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SOS Need help on road

Hi Buddy. I don't think that the WG actuator is stuck. I can see it opening and closing when revving from idle in Park.

I'm not sure what-all is wrong, since I don't have a scanner all I can give you guys is my subjective analysis while driving.

I do think that with the WG wired shut, it does seem to defuel on hard throttle up the mountain passes. It just seems pretty gutless. I'm afraid to stomp on the throttle or give it sustained hard throttle because of the WG being wired shut I am concerned about stressing the engine with too much pressure.

I have not messed with vacuum lines nor have I changed the setup at all from stock.

One guess I have is that boost sensor is reading high, causing the system to think that it cannot control the boost, since it calls for a certain amount of boost, and sets the vacuum control to give X amount of boost, but it reads X++ amount of boost. Then the program says "too much boost", and defuels the engine. Does this seem plausible?

-Rob :)
 
Stuck in full vac ??? possibly but IIRC it is spring loaded to fail open on loss of vac, so would need to be pretty crudded up for it to be stuck closed allowing full vac, I'm leaning to bad MAP now indicating over boost vs actual over boost.

Rob tomorrow see if you can get those tee fittings and put gauge between the WG solenoid and the WG actuator and observe what happens with vac, 15" or better shown in post 9, how much or better you showing, 15" IMO would not cause a real over boost condition, as flowing exhaust gas would overcome 15"
 
That is certainly plausible, just dont hear about too many MAP sensors going bad, but possible. The PCM uses that solenoid on the valve cover to control the amount of boost it allows, so if the solenoid is failing (which is common) it would do same thing.

And this suburban has no EGR on it right?

If something uncommon would fail, it would be when you were on a long drive with the family trying to have a good time.
 
FWIW Rob you won't be anywhere near "risking engine " with it wired shut with type of driving you are doing it is prudent to drive normally, but one really has to be putting the fuel to it to put engine at risk, I won't say how far to push to hit the boundary as some "youngin" will try it to see and then go boom :D , but I ran for a good while configured with ability to make mine go boom where it not for me running with gauges and scanners to know when I should back down.

I assume you are running normal highway speeds with the odd truck passing, you'll be fine with that, as I said before with ambient conditions, once you start nearing high boost you'll also be looking at IAT defuels before getting very high boost territiory
 
Unhook the vacuum line and plug it, get a screen-door spring from the hardware store, and tie that on the actuator so it puts a constant pull on it ... if the problem goes away, have Bill overnight you a Turbomaster.
 
buddy said:
That is certainly plausible, just dont hear about too many MAP sensors going bad, but possible.
Click to expand...
2 on mine one bad low, and another bad high, one that would surprise me would be stuck closed WG solenoid, many failed open, and no vac, but if stuck closed Rob's would be the 1st one like that I have seen. have trouble shot many bad MAPs over the years thru the sites, but more bad open solenoids than anything.

Another thought though would be bushing wear on the turbos WG shaft keeping it stuck closed or open, that has happened before and would have same crappy boost building issues.

No substitute for gauges or scan tool as it really helps in these situations to diagnose the problem vs swagging solutions in middle of the night.
 
Turbine Doc said:
Stuck in full vac ??? possibly but IIRC it is spring loaded to fail open on loss of vac, so would need to be pretty crudded up for it to be stuck closed allowing full vac, I'm leaning to bad MAP now indicating over boost vs actual over boost.

Rob tomorrow see if you can get those tee fittings and put gauge between the WG solenoid and the WG actuator and observe what happens with vac, 15" or better shown in post 9, how much or better you showing, 15" IMO would not cause a real over boost condition, as flowing exhaust gas would overcome 15"
Click to expand...

15" at idle, but how much vacuum does it makes at 2500rpm. The vacuum system is able to hold the wastegate shut through full acceleration. At idle the PCM puts a 95% duty cycle PWM signal to the solenoid to keep solenoid's vacuum leak fully closed, duty cylce lessens to decrease boost by leaking more vacuum.

So to easily check solenoid you can check the vacuum at idle, then disconnect the electrical connector on the solenoid and make sure all vacuum is lost at wastegate.

Our OBD1 trucks have two MAPs and I dont hear them going bad much, maybe the later models arent the same quality :D
 
Try replacing Turbo Wastegate Solenoid first? It is the cheapest part.

I like Tim's idea for Bill to ship the TM to your next destination.
 
In the S we still have 2, in the F truck they have just the one, and on yours one is a MAP, and other is a BARO, and they will not interchange on the the OBD-IIs possibly on the Is they use same sensor.

Yes we do need to know the vac @ 2500 rpm, but he could not get tee fittings to test that tonight. Agreed simple check for stuck solenoid is to unplug it.
 
Rob did some homework for Ya

Depending what you have nearby

O riley MAP sensor pn 2MS21 Master pro brand $49.99
Advance pn EC1765 BWD brand $40.19 or AC Delco 213-1520 $79.39
Auto Zone pn SU105 Duralast brand $38.99
Napa pn $ 49.49 Eichlin brand $49.49
 
Since he says it's opening when he revs it in park, I would lean towards a bad boost pressure sensor as well. Most auto parts stores should be able to get you one as GM used that same MAP in there turbo'd gas engines as well back in the day. It's a standard 2 bar MAP sensor. If you were close to Fl I'd give you my old one as it didn't have many miles on it. My origanal would also allow the wastegate to open at idle when I revved it, replaced the sensor and it stayed closed until I got out on it and got the boost up.
 
buddy said:
3-4psi doesnt seem very good static fuel pressure, did you mean with engine off or just static as in idle?
Click to expand...

Back to the fuel pressure at idle. You should have 7 PSI. At least for a 1993 and a Auto Zone replacement is rated at 7-14 PSI on the side of the pump. Try engine off and lift pump on. Quart jar and flow test it - mine I could pee faster when it died. Noise doesn't mean lift pump is working.

Big hiss when removing the fuel cap? Leave it loose.

Snot in/ plugged stocking as suggested is also possible. Blow air back through the line with lift pump out and cap off just to be sure.

Low fuel pressure --> This will drop boost at higher RPM's. I have seen it with a failing lift pump and the SOB would test good/7PSI at idle till it died completely in 15K miles. Tested weekly and 3000 miles a week. I had to turn down the Turbo Master after replacing the pump as the boost went over 15 :eek: just after replacement.
 
Hey guys, for 'swagging solutions in the middle of the night' I wouldn't have any guys better than you guys! Thanks so much. Methinks that the MAP sensor is probably bad - stuck high, as you say, but it is true that without scanner and gauges it is impossible to tell.

I'm going to try replacing it, as the burb was just gutless going through the Siskiyou mountains even with the WG wired shut, and I would hate having to drive the next couple of weeks with the burb all messed up. I'll gamble the $50. Thanks for the research Doc, and for the encouragement.

You guys really are great.

-Rob :)
 
Update, Rob will be checking in later, but I just got off the phone with him, he is underway again with a healthy vehicle, he & family spent the day trying to get the parts together, couple of part stores showed inventory but were out, another tried to sell a Map that was actually a Baro sensor.

Got a recommendation from part store for a good dealer to visit that had both a GM WG sol and a MAP sensor, he acknowledges changing both at same time does not drill down to THE issue but decided a bird in hand better than one in bush and went ahead and changed both, he can swap out later to define which of the 2 devices were causing the problem.

While shopping he bought tees & hose he could not get last nite, and was able to check wg vac, 15" at idle, 22" at cruise and pulsing up & down 10-22" per PCM command to regulate boost.

Final word to me was thanks to TTS members, who weighed in on this , he said we are the 6.5 family here :grouphug: , and he and his real family were glad to know we had their back on this, Thanks to all of the TTS family/team this sort of thing IMO is what sets us apart from other sites :thumbsup::thumbsup::thumbsup:.

Rob said he was able to recover for just under $200 with parts and test equipment purchases, and untold $$$ saved not having to stop and wait for a dealer to try to diagnose/correct the problem.
 
Hi guys,

Tim called me on my mobile (Thanks Tim!) and his report above is VERY accurate. (Wow, steel-trap for a memory!)

Absolutely I am feeling warm and fuzzy - TTS members are my extended family, and I can't thank you guys enough! Truck is back to normal, I think it even has better power than before (probably due to all the changes- new air filter = better and easier air flow, new MAP sensor = PCM not being fooled by high reading, is giving full fuel now.)

It was really funny doing the vacuum readings. I got the NAPA store guy to sell me all the right fittings to T into the WG vacuum line right at point of connection with WG vacuum actuator. (pictures to follow). Per Tim's suggestion, I T'ed into the line with enough hose to go out of the hood and into the cab through the window. My beautiful wife was holding the gauge and giving readouts while we would pass semis on I-5. We passed like 10 of them before I was satisfied it was all working. So she's saying "15", now moving to 22, now 20", now dropped go 12..." while we're zooming along. It was just a picture I won't forget.

Tim captured the results exactly right above.

Anyway, a big SHOUT OUT and THANK YOU to you, my TTS family. The truck is just humming along fine, and we're continuing the trip to La La land. I know I would have sold this truck if I had to do everything at the dealer/shop. But, once again, you guys come through in the clutch! I am well aware that people were posting at late hours in response to my SOS, and I am duly humbled and grateful.

Thanks, and I really owe you guys one! The kids are thrilled we're back on the road to resume our vacation!

-Rob and the whole family (in Sacramento) :)
 
Hey guys, friend of brookyn tow here {louis} and he told me what you giys did for him and the whole story. now i read this and and cant believe how close of a family you 6.5 giuys are. kinda makes me want to go buy a 6.5. although been helping hom with his truck and feel like now i know why he speaks so highly of you people. Ive learned more off this site lurking around than i think the dealer could have taught me. you are some great bunch of guys and now I see why Lou hangs out here. he even made join up and get my own screen name even tho i dont have a diesel.
 
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