1998 S70 stalling no codes?

marcusheard · Post by **marcusheard** » 15 Feb 2013, 13:58

I have a 98 S70 that just recently began to stall. I was driving as usual and all of a sudden I felt a drop in torque (quick intermediate stall). This happen a few times so I decided to park it - I then let it idle and increased the engine's rpm to see if I could get it to stall while parked. Eventually the engine began to putter out and stalled.

I have replaced my IAC valve and the engine still stalls. I don't have any codes - this is why I need your help. I think that it might be my throttle position sensor, but I don't have any codes.

I'll take all ideas, thanks for the help.

Post by **rspi** » 15 Feb 2013, 18:29

Most common no code stalling problem is the fuel pump relay or fuel pump going bad.

marcusheard · Post by **marcusheard** » 15 Feb 2013, 21:07

What is the best way to check my fuel pump? Also, I have noticed the opening in my trunk for the fuel pump mount, can I remove the pump from that opening?

marcusheard · Post by **marcusheard** » 15 Feb 2013, 21:09

Can my TPS go bad without a code?

Post by **rspi** » 15 Feb 2013, 21:13

TPS?

As for the fuel pump, you can hear it running if you turn the key on. You can lean the seat back. Yes it is accessed from the trunk but don't go trearing into that unless you know that pump is bad.

marcusheard · Post by **marcusheard** » 16 Feb 2013, 09:49

The car starts right up, so I let the engine stall - after stalling I removed the cap from the end of fuel rail and there was fuel present (About what I can recall from the last time I checked - however that was close to a year ago so I'm not positive). Then, I spanned my TPS (Throttle Position Sensor)and I'm getting 0.5V to 4.19V. Is this a decent span - it sounds good but I'm not sure. I'm going to pull my plugs to see if they are fouled, and check my oil to see if its milky. I wounder why I dont have any codes, these are the most difficult to solve

marcusheard · Post by **marcusheard** » 16 Feb 2013, 09:54

Just read that 0.55V to 4.20 V is normal for a TPS on a S70

Post by **erikv11** » 16 Feb 2013, 11:06

Here are a couple comments:

(1) Yes, for sure a bad TPS can cause a stumble without codes. But it sounds like you have checked out the TPS.
(2) A persistent stumble could be the fuel pump relay, but it is unlikely. Usually when that relay goes bad (when is very common), the car intermittently dies (won't run at all). Sounds like your car intermittently stumbles.
(3) Most likely causes of a no-code stumble are a bad MAF (by far and away the first thing to check), a bad ECT sensor, a vacuum leak, a bad TPS, dirty IAC and/or dirty throttle plate.

I'd check the MAF by unplugging it, see if the stumble goes away. It will set a MAF code you will have to reset with a code reader.

marcusheard · Post by **marcusheard** » 16 Feb 2013, 11:13

I'll check my MAF after I replace one of my spark plug wires (fell apart during removal process). I'm not sure if it was faulty before or after I began pulling. Spark plugs look normal.

I just ordered my plug set so they will be here next week - 50% less than the set at Autozone

Post by **mercuric** » 17 Feb 2013, 19:10

Probably wouldn't be a bad idea to clean the MAF when you inspect it -- the hotwire itself, the connector, and the harness connector. Use quality zero-residue electronics contact cleaner, and be sure to let if all fully dry off before re-installing.

The other thing that comes to mind is the fuel filter. One of my RWD bricks once exhibited similar symptoms from a clogged filter.