93 Volvo 850 engine revs high by itself

jreidko · Post by **jreidko** » 09 Oct 2010, 20:24

Good suggestion, i actually pulled the entire cruise control control circuit when it first started happening thinking maybe it was related, but it didn't have any effect.

Not sure about the alternator, but the idle speeds at start up and at warm up and when in neutral have all been really consistent with the idle before the problem started occurring.

Does anyone know if there is there any way to eliminate the vacuum system as a potential culprit? Is there any specific things that happens when the brake or clutch are slightly depressed that would point to the system/s that might be malfunctioning?

- jreidko

Marcobrick · Post by **Marcobrick** » 10 Oct 2010, 01:06

Quite a tricky problem. The only thing I can think of that the clutch pedal has anything to do with is the cruise control.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 10 Oct 2010, 06:50

The throttle regulates the amount of air into the intake manifold, thereby controlling speed...Any air entering the intake AFTER the throttle will cause a high rev...The throttle body-to-intake manifold gasket would be most suspect as well as the intake manifold gasket itself...Also the "O" ring on the vacuum distributer mounted on the top of the throttle body...Your problem is almost certainly vacuum related, just where is the problem...Unmetered air is getting in somewhere...

jreidko · Post by **jreidko** » 11 Oct 2010, 08:48

Thanks Jerrymcc, your comment gives me a new place to look. I've had the intake and some of the throttle related components on and off enough that it seems very plausible that i could have introduced a weak point somewhere. I'll post what i find.

Thanks again everyone, - jreidko

z31jaime · Post by **z31jaime** » 20 Oct 2010, 12:04

Glad to see I'm not the only one with this issue.

After searching and with the Help of ROBTHEMODD we found on Volvoforums a thread of people that had the same issue. IT turned out to be the water Temp. sensor. THE sensor tells the car its "cold" and the IACV starts to pump to warm the car and revs it to 4k rpm trying to heat the water....

Most of them said they noticed the TEMP guage in the car go dead when the Reving happens...so check that. What I did was when the car was reving @ 4k RPM I pulled the Plug for the IACV...and Bam the car dropped to normal idle. so I knew It had to do with that, and it wasnt a vac leak or anything like that. I wasn't throwing CEL because thats a normal function of the car, to warm the motor.

I pulled one for the junk yard and suddenly CEL came on for low coolent temp. and the reving went from 4k to only 2k. so I knew I was looking in the correct place. I decided to clean the contact of the sensor because it was in a junk yard and exposed and noticed that the female side of the plug (attached to cars harness) was not looking good. IT has the same rubber insulation as the Injector relay that gets brittle and causes loose contacts so I pushed the wires up and they right out of the plug so i knew it was bad. I connected each wire by itself to the sensor then slid the plastic part over it all and so far today I havent had the reving issue.

sorry its a long story but I figured the more detail the better. I tried a NEW ECU< MAF< AND IACV and it looks to have been just a plug. GOOD LUCK>

jreidko · Post by **jreidko** » 24 Oct 2010, 13:29

Thanks for the thought z31jaime.

I have actually tried pulling the connection to the IACV and it didn't cause the revving to stop. But i hadn't tried looking at the temp gauge or the temp sensor itself. Looking for this gremlin has been such a pain since it only happens periodically. I've been compiling a list of things to try next time it does it and based on what you mentioned maybe i'll try pulling the connection to the temp sensor and see if that changes anything.

Cheers, hope to report back before it's below zero here in Chicago. - jreidko

Post by **sariano** » 25 Oct 2010, 18:14

Do you have any problems with your car not starting after this happens? Our 850 revs high off and on then will not start if we shut it down, wait time is 20 minutes (somewhat annoying).

GoinFor300KMi · Post by **GoinFor300KMi** » 25 Oct 2010, 18:57

jreidko - it looks to me like your Throttle Position Sensor has failed. I missed reattaching mine while putting things together after doing a PCV job. The TPS on my N/A engine is difficult to see - its underneath the throttle body and I didn't notice the plug lying loose. Anyway, when I started the engine I had accelerating idle just like you describe. My '96 has OBDII, it gave me P0120 and P0123 codes so I knew instantly what the problem was. I think the 93 is different, no OBD, but you have some kind of error codes. A new TPS costs 50 to 100 bucks and is easy to replace but it would be nice if you can verify that's what the problem is.

jreidko · Post by **jreidko** » 26 Oct 2010, 08:37

Hey Sariano,

When my 850 does the revving it will start without a problem. You might check your main relay, it's mounted right above the radiator under the lip of the plastic cover that sits across the front of the engine compartment behind the hood latch.

I had a problem where my car would randomly die and then wouldn't start for 5/10/15 minutes and replacing the main relay and the fuel pump relay was what fixed it.

-jreidko

jreidko · Post by **jreidko** » 26 Oct 2010, 08:40

Hey GoinFor300KMi, i'm not getting any engine codes, but i will take a look and verify that the TPS sensor is hooked up properly. On the 93' 850 it's OBD-I where you can pull codes by watching a blinking red LED in the engine compartment.

Cheers - Jreidko

93 Volvo 850 engine revs high by itself

Re: 93 Volvo 850 engine revs high by itself