[xylopagus]

I recently changed out the air box on my 93 240 with 176k miles. The box probably didn't need to be replaced but it was melted on one side from an old leaky battery. I also topped off the coolant.

There's a possibility that I overfilled the coolant resevoir because it isn't level and I couldn't really see where the fluid level was.

The problem: At idle, especially when braking, the rpm "bounces" around 1000, sometimes hitting around 500 and even sometimes stalling.

Any ideas?

--Also, I am in the Houston Texas area for the summer and don't have access to many tools or a place to work on the car *(except for the parking garage...). Are there any reputable Volvo repair places that you guys would recommend (if the situation called for it)?

Thanks, Nick

 

[gdill2]

Re: RPM Dipping at Idle (xylopagus)

Sounds like a leaking and/or faulty vacuum valve on the brake booster.

This little white gizmo may look just fine but give it a little wiggle and it may break off and fall in your hand - brittle from too many Texas summers (just like me).

Other areas to look at would be the mass air meter, throttle body and idle motor.

Remove the flexible hose between the mass air meter and throttle body then bend it around like playing an accordion looking for tiny holes and cracks.

With the car idling unplug the mass air meter - no change in idle may mean a faulty meter.

When you replaced the fresh air box did you check the hot air thermo and flap?
Have you cleaned the throttle body lately. Fuel filters new? Clean fuel injectors?

Parts...

http://www.ipdusa.com/Volvo-200/c-1-69/

George Dill

 

[xylopagus]

Re: RPM Dipping at Idle (gdill2)

I am going to check the brake booster tomorrow morning as well as look at the AMM and the accordion-style hose. The hot air thermo/flap was tested (I dipped it in hot and cold water to insure that the flap was moving to "full cold" and "full warm").

The throttle body is clean, but I am unsure about the fuel filters.

Thanks George, I'll keep you updated

--Nick Hindes

 

[xylopagus]

UPDATE: I am becoming more convinced that at least part of this problem has something to do with the brake booster. I can get the idle to turn rough by repeatedly hitting the brakes after the car has been on for a bit and.. when I start the car the brake pedal doesn't move down at all.

I just took a good solid look at the air ducting around the AMM. Everything seemed all well and good. There's one vacuum hose that likes being "loose enough to rotate" that attaches near the throttle body. I also noticed that with the hood up, I notice what sounds like air being released from a valve directly after turning off the car *(for a couple of seconds afterward, actually).

I already bought the brake booster vacuum check valve from IPD. Will update when I install.

Thanks, Nick

 

[gdill2]

Re: (xylopagus)

Some good reading while you wait...

http://autoforum.classifieds1000.com/Volvo-240

http://autoforum.classifieds10...oblem

When installing the brake booster vacuum valve check ALL vacuum lines, junctions and valves both under the hood and under the dash. Note that a vacuum line goes from the engine then through the firewall into the car's interior. This vacuum source controls various under-dash functions and must be in good condition to operate properly including the inline one-way vacuum valve.

Your description of the brake pedal's behavior implies a possible internal problem with the booster.

If you plan to keep this car long-term (YES!) then hit-n-miss repair efforts may not be the route to take toward a smooth-running engine.

Mentioned in the links I posted above (in this reply) was idle problems caused by AC components being faulty (sometimes intermittently). Yet another area to look over.

Your car is approaching age 16 and has spent some years in the changing seasons associated with north central Texas - 20F below and (today's?) 102F+. This weather can deteriorate rubber, wiring, electrical components, etc.

With this in mind make a thorough inspection of the engine wiring harness especially near both manifolds, at the curves near the engine block and at the junction near the firewall. Just because an electrical connection/junction "looks OK" does not assure good and continuous conductivity.

It is understandable that one may become frustrated with ANY poorly-running automobile but something tells me that once your 240 is up-n-runnning perfectly again you will be a happy camper.

George Dill

Modified by gdill2 at 12:02 PM 6-28-2009

 

[JBLasVegas]

Re: RPM Dipping at Idle (xylopagus)

I''m ignorant as far as non-turbo Volvos are concerned, but when my harness was deteriorating at the engine side of the firewall, I had exactly the same problem until I made a few splices. One of the wires goes to the idle solenoid. I would say that there is a good possibility that your fix is simple if you were to un-snap the grey connector and make sure that the contacts are good.
That plug / contact system that Volvo used is not infallible, and once a bit of corrosion sets in, the idle solenoid falls into the engine-off mode. I would also check the other big, grey connector that is closer to the driver's side, where the wires to the constant-idle solenoid run directly to the solenoid. Unsnapping those connectors from the firewall is the hardest part... and then getting them snapped back in. It's a bitch! But, once you get the contacts cleaned up with some contact cleaner, your problem might be solved. Just be sure to be very careful while handling those connectors because the wires going in to and out of them on the male and female side get pretty funky after 20 plus years. If you disturb them too much, then you're in for a heap of trouble.
I can remember that when my wiring loom was first going bad, my idle would drop down to about 500, until I started to do some digging while the engine was running. I'd touch the loom on the firewall, and Presto!!! The idle would come back up to about 850.
Good Luck!!!

As far as "reputable" Volvo repair places are concerned... If one of those places has an "Old Guy" there (like me), then they might know what to do. Otherwise, they will use the Shotgun approach, and then still may never get it right.
Try what I told you first... wiggle all of those wires coming from the ECU through the firewall, and tap both of those grey connectors while the engine is running and see if it makes a difference, even momentarily. If it does make a difference, then you know where the problem is.

Even though my old Volvo is extremely low mileage for its age, there are certain things that deteriorate that are not mileage-dependent.

 

[gdill2]

Re: RPM Dipping at Idle (JBLasVegas)

On any 240 with electrical fuel injectors test the conductivity to the injectors by pressing on the side(s) of each connection while the engine is idling.

If any change in idle suspect a poor electrical connection.

George Dill

 

[xylopagus]

Re: RPM Dipping at Idle (gdill2)

I just replaced the Brake Booster Vacuum check valve with no change. I also still don't think that the booster holds a vacuum when the car is off due to no movement of the brake pedal when I start the car.

Usually what will happen is during a hot start, the RPM may dip down to 500 and die, OR it will bounce around for a bit and settle around 850. I'm going to get together with a co-worker in a couple of weeks and start some troubleshooting.

I'll post updates as they happen and I'll be sure to look at the various electrical connections that were mentioned in earlier posts.

--Nick

 

[gdill2]

Re: RPM Dipping at Idle (xylopagus)

Refresh my memory - have you dumped the OBD codes lately?

George Dill

 

[xylopagus]

Re: RPM Dipping at Idle (gdill2)

I just dumped them *(haven't done it in a while). I got 2 codes: 2 - 3 - 2 and 1 - 2 - 1. The 2 - 3 - 2 code has been there for quite some time and has been accompanied by my hot start issues.

The latter is interesting. No check engine light like my Bentley manual claims. I had the AMM replaced a few years back, maybe there's something up with the harness or it's gone bad again? I still have the old AMM up in DFW and I happen to be going home for the 4th of July weekend, so I'll pick it up when I get there.

--Nick

 

[xylopagus]

Re: RPM Dipping at Idle (xylopagus)

I erased the stored codes after checking them. The 1 - 2 - 1 error could have been from when I was "testing" the AMM by unplugging it while the car was idling. I'll check again tomorrow night after the car has been driven some more to see if it regains the code.