: '98 STS - "Service engine soon" light was on for two days...now off...car runs great



JohnnyLfromCT
02-03-04, 10:21 PM
Hey all,

About a week ago, I pulled into my garage, stopped, & the idle surged from it's normal 650-700 up to about 800. I turned the car off, turned it right back on, & it was fine.

This past Sunday morning, I was backing into a parking space, & when I put it in reverse, it surged again, only for a second. That afternoon, I got in the car after letting it warm up to about 50% of op temp, & noticed the SES light was lit. It stayed illuminated until this morning, when I let the car warm up to about 70% of op temp, & got in to notice the light is now off...

The car has run flawlessly the whole time, & the idle hasn't surged (it's only done it those two times).

I pulled the codes, & got these -

PCM0300History
AMPU1064History
SDMB1147History
MSMB2118History
RIMB1009Current

None of these seem to be engine-related...the car runs as awesomely as usual.

What do you fellows think?

*Bbobynski, I'm looking at you* :worship:

BeelzeBob
02-04-04, 01:23 AM
Hey all,

About a week ago, I pulled into my garage, stopped, & the idle surged from it's normal 650-700 up to about 800. I turned the car off, turned it right back on, & it was fine.

This past Sunday morning, I was backing into a parking space, & when I put it in reverse, it surged again, only for a second. That afternoon, I got in the car after letting it warm up to about 50% of op temp, & noticed the SES light was lit. It stayed illuminated until this morning, when I let the car warm up to about 70% of op temp, & got in to notice the light is now off...

The car has run flawlessly the whole time, & the idle hasn't surged (it's only done it those two times).

I pulled the codes, & got these -

PCM0300History
AMPU1064History
SDMB1147History
MSMB2118History
RIMB1009Current

None of these seem to be engine-related...the car runs as awesomely as usual.

What do you fellows think?

*Bbobynski, I'm looking at you* :worship:


Pressure is on, huh....LOL

Not much to go on here. The 300 indicates an engine misfire...so...with no other codes from sensors or anything got to think maybe ignition related since it seems to be intermittant. Maybe it has been damp there..????..possibly a plug wire reacting to the dampness/salt on the roads and salt spray??

Just for grins, park in a dark area, open the hood and mist the wires with water from a spray bottle and watch for arcs and sparks and and listen for the engine to misfire. If you see something maybe there is a wire with a cut or abrasion or something that is leaking and is sensitive to the dampness and salt.

I wouldn't think injector or fuel pressure regulator since the engine runs OK all the time other than this...??? No hard starting or rough running or anything?

Look at the wires as a first guess.

JohnnyLfromCT
02-04-04, 10:42 AM
Pressure is on, huh....LOL

Maybe it has been damp there..????..possibly a plug wire reacting to the dampness/salt on the roads and salt spray??



It's funny that you mention wet weather, since the first time I noticed the small idle jump, I had just been through the car wash 5 minutes before…

I know, I know, I'm going to hell for putting my car through the car wash...but it's been snowing twice a week here for a month, the roads have been an absolute disaster, & the Caddy was so dirty it was making me physically ill to look at her.

Anyhoo, It's been very wet & damp around here with the hard-packed snow & the melting snow. Although I did drive home from the gym last night in a friggin' torrential downpour, & nothing was amiss.

Since she's got 78k on her now, I figure she's due for new wires & plugs…if only I had the balls to do it myself!! The Northstar doesn't look quite as easy to work on as the straight six in my Cherokee. IYO, can any good GM-certified mechanic change the plugs & wires on a NS without f-ing things up, or should I go the dealership route & pay through the nose?

Bbobynski, please move to southwestern CT & run a NS shop so that I may solicit your services at will. :D :worship: :cookoo:

BeelzeBob
02-04-04, 12:36 PM
Really, if you look at the plugs and wires on the Northstar engine is has to be one of the easiest engines to change plugs in the world. The plug wells are in the center of the cam covers, the wires are all up top and accessible. Just do the wires one at a time and do the plug for that wire at the same time. Very easy to do.

Check the wires like I suggested, first though, to see if it indicates a problem. Don't just dive into a plug/wire change to shotgun the problem. The dual platinum OEM plugs and the silicon jacketed wires will easily last 100K or longer so you shouldn't just need new plugs and wires as a matter of course. There is probably a specific issue with one wire or plug that was cut or something along the way and the mist check may point it out easily.

zonie77
02-04-04, 12:43 PM
Take a look at this thread:

http://cadillacforums.com/forums/showthread.php?t=7561

Cadillacboy
02-04-04, 06:39 PM
Thanks for the link ,as to my cents I guess it's a common problem because many Caddy owner mention that .By the way I am also getting same message on my car

STSNZ
03-15-05, 06:02 AM
Great reading - but how do I pull the codes on my 98 STS. Everyone talks about the OFF and WARMER button... but STS does not have these? any help appreciated

Ranger
03-15-05, 04:58 PM
Great reading - but how do I pull the codes on my 98 STS. Everyone talks about the OFF and WARMER button... but STS does not have these? any help appreciated
Yours uses the INFO & ON?OFF buttons. Do a search for codes. I think it was Jim D that posted a very good "how to" for your year.

JimD
03-15-05, 05:14 PM
Yours uses the INFO & ON?OFF buttons. Do a search for codes. I think it was Jim D that posted a very good "how to" for your year.


Some would say it is more than you need to know, but here it is.

BTW. Ranger, was it you who built the water pump tool that you hope to never need? If so, GM has added a back plate that prevents the tool from backing out due to torque. Will post a pix for laughs if you want to see it.

kjd03842
03-24-05, 01:22 PM
if you look at the plugs and wires on the Northstar engine is has to be one of the easiest engines to change plugs in the world. The plug wells are in the center of the cam covers, the wires are all up top and accessible. Just do the wires one at a time and do the plug for that wire at the same time. Very easy to do.

Sure, the front plugs are wicked easy, but the rear ones are a little less accessible. Do I just move the miscellaneous cables out of the way as I proceed, or should I pull off the entire ignition control module first, or...???
I plan on doing a compression check, too. Any hints for that? I have the alldatadiy info.

Thanks
KD in NH

caddydaddy
03-24-05, 01:46 PM
It's much easier to get the rear plugs out with the coil pack removed.

BeelzeBob
03-24-05, 03:32 PM
It's much easier to get the rear plugs out with the coil pack removed.



True....but....even with the coil pack in place it is not THAT hard to slide a socket and extension thru the jungle and pull the plugs out.

caddydaddy
03-24-05, 03:48 PM
Maybe I just have fat arms???? I found them to be in the way on my old '94 Concours.

BeelzeBob
03-24-05, 04:05 PM
Maybe I just have fat arms???? I found them to be in the way on my old '94 Concours.


In the way....???....yes. Impossible to work around....???....no. Still the rear plugs are way way easier to get to than most engines where the plugs are down under the exhaust manifolds and such.

caddydaddy
03-24-05, 04:12 PM
LOL, yeah, like the 4.9! That left front plug is a PITA to get to! Good thing I only have to change them every 100k miles!

Ranger
03-24-05, 05:25 PM
Some would say it is more than you need to know, but here it is.

BTW. Ranger, was it you who built the water pump tool that you hope to never need? If so, GM has added a back plate that prevents the tool from backing out due to torque. Will post a pix for laughs if you want to see it.
Yeah Jim, that was me. So far it is still a virgin. Just sitting in my tool box waiting to be called into service.