Anyone figure out what's wrong with my enigine?

[Dacvolvo]

Noticed something interesting about my Volvo today (C70 2.5 ME7 on a 2000 plate).

The car is perfect and gives me no cause for concern. However, today, whilst stuck in a traffic jam (facing down hill), I was stationary and had the handbrake on and the car wasn't in gear. The traffic started moving forward very slowly and then stopped again. The car in front of me had moved about 5 feet. I simply released the handbrake and let the car roll forward a few feet in order to "close the gap".

As I was rolling forward for that short distance, my rev counter dropped from the usual rock steady idle of 900rpm to about 500rpm and then as soon as I stopped, she went straight back to 900rpm.

I've now been trying different things out with the car tonight in order to re-create the rev drop.

Basically, I've found that if my car is moving and not in gear, the revs drop to 500rpm and will stay there until I either touch the throttle pedal or come to a complete stop. The engine doesn't stutter and none of the dash lights dim, but she's definitely dropping to 500rpm (I can hear the revs die down as the counter drops to 500rpm).

So what's the problem? Or is this just a normal characteristic of the ME7 engine?

[flyingbrick]

I dont now bud. Its sounds like your looking for problems it thats the only thing wrong with ya motor then happy days mate. Sounds like just a glitch mate. Dont worrie to much about it fella.........:thewave:

[wegal]

My 06 plate does the same thing.

[Liddo]

Dont suppose your Climate was on :buttkick: :D

[Enigma666]

Anything electrical when the car is moving will cause a dip in revs....we wont see it because we are revving the car as a general rule... try turning your wheels....you will see a dip there too as the PAS is being used....perfectly normal :)

[Dacvolvo]

FlyingBrick - Ha ha ha; totally agree, Bud. But I'm just curious in case it's the tell tale sign of something (ie; the ETM) that's about to give up. Don't want to be driving out in the countryside late one night when the car suddenly dies on me. Specially if there have been warning signs ;)

Wegal - Interesting... Maybe it is just a characteristic of the ME7 then. I was thinking it could possibly be a fault in the MAF, but the engine doesn't struggle or seem laboured in anyway. Has your engine always done this? I've only had my ME7 for the last 3 months and this is the first I've noticed the Rev drop.

Liddo - I've tried it with and without the AC / Climate Control on. There's no difference. I've actually tried everything I can think of - I've turned everything elcetrical on to try and get her to stall under load when I do it and I've then tried with everything switched off. I've done all this numerous times and there's just no difference. I've replaced the spark plugs, sanded all Earth conections, replaced the battery, air filter and fuel filter - there's just no difference.

It's not causing any problems, I've just never seen a car do this before and I'm just wondering if it's normal.

[Dacvolvo]

Anything electrical when the car is moving will cause a dip in revs....we wont see it because we are revving the car as a general rule... try turning your wheels....you will see a dip there too as the PAS is being used....perfectly normal :)

Hey Enigma

Oh, Agree completely. There's always a slight dip whenever anything that uses up a lot of juice is being used - PAS, AC, loud sound system with amps, etc. But to simply be pulling up to a red light with nothing electrical switched on and the rev counter drops to 500rpm and then bounces back to 900rpm does seem a little "unusual".

[Enigma666]

Yeah agreed on that one....perhaps you are right with the fly by wire system....whatever the cause I am intrigued by this one :)

[mauler]

If you say you were in a trafic jam could the drop in revs be caused by the electric cooling fan kicking in????

[Dacvolvo]

If you say you were in a trafic jam could the drop in revs be caused by the electric cooling fan kicking in????

Nope - I can make the car do the rev drop whenever I want - It's nothing to do with anything electrical being switched on or off. On a side note - the radiator fan comes on and there's no difference; the engine still remains at a constant 900rpm. It's only when the car is moving and she's not in gear.

[timbo_1975]

Must be a percularity of the mapping!

[Liddo]

IF i remember, I'll try mine tomorrow and let you know

Personally, I think your going :cuckoo: but I'll let you know for sure :D

[Dacvolvo]

Must be a percularity of the mapping!

That's exactly what I was thinking. I tried it a few times tonight in the freezing cold (thought maybe temperature would play a factor in it), but nope - no change.

The engine will dip to 500rpm (I can physically hear it dropping as well as see the rev counter drop) and it's only when the car's moving and out of gear. Even though she drops to 500rpm, the engine doesn't stutter or stall. She's still smooth and quiet.

Liddo - ha ha ha ha ha. I thought I was going mad the first few times I noticed it too. Just put your car on a gentle hill and let her roll forward at about 5-10mph in neutral (mine is a ME7 with manual box).

[Liddo]

Well, I tried mine yesterday, same scenario, and my rev counter doesnt move a milimeter.

SO, either YOU are :cuckoo: or the car is :cuckoo: :D

[Baj]

Mine does it all the time but not moving. If I drive somewhere and then park up but leave the engine running after about 30-60 secs the revs will drop, hit a point then bounce back up.

I assume it is some electronic check system.

[LeeT5]

S h i t in yer carburettor?? :saythat:

Think your worrying too much... I would worry about that fly that just crawled into your air filter...he may cause a blockage!! :hidesbehi