1998 C70 T5 - No upshift when L gear is engaged/Idle dipping

andreborges · Post by **andreborges** » 08 Jun 2014, 17:40

Hello, fellow MVS contributors.

I have for long been an MVS reader while working my beloved C70 to top shape, completing the Stage 0 "tune-up": replaced Fuel Pressure Regulator (not Bosch, but 3.5/4bar regulator of a similar system), replaced Throttle Position Sensor, replaced Idle Air Control valve, replaced fuel pump and filter, replaced intake and intercooler hoses and cleaned intake housing, replaced rotor, distributor, ignition cables and spark plugs, replaced Mass Airflow Sensor and replaced the whole PCV system (cleaning PTC nipple included). Also gave a full 2 turns tightening to my wastegate actuator (which improved strongly the cars' response under throttle).

So, the problem: my vehicle has developed an idle dip under braking to full stop and an unusual and intermittent "coughing" while idling. It does jerk a tiny bit when upshifting in D and 3 gear modes. Secondly, I've figured it does not upshift to 2nd gear as it should, while in L gear mode. I have been banging my head to find out it's problem, as I bought it in a somewhat bad condition and I am absolutely crazy about it...

Please, could any of you help me, it would be greatly appreciated, guys!

Yours truly,
André Borges

Post by **abscate** » 08 Jun 2014, 19:51

Andre - Often a dip like this is from a bad vacuum hose or small leak in one of the hoses. Look over them as carefully as you can.

Welcome!!

andreborges · Post by **andreborges** » 08 Jun 2014, 20:15

abscate wrote:Andre - Often a dip like this is from a bad vacuum hose or small leak in one of the hoses. Look over them as carefully as you can.

Welcome!!

Thanks, abscate, for your insight and the welcome!

Would that explain the little jerk and the non-upshifting Low gear? Any places in particular to look for, since I've replaced the intake/intercooler lines (with FCP silicon lines, to be more accurate)?

Why would it say, in the Volvo technical data for this tranny, to check and see if it upshifts in L mode? It seems to be kind of a diagnostic for a problem...

Appreciate any help or insight provided!

andreborges · Post by **andreborges** » 08 Jun 2014, 20:43

Add a clue to the mistery: I have also found some oil beneath the turbo housing, in the "snail". Could it be the leftovers from my recent intake/intercooler hoses replacement?

Could that cause the dip and the 'non-upshift' situation?

Post by **jblackburn** » 09 Jun 2014, 07:43

If starting out in "L", not upshifting to 2nd is completely normal. It will hold 2nd once you're already in 2nd, but it will not upshift from 1st on its own.

Agree on vac. line being the cause of idle dip. Check the line behind the power steering pump - if this one falls off, it will also cause the oil leaking down the turbo, as no vacuum is provided to PCV system @ idle.

Also, pull the spark plug cover off and look for oil in the little valleys - it will pool up from a bad oil cap seal or loose valve cover PCV hose (the U-bend hose that snakes up there), and then leak down on the turbocharger/exhaust.

Have you done a PCV job on this car in the recent past?

andreborges · Post by **andreborges** » 09 Jun 2014, 08:06

Thanks very much, jblackburn, for info regarding the L gear!

I was starting to go slightly mad about it, as the sources I had all specified wrongly about it.

I will watch for this vac leak thoroughly and post back here. Full PCV job was performed after 1-2 months of possessing the car. For any reference, check first post for the list of things I have replaced!

Post by **jblackburn** » 09 Jun 2014, 08:10

andreborges wrote:Thanks very much, jblackburn, for info regarding the L gear! I was starting to go slightly mad about it, as the sources I had all specified wrongly about it.

I will watch for this vac leak thoroughly and post back here. Full PCV job was performed after 1-2 months of possessing the car. For any reference, check first post for the list of things I have replaced!

Sorry, I missed that.

But good, you're probably familiar with the 2 hoses that I was talking about! After my first PCV job, the little buggers kept slipping off.

andreborges · Post by **andreborges** » 09 Jun 2014, 08:19

Only mildly familiar... :/

I am a bit too young and insecure for a job such as the PCV, so I opted to have a mechanic perform the job. Could you help me with the locations, jblackburn? Also, there seems to be a small whiff of dipstick smoke just as I apply the throttle, as soon as a split second, it is gone. Could this prove/disprove some error/failure regarding the PCV?

Post by **jblackburn** » 09 Jun 2014, 08:57

One small puff when going from vacuum to turbo boost is absolutely nothing to worry about. As long as there is not constant smoke when the throttle is open, or at idle.

^That's the small vacuum line - tucked behind the power steering pump when intake manifold is lowered.

There's the PCV hose to the top of the spark plug cover - give it a very light tug to make sure that the clamp is still holding it down.

If both of those check out, but there is still oil everywhere like in my picture, replace the seal on the oil cap.

andreborges · Post by **andreborges** » 09 Jun 2014, 09:59

I'll do it and post back, jblackburn! Thank you very much for all this.