1998 S70 Dies, restarts , 9434225 fuel pump relay Topic is solved

jotzgr · Post by **jotzgr** » 15 Feb 2014, 12:43

1998 S70, 2.4 Turbo, 165K. Starts up and runs fine, go about 1/2 mile or so and engine abruptly dies down to rough idle, will not rev up, will not do anything, sometimes stalls, but starts right back up, again at rough idle. Will not rev or go above idle speed. Doesn't die when you try to rev it, just does nothing but rough idle. No CEL or other warning lights coming on, nothing else shutting off or going awry (radio, gauges, etc.). After a few minutes, the engine comes back with a vengeance and runs fine. First time, I was over 30 miles from home, after a few minutes at side of highway trying to figure out what was going on, started running fine and made it home with only 1 little hiccup along the way. Second time was trying to idle up a hill with it in drive to get back home, and then all of sudden revs up and everything is fine. Made it home and here she sits. Anyone else had similar problem or give me a suggestion on where to start looking. I know it could be anything, but it seems consistent after you start up and go about 1/2 mile. Thanks.

Post by **erikv11** » 15 Feb 2014, 12:53

Is the Check Engine light on?

Try unplugging the MAF, and then start it up. Give it a few seconds to adjust to no MAF. Is it the same, better or worse? This procedure will set a Check Engine light that will need to be reset, keep that in mind.

jotzgr · Post by **jotzgr** » 15 Feb 2014, 13:02

No CEL or other warning lights on at any point, unless it stalls, then they all come on like they are supposed to. Everything goes out once it starts. It starts and runs perfect until you go about 1/2 mile down the road. I can try unplugging the MAF, but since it runs fine until you get a little ways down the road, not sure if that is gonna tell me anything. I'm a little afraid of getting stranded now and having to pay a wrecker to get me back home. BTW, I'm an experienced mechanic currently with 14 vehicles (5 Volvos, 4 Saabs, Triumph TR7, 82 BMW 320i, two Cutlass convertibles, and a Chrysler).

Post by **erikv11** » 15 Feb 2014, 13:32

Yeah if no CEL then I don't know if the MAF test will help, but worth a try? When unplugged the car goes into a default fuel:air mode.

I also wondered if the IAC (Idle Air Control valve) is dirty and sticking, but that requires some disassembly and a cleaning.

Post by **erikv11** » 15 Feb 2014, 13:34

Maybe it is dying when it goes into closed loop?

Post by **erikv11** » 15 Feb 2014, 13:35

Or maybe it is fuel delivery. Check pressure at the rail right after it dies. Could be the ubiquitous fuel pump relay failure.

Post by **northernlights** » 16 Feb 2014, 21:55

I had a car with a bad cam sensor that would act possessed at times, running rough and missing, and then as if someone flipped a switch it would run fine. This one was pre OBD II so the diagnostics were not the greatest. FWIW, my factory book says the car will not start with a bad cam sensor, but nothing about running. It does say the car will not run with a bad crank (RPM) sensor.

Your note about it being a possible closed loop problem is a possibility, and if that is the case then I would look at the EGR (if you have it) or the EVAP purge valve as I believe the engine needs to warm up (a little) before either of those work, and they both can cause air leaks. Unplugging or disabling them will almost certainly throw a code, but preventing them from being potential air leaks will help you diagnose the problem.

One other weird possibility I've run into is with the power brake booster. If the check valve gets flaky and/or the booster is leaking, it becomes potentially a giant vacuum leak into the engine of unmetered and uncontrolled air. The ECU has no idea where the air is coming from.

Post by **cn90** » 17 Feb 2014, 08:25

I agree with erik, when the car dies but comes back quickly, there are only a few suspects:
1. Bad MAF
2. Dying fuel pump
3. Bad fuel relay
4. CPS

jotzgr · Post by **jotzgr** » 17 Feb 2014, 20:42

Thanks. I'll keep you posted. I took the relay out and took the cover off. Didn't see any cracks or anything obvious; in fact, it looked spotless, but I'll probably replace it just to be sure. Gonna change the fuel filter too. It's usually the first thing I do when I buy a car used, but it looks like it's been on there a long, long time. Would a bad MAF not throw any codes at all?

Post by **erikv11** » 18 Feb 2014, 00:30

On these cars a bad MAF usually throws codes, but not always. That's a reasonable argument against the MAF idea. But unplugging the MAF is a quick, free way to test it.

You can jumper the relay, see if that solves the issues, before you replace it.