1998 S70 5-cylinder high-speed stalling and stuttering

sinican · Post by **sinican** » 08 Nov 2014, 16:18

Hi, I am new to the forum. I have a 98 S70 5-cylinder that has 144000 miles. It has been a great car since I bought it used in 2003. About 6 weeks ago, the car started to have the following symptoms:

1. I was driving on the highway at speed and exiting on the off-ramp. I engaged the clutch to let the car coast. Before I could down-shift and brake for the intersection, the car idle/lost power--all the light came on, the car is off.

2. At low speed, as I engaged the clutch to turn into a parking lot or make a turn, the car did the same thing--all the light came on and the car lost power.

In both of the cases above, once the car came to a complete stop, I can restart it instantly and the problem won't return for a while

The shop I go to 1) replaced the distributor cap, 2) lube the "stalling motor", 3) changed the ignition coil. And the problem went away for less than a week before returning

Then the car started to exhibit the following symptom:

3. Stuttering/stumbling at speed or while accelerating as if there was a gust blowing right at the car, even though there was no wind. At first, this only took place at high gear and high speed, but later at pretty much every gear and every speed this symptom showed

3a Predictably, symptom 1) and 2) follow symptom 3. i.e., once the car exhibit symptom 3), the next time I stepped on the clutch to coast without downshifting immediately, the car idle/loses power, like clock works

4. the car "hunts for idle" at low speed. At low speed, the car threatens to idle, or actually idles. Stepping on gas tends to placate it but not all the time.

After 3), 3a), and 4) I also had the shop replaced the crankshaft sensor. And it still didn't solve the problem.

I read this thread about ETM and MAF but realized that the 98 S70 may or may not have ETM. I asked my question there and someone suggested "full spark discharge replacement including rotor button and leads as well as cap and new spark plugs".

I also read this thread on S70 dying on highway, but I don't know if the two problems--symptom 1) and 2) vs 3) and 4)--are caused by the same failing components.

Unfortunately, I am really out of practice and tools after not tinkering with a car for more than 10 years (nowadays I am mainly a home bicycle mechanic), so it's hard for me to figure out the problem and assessing the cost.

Any advice is highly appreciated!

Post by **FLXC90** » 08 Nov 2014, 18:06

Is your Check Engine Light On? If so, what codes are present?
Have you pulled the plugs to look at them?
When is the last time you: Changed Fuel filter
Checked vacuum lines for splits
How many miles since the last full ignition tune up: plugs, wires, cap and rotor?
PCV service? Any oil under the distributor cap? How's your air filter look? Are all the air hoses fitted and sealing? (the big ones) Survey the basics first, then if necessary, check fuel pressure maybe?

sinican · Post by **sinican** » 09 Nov 2014, 07:08

Hi, FLXC90,

thanks for the quick response. There has never been any error codes. I believe when the shop replaced the cap, they replaced the wires, but not sure if they replaced the rotor and the plugs.

I think when they replaced the crankshaft sensor, the fuel filter was replaced. They actually measured the fuel pressure pretty closely but found pressure to be normal. But I will ask them about the rest.

Post by **rspi** » 09 Nov 2014, 07:52

No error codes usually point to a fuel pressure problem.

Post by **rmmagow** » 09 Nov 2014, 08:02

What wires did the shop use? OE or Bougicord is the only ones acceptable. Spark Plugs, ONLY OE Volvo plugs ever. Look around here for fuel relay jumping or buy another fuel pump relay, always good to have a spare. Cap and rotor have to be Bosch. If the shop replaced you cap but not your rotor, find another shop. Turbo car?

sinican · Post by **sinican** » 09 Nov 2014, 08:40

HI,

Thanks for the advice. The shop is a very reputable one that works on Volvo almost exclusively in Berkeley. I am sure they did the right things when replacing the cap, I just don't have the paper work in front of me.

In reading over the last invoice, I realized that the shop has also replaced the fuel pump relay along with the ignition coil.

I will ask them to check the spark plugs, the vacuum hose, and whether there is oil under the distributor cap.

This is not a turbo car.

Post by **abscate** » 09 Nov 2014, 13:11

I think during this work they bumped a vacuum line or a line broke/split from age. Not their fault, just a consequence of running a 15 year old car!

Look around the Idle Air control valve (IAC) that is on the rear of the engine, near the manifold. Thats a bit to our right looking under the hood. You need a mirror to inspect all the hoses if you don't remove the IAC, so look closely. A split here will give you decent running with stalling at idle.