1999 S70 AWD surging under load karlaKat

[abscate]

Have only 98k on this beauty

Under heavy load I get a surging of power, rpm varies from 2000-2200 rpm , and power fluctuation can be felt.

I’ll be running the gamut of tests on fuel pressure and ignition systems.

Driving around town with my adult foot, car feels perfect

I’ll probably look at ignition first. No idea of history of coils and plugs

No codes

[bronco]

does the 99 have the electric throttle body? I dimly remember some issue along that line that didn't set any code but was coming from a funky throttle body.

this had to be around 2010 so my memory is fuzzy I had a black S70 at the time but it was a 2000

[850 LPT]

No idea of history of coils and plugs

That's your starting point right there I would at least do the plugs and check the air filter as a first step. Not sure if a bad coil would cause surging, they usually just make the engine run lumpy when they cut out.

[abscate]

First year for the sexy Italian throttle with its computer control, loved everywhere.

The surging is so smooth it has me wondering if it’s boost related. I’m taking a field trip to Germany this week so it will be a weekend job earliest. It drove us to the train station fine.

[bronco]

First year for the sexy Italian throttle with its computer control, loved everywhere.

The surging is so smooth it has me wondering if it’s boost related. I’m taking a field trip to Germany this week so it will be a weekend job earliest. It drove us to the train station fine.

Do the boost sensors in these have meaningful input to fuel or spark curve ?

[scot850]

ETM is the most likely issue here. Try giving it a good clean. You likely know this, but easiest way is to remove the engine cooling fan. I disconnect the upper hose from the intercooler and hard plastic pipe to the throttle body. A little Braille work or help using a mirror on a stick and loosen the pipe clamp where the head is usually on the RHS looking from the front, and set back slightly. This allows you to rotate the hard pipe rewards enough to persuade the fan out the top. You then have way more access to the ETM.

You likely have an LPT spare ETM, but if not, I have a few.

Neil.

[abscate]

First year for the sexy Italian throttle with its computer control, loved everywhere.

The surging is so smooth it has me wondering if it’s boost related. I’m taking a field trip to Germany this week so it will be a weekend job earliest. It drove us to the train station fine.

Do the boost sensors in these have meaningful input to fuel or spark curve ?

On ME7, these are all integrated. When you mash the pedal you will see huge changes in the timing and boost pressure of course. I seem the remember the timing gets retarded, which usually costs you power but it may be the charge pressure mixture burns a lot faster than the NA charge

[bronco]

First year for the sexy Italian throttle with its computer control, loved everywhere.

The surging is so smooth it has me wondering if it’s boost related. I’m taking a field trip to Germany this week so it will be a weekend job earliest. It drove us to the train station fine.

Do the boost sensors in these have meaningful input to fuel or spark curve ?

On ME7, these are all integrated. When you mash the pedal you will see huge changes in the timing and boost pressure of course. I seem the remember the timing gets retarded, which usually costs you power but it may be the charge pressure mixture burns a lot faster than the NA charge

Boost sensors that are over or under reacting might be sending signals that cause the computer to pull out advance or add fuel then maybe 02 sensor doesn't agree so there is a correction in the other direction.


Knock sensors on these are 2 wires as I recall. What if when you tip in to the throttle it thinks it senses detonation and timing gets backed out or extra protective fuel added but then added in but 02 sensor disagrees
When I'm annoyed by something I'll just unplug something like that and let the computer work around the missing input and see if anything changes. Disclaimer here , stay away from your nitrous button when knock sensor is disabled

blah blah blah I guess but forcing the car into open loop sometimes help me rule things out. Even if nothing changes I feel like open or closed loop state helps me draw a box around some problems on my little pad of paper.

Sounds primitive but its kind of how I work , I write sensor names and part names on a pad of paper and draw boxes around the actual name of the part I'm suspicious of then try to isolate manually then draw connecting lines and question marks and check marks as I go

Its probably an ADD coping strategy for me but I've been doing it longer than people have been saying ADD or whatever its called now.

[abscate]

Plugs were decent but I put new ones in , look a bit lean running, but reading plugs is a lost art now ( and less useful)

[abscate]

Do Bosch Olatinum plugs have that taper on the ground electrode or is that wear?

I only run coppers so haven’t seen those before. The FCP photo shows a different electrode configuration with no taper.