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

[draser]

All very good points. At this stage it sounds like a lot of parts were replaced and mechanic knows this engine by heart. However, unfortunately something was missed. Even though the decline was gradual, which may point to normal wear, other symptoms still point to fuel management. On my cars I like to do at least one compression test, just to know where engine is at. So that idea was mentioned, and it's good and makes sense. I was just wondering though if you could get the Vida printout from mechanic and post here. I'm talking about a parameter scan which will actually tell what's going on inside engine and take some of the guessing out.

[Chapelgirl]

Lots of great ideas. Borrowed a compression tester today. Only have time for a quick test tonight. Checked ECT and had 2.36K ohms cold and .21K ohms (using the 20K scale) when up to operating temp. That sounds ok I think. Can't remember if I bought it from the dealer but pretty sure I did knowing there have been issues with aftermarket ones. Will proceed with other suggestions here and report back. Thanks everyone.

[Chapelgirl]

More test results. Bypassed fuel pump relay - no change.
Tested compression, engine cold, throttle to the floor, eight revolutions.
#1 - 145 psi
#2 - 145 psi
#3 - 135 psi
#4 - 156 psi
#5 - 151 psi

I will see if I can get VIDA printout. I would also like to try the 1K ohm resistor on the ECT sensor connection but have to round up a resistor.

How do these compression numbers look?

[precopster]

More test results. Bypassed fuel pump relay - no change.
Tested compression, engine cold, throttle to the floor, eight revolutions.
#1 - 145 psi
#2 - 145 psi
#3 - 135 psi
#4 - 156 psi
#5 - 151 psi

I will see if I can get VIDA printout. I would also like to try the 1K ohm resistor on the ECT sensor connection but have to round up a resistor.

How do these compression numbers look?

They are about 40% lower than a healthy engine. Good NAs produce 200-210 psi. Still the car should start and run but be underpowered of course.

[E Showell]

Mike -- could those numbers improve if the engine were warmed up when the readings are taken?

[precopster]

Usually it is what it is.

The tension that a compression ring places on a warm cylinder liner compared to a cold one is pretty negligible. The 2000 and above engines have oil squirting so cylinders are always wet. Perhaps 5 psi higher when warm.

[draser]

For kicks and giggles I'd still pour 1 teaspoon of oil in each bore and redo compression, since you have the gauge... I know it's got squirters. If no change, hopefully, I'd pull the head.

[Chapelgirl]

Ok. additional testing has been done with the following results.

Did wet compression test and unfortunately the numbers came up anywhere from 175 to 195 psi. I can live with the fact that my compression is a bit low but I struggle with the fact that the car ran great and slowly declined to its current state in about 300 miles.

Additional test results:
Put 1K ohm resistor across the ECT connector: no change.
Replaced the engine management relay: no change.
Tested voltage to the fuses and they are all seeing battery voltage.
Had 12.3 volts on the battery with the engine off.
Tested voltage at ETM connector between the brown and green/white wire: 12.25 volts.
Bypassed the fuel pump relay and tested fuel pressure at fuel rail: found 55 psi with engine off or running. My alldata site is telling me 43 psi is normal. I couldn't test it after 20 minutes because the fitting on the gauge is leaking very slightly allowing the pressure to bleed off while at rest. Never had a starting issue though. When I finally was able to rev the engine the gauge held steady at around 55 psi.

When I could still drive my car the fuel mileage had dropped down to about 7 mpg.

Any thoughts on this amount of fuel pressure? Its the only thing out of spec that I have found at this point.

Have the ECU removal tool on the way so I can safely remove it and check for corrosion on the pins.

[draser]

Fuel press looks good, do you see blue smoke out of the tail pipe when accelerating?

[Chapelgirl]

No blue smoke. There is a glimmer of hope however. I bought some electrical cleaner and only touched four things: the connections for the ETM, MAF, ECT and VVA solenoid (just because the top cover is still off). I started the and I instantly knew something was different. It was suddenly normal. I drove the car back and forth in the driveway and all was good. I shut the car off, went in the house to go get my wallet so I could go for a test drive and went back out and started it again but I was back to the same old problem. Something I touched made a difference but only for those few moments. I went back and recleaned the same four connections as well as the ECU and most other connections but "normal" has not shown back up. I am thinking I must have a wiring issue with one of those components.