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1992 Volvo 940 Running RICH

Smokey77

Smokey77

Member
Joined
Jun 9, 2024
Location
Goodyear Arizona
So, I did an emissions test to register the car. Lets say that CO was 5.8X requirement!! AZ Phoenix btw. And HC was about 3.8X. NOX was good. So, obviously running rich with a possible cat failure too. Pulled the plugs, cyl 1 barely smelled like fuel, (I couldn't smell it but my co worker did) . 2,3 and 4 wreaked of unburnt fuel. Fuel regulator seems fine (didn't leak when engine off and small fuel line pulled off) new plugs. I haven't touched the 02 sensor yet, and MAF or whatever you want to call it (I don't entirely know the differences yet) looked clean. No idea if they actually work. And don't know if the injectors are leaking or if they are not pulsing correctly. Engine temp is OK and blows hot when I turn on the heat.

So, here are the symptoms. Lack of power (especially when cold) and revs up and down when idle and cold (I live in Arizona now so it is kind of hot all the time lol!) . Warm it isn't noticeable. When I lightly tap and release the throttle, it bogs and wants to stall after throttle is released. Doesn't matter what RPM I rev it to, same thing. Inconsistent misfire even on new plugs when cruising at 30mph plus. And what I find most odd, is a long whistle sound when I turn the engine off. A few seconds and a consistent whistle and then fades out after a moment. No idea if it is related? I tested some of the vacuum lines with flammable brake clean and nothing.

I haven't tried the OBD1 diag yet, I just genuinely don't have the code list or anything. And no check engine light. So everything so far is based off of process of elimination. If anyone can direct me to that, that would be awesome. Really with this I am trying to get opinions of what to do. And hopefully someone else like me who doesn't have much diagnosis experience. Or maybe even less. Will know what to do, if there even is someone else like that on here haha.

I would attach videos but by the looks of it I can't.
 

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Possibly a bad intake gasket? Also could be the vacuum line to your climate control. Pretty sure that pressurizes or vacuums when it is running. Could be losing the vacuum through the one way valve?
 
Smokey77 said:
I haven't tried the OBD1 diag yet, I just genuinely don't have the code list or anything.
Click to expand...
I didn't have it at first either. But then I Googled it.
I suggest taking the measurement of the manifold vacuum at idle, tracking down and eliminating the whistle sound (likely a vacuum leak), measuring the temp sensor and O2 sensor outputs. Or just take it to the shop and have them fix the problem.
Spark plugs don't look too bad.
 
PCH said:
I didn't have it at first either. But then I Googled it.
I suggest taking the measurement of the manifold vacuum at idle, tracking down and eliminating the whistle sound (likely a vacuum leak), measuring the temp sensor and O2 sensor outputs. Or just take it to the shop and have them fix the problem.
Spark plugs don't look too bad.
Click to expand...
Not exactly sure how to check the manifold vacuum, but I will look into that. And for measuring the outputs of those sensors, I am checking for current?

Also, I work at the shop, my issue is that one master technician who knows most about these sort of problems almost refuses to do it and comes up with excuses not to do it. Partly because the boss wants to have it diagnosed for free so that I am not paying for it and I can replace the parts on my own, which means this guy doesn't get paid for it. And I don't feel like dumping a lot of money on some other shop when I have the capability to do it at my own shop.
 
You can get a vacuum gauge for under $20. It may even come with the instructions.

s-l960.webp
 
Smokey77 said:
Not exactly sure how to check the manifold vacuum, but I will look into that. And for measuring the outputs of those sensors, I am checking for current?

Also, I work at the shop, my issue is that one master technician who knows most about these sort of problems almost refuses to do it and comes up with excuses not to do it. Partly because the boss wants to have it diagnosed for free so that I am not paying for it and I can replace the parts on my own, which means this guy doesn't get paid for it. And I don't feel like dumping a lot of money on some other shop when I have the capability to do it at my own shop.
Click to expand...
see link above.

change all rubber vacuum lines with NEW silicone hoses. EVERY SINGLE ONE OF THEM.order from Amazon

the smaller hard plastic lines last forever.
change all pcv hoses and clean, put in a new flame trap.
clean amm intake hose with soap and water to remove all oil and dirt.
clean amm gently. reinstall and make sure no leaks. if there are leaks either use a new clamp and or smear a little bit of RTV sensor safe on all the junctions to create a good seal. hairspray works well on the smaller hoses to create a seal.
blow into the check valve to make sure it works.
replace the brake booster hose and
once you have done this add a vacumm gauge.
if your vacuum is still low get soap bottle and starter fluid. spray all intake and exhaust gaskets. if you see bubbles with soap, you found a leak.
if you spray starter fluid and car suddenly revs up, you found a leak.


It's pretty easy to do all this but takes forever. expect to put in like 20-30 plus hours to do it right.
.
 
240 240 said:
see link above.

change all rubber vacuum lines with NEW silicone hoses. EVERY SINGLE ONE OF THEM.order from Amazon

the smaller hard plastic lines last forever.
change all pcv hoses and clean, put in a new flame trap.
clean amm intake hose with soap and water to remove all oil and dirt.
clean amm gently. reinstall and make sure no leaks. if there are leaks either use a new clamp and or smear a little bit of RTV sensor safe on all the junctions to create a good seal. hairspray works well on the smaller hoses to create a seal.
blow into the check valve to make sure it works.
replace the brake booster hose and
once you have done this add a vacumm gauge.
if your vacuum is still low get soap bottle and starter fluid. spray all intake and exhaust gaskets. if you see bubbles with soap, you found a leak.
if you spray starter fluid and car suddenly revs up, you found a leak.


It's pretty easy to do all this but takes forever. expect to put in like 20-30 plus hours to do it right.
.
Click to expand...
Awesome, thanks! Some of the work is already done, specifically with the flame trap. I will find the vacuum hoses.
 
Smokey77 said:
I haven't tried the OBD1 diag yet, I just genuinely don't have the code list or anything. And no check engine light. So everything so far is based off of process of elimination.
Click to expand...
So! I tested the built in OBD. Here are the codes I am getting. 221 and 232. Which my guess now, since it is obviously running rich, is that a sensor is sending an incorrect reading, telling it that it is running lean, and then over fuelling to compensate.
 
The most common issue would be boost leaks. Put a smoke machine on it and see what is leaking.

I finally found a big air leak in my 740 in the brake booster hose at the intake manifold.

I would start by pulling the hose from the airbox to turbo and inspecting it. Also inspect the hoses where they connect at the intercooler. I would remove them and inspect the bottom. I would also inspect the Idle valve hoses. They commonly tear.
 
ZVOLV said:
The most common issue would be boost leaks. Put a smoke machine on it and see what is leaking.

I finally found a big air leak in my 740 in the brake booster hose at the intake manifold.

I would start by pulling the hose from the airbox to turbo and inspecting it. Also inspect the hoses where they connect at the intercooler. I would remove them and inspect the bottom. I would also inspect the Idle valve hoses. They commonly tear.
Click to expand...
This is a non turbo. But yes, I was going to put a smoke machine on it today. And I will also look into the TPS. I also found an obd code list specifically for Regina cars and both of the codes I got point right to the 02 sensor
 
Note - the Regina O2 sensor is special (titania) and pricey (~$170). Before firing the parts cannon, I'd inspect the wiring and the sensor. If you disconnect the O2 sensor temporarily, does the engine run better (less rich) and do you a get different diag code(s)?

What were your exact emissions values? Was the high CO/HC at multiple RPMs?
 
Smokey77 said:
Fuel regulator seems fine (didn't leak when engine off and small fuel line pulled off)
Click to expand...
They tend to not leak when they're not pressurized (running).
You're pulling the vacuum line off the front, right?

Smokey77 said:
and MAF or whatever you want to call it (I don't entirely know the differences yet) looked clean.
Click to expand...

With Regina, you don't get a MAF.

You get an intake air temperature sensor, plugged into the big pipe between the air filter and the throttle body.
If it thinks the air is cold, it tells the ECU to add more fuel.

You also get a MAP (Manifold Absolute Pressure) sensor, a box attached the the left rear diagonal strut tower brace. It tells the ECU how hard you're stomping the gas by measuring intake vacuum. High vacuum signal = idling or cruise. Low vacuum signal = foot to the floor (or a leaking/unplugged vacuum line to the manifold) so more fuel.

air-and-map.jpg
 
I doubt you are running rich. If you are misfiring for some reason all that raw fuel is going into the exhaust.

You could have a fouled plug, failed cap/rotor/wire. And if you drive with misfires you kill the cat
 
ZVOLV said:
I doubt you are running rich. If you are misfiring for some reason all that raw fuel is going into the exhaust.

You could have a fouled plug, failed cap/rotor/wire. And if you drive with misfires you kill the cat
Click to expand...
Plugs and the fuel smell with the bogging and codes saying that the 02 sensor has failed sugguest it is running rich. Ignition system was re done not long ago. (I found a code list specific to Regina cars and it is different than LH.)

Edit: the cat is totally fine considering the NOX levels
 
Smokey77 said:
So, I did an emissions test to register the car. Lets say that CO was 5.8X requirement!! AZ Phoenix btw. And HC was about 3.8X. NOX was good. So, obviously running rich with a possible cat failure too. Pulled the plugs, cyl 1 barely smelled like fuel, (I couldn't smell it but my co worker did) . 2,3 and 4 wreaked of unburnt fuel. Fuel regulator seems fine (didn't leak when engine off and small fuel line pulled off) new plugs. I haven't touched the 02 sensor yet, and MAF or whatever you want to call it (I don't entirely know the differences yet) looked clean. No idea if they actually work. And don't know if the injectors are leaking or if they are not pulsing correctly. Engine temp is OK and blows hot when I turn on the heat.

So, here are the symptoms. Lack of power (especially when cold) and revs up and down when idle and cold (I live in Arizona now so it is kind of hot all the time lol!) . Warm it isn't noticeable. When I lightly tap and release the throttle, it bogs and wants to stall after throttle is released. Doesn't matter what RPM I rev it to, same thing. Inconsistent misfire even on new plugs when cruising at 30mph plus. And what I find most odd, is a long whistle sound when I turn the engine off. A few seconds and a consistent whistle and then fades out after a moment. No idea if it is related? I tested some of the vacuum lines with flammable brake clean and nothing.

I haven't tried the OBD1 diag yet, I just genuinely don't have the code list or anything. And no check engine light. So everything so far is based off of process of elimination. If anyone can direct me to that, that would be awesome. Really with this I am trying to get opinions of what to do. And hopefully someone else like me who doesn't have much diagnosis experience. Or maybe even less. Will know what to do, if there even is someone else like that on here haha.

I would attach videos but by the looks of it I can't.
Click to expand...
Update on this, tested for vacuum leaks on the intake manifold, had to block off the pcv in order to prevent leaking from dipstick tube. Found no vacuum leaks. Other than a minor bit at the temperature sensor which was to be expected and not that important, and a slight bit at the plastic intake tube near the throttle body, a bit more important.
 
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