1999 S70 GLT, hard time starting, intermittent RPM, misfires

z80 · Post by **z80** » 12 Sep 2023, 11:28

Hello!

The car is 1999 S70 GLT. Starting today morning it experiences the following symptoms.

0) Check engine light is off. There are no trouble codes I can read.
1) It is needed to crank the engine for considerable time to make it start. May be it is about 3-4 seconds.
2) RPM is unstable, pulsating, feels like multiple misfires, sometimes it is almost ready to stall.
3) When starting cranking, sometimes right at the moment the key goes to position II, RPM needle instantly jumps to a very high value like on GM or Chrysler and then goes to actual cranking RPM. OBD2 doesn't register this jump though, plot is first at 0 and then at idle RPM. When this happens, it is necessary to crank it for about ~2 seconds longer than usual for the engine to start.
4) When pulsating and experiencing what feels like misfires, STFT exhibits massive spikes.
5) Timing advance also shows some spikes.
6) Engine RPM signal wiggles up and down and looks like matches to what RPM needle shows.

Please see the pictures attached. BTW, I'm very sorry, I don't know how to make attachment images collapsing/expanding.

I'd appreciate any hint!

UPDATE: The above phenomena was observed at around 9am when it was mild ~70F (19C). Now, at around noon, when it is close to 90F (32C) and the car body and internals are very hot, I've re-tested the car and it feels perfectly fine, no visual issues. The crank time to start the car is <1 second. Data doesn't show any pulsations neither.

Post by **scot850** » 12 Sep 2023, 16:02

Have you checked the fuel pressure at the injector rail?

When you turn the ignition to Pos II, do you hear the fuel pump priming?

If you can find a junkyard fuel pump relay I would consider a swap on that first. Looking at your list of issues it would sound fuel related but it needs to be eliminated from the possible sources.

Neil.

z80 · Post by **z80** » 13 Sep 2023, 10:18

scot850 wrote: ↑12 Sep 2023, 16:02 Have you checked the fuel pressure at the injector rail?

When you turn the ignition to Pos II, do you hear the fuel pump priming?

Hello! Thanks for the hint! Yes, I can hear the fuel pump priming when listening right next to the fuel tank.

Thank you for the advice regarding the fuel rail pressure! No, I didn't measure it yet. I'm going to rent a tool and measure the fuel pressure over the weekend. Is the specification around 60 PSI?

Thank you!

Post by **scot850** » 13 Sep 2023, 11:59

There seems to be debate on this, but for up to 98 I have always known it to be 43 psi static and maybe a little less for running, and for later cars 50 psi and above. Abscate recently posted they are the same, but we have to differ on this as the dealer measured my 00 V70 at just under 60 psi at the rail. The main thing is you need to be seeing a steady fuel pressure ideally. If it is fluctuating then there is an issue. A buddy recently was having issues with his car. Worse when warm. He swapped his fuel pump relay and all the random running issues have disappeared for now (hopefully for good).

Neil.

jmartin919 · Post by **jmartin919** » 13 Sep 2023, 13:02

What is the same - static and running or 98 and later?

Post by **scot850** » 13 Sep 2023, 14:55

99- is a higher pressure. I'd be looking for at least 50 psi running at the rail. Up to and including 98 (first year V/C/S70) is static around 43 psi and may drop when running. The main thing that when your car is running it stays even. If it is fluctuating there is likely a pump issue.

Neil.

z80 · Post by **z80** » 17 Sep 2023, 13:39

scot850 wrote: ↑13 Sep 2023, 14:55 99- is a higher pressure. I'd be looking for at least 50 psi running at the rail. Up to and including 98 (first year V/C/S70) is static around 43 psi and may drop when running. The main thing that when your car is running it stays even. If it is fluctuating there is likely a pump issue.

Neil.

Hello!

I've taken fuel pressure measurements and also obtained some new data.

1) I measure 54 PSI no matter if car runs normally or tries to die. It does not depend on RPM neither and stays exactly at 54 PSI.

2) Fuel pressure is very stable. I see almost no needle movements. If there are any irregularities, those are less than 1 PSI.

3) The rough running condition has been observed exactly 2 times. First time when I wrote the very first post (Tuesday September 12-th), and the second time today (Sunday September 17-th) when I took the measurements.

4) When the condition was observed for the 1-st time, it didn't go away no mater how long the engine ran. I kept it running at idle and at around 2000 RPM collecting the data up until the radiator fan started spinning and longer. Only when I shut the car down and returned back a few hours later the condition's gone.

5) When the condition has been observed for the 2-d time, it didn't last for very long. Today I started the car 4 times for ~30 seconds each time to take the measurements and shoot a video. And on the 4-th time the car was running normally with no issues.

Rough running condition: https://odysee.com/@z80:6/20230917_0910 ... tn6ZVA3yGD.
Runs fine a minute later: https://odysee.com/@z80:6/20230917_0911 ... tn6ZVA3yGD

NEW DATA:

6) When the car was fully warmed up during the day and working normally, it's suddenly lit up the ETS light. I've replaced the position sensor with a contactless one in the throttle body about a year ago. After I've restarted the car with the OBD scanner attached, the ETS light went away and didn't come back but I've recorded the throttle position sensor and RPM data anyway. Please see below.

My suspicion is the two problems (rough RPM in the morning and ETS) might be not completely independent.

I'd appreciate if one could compare it to what it looks like on a healthy car to see if the amount of throttle wiggle I observe is normal or excessive.

Thank you!

: Screenshot_20230917_120048.jpg (41.61 KiB) Viewed 506 times

Post by **scot850** » 17 Sep 2023, 16:57

Just for clarity, when you said you replaced the throttle position sensor (as in one) was that what you meant or do you mean you replaced the pair (one either side)? Sensor #1 and Sensor #2

Neil.

z80 · Post by **z80** » 17 Sep 2023, 18:43

scot850 wrote: ↑17 Sep 2023, 16:57 Just for clarity, when you said you replaced the throttle position sensor (as in one) was that what you meant or do you mean you replaced the pair (one either side)? Sensor #1 and Sensor #2

Neil.

Hello!

I purchased a contactless sensor kit, I guess it is a Hall sensor-based one. The kit instruction was to replace one of the original sensors (on the side with 3 terminals) and override the signal of the other sensor (side with 5 terminals) by routing the wire to the appropriate terminal. I guess, it is to make the throttle module to believe that both sensors are in perfect agreement.

So the second sensor is mechanically still in place, but its signal is ignored and instead comes from the replaced sensor.

And it was about a year ago.

Post by **scot850** » 17 Sep 2023, 19:48

Ok, that explains many of the 'repairs' I've seen on YouTube which only replace one but have a link to one of the terminals on the other.

I'm still wondering how that works. Does it basically bypass the signal? There are I think 5 terminals on the 2nd side, so I am struggling to understand how that works with only one jumper wire. Beyond my pay grade that one!

Fuel pressure is spot on, so we have eliminated that I think as an issue.

If we assume the fuel filter is good, then the only other real possibility would be bad injectors, but the fact you are seeing such a random and so far few occurrences seems strange.

Did you ever change the fuel pump relay? My buddy was getting random stalls and loss of power and it threw an ETM light. He has replaced the ETM twice now with junkyard units, but it returned again. This time he swapped the relay and the car has been running well since then.

Neil.