 5500rpm.
Gear changed at limiter. About 6000 (?)
Got a loss in power, then CEL. Was it fuel cut??
Boost gauge read about 14 psi.
Boost Warning alarm @ 17psi never sounded.

Everything should be okay, right?
Gonna reset the CEL. and try the same again at full throttle.
Any thoughts/suggestions?

PS - DSBC set at 7/14psi @ Full throttle.

[Gear_Head]

Rob, I have not hit fuel cut yet, but thats what it sounds like. Just for fun, you might try teeing the boost gauge at the Vacum connection in front of the throttle body. Thats the line that feeds the boost to the ECU. I don't think it will make any difference but it wouldn't hurt & easy to do/undo. It could possibly be that the qiuck change in boost level (7-14) at Hi RPM may have triggered the cel w/out an actual overboost condition existing. Your course of action sounds appropriate. BTW how many bars did the TT read at peak hold (if you had it in the peak hold mode) You might consider running the TT boost in the peak hold mode for a few days or until (if) it were to happen again. In any case I don't believe you hurt anything, Thats why fuel cut is there. How was the EGT reading at the time? [:I]

Alan

[RobGT]

quote:Originally posted by Gear_Head

It could possibly be that the qiuck change in boost level (7-14) at Hi RPM may have triggered the cel w/out an actual overboost condition existing.

I agree. Peak hold was still @ 1.08hkpa (17psi?) from the other night (no code).
Warning is set @ 1.05hkpa and again, no alarm.
EGT was normal, not sure probably between 10-12.

Hmmm. I think its a partial throttle thing.

Hey Alan whats your minimum Auto time set to? Im on 30 sec right now.
I switch to 3 min manual after a hard run.

[amx1397]

this does not happen at full throdle at 1/2 throdle you are getting a lot of boost and the not so much gas so your ox sencer tells the computer to shut down now at full throdle you have more fuel and 15 or so boost if you disconnect the boost sencer line next to and in front of the throdle body, leave both ends open. you can run 18 to 20 lbs of boost just dont do it all the time, even then if you are 1/2 throdlrwe and your boost goes above 12 you will get shut down after 7 seconds we need a new ecu or always stay at full throdle

[Gear_Head]

I am set at a minimum of 1 minute and have the auto mode set to 130 seconds for every hour driven. I very rarely run it hard close to shutdown, but when I do I'll add 2 min. If the EGT is high at shutdown, I'll add some time too. How was the CTFIII couldn,t go this year, maybe next year. You goin to watkins glen?? Am considering goin there. I would love to meet any of the people on this forum !!!
[^]
Alan

[Gear_Head]

Has anyone put a regulator set to 13-15 lbs max (or even lower) in the line that reports boost to the ECU? I get nervous leaving that line off completely. Would a regulator work in this application ??
[:I]
Alan

[PETEY_CRUISER]

I have had this happen alot over boost and p1188 with fuel cutting out. So far it seems to be anything over 5 PSI if done for over 6-7 secs if it is not full throttle. Pain in the butt on the highway. I guess the ECU gets confused that its reading 15 PSI at 1/4 throttle and thinks somthing is wrong. I don't know why the ECU is read how much fuel is to be add from throttle postion and not from how much air is entering the engine. If any body has a fix do tell.

[flashbk2]

Gear head not sure if I'm going to the Glen but it's only about 60 miles for me . If you coming email me and even if I don't go we'll hook up !

[Ian-PT-GT]

quote:
I agree. Peak hold was still @ 1.08hkpa (17psi?) from the other night (no code).
Warning is set @ 1.05hkpa and again, no alarm.
EGT was normal, not sure probably between 10-12.

Hmmm. I think its a partial throttle thing.

Hey Alan whats your minimum Auto time set to? Im on 30 sec right now.
I switch to 3 min manual after a hard run.

If I am not mistaken,

17 PSI should be 2.15 hkpa as per conversion (PSI + 14.6)/ 14.6 = Whatever that mesurement is.

Most likely I may be confused but in my controller I set it for 1.90 and using the calculation it is 13 PSI. My autometer gauge agrees with it. But in the monitor area of the controller it show 0.90 So I guess there are many measurements of boost.

Ian

[Gear_Head]

Rob, been mulling over the fuel cut that you had. I am not privy to the way the ECU works, but I have a theory. I may be way off base here but here it is: By connecting boost controller to waste gate directly and blocking off the signal from the WGA solenoid (Sol#2), and by removing (or bypassing like I have done by connecting to throttle or manifold pressure) you have effectively removed ANY control (on boost level) that the ECU can exercise when it feels the need to do so. I don't know how the ECU senses the need to exercise any immediate need to dump some boost pressure, but however it does the only way that it can dump this boost is to open the waste gate, or to vent some of the boost thru the surge valve. I have watched the boost gage and the boost has gone down for what seemed like no reason at all. If boost pressure, throttle position or air/fuel ratio reading is causing the ECU to dump some boost its done via the #2 solenoid opening the waste gate (a supposition on my part but it makes sense). If that line (WGA line from #2 solenoid) is blocked off and the ECU tells the #2 solenoid to dump some boost and it cannot the ECU will not read a reduction in boost. In fact depending on the timing on reading the boost it may even read an increase in boost and feel that because it tried to dump boost without success an emergency (and immediate) fuel cut is needed to avert possible engine damage. If this is true the only way around this is to fool the ECU into thinking that the boost is lower than it actually is. If this can be done then the ECU will see no need to exercise a fuel cut. The other way around it is to connect the boost controller to the #2 solenoid, and reconnect the waste gate actuator line back up to the waste gate. This way the ECU can reduce boost using the #2 solenoid and avoid a fuel cut. All this is supposition on my part, and if I am all wet on this I hope that someone will respond to this post and let me know.[:I]
Alan