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Hello board,
Calif emissions test numbers:
15 mph(1732 rpm)
co2: 14.4,
02: .3
HC: Max 81, ave 37, meas 27
co: Max .52, ave.11, meas .02
no: max 791, ave 388, meas 1025
25mph(1821 rpm)
CO2: 14.5
02 : .2
HC: Max 63, ave 27, meas 23
CO: Max.43, ave.08, meas.02
No: Max 511, ave 306, meas 1049
Failed!
Car is 87 740 non turbo. Still starts and runs well.
250,000 miles
Original cat. O2 sensor about 90,000.
02 ranging between .2v and .6v, and responds to sudden vacuum leak,as well as blocked air passage.
Plugs and wires good.
No apparent vacuum leak(sprayed around with carb cleaner)(also vacuum guage
reads 20, with a very slight rapid movement of the needle.
I did note brown stuff leaking)(more like oozing) from end of radiator hoses. Temp guage registers normal. No oil in coolant, or oil filler cap. Thermostat and housing recently replaced.
I will appreciate any assistance.
Thanks
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Remembered I had an extra fuel rail gathering dust in the corner, so swapped out the fpr. Pressure now reading 43.5 with vacuum plugged and 36 otherwise.
The exhaust was leaking between the manifold/downpipe joint. I pulled the manifold and replaced all gaskets, and suceeded in moving the leak to the other side of the the same joint.
I dont know whats wrong with this joint, or what I did, that it leaks, even with a new gasket. The gasket I used was in a blue/white package with the volvo name on it. It is an all metal gasket. It was sitting on the shelf for a number of years. Price marked on it was $7.00. Was there a problem with this gasket? Or is something warped. What else could be wrong?
thanks
Larue
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Groovy. Thanks for posting the solution.
Hm... I hope you can find an easy, cheap solution to the leaking joint. Maybe a different order of assembly would help, though I don't think it really would. Any chance you're missing any exhaust hangers?
Cheers
Will
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Exhaust leak sealed. For now.
I used two gaskets. Put copper high temp gasket maker between the gaskets and a liberal bead on all sealing surfaces(an idea I got from this great board). So far its holding.
Sadly, it did not fix the high nox problem. That problem was solved by a new catalytic converter. 0 nox. The tech found no other problems, but tests indicated ineffective cat.
179.00 for diagnostic. 296.00 for the cat. And of course the california smog check and certificate(54.00). Throw in labor the total was 610.00.
I very seldom hand over cash to "have" this car repaired. How do you say "ripped off".
Turns out the cheapest route would've been to install the cat and retest.
What was that about bought sense?
thank you brickboard.
Larue
1987-740 non turbo. 250,000 miles. Original.
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"I pulled the manifold and replaced all gaskets, and suceeded in moving the leak to the other side of the the same joint."
That sounds like an aftermarket downpipe I got from FCP a few years ago. It was "high-centered" like a see-saw, rather than flat. I sent it back and paid for a good quality OE pipe, from Tasca I think. It was like museum quality art compared to a framed turd.
PS: That gap can suck air in between exhaust pulses, giving the (downstream) O2 sensor misleading info affecting the fuel mixture.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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thank you Lucid.
I wonder if theres a fix that doesnt involve buying another downpipe.
Im just trying to get by for now. I might retire the car before long.
I guess the pipe can distort after awhile. Especially if nuts are missing.
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A good exhaust shop should be able to flatten out the down pipe flange, i had to have it done to my 91, it the was original downpipe and i needed more time before i could order and replace it, they took it in the back and flattened it out and it sealed nicly after that, sadly it was so old the Y joint weld fell apart 6 months later.
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Ive got till the end of the month before my tags expire. Ive half a mind to retire the car, but, on the other hand I keep working to resolve this issue so I can roll the volvo a bit longer. It still runs good.
Also, I realize now that when I checked the fuel pressure, it was with the vacuum hose connected to the fpr. I changed the fuel filter today and rechecked with the hose disconnected and plugged. Its now showing 39 psi with the hose plugged and about 31 with the hose unplugged and connected to the fpr.
I hear a very strong hissing sound that I want to think is a vaccum leak, I just havent been able to pin it down. I hear it strongest at the intake right next to the hose thats attached to idle air valve. Ive sprayed cleaner in there with no uptick in rpms. So I cant be sure. I'll look again. I will also be following other suggestions made here, like looking into the vacuum hose that supplies ac doors.
The amm idea is also getting some thought.
Thank you brickboard.
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"Its now showing 39 psi with the hose plugged and about 31 with the hose unplugged and connected to the fpr."
31 should be 36 (with FPR hose connected and engine idling)
39 should be 43.5 (idling with FPR hose disconnected and plugged)
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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posted by
someone claiming to be Farm Boy
on
Fri Sep 14 23:02 CST 2012 [ RELATED]
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In addition to the good suggestions already made, I would add:
If NOx is a problem, run premium fuel when you go in for a smog check.
Make sure you are not pulling hot air from the exhaust manifold into your air box during the test. The thermostat controlled damper in the air box fails in the open position.
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I had a very elusive vacuum leak on my 87 740 and found it on the hose that feeds vacuum for the AC. That hose comes from the manifold between runners 2 and 3 and gets into a larger hose. If you pull up on the large hose it is a cover for a check valve and a T fitting that connects to the entry to the firewall. The hose coming from manifold to valve had somehow become larger and did not seal tight. Changed that hose and problem solved- It got so the AC flaps did not work.
Hope this helps you.
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I have a 1989 740GL that failed NOX three times. I changed O2 twice, cleaned EGR, cleaned catalytic convertor, changed intake and exhaust gaskets, changed plugs and wires, tested MAF and it tested fine. After doing all the above I switched the MAF WITH ONE FROM PICK AND PULL AND THE NOX CLEARED UP AND PASSED FINE. I chased many logical dead ends and spent unnecessary funds. I had a great muffler man that kept telling me that the catalytic was fine even tho the dealer kept telling me to replace the cat. The switching of the MAF[or MASS AIR METER] was a HAIL MARY attempt because it had tested fine but enough of the signs pointed that way so I tried the used MAF and it worked.
I hope this helps as I know the frustration of not passing the NOX when everything else passes.
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30 psi is low for fuel. You might look into that.
High NOx and super low CO and low HC sounds to me like maybe a vacuum leak.
NOx comes from high temperatures and/or lean mixture. High temperatures can be caused by piston top/combustion chamber deposits that increase the compression ratio, OR by lean mixture.
Your O2 sensor should range from 0.1 to 0.9.
0.9 is the rich end, and your car should hit it. That, plus the hissing, make me think you have a split/disconnected hose somewhere. Try pinching off vacuum hoses at the manifold to see if closing one of them eliminates your hissing.
The other thing I would do is run seafoam and distilled water through the engine. Look up the instructions (it's also called water torture), and don't dip the hose in the water for more than a split second. I've done it to 3 engines with no problems, but some people think it's possible to hyrdo lock an engine doing it.
If you get a lot of soot out when you re-start the car, it's an indication that you had cylinder deposits (but it could have come from elsewhere in your exhaust system).
You could also check the exhaust end for leaks, but I think your issue is on the intake side.
EGR was developed for turbo cars, but I thought there were NA cars that had it as well. If so, you can check to see if the valve is working by applying vacuum to the hose leading to the valve. You shouldn't be able to draw any air through the hose, but sucking on the hose should cause the idle to drop. I think 87 is too early got EGR, I know it's too early for OBD1.
Either way, good luck!
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Hello,
I am pretty sure your 1987 Volvo 740 non turbo does NOT use an EGR system.
And therefore the only device that controls NO(X) is the catalytic converter.
And since your CO and your HC emissions are within spec and actually below average, it is almost a slam dunk that your problem is a bad catalytic converter.
Was it really hot outside when you had the car tested?
We have found that on some cars without EGR and old catalytic converters, that it is best to have the car tested when it is cool outside and right after the car arrives at the smog shop.
If the car sits a long time with the engine idling before testing, the car will almost always fail.
Our theory is while the car sits idling, the intake air temperatures rises due to the low air flow over the engine and intake system from sitting while running.
1 of the smog stations I have visited had a tech that would put an ice cold rag on the intake manifold to try to cool the intake charge.
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
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I second Eric's suggestion. Your cat may not leak but it is 25 years old. If you plan to keep the car for any length of time you might consider replacing it.
If it were my car, however, I would first try what another poster suggested and run premium fuel in it before the test. Combine that with a bottle of pre-emissions test cleaner and that might do the trick. Also double-check for vacuum leaks.
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I'll 3rd Erics suggestions. I had a Dakota pickup that was always boarderline for NOX. It seemed to be worse when there was a long wait in line for the test. The technician would have me turn on the heater full blast to help cool down the head temperature. Also, on one or two occasions he would lock it OUT of overdrive so that during the 25 MPH test it wouldn't step into OD and cause the engine to labor quite so much - he said it was better to let the RPMs go higher and actually have a lighter throttle pressure. You might also try a cooler thermostadt to keep engine temp lower.
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High NOX is often due to vacuum leaks. For help in locating, see:
http://www.brickboard.com/FAQ/700-900/EngineFuelinjection.htm#VacuumLeakDiagnosis
--
See the 700/900 "FAQ" at the menu bar top screen left side.
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Thanks.
Ive been using an auto stethoscope. I did hear some hissing in center of intake near the idle air hose. But when I sprayed with carb cleaner , I got no response.
I will re check.
I also did fuel pressure test. It was 30 psi. Thats a little low. I dont know if its enough to cause high nox.
Thanks for the response.
La
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Iam fence setting on the cat issue. I dont know how much longer I will keep the car. Be great if I can get by for now without buying a cat.
I didnt mention that my timing is at 10 degree btdc. May be playing a small part.
I think I will address all the issues,ie set the time, address the fuel pressure, try to find and fix vacuum leak, if there is one, and change out the o2 sensor,fill her up with premium gas, and have it re-tested.
I wonder what the tech would do If I left the heater on high? Hmmmm? Outside temp was 97 on the test day. But temps are starting to fall. I also plan to arrive at test sight in the early am, early enough to let it cool a bit.
Thank you all!
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Look up Magnaflow cats, good quality, good price (even for Calif. versions).
A 25 year-old catalytic converter is burned up! Somehow it didn't clog up, just slowly disintegrated. I would be surprised to find any material remaining in it that is actually reducing emissions.
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"It was 30 psi. Thats a little low. I dont know if its enough to cause high nox."
I don't know either but 30psi is about 6psi below spec, possibly leaning the mixture enough to cause high NOX reading.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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