SES Light, Stumble at Idle

TexasAxMan · #1 (**permalink**) 06-03-05, 06:59 PM

My 95 SLS has been driving me crazy. At idle, usually ~600, it will stumble to ~500 then surge to ~800, then settle back down. Getting crappy mileage too, even with 93 octane (13.5 per computer). I've checked codes and got the following:

P036 History (cleaned EGR yesterday)
P039 History (ordered new PROM chip)
P056 History (Input Speed Sensor)

No other codes. The SES light comes on after about 5 minutes of driving. I have cleaned the throttle body. I hooked up a timing light and all 8 wires lit it up. Pulled the front 4 plugs and they look normal.

What else can I check?

I want to do a tune up but can't find the part numbers for the plugs and wires on gmpartsdirect.com (the existing wires are not GM). Oh yeah, had the fuel rail recall done today.

Please help if you can.

Thanks in advance.

TexasAxMan · #2 (**permalink**) 06-03-05, 09:05 PM

BBOB help!!!!!!!!!!!

**Ranger** · #3 (**permalink**) 06-03-05, 11:42 PM

Plugs are 41-950's. Don't remember the wire number but I got them at rockauto. I think they had a better price than gmpartsdirect. Wires may well be your problem.

TexasAxMan · #4 (**permalink**) 06-05-05, 06:06 PM

Thanks Ranger, I'm planning on doing a tune up. Hopefully that will get rid of the problem.

If anyone else has an idea, I'd be most grateful.

STS 310 · #5 (**permalink**) 06-05-05, 06:26 PM

Ranger said it best to this point. And, I dont know where BBOB hs been the past couple of weeks...

TexasAxMan · #6 (**permalink**) 06-06-05, 03:43 AM

I found the part numbers, finally. Rockauto was a good source to find the part numbers, but they were ~20% higher. Here they are for future needers:

Wires - 12192049 (118.79 @ rockauto, 96.55 @ gmpartsdirect)
Plugs - 88892834 (5.66 @ rockauto, 4.44 @ gmpartsdirect)
Fuel filter - 25121468 (12.67 @ rockauto, 11.26 @ gmpartsdirect)

Hope this helps someone, but I really need help with the aforementioned problems.

ANYONE PLEEEEEZE HELP!!!!

davesdeville · #7 (**permalink**) 06-06-05, 04:04 AM

GMpartsdirect rips you off for shipping but parts are usually still cheaper there than rockauto and most other places.

Eldyfig · #8 (**permalink**) 06-06-05, 08:47 PM

If your wires turn out ok, check your coil packs. A little over a year ago, I had one start to give me problems. Now, just a week ago, I had another pack start to give. I have a 94 with 117k on it. Replaced the coil pack and I am running good. Just like your case, the car would stumble every so often at idle and mileage went down. Checking with a timing light didn't help me any.

**Ranger** · #9 (**permalink**) 06-06-05, 09:54 PM

Quote:

Originally Posted by davesdeville

GMpartsdirect rips you off for shipping but parts are usually still cheaper there than rockauto and most other places.

When I compared prices (incl shipping) I found Rockauto to be cheaper on wires and gmpartsdirect cheaper on the blower motor.

TexasAxMan · #10 (**permalink**) 06-07-05, 06:28 PM

Look at the prices above, total savings at gmpartsdirect.com v. rockauto.com was $33.41. Even if rockauto ships free, I'm still $3.90 ahead, and I doubt they ship free.

TexasAxMan · #11 (**permalink**) 06-10-05, 02:44 AM

Against better advice (that on this forum), I put in STP fuel system cleaner and the stumble at idle has all but gone away. Too early to tell about mileage, but I suspect it's on it's way up. Still gonna do the tuneup, if gmpartsdirect.com ever ships my order. BTW, I found them cheaper that rockauto.com, even with shipping, but they are soooooo slow to ship I may not ever use them again.

Thanks to all that replied!!!!

davesdeville · #12 (**permalink**) 06-10-05, 04:09 AM

If you suspect it's on its way up you're probably going to subconciously start driving less agressively anyway.

**Ranger** · #13 (**permalink**) 06-10-05, 12:39 PM

I ordered a blower motor from gmpartsdirect and while shipping was not super fast it was about what I would call normal (a week maybe as I recall). Rockauto on the other hand amazed me. I placed the order at about 2000 on a Thurs. night and had the wires delivered on Sat.

TexasAxMan · #14 (**permalink**) 06-14-05, 12:12 AM

Well, my problem is solved. Used STP fuel system cleaner, did a tune up, and it's running like a scalded ape.

Idle is rock steady, runs like a top. I certainly haven't babied it, in fact I'm on it every chance I get. I figure my mileage is low because I've been jobless for a couple of weeks and the longest trips I make are to the beer store (about 1/4 mile away). My average MPH has been around 22.

Gonna road trip it this weekend to the beach if it doesn't rain.

LuborK · #15 (**permalink**) 06-17-05, 06:37 PM

Quote:

Originally Posted by TexasAxMan

At idle, usually ~600, it will stumble to ~500 then surge to ~800, then settle back down

Hi! I got these symptoms too on my 98 STS. Although no SES light, no error codes at all, there are vibrations at idle and stuble down to 500, then quick (with bigger vibration) to 800 and back to 600, excatly like you.

Quote:

Originally Posted by TexasAxMan

Well, my problem is solved. Used STP fuel system cleaner, did a tune up, and it's running like a scalded ape.

Since this is not sold here, I would like to ask you more about this product. What special ingredients does it contain etc., because I will need to look for an alternative which is being sold in Europe.
There is a lot of "fuel system cleaners", but I simple don't believe it. And if STP worked for you, I would stick with it if it was possible. Thanks for the help.