Stalling 99 STS mystery - Page 2

**Ranger** · #16 (**permalink**) 03-20-07, 08:41 PM

Plastic threads? Are you sure you are on the correct fitting?

whack_lac · #17 (**permalink**) 03-21-07, 02:37 AM

I'm sure I was on the right fitting - on the front of the front fuel rail - gas was coming out of it. The threads appeared to be plastic, I will look at it again when I have a cooler head and my patience aren't running so thin.

Is it possible that running the can of TEC through the car would foul up the O2 sensors? I think I will change those and see what happens. After that I think I am pretty much done just throwing money at things hoping for a fix.

**Ranger** · #18 (**permalink**) 03-21-07, 05:57 PM

No, I would not think Tec would hurt the O2 sensors if used as directed. I'd return the gauge and get one that fits.

02pearlSTS · #19 (**permalink**) 03-21-07, 06:35 PM

This may sound strange, but do you think it may be an ignition switch?
Did you try to pull codes after it stalled? If so, did anything come up? You're saying it won't idle when warm and it stalls when you stop...hmm...I'll talk to my girlfriends dad (he was a GM mechanic for 11 years) I'll see if he can come up with something.

02pearlSTS · #20 (**permalink**) 03-21-07, 06:43 PM

Alright, it talked to him and he said that if it was a vacuum leak you more than likely would have a code. He also said if you are worried about spraying carb cleaner because of it messing with wires or rubber fittings, try start fluid. He said he had the same problem in his 2000 silverado and he put 2 bottles of Neutra (schaeffer fuel additive) and after 30-40 miles it straightened out. How far did you drive it after you added the tec? It may take a bit to clean it out. It may be that you have bad gas or water in your gas. Add some of that neutra ( 2 bottles) and see what happens.

whack_lac · #21 (**permalink**) 03-21-07, 07:01 PM

I have no codes, I had driven for about 10 days after putting in the TEC, at which point I changed the plugs, wires, and cleaned the throttle body. After changing the plugs, wires, and cleaning the throttle body what was a once every couple week issue became an instant all the time issue. I've run different tanks of gas through the car from different stations, so I don't think gas is the issue.

I'll get a new fuel pressure tester and pick up there again.

Does anyone know where the PCM is located? I would like to try the 'slap test'

I have also read a thread with a similar problem that turned out to be the igntion module - if this was the case wouldn't the car stall when cold also?

**Ranger** · #22 (**permalink**) 03-21-07, 08:44 PM

PCM is under your air filter. It is there so intake air is passed over it for cooling.

whack_lac · #23 (**permalink**) 04-09-07, 11:38 PM

Well, I finally broke down and took it in to the $tealer$hip. Turned out to have an intermittant crank sensor signal... The dealership I purchased the car from "supposedly" changed them out 3 days after I bought the car, or so says the receipt I have. The mechanic who just worked on my car said that the sensors he pulled out looked like original stock... Hmmm Anywho, I will be paying a visit to the original dealer (Frank Boucher - Sturtevant, WI) with old sensors and receipt in hand to give them a little piece of my mind about the grief they have put me through for the last 18 months.

So far the car runs good, I have put maybe 35 miles on it. Hopefully it keeps up it's good behavior.

Thanks to Ranger for all of his help!

SevillianSTS · #24 (**permalink**) 06-04-07, 12:07 PM

It is the 2 crankshaft position sensors. My car did the same exact thing. gmpartsdirect.com Got 2 new sensors. Need to take off the oil filter housing to get to the sensors, but mabe an hours job and $50 for the 2 sensoars. Be careful of the aluminum block.
The dealer will charge you probably 150 to do the job, if not more.

locorebob · #25 (**permalink**) 04-21-08, 06:22 PM

I have 99 STS with exact same symptoms. I see
U1064 history
U1128 history
B2947
Is there a way to check if crank shaft position sensors are faulting before purchasing new ones. Assuming need two.
Thanks, Bob

submariner409 · #26 (**permalink**) 04-21-08, 06:37 PM

loco, those DTC's are not associated with CKP faults.

U1064 is a data transmission fault in the Dash Integration Module
U1128 is associated with the radio
B2947 is a data output from the Theft Deterrent Module which sends fault codes to the PCM concerning possible theft attempts or key faults.

There are two different part numbers for CKP's, all covered in great detail down in the 8 pages of Technical Tips. If a CKP is faulty it will set a code giving the unit (A or B) and fault. There are no "checks" to perform. $ 450 if both done by dealer, $115 if you order them from www.rockauto.com, but I don't think you're in the CKP business yet.

locorebob · #27 (**permalink**) 04-23-08, 10:26 AM

No codes are being logged relataive to this problem. The engine is studdering so bad at stoplight I am afraid it might stahl. Yesterday, when cranking for starting after work to head home, the engine backfired quite loud. It's done this before a few weeks and months back but only occassionally.
I did change the plugs (stayed with AC) two weeks ago but the problem has worsen in the last few days. What's the next step in diagnosing this problem?
I always ran Chevron gas and coincidentally swtiched to "Flying J" gas when this started happening. I have a hard time beleiving this problem is related to the brand of gas. This is 99 STS with 102,000 miles. It does not seem to misfire or stumble when accelerating or crusing speed.
Any suggestions on what to look for or steps to further diagnose/isolate source of this problem?
Thanks, Bob

**Ranger** · #28 (**permalink**) 04-23-08, 11:00 AM

Brand of gas has nothing to do with it. Have you changed the plug wires?

submariner409 · #29 (**permalink**) 04-23-08, 11:10 AM

loco.......Go to Walgreen and pick up a cheap stethoscope, modify it with an extra piece of tubing connected in place of the diaphragm and begin listening around the base of the intake manifold for a vacuum leak, also in the "front" end of the manifold for a vacuum leak in the overpressure valve in the center of the manifold tunnel. Also the connections for the PCV system under the engine cover. (A vacuum leak should set an O2 sensor code, though.......) If you can't find a stethoscope, a few judicious light squirts of starting fluid around the manifold base and overpressure valve may reveal something by the engine smoothing out or speeding up as it ingests the vapor instead of air only.

Also, with the engine off, pull the vacuum fitting/hose off the tit on the fuel pressure regulator which is under the engine cover, right rear of the fuel rail, looking from the front of the car. The hose and interior of the regulator diaphragm should be dry. ANY gasoline is a ruptured diaphragm.......$30(?) at www.rockauto.com .

Backfiring usually indicates a fuel/air/timing problem. Concentrate there first.............(and Ranger's plug wire suggestion has cured a LOT of pre-'00 Northstar problems......ACDelco originals only.)

locorebob · #30 (**permalink**) 04-24-08, 02:25 AM

Sub, I picked up a set of AC plug wires today. Should I install as-is, or apply some diaelectric.? Nothing came in the AC-Delco box.. just the plugs. They appear to be same as original. I pulled the beauti cover and sprayed starting fluid on all vacuum lines. The was no difference inthe idle. I pulled the vacuum fitting from fuel pressure regulator and it was clean. I did not inspect diaphram, but I;ll look at that tomnorrow. The vehicle had a shutter at crusing speed today on freeway. Hadn't had the car on freeway in several months. It was noticable. I also note when first accelerating from idle at stop light... it lurches. Still no codes. It;s hard to believe it's not posting error codes. I'll try the starting fluid test again when it's hot tomorrow. I'll also pick up stethescope tomorrow.
Thanks, Bob