960 has rough idle when gettin warm/hot + more

[Hjaltih]

Hey there.

I'm having problems with my 960. It's a 1995 model with the M90 and the 3 litre engine (1992).
Engine has around 140.000 miles on it, rest around 235.000 miles.

Alright so this is where it's at:

Car starts fine cold, runs fine but as soon as I've driven 1-2 km it starts to have a rough idle (getting warm i guess) and seems/acts like it's having a misfire. Enough so that I can feel the car shake a bit when I'm sitting inside it.

If I turn the engine off and back on again it starts just fine, but if I turn it off, wait a couple of minutes and then try to start it.. it wont start unless I give it a bit of gas and then only after a few seconds (this problem seems to be no-more after I swapped IAC's with a friend of mine and back again).

The car also sometimes hesitates when giving it small/average amounts of gas, even when I have the pedal perfectly still.. it's like I'm tapping off it just a little bit for a second at a time.

Other than this it runs fine when driving, seems to have good power too.

The OBD gave us these codes (Note, we disconnected a couple of things before checking the codes, the OBD computer was giving us trouble before):
2 2 3 - 2 3 3 - 4 1 1 - 1 2 1

I cleared them and got 2 2 3 back, cleared that yesterday and haven't got it again.

What I've done so far:
Changed the sparkplugs.
Cleaned the throttle body.
Cleaned the IAC (also swapped it into a 850 a friend of mine has to check if it was working, also put his into mine and the idle was still the same)
Unplugged the IAC while at idle, no change in idle, which should point to a faulty IAC.. but the test above shows it's not!
Fixed a major air leak above the throttle body.

Disconnected each spark-plug/coil one by one and it always went worse so I think it's not a cylinder misfire that's causing this.

I hope that someone can give my some clues as to what the hell might be going on with the car.

[danr960]

It sounds like you still have an air leak.
The clue to me is the car starts fine when cold, and progresses to a stumbling idle when hot or no start condition.
When the engine is cold, the fuel mixture is very rich, which makes any extra unmeasured air able to burn without any notice, but once the engine warms up and the fuel mixture leans out, any extra unmeasured air cause mis firing.

Recheck air ducting after the MAF, also check the oil trap fittings and hoses.
Also, do you have the little hose that is connected to the IAC valve? That one is so basic, but have to ask. The brake booster hose? Does the brake pedal feel normal. Maybe you should get a hold of a vacuum gauge and measure vacuum.

DanR '94 964 385,000 miles (151,000 in the new engine)

[Hjaltih]

Just found out it was leaking round one of the cylinder-rubbers (where the intake manifold meets the engine), turns out the hose clamp wasn't sufficiently tightened.

Also found out that that gaping hole wasn't fully sealed shut the last time. I'm going to make sure it's fully sealed and buy a new one soon since this is just absurdly ripped. It's where the oil-trap sits (the trap itself is in good condition.

The short hose from the IAC is also in place I also took my time to clean the IAC really well with some carb cleaner, shaking the dirt out (and I thought I had cleaned it decently the last time.. guess not!).




I'll make sure everything is 100% airtight tomorrow and see how it runs.

Thanks for the reply!

[Hjaltih]

Well that hole is closed but it seems to be leaking around the intake-manifold gasket, at least the manifold is not airtight.

The engine is all shaking when cold too.

Edit: Confirmed leak at the intake-manifold gasket, I'll replace it tomorrow.
Thinking about having the injectors cleaned and tested, but that can wait. But when I took the injectors out I noticed one of the holes for them had more dirt than the others so might be a small air-leak there.
Edit2: I'll have to wait a couple of days, that gasket isn't available on this little block of ice right this moment!

[98T5]

I have the same issue but the car runs fine even with the "shudder" at idle and the A/C on blast. I narrowed mine to possibly gummy injectors, so what I'm currently doing is running a daily treatment of GUMOUT injector cleaner through the system. I plan to do this everytime I get gas, buy a bottle of GUMOUT. then, when I change my fuel filter in a couple weeks, keep the process going until I can afford to buy all new injectors. . Currently, the "shudder" at idle has gone down dramatically and my exceleration is a lot better eventhough I still need to do a valve adjustment.

These cars are old and I'm sure my injectors haven't been changed since it was bought in 1993 by the first owner. since it's a 4 banger i plan to buy all new ones but until then, I will be doing the GUMOUT treatment. It's working for me.

[Hjaltih]

Alright, changed the gasket but the car is still the same!

Seemed to be a little bit better in the beginning but when it started getting warm (about half way to normal) it started to go rough and shake.
Strange that very shortly after I started the car the Lambda light turned on and the car is now giving us the 1-1-3 code witch (among other things) points toward the injectors.

I think I'll just take them all out and have them cleaned.. although I'm not having any luck in finding a place that does that. Anybody have something else I should check out?

Thanks for the reply 98T5, does/did yours go worse when going warm?

[Hjaltih]

Alright, so the intake manifold is still leaking air.

We found out that the air is coming out of the exhaust (put a glove over it we could clearly see it).

Now, my father once had a problem with his old 200 car where a metal pipe leading from the intake-manifold to the exhaust manifold was leaking air, back then he just removed the pipe and closed both holes and thus fixed the problem.

Here is a picture of the pipe coming from the exhaust on my 960:


Has anybody heard of this problem before?

EDIT: Removed the pipe coming from the EGR valve to the exhaust, blew into the system and could clearly feel the air. So the EGR valve is most likely just stuck open, I think I'll just close it off for now, does the car need that system for any purpose other than to be nicer to the environment?

[Hjaltih]

Well, got a special tap for the EGR valve and another to close the pipe connecting to it. Intake-manifold is now 100% airtight!

The car idles quite a bit smoother, especially when warm (haven't taken it for a ride yet though).

It's not as smooth as I want it to be though, still shaking a bit. And the Lambda light came on a again with the 1-1-3 code. I'm going to clean some ground points better + change out the wires leading to the ignition coils tomorrow and see what good it does.

Also, does anybody know if the IAC is supposed to give away a buzzing sound + vibrate a bit when the car is switched to the ON position (not starting it)?

[Hjaltih]

Alright, the idle has finally been fixed.

I believe it was a combination of a couple of things.

1. The damn EGR valve that was stuck open. I simply closed it up (was adviced to still keep it plugged in electrically though). I will eventually try to clean it but not right now.
2. The wiring to the coil wires.
3. One of the Ignition Modules.

The wires leading to the Coil Wires were really bad so I changed them out for this: http://www.davebarton.com/volvoharnesses-960.html

This is really easy to exchange, all the wires have the correct color so you just match them up.

After changing them out and closing the EGR valve the car was a lot better better but still sometimes a little odd. We found out it wasn't always running on cyl 4 and we traced the problem to one of the Ignition modules, changed that out and now it's running really smooth:

[Piet22]

Well done!

Piet