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Discussion Starter · #1 ·
1993 940 wagon non-turbo - 272K miles

This is a clean and well-running vehicle bought from the original owner who servived it every 5K.
I've got all the warning lights and codes to clear by having the fuel injectors cleaned, replaced all the vacuum tubing under the hood.
It's passed smog with flying colors the last two times.

Yesterday everything tested O.K. but failed NOX and the Evap test. Evap I attribute to it failing the gas cap test and a loose evap canister hose as pointed out by the technician...I won't worry about that right now. I checked the filler neck rubber and it doesn't feel dry or cracked. I did buy a new gas cap as well.

The NOX I've been reading points to the EGR valve (per technician) or possibly the catalytic converter, or...?

I pulled the EGR tube that goes to the manifold back and ran a wire down it and flushed it with Sea Foam Deep Creep.
Manifold hole had some carbon, but not blocked. I also Deep Creeped the manifold at all the orifices I could find and through the throttle body. I'm running a bottle of Redline fuel treatment through it as well. This was recommended by two mechanics I spoke to.

What else should I look for? I'm wondering if I should pay to retest or take it in to smog repair shop first.

NOX readings: 15mph 674 ( 486 max) 25mph 790 (502 max).
 

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BTW, two people have said the cat converter..
Having 273K on it, I'd suspect that could be the case and I'll check it out.

There doesn't sound like any exhaust noises are present. Since it's a Southern California car there is no rust at all. Reason I bought the car is becasue the engine look like it came off the showroom floor!

As far as the intake manifold, it looks fresh as a daisy, the gasket looks brand new so I doubt any leakage there either.
I replaced all the vacuum hoses when I had the injectors sent out to be rebuilt as well.

I checked the EGR by applying a vacuum pump at the rubber tube going to the EGR at idle. The idle would stumble under pressure. When the pressure was released it would stabilize. I assume this means the EGR is working.
Not real clear on this I admit as the vacuum pump gauge, noot being entirely accurate, read between 5-10 lbs if I recall. I've read something about the EGR and too muc/not enough pressure, but didn't really understand it. So I'm unclear there.
To be truthful, I'd rather not tackle removing the EGR if possible.

As a note, the only noticeable ****le in the way the motor runs is when at a stop sign the car is in Drive foot on the brake, it doesn't idle cleanly, almost feels like it wants to die at times, especially in hot weather with the A/C on.
Before I did the injectors/vacuum hoses we had the 'Check Engine' light on constantly and it would die at stop signs. I found one bad thing was a melted wire on the speed sensor going to the tranny. That I replaced.
It had bad codes as well.
Now that's all cleared up, no bad codes at all, no lights on either.
 
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