Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Intermittent Stalling Issue - 1998 Cadillac Seville [SOLVED!]

I have a 1998 Cadillac Seville STS which has recently developed an intermittent stalling issue. Here are the details:

-Happens occasionally when I’m slowing down or coasting, such as turning into a parking lot or going around a sharp entrance ramp
-Has not yet happened during acceleration
-No bucking or jerking while accelerating
-No apparent warning that it is going to stall
-Has happened once each of my last two trips

The first few times it happened my fuel level was pretty low, and one of the times I tried several times to restart it and it would start but die right away. I managed to get it started again, then I filled the tank and tested the fuel pressure at the rail, and I got 45-50 psi with the key turned but without the engine running.

After that time, I have not had any difficulty restarting it when it stalls. I look forward to hearing your suggestions.

UPDATE 03/05/2013:


Last Friday, I found an old post on a forum somewhere about someone having the same issue. They mentioned that they had cleaned the EGR valve, so I figured with two bolts and a connector being all that needs to come off to remove it, I might as well try.

I held the valve in basically the same position that it is installed (meaning I didn’t turn it upside down) and sprayed in the opening with throttle body cleaner (not carb cleaner). I then used a “pipe cleaner” to clean the inside, and I also worked the plunger up and down after I sprayed it.

I had a few “false alarms” in the past thinking it was fixed, so I wanted to wait until I was sure before posting. I now have to lose the habit of constantly glancing at the tach to see if it’s about to stall.

Thank you to everyone who posted here to help me. It would be interesting to know why cleaning the EGR valve fixed it.

The nature of the stall is a big clue. Does it stumble as it stalls, or does it die like you flipped a switch? A stumble typically means a mechanical fault, like a fuel problem, and a sudden dying points to electrical problems, like ignition issues. Of course, on many modern cars, these are not exclusive to each other, but it helps narrow things down.

Pull your codes. Caddys have on board diagnostics.

Thank you for the replies.

Does it stumble as it stalls, or does it die like you flipped a switch? A stumble typically means a mechanical fault, like a fuel problem, and a sudden dying points to electrical problems, like ignition issues.

It dies with no warning at all like someone flipped a switch.

Pull your codes. Caddys have on board diagnostics.

I’ll do that and post them for you.

Here are the codes:


-Current: NONE
-History: B1327, U1255, U1064, U1128


-Current: NONE
-History: U1301


-Current: NONE
-History: B1652, B1983


-Current: NONE
-History: B1344


-Current: P0135, P0146, P0147
-History: P0134, P0603, P1258, P1599, P1611


-Current: C1780
-History: C1326, C1658, C1715, C1716, C1727, C1735, C1761, C1762, C1783, C1784, C1788


The idle air control valve may be your problem. It has some of the classic symptoms. Clean your throttle body first, though.

Here’s another link. Several of the codes are in here.

Hopefully this helps!

Let us know how things turn out!

I don’t mean to discourage but I had the same thing in my Riviera and finally gave up. Stalling on a slow down would lead to the IAC (had mine cleaned). Also the crank sensor is a known issue (had that replaced). Ruled out fuel after replacing the pump, wiring and relay, then would test run it with the fuel pressure tester on it and test light but when it stalled still had fuel pressure and power to the pump. Had swapped the computer with a spare just to make sure and the ignition module. Finally I replaced the ignition switch on the steering column out of desperation. Drove it for two months with no problems then and then started again out of the blue. Had a new car four days later. I still wish I knew for sure what it was but that’s history. Myself and two shops couldn’t find the problem over a four month period.

So rule out fuel, clean the IAC, check the crank sensor, ground wires, coil, ignition module and so on. If you ever find the problem let me know. It seems to be an older GM thing.

@Bing why are you so pessimistic? The guy knows what fault codes he has. Plus he can look at that website I gave him and read up on what causes the codes.
If it were me, I’d be concentrating on the current codes.

Several O2 sensor codes. I assume your CEL has been on a long time? I see engine stall code, long term battery reset. Did u disconnect battery to try and clear codes? My memory is vague. I know the 2000 northstar motors had a throttle body plenum that liked to split on the bottom and cause idle issues. Hard to see unless u took it off and looked. I am not sure if the 98-99 sevilles had the same part.

I assume your CEL has been on a long time?

It sure has! The current PCM codes seem to be related to the oxygen sensors, and I haven’t noticed any decrease in fuel mileage, so I just put it on my wish list. I didn’t disconnect the battery to clear the codes, but I did months ago when I replaced the fuel pump. I clear the codes through the dash buttons after I retrieve them.

I had an issue in the past where the MAF sensor had cracked and was pulling away from the throttle body when the engine would move, causing it to stumble badly on acceleration, but I fixed that a while ago.

I was looking carefully at the tach today, and I noticed that several times while I was decelerating or coasting, usually below 30 mph, the tach would seem to randomly dip to about 250 rpm, then recover. My idle speed is usually about 700 rpm. This only seemed to happen when I was moving, not parked or stopped at a light.

Anyway, I’m going to clean the throttle body and clean or replace the IAC with another one I have on hand from the junkyard tomorrow and I’ll update everyone on what happens.

While you’re at it, take a good look at the bellows going to the MAF as long as you have it apart. Make sure there are no cracks or leaks in it that would cause air to be drawn in after the air flow sensor. Good luck.

I’ll check them, but they are on the air cleaner side of the MAF rather than the throttle body side, so if they were cracked, then the air would still have to go through the MAF.

The air sensor should be on the air cleaner housing, then the bellows connected to the MAF, if I’m picturing it right. So if there is a crack in the belows it would draw air in on the down wind side of the air sensor to the MAF. So in other words the air sensor would never see it to report to the computer how to adjust the fuel mixture. That’s the extent of what I know or don’t know.

An update on my progress.

I replaced the IAC with one that I got from the junkyard (and cleaned the external parts of it), and I also cleaned the throttle body and MAF sensor. I checked the bellows connected to the MAF and there were no cracks.

When I test drove it, it did not stall in any parking lots as it usually did once per trip before, but although the car was up to operating temperature, it was a short trip compared to the others where I had been driving on and off for 45 minutes or so.

One thing that I did notice which was the same as before is that when I was coasting at 25 mph, the tach would randomly dip from the usual 1000 RPM at that speed to just below 500 RPM, then quickly recover. The voltage display on my dash would also simultaneously drop from 14.3 volts to 12.5-12.7 volts, then quickly recover, and my high beams would dim momentarily. I’m not sure if this happened in the past because I wasn’t watching closely like I have been recently. This does not happen when the car is idling in park.

Any suggestions?

@98caddy well, you’re getting somewhere!

How old is that battery? I would test it and the alternator also. How’s the belt looking? How’s the belt tension? How are the battery connections?

@db4690 The battery was about 2 years old. The belt feels pretty tight, I replaced the tensioner about 2-3 years ago.


After the battery died in a parking lot when I had my car doors open for about 15 minutes today, I got a jump and went to the auto parts store where I bought the battery for them to test it. They said that the test came back as “bad battery” even though it was 84% charged. He said that he wouldn’t be able to test the alternator then because the battery was bad.

I went elsewhere and bought a new battery, but the auto parts store was closed after that, so I couldn’t get the alternator tested. Unfortunately, even after replacing the battery, I am still having the same issue with the voltage and tach momentarily dropping as in my previous post. The car didn’t stall today, but it got close once.

I’m hoping that I’m not going to damage the new battery (not cheap!) with a potential alternator issue. The voltage stays right at 14.1-14.3 when I’m on the highway or driving over 35mph with no fluctuations.

One other minor question: I seem to have partially stripped the threads of one of the terminals of the new battery (today was an “if it could go wrong” day). It is a side post battery where you screw the terminals in, not like a traditional battery with clamps. Is there a thread insert for batteries?

@98caddy I’m well aware of the side post battery design.
Did you strip the female threads of the battery itself?
Or did you strip the male thread of the terminal?

This is the terminal I am referring to

I’m not aware of an insert for the battery itself. But I haven’t really looked.

But those terminals are available at the major auto parts stores.
If the terminal is bad, ask the parts counter guy for a terminal for a group 75 or 78 battery.

Are the threads stripped all the way to the bottom? You could run an SAE national course bolt and a nut if there’s still threads further down.

By the way, did you get reimbursed for that defective 2 year old battery. Even the junkiest

batteries usually have a 18 month free replacement period. After that, they’re prorated.

My side post battery terminal snapped off so a plug about the size of a grape came out. Battery was totally fubar.

@db4690, I am getting somewhat reimbursed. It was already replaced two years ago, so they’re now going by the date that I bought the original battery.

I should have said that the terminal is not “stripped” from over-tightening, but I’m not sure it was tapped properly from the factory, as the stud didn’t seem to screw in smoothly like the other terminal, and it’s not letting me tighten it enough like I was easily able to do with the other terminal. I think I’m going to exchange it.

My main concern is still what is causing the intermittent RPM/voltage drop and near-stalling. I will eliminate or confirm one possibility when I have the alternator tested, but I’m wondering which is the symptom and which is the problem.

In other words, are the RPMs dropping because of a mechanical issue and therefore causing the voltage drop because the engine isn’t turning as fast, or is the voltage dropping because of an electrical issue and therefore causing the RPMs to drop? That might be a silly question, but I’m not as knowledgeable about the technical workings of cars as many of you regulars are.

One more hint might be that it seems to get somewhat worse the more I have been driving that day.

@98caddy I’d hold off on any more diagnosis until that battery terminal problem is resolved.

I know from personal experience that those GM sidepost systems are temperamental. It’s next to impossible to properly diagnose a battery or charging problem with dirty/stripped terminals.