02 XC70 - throttle falter/drop when returning to idle

[scot850]

I've decided when I need specifics info on this car, I will post a separate thread and then link it and any responses back to the main thread.

So have gotten beaten up, scratched and bruised fighting the intercooler hoses back on, I started the car to see if by any miracle I had managed to improve how it was running. I never actually drove the car before working on it so it will be unclear if driving it will make any obvious improvement to me.

I have still to remove the DTC's from the ECU memory (all 10 of them) to see if any have been fixed or if I am no further forward.

What I have done is:

1) Fitted new NGK plugs gapper to -.028"
2) Cleaned the CVVT exhaust solenoid and replaced the gasket and filter (no filter in previous gasket). Unit had around 4.5 Ohms which is not terrible and actuated fine when triggered. The valve portion was not particularly dirty.
3) Replaced the split rubber inlet pipe to the intercooler, and the cracked outlet intercooler to TB pipe.
4) Replaced all the cracked coils (but I think they were still working) with newer used coils with no cracks.
5) Cleaned and removed all the leaking engine oil from the coils and boots.
6) Cleaned all electrical connections that were taken apart during work
7) Cleaned the MAF
Cleaned the MAP sensor
9) Cleaned the inlet temp sensor to the TB
10) Cleaned the throttle body (TB)

When we restarted the car it ran a little lumpy initially but quickly cleared and ran smoothly which it did not before. So a win.

I got my son to raise the idle speed for a few seconds and let it drop back to idle.

When he did that, the engine revs dropped below idle and stumbled, but quickly returned to normal.

Any thoughts on the possible cause(s) for this might be? Air leak, O2 sensors (upstream is not registering), fuel pressure, etc.,

Appreciate any help. I hope to take the car for a brief run (I don't like driving on 13 year old tires!!) to see what is any codes resurface.

Thanks,

Neil.

[MoVolvos]

.
On my 00 S70 SE Base that little bit of stubble and drop was due to the ETM which with a cleaning did the trick. Your have no codes so perhaps it's still a glitch in the ETM. I did replace the MAP on the 02 V70 XC as one of the running issues besides one injector.
.

[dikidera]

On my 2005 S60 with the ETM I also get a drop to around 630 rpm so well below idle, and have had this for a long time, especially when braking to a stop, it is annoying but cleaning it did not help.

[scot850]

I did clean the ETM, and with the rough running it had before that it was hard to know if it was there before and now as the car is not misfiring it is more noticeable. I'll clear the codes and take the car for a run in the next couple of days and see if any return. I don't know if some or all of the codes are recent or old. There is a couple related to cam signals, an air leak and also may have an ETM fault. The list is below:

Fault Codes - (These are Autel codes, but I believe these will also be what Vida would give) :

1) (643A) ECM-643A : Cam Position - exhaust: Signal too low
2) (2810) Permanent fault ECM-2810 : Front O2 (upstream) sensor (HO2S) bank 1 heating : Signal missing
3) (531D) Intermittent Fault ECM-531D : Malfunction indicator lamp (MIL) CEM: Signal missing
4) (280A) Permanent Fault ECM-280A : Front heated O2 (upstream) sensor (HO2S) bank 1 : Faulty signal
5) (3000) Intermittent Fault ECM-3000 : Inlet camshaft sensor : Faulty signal
6) (400C) - ECM-400C : Fuel tank system leakage : Minor leak
7) (6806) Intermittent Fault ECM-6806 : Turbocharger (TC) control system flow fault : Flow too low
(130A) ECM-130A: Air leakage intake
9) (990A) ECM-990A : Idle air trim : Faulty signal
10) (914F) ECM-914F : Throttle valve : Faulty signal

Thanks for your inputs!

Neil.

[scot850]

I did not remove the ETM when I cleaned it as it was not too terrible. An air leak could only be the gasket to the intake possibly? 2 of the intercooler pipes were leaking, on had a 1" tear in it and the plastic hose to the ETM had a crack but not sure if it was all the way through.

Maybe I'll have to pull it and check the gasket and the TB more closely.

The car did have a recent cam seal blow out so not sure if any codes were cleared when that was replaced at a shop.

Neil.

[yanga001]

I saw another xc70 from 07 go through this exact behaviour. The owner had to sell the car but he had a terrible idle with an otherwise well running car. He did plugs, coils, new maf, new air filter, throttle body cleaning, and we reset the adaptation. He originally had a bad VVT solenoid but i dont recall if it was changed or not in the end. It sometimes had a misfire too.

[scot850]

I have a replaced the plugs with new, the coils with good known used, cleaned the throttle body in situe. Was going to remove it but as I don't have the gasket left it fitted but it was not terribly dirty. Cleaned the MAF, and air filter is good. The MAP sensor was swapped with a used one I cleaned, and the inlet temp sensor was cleaned. I also replaced the torn intercooler inlet hose and cracked intercooler to TB hose.

I need to take it for a run after clearing all the codes and see what (other than the O2 sensor) returns to see if they were old codes and had not been removed.

I have working on a good low mileage (less than 5000km) throttle body.

I have to temporarily swap my son's winter tires onto the car before driving it. I will not drive it on the 12+ year old tires!!

Neil.

[scot850]

Ok, ran the Autel and cleared the 10 codes above. Car started and no check light and engine ran really smooth with no faltering.

Check engine light came back on after idling for a few minutes.

Checked for codes again and so far (haven't driven the car yet) 4 of the codes have come back already, plus a new one:

1) P0016 or (643A) ECM-643A : Cam Position - exhaust: Signal too low
2) P0030) or (2810) Permanent fault ECM-2810 : Front O2 (upstream) sensor (HO2S) bank 1 heating : Signal missing
P0101 or (130A) ECM-130A: Air leakage intake
10) P1293 or (914F) ECM-914F : Throttle valve : Faulty signal

The new one is:

11) P2109 or (918A) ECM-918A : ECM internal fault - Permanent fault.

# 2) is obvious, the O2 sensor is dead. I can replace that, but waiting until the car has been driven to see if this list grows.

#1) ?? - Cam position - exhaust: signal too low? Is this possibly the CVVT valve or is there another position sensor at the other end of the cam?

Intake air leakage - Does this mean there is as it says an air leakage somewhere on the intake system? Anyone know where I need to start the check from and to? I have a smoker I have never used I can try for this.

10) Throttle valve? - What is a throttle valve? Is this just a generic term I don't understand? Or is this the Throttle Body?

11) ECM Internal fault - permanent. Doe this likely mean the ECM is goosed?

Any wisdom on these are appreciated!

Neil.

[jonesg]

no I think permanent fault need a repair before they can be cleared.
heater in the O2 sensor affects other things , it might cause a maf code but its not the maf.

big air leak is causing a lot of the problems, just smoke it. block the hose in front of the maf, no sense smoking that.

Cam sensor is not the vvt solenoid, ithe sensor is at the rear end of the cam shaft, you have to remove some stuff to get to it.
Check the plug, I had a loose cam sensor, 2 torx screws that secure it were not fully tightened..

[scot850]

I was talking with Blacklab247, and a bit more time, I decided to start the car again, and see if the car ran as well as last time and try rev'ing it as I hadn't done that the last time. It started rough again. I have to say that the TB initialisation is long and sad sounding. I think there may be an issue with the TB. Car ran rough and I rev'd it. It rev'd ok, and then dropped down to idle and lumpy but rev's did not faulter. I tried a few times and it settled down again.

Muffler smelled like burnt toast!? It is clearly running rich. No new codes either.

Neil