Cadillac 1998 seville sls engine idles rough and stalls at stoplights

[devanbergerson]

My sister had this car while hers was getting fixed. She said the car would kill on her and then on her way home from work the other day it killed five times. She said every time it killed was at a stoplight. So about a week ago i traded cars with her and have been driving the Cadillac around all week, but it has yet to stall on me. I have noticed it idles rough but anything over 2000 rpms and it seems run fine.

I reset every code when I first got it from her and then I have gotten the following codes

P0174-Too lean bank 2

P0305-Cylinder five misfire

P0741-Torque Converter Clutch Circuit Performance or Stuck Off

It may have had another bank lean code but it hasn't popped back up yet after I reset it earlier today..i can't remember as my previous list is 200 miles away.

Under the abs codes

C1252-left front normal force malfunction

C1253-right front normal force malfunction

U1255-lost communications

Under the enhanced codes some are repeats but the addition is P0300- Random/multiple misfire

In advance I'm not an expert when it comes to mechanics or the right names of the part I'm referring.

I read earlier that you aren't suppose to use carb cleaner but I took off the air intake and cleaned out the throttle body and butterfly valve with carb cleaner and re installed everything before I read that on this forum. I took carb cleaner and sprayed it around the intake gasket and the car started to rev up when i sprayed in the front passenger side of the intake so i'm assuming that the intake manifold gasket is leaking.

I took off plug wire 5 it says 7mm low ohms on the wire...i'm not too familiar with testing plug wires on what the reading should be, but i put the mulimeter on ohms 2000 setting and i get 1366 ohms

[BodybyFisher]

Good diagnosis, I would torque the intake bolts to spec, that should stop your LEAN and misfire codes, if not then you can branch out from there. But misfires, lean codes and roughness could be caused by loose intake bolts. If you dont have an inch pound torque wrench, you can just snug up the bolts, no doubt you will find them loose. If that does not correct the problem new intake seals could be needed but normally snugging up the intake bolts solves this. Let us know how it is once you snug bolts

By the way, are you getting a whistle sound?

Are you getting any EGR codes?, those are the only codes?

How are you checking codes?, a reader? Look at the bottom of my post here and read How to Retrieve codes if you are using a code reader. I was wondering how you got the "enhanced" codes you mentioned

[devanbergerson]

I'll try snugging up those bolts but i forgot to add some information. Yes those are the codes i am getting from my innova 3160.

http://www.amazon.com/3160B-Professional-CanOBDII-Diagnostic-Enhanced/dp/B001QIUGVI

Something like that not entirely sure how to use all the options on it but it will list the dtc codes and when i go through all the dtcs ill get an option to scan enhanced codes and abs codes not sure exactly on the wording ill pay attention next time to relay it better.

My freeze frame Data must be only for p0174 code as its at the top

Fuel system 1......... CL

Fuel system 2......... CL

Calc load %.............0.7

ECT(F)....................201

STFT %..................10.9

LTFT %...................7.8

STFT %...................12.5

LTFT %...................29.6

MAP (inHG)............10.00

Eng RPM................665

Speed.....................0 mph

MAF (lb/min)............510

TPS %.....................0

I made a video. I think I might have had the heat on in the car should of had that off for fan noise ill make another and compare unless its irrelevant.

[devanbergerson]

After tightening the bolt and resetting the computeri let the car idle for awhile and got lean codes. The lean bank one is on again. Figured it would come back

P0171

P0174

I'll take it for a longer drive tomorrow to see if any of the misfire codes come back.

[BodybyFisher]

I am pretty sure I hear a vacuum leak in that video....members please view the above video and comment on whether you hear a vacuum leak. This noise could be caused by the throttle body snorkle being off, but I didnt notice it was off.

A lean condition can be caused by too much air or too little fuel (low fuel pressure). Since we seem to be hearing a vacuum leak and your test indicated an intake seal leak a potential vacuum leak must be eliminated. If you had one, I would test the fuel pressure with a fuel pressure gage attached to the shrader valve on the fuel rail, you should get about 40 to 45, lower pressures cause problems.

Those codes indicate a lean condition on both banks. So you are looking for a vacuum leak that impacts BOTH banks. A common failure for SOME Northstars is the rubber intake plenum. But you do not have an intake plenum on that year (I don't think so anyway, members?). Look at the vacuum line on the brake booster, look at the PCV valve it may have pulled out of the cam cover and there is a pipe on the front bank that can come out allowing air into the crankcase. In general you are looking for a large vacuum leak. Listen for it, use a 3 foot 3/4" hose as a listening device and listen around.

I hate to say it, but dont overlook a cracked intake manifold, we have seen cracks, and the over pressurization valve can leak.

I asked if you had a whistle noise and you didnt reply. There is an over pressurization valve on the passenger side of the intake behind the power steering pump that can leak, and it can whistle.

Were the intake bolts loose? Did you try spraying the intake again to check for leaks?

From the data you provided, assuming your engine was warmed up, the 665 idle speed is indicative of a vacuum leak, normal is 625.

Let us know what you find... and please try to answer our questions to help us along we are only as good as the information we have

By the way, you may have stopped the misfiring by snugging up the intake bolts.

[BodybyFisher]

Review this thread:

http://caddyinfo.ipbhost.com/index.php?showtopic=38167&hl=ohms&st=0

[devanbergerson]

Thanks I will read that thread when I get time. I read part of it so far and the ignition could be a possibility. The day it killed on my sister a lot the temp was in the negatives. I think it was around that time Minnesota\North Dakota were having a windchill of like negative 40, but it has done it other times on her as well. I have just had it parked in the garage this whole time so i haven't had a chance to drive it around much yet. I plan to look at it again tonight or tomorrow. As far as the whistling I have never really diagnosed a vacuum leak so i'm not entirely sure what the whistling would sound like. I do hear a whistle or maybe its a grinding type noise from the drive belt side of the car. This could be from a pulley though. I think i'll make a more accurate video with the air off and move around slower and hopefully you'll be able to help me pinpoint better as you know what to listen for more than me.