99 S70 rough start up

454cid · Post by **454cid** » 03 Dec 2023, 17:31

The last few weeks, I've noticed that my S70 is starting poorly. This isn't a battery/starter issue, it turns over fine. It starts, but the rpm drops suddenly, the ECU revs the engine, and then it drops to about normal idle, runs a bit rough for a few seconds, and then it smooth out. One time the RPM dropped too low to recover, and the engine died.... it was super fast. Very abrupt. It restarted fine. This happens one time a day, at the first startup.

I've also noticed that if the engine is run a short time, is shut off (such as while at a gas station) it may take two turns of the key to get it started again.

I noticed the first behavior when the temperature dropped for the season. I'm thinking a few different things here. ECT? Temp sensor under the bumper? Maybe plugs/coils?

I think the warm restart has been happening longer, off an on.

Temp gauge reads slightly below 3 on the S70, when fully warm. I don't know if it's always been that low, or if it's dropped. My 850 reads slightly above, I think... the difference could be just variation between vehicles. It's not like they're precision instruments.

My first test will be to check what the ECM sees for temperature, I guess. I'll have to do that tomorrow since I've already driven the car today. Last few first starts have not been severe.

No dash light. I've read some threads on the forum already. I will check to see if the fan is coming on too soon. I do notice after starting that the lights dim for a second. which could be a startup load of the fan.

Post by **MoVolvos** » 03 Dec 2023, 21:03

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Try cleaning the ETM. Mine misbehaved for about a year though there were other issues that added to the difficulty of troubleshooting. With the others out of the way cleaning the ETM smoothed out everything so try that for starters.

Do this in place first with a lint free towel to see how much it helps? You can always remove it later if you feel you can get more done but be sure to purchase a gasket before doing so. Also, put another towel to catch the spray as the fumes and residue that enters will cause a hard start and stumble. Be sure to clean both sides of the butterfly and the pivots as they can gunk up. Be gentle with the butterfly careful not to bend it. Do not saturate but rather spray and wipe except for the pivot area which requires a little more spraying.

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jmartin919 · Post by **jmartin919** » 13 Dec 2023, 18:07

454cid, any luck resolving this?

454cid · Post by **454cid** » 13 Dec 2023, 20:01

No, I haven't done anything about it yet. I did purchase a thermostat and cts, but dont really expect that those two items will help. I'm still thinking plugs and coils could be involved. The throttle body is a good suggestion, but ill have to research how to get to it. Time has been limited

It hasn't been too bad recently either.

Post by **scot850** » 13 Dec 2023, 23:32

Throttle body on a Turbo 99-00 is a pain to access unless you are double jointed and have skinny arms and baby hands.

1) What I do is to disconnect the top intercooler hose to the intercooler

2) It is a struggle to get to, but if it has been refitted correctly, you need to access the pipe clamp on the throttle body. The is normally under the RH end when viewed from the front and hidden about 1" out of view. M7 socket and a mirror may help.

3) The intake pipe to the throttle body can be a dog to remove as the plastic gets tight with age.

4) What I normally do is to remove the engine fan from the shroud. There are various cable to disconnect and then remove the 2 top Torx screws and then reach down the sides and loosen the 2 lower torx screws. You don't need to remove the lower ones. Can't recall is they are T25 or T30.

5) It is a tight squeeze, but if you push hard on the intake pipe to the throttle body way from yourself, you can make enough room to lift the fan out from the top.

6) This then gives you way more room to access the throttle body/ETM. There are 4 bolts on the bottom face (10mm heads?) that need to undone by braille. First remove the intake pipe. Try spraying to silicon oil or WD40 around the join to the ETM and it may help it come off more easily and more importantly back on!

7) The ETM cable is usually routed down the back of the starter motor making it impossible to remove. Only way is to either remove the 3 bolts for the starter motor or remove the rear bracket on the LH end looking from the front. P2's if I recall do away with the additional bracket, so you could remove it and leave it off, or remove the cable and then make sure it is cable tired out of the way for the future so you don't need to remove the starter again.

You should be able then to clean the ETM. I suggest not trying to separate the ETM cable unless you want a lot of hurt. They get dirty and do not like to separate. It is mounted to a metal bracket on the main wiring harness just behind the radiator with a flimsy clip. I have had to use 2 channel locks and a bunch of silicon oil or WD to spray on the join to try to get them apart. If you want to go that far then do that and then clean the 2 halves and reinstall on re-assembly.

Clean the ETM with ETM cleaner/throttle body cleaner and spray it on a cloth. DO NOT soak the throttle body. You can damage the controllers for the flap.

Good luck,

Neil.