With wide open throttle my car only get 3500rpm and then trip to 1000rpm

DEWALDS40

MEMBER
1998 VOLVO S40
30,000 MILES

Its a 1998 volvo s40 2.0t automatic. If my throttle touch wide open throttle it only goes up to 3500rpm and then trips down to 1000rpm and then goes up to around 3500rpm then down again to 1000 rpm. Also another symptom is if I drive my gearbox is shifting on high rpm's like around 3500rpm's to around 5000rmp's with me driving slownly. Also when it is doing the trip thing some times it like a tipe of backfire sound I hear but its very soft but its also doing this soft back fire sound only some times.

4 Replies

JIS001

MECHANIC
3,408 POSTS

Are you complaining of a very high idle? If you have an issue with the idle been very high then I would suspect a faulty engine coolant temp sensor. Another indication it is faulty is that you could have a hard start. If you do then remove the spark plugs to see if they are fouled out with fuel. Good luck to you and let me know what you find?

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Wednesday, October 26th, 2011 AT 6:18 AM

DEWALDS40

MEMBER
3 POSTS

It start each time real quick no prob at all with that aswell as the idel is also good its around 750rpms. Another thing it also do is let say if I drive on the highway and I stop at a robot and as soon as I put it in drive the rpm's goes down to around 300rpm's then if I give gas it just dies. So the I have to keep it in neutral and rev it to around 1500rpm's and go to drive then it pulls away. If I take it for a quick drive around the block its fine with stops and stuff it pulls away good. Thanks for your reply

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Wednesday, October 26th, 2011 AT 7:19 AM

DEWALDS40

MEMBER
3 POSTS

Thank for your response. No the idel is good (750rpm's) and the staring is also good it start first time always quick. But the rmps drop after the car was runned for let say 20min if I stop at a robot and want to pull away in drive the rpms go down to around 300rpms the if I step on gas the car dies. Another symptom also is if I rev my car up and I step on the pedal "normal" it goes up en revs nicely but as soon as my pedal is flat down it trips.( I was wondering if it wasnt something to do with my cars overdrive feature) thanks.

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Wednesday, October 26th, 2011 AT 7:32 AM

JIS001

MECHANIC
3,408 POSTS

Try cleaning the idle control valve and the throttle body as well. When cleaning the idle control valve, make sure the valve inside slides back and froth freely. If it does not then replace the idle control valve. Let me know what you find.

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Thursday, October 27th, 2011 AT 4:19 AM