2000 S70 N/A Stumbles, no CEL, no codes, idles ok

Chapelgirl · Post by **Chapelgirl** » 15 Mar 2015, 22:58

Apparently this is one for the history books. This was a gradual decline in power to the point that the engine idles ok but stumbles badly when trying to accelerate. Current symptoms are:
Starts normally but will only idle at a very low 400 rpms but idles smoothly but if pedal is pressed while in park it will try to die out and the mode "W" light flashes intermittently.
After a few minutes of warm up time the rpms suddenly jump to 900, still idles smoothly but engine again tries to die out when the throttle pedal is depressed, still in park. "W" light no longer flashes (only flashes at very low idle when engine is almost dying out)
After more warm up time the engine will stumble but pumping the throttle slightly I can eventually get the engine to rev up as high as I want to go while in park. But as soon as the car is put in gear it stumbles badly again.
The car will move when in gear and just idling but the stumble keeps from being able to accelerate.
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Here is everything I have done to date:
Seafoam treatment, 1/3 in fuel, 1/3 in intake, 1/3 in oil.
Oil pan o-ring replacement.
Took to dealer for sweep test and confirmed ETM failure.
Removed yellow stickered ETM and had rebuilt by Xemodex, reinstalled. No change.
Removed CVVT valve for inspection and found it clean, reinstalled with new gasket.
Unplugged MAF sensor, engine quit and logged a code. Plugged back in and cleared code.
Later replaced MAF sensor with a known good used one.
Replaced coolant temp sensor with new one.
Repaced spark plugs with OEM.
Replaced MAP sensor with used one.
Replaced vacuum lines from intake manifold to air cleaner and canister purge valve.
Cleaned ground connections at left wheel well, one located between battery and left headlight assembly, two ground straps between the block and the firewall, and where blue ground wire from battery bolts to the block near where the dipstick tube is mounted.
Replaced fuel filter
Replaced all fuel injectors with reman units.
Had muffler shop cut exhaust pipe before the catalytic convertor, no change. CAT ok.
O2 sensors reading correctly on scanner.
Took to indie mechanic with 25 years experience. He checked fuel pressure, ok. Checked wiring junction near battery that feeds ac compressor and ETM and it was ok. Ran jumper wire from hot source to ETM. No change. Ran sweep test, checked air gap, visually checked ETM movment, ok. Checked with VIDA and still no codes. Verified timing belt in correct position. Swapped throttle pedal with a known good one - no change. Mechanic simply did not know what else to do. Alternator failed while in shop. Towed home.
Replaced alternator and output is now 14+ volts.
Xemodex sent another ETM. Swapped ETM. No change. No codes, no CEL, no fault lights of any kind.
Ran test on ETM by turning key on, connecting battery cable and listening for the click, the high pitched whine and the second click, ok.
This is going to take somebody out there with some serious experience. At 168,000 the car is in excellent condiition. Too nice to give up on her especially with all of the suspension work I have done, too.
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All the work the indie did only cost me $179, really don't want to take it back to the dealer as I have not been impressed with their service. My indie guy had VIDA so not sure what more the dealer could do.

Thoughts?

Post by **E Showell** » 16 Mar 2015, 06:08

Are the ignition coil packs all original? They can go bad. I do not see that they have been replaced and at 168k, they could well be past their sell by date. I am not electrically inclined, so I can't give you a test procedure, but others will, no doubt, be by.

Post by **precopster** » 16 Mar 2015, 06:47

The 2000MY was a crossover for the newer style electrical portion of the ignition switch. Check FCP Euro's site as it shows the VIN breakup. If using the older ignition switch which is shared with 850s this should be first on your list.

Rockauto sell the older style OEM switches repackaged as another brand (can't recall the brand now) and are much cheaper than dealers.

If you have the newer version it may still pay to swap it out with a known good used one.

Chapelgirl · Post by **Chapelgirl** » 16 Mar 2015, 19:19

Have one new coil pack to replace one I robbed to get our V70 going. Idle is smooth at whatever rpm but there is a way to test the ohms of each coil. My next step will be to remove all the coils and test the resistance of each and go ahead and check compression on each cylinder while I'm at it. At least that will help gauge the mechanical condition of the engine. Thanks for the input. Will also look into the ignition switch. I can't wrap my head around that being a problem when the car starts fine but hey, it's one more thing to look at that I have not as of yet.

Post by **misha** » 16 Mar 2015, 19:24

What is the actual fuel pressure?
Did you measured fuel pressure when engine starts to stumble or just at idle?
Verify that you have proper fuel pressure when it begin to stumble...when you put it in gear.

Chapelgirl · Post by **Chapelgirl** » 16 Mar 2015, 19:39

Good question. I have not checked that personally. The muffler shop that checked the CAT verified fuel pressure and said it was ok and my indie guy checked it and also said it was ok but I don't have an actual reading. Might be good to double check myself.

Post by **northernlights** » 16 Mar 2015, 21:59

I believe I remember this one. I think the car was low enough on power that you couldn't get up a driveway. You had a shop cut the cat and it didn't help which I though was bizarre from the way you described the problem.

It really sounds like a fuel delivery problem given the evidence and tests that you have done.

Did anyone check the fuel pressure control relay, and temporarily bypass it? I've seen those become possessed and do weird things.

Here's something else. I think on the NA 850's they had a variable speed fuel pump in order to reduce evaporative emissions by spraying less gas into the tank under low load. I don't know what controls that, but it is probably the ecu. I do not believe the turbo's had this feature.

How old is the fuel pump? I have an old reference for the 850 NA that says you should see about 8.5 A max at 13 VDC into the pump at 3 bar pressure. Can you stick a clamp on ampmeter on the wiring, stick it up on jackstands and see what it does?

Post by **misha** » 16 Mar 2015, 23:27

northernlights wrote:...Here's something else. I think on the NA 850's they had a variable speed fuel pump...

No.They didn't had such a thing.

Post by **abscate** » 17 Mar 2015, 04:40

I made resistance measurements on new coil packs on my 1999 in a thread.

https://www.matthewsvolvosite.com/forums ... il#p325109

You need to go back to compression test when you are in this deep.

Bypassing fuel relay is quick though, and worthwhile.

Post by **precopster** » 17 Mar 2015, 04:57

Recently one of my ETM customers with a 1999 2.4LPT had starting problems. He went through and replaced everything however I asked him to re check the coolant temp sensor with a meter. He measured mega ohms. It was a IPD aftermarket one I bought and supplied to him and I felt awful for doing so.

Fortunately IPD no longer stock these.

He placed a 1000 ohm resistor across the terminals instead of the temp sensor and voila she started like a champ. At mega ohm readings the temp sensor will allow the ECU to dump even more fuel into the cylinders.

Try measuring the resistance of the temp sensor at low temps and report that in. Perhaps even try the 1000 ohm resistor. Do the plugs get wet?? Perhaps engine is flooding. Have you checked gaps for the plugs? Are they multi electrode (not adjustable) or single (adjustable) ?

Has the engine ECU and transmission ECU been removed to check edge connectors for corrosion? (You need a special tool, however is cheap to buy)