Stumbling/hesitation '98 V70, stick FWD, 192K mi.

Post by **E Showell** » 29 Jul 2010, 07:53

Thought a bad negative ground to the block was the source of my hesitation/stumbling problems. Not so.

So far air mass sensor has been changed and ignition system components are all new (except coil) from 6 mos. ago. All OEM replacements.

Had been getting random misfire check engine light codes.

Have run a few containers of Techron through the fuel system as well. I've also revved the snot out of the engine on the theory that I might have a stuck valve -- no joy.

Spark plugs have been pulled from the misfiring cylinders to check for a piece of carbon on the electrodes -- no signs of same.

Do not appear to have any vacuum leaks

The car hesitates and stumbles under load -- once up to cruise does not seem to be a problem.

Throttle body has been cleaned.

On start up idle is consistent around 875 rpm after engine warms up, idle can fluctuate a bit.

Starting not to enjoy driving this car anymore.

Thoughts?

SirSonic · Post by **SirSonic** » 29 Jul 2010, 08:20

I too have just developed that problem under load going from about 50mph to 70mph in 5mph increments to 70, probably higher too, didn't test that.

I noticed also in my case that I have an Economy/Sport mode switch and the car does not do the problem in Sport mode.

I think the V70 is just after my year of 850, so might be a similar problem.

Post by **E Showell** » 29 Jul 2010, 08:24

My hesitating is mostly at lower speeds. I'd say under 30 mph.

smokingslash · Post by **smokingslash** » 29 Jul 2010, 08:57

hi
i had some thing like that at about 2000 rpm,but got a code for a crank senser(rpm). changed it out and for the last few days its fine.
one thing that was strange is that the tack would hang as i changed gears and now its better.

Post by **E Showell** » 29 Jul 2010, 09:54

Haven't had a crank sensor code. Most I've gotten is random misfires.

Post by **jblackburn** » 29 Jul 2010, 10:18

If there are ANY wires that have come close to the crank/cam sensor wires, move them as far away from each other as possible. That's one suggestion I've got. The other is something's dumping fuel into the intake at low speed, either a bad regulator, bad ECT sensor, orrrrr a purge valve.

When you get the revs on up there, it doesn't stumble anymore, right?

C@lvin · Post by **C@lvin** » 29 Jul 2010, 10:24

Random thoughts......just some brainstorming......

Fuel pump relay? Injector relay?

Don't suspect the coil? Can you see sparks from it in the dark?

Tried Seafoam in the fuel, crankcase and intake?

ECT?

Post by **E Showell** » 05 Sep 2010, 07:26

It did turn out to be a bad ground after all. Replaced negative battery cable and all is well.