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Hi everybody!
For the past few months I have had a rough or low, sporadic idle on my 1990 740GL with regina. It sounds like there is a slight miss at idle when standing next to the exhaust pipe. It has a hard pulsing sound to it. The car runs great at speed and still gets 26 mpg. No abnormal smoke out of the tailpipe. Occasionally when you are on the interstate and go to accelerate a slight bit more, the car will hesitate 3 or three times very quickly. Other than that it runs great at speed.
At idle, sometimes it starts fine and idles initially at 1000rpms before settling down to around 800 rpms. Other times it will die as soon as you start it until you give it some gas to keep it running. It will run very rough for a few seconds before smoothing out, but still only idles around 500 rpms. While it is running at 500 rpms, it will still sound like it is missing if you stand by the exhaust pipe. Other days, it will idle around 1000rpms, but still sounds like it is missing.
I have replaced: IAC valve, ECT sensor, MAP sensor, Intake air temp sensor, O2 sensor(NTK # 25002), spark plugs, timing belt.
I recently took it through emissions and the Hydrocarbons reading was 900 (limit is 220) with a CO reading of 0.5(limit is 1.2). This would indicate that it is running lean, correct?
I've pulled a couple of spark plugs and they are grayish white on the electrode area with black carbon marks on the base of the metal threaded area. This points to a lean condition too.
My question is: Can a slowly failing fuel pump cause this condition? Maybe its running at about 40 psi instead of 43.5psi, which would cause these erratic symptoms?
I have pulled the vaccuum line off of the FPR, and there is no fuel leakage.
The car has no fault codes other than the normal 3-2-1 for the cold start valve fix.
Thank You,
Ben
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Sounds like a leak of some sort to me also. I would consider the temperature sender for the ecu, but I think you replaced that. Also, have you properly set the throttle?
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Thanks for the suggestions guys!
Earlier I said that I replaced: IAC valve, ECT sensor, MAP sensor, Intake air temp sensor, O2 sensor(NTK # 25002), spark plugs, timing belt.
I forgot to say that I have also replaced the flame trap, nipple, and hose going from the intake baffles. I have cleaned my throttle body, made sure my linkage was properly adjusted so I could hear the click as you just start to turn the throttle wheel, replaced the throttle body gasket, and checked the intake hose for leaks between the baffles.
I have also done the carb cleaner and propane test to see if the idle would change at all around potential leaking areas. When sprayed around the intake manifold gasket area nothing changed. Could the intake manifold gasket still be letting air in somehow?
I even rigged up an air pump that was sealed off blowing air into the intake baffle tube to listen for leaks. The only place I could feel/hear air leaking out was the oil dipstick tube.
One other thing I have noticed is that I can sometimes smell emissions or exhaust smell while driving in the city with the blower motor on, and occasionally when going 75mph or so on the interstate. I know it is my exhaust because usually all the other cars around me are much newer, and you grow accustomed to your vehicle's particular exhaust smell. I don't know if that helps or not.
I just drove the car 180 miles today, and it did great on the interstate with no loss of power or anything like that. So I would assume it's getting adequate fuel pressure. It really just occurs when the car is running under 2000rpms.
Oh, I also wanted to add that I can hear a whistling sound while driving around 45mph. It sounds like a jet airplane engine winding down after they cut it off as I slow to a stop.
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mmm... throwing this out... maybe a leak in exhaust down pipe (rusted)? The whistling sound is some clue, like air movement. A leak here could affect the O2 sensor (but I think it would be rich not lean?), and the exhaust would pull up into heater unit , into interior, at lower speeds.
Or maybe downpipe connection is loose, exhaust manifold loose too?
Is there a turbo?
On my car I tried the intake leak test too without indicators. However, I am going to replace it as I found some loose manifold nuts, I'm going to replace gasket to make sure. They are $5 plus shipping.
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I own a Volvo or Does Volvo Own Me? Try the easy to search Expanded Style FAQ Index http://40mph.com/Brickboard_700-900_FAQ_Expanded_Index_Version/
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My car does not have a turbo.
Is there any good way to check for an exhaust leak other than feeling around it or smelling? My exhaust manifold feels solid & all bolts are tight. Down pipe isn't too rusty, since the car has been in Tennessee it's whole life.
I think my transmission is slightly overfilled with fluid. Could that be causing the whistle too? I changed the fluid and filter about 6,000 miles ago.
I can't smell the exhaust fumes all the time. I can only smell them maybe once a day while driving.
I think I'll change my exhaust manifold gasket this weekend. Can I get one of the brands at autozone, or should I go with a volvo, fcp, or ipd gasket?
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The exh side has 4 small gaskets. Maybe you mean the intake side?
Trans; if you check the dipstick when the trans is hot, you can tell if it's full or overfull, no thinking required. No, it won't make a whistle if it's overfull.
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Elring or OE seems to be preferred brand. Autozone has Fel-pro, less favored, see what a search turns up.
Trim off extra holes, if necessary, gasket one size fits many Volvos
--
I own a Volvo or Does Volvo Own Me? Try the easy to search Expanded Style FAQ Index http://40mph.com/Brickboard_700-900_FAQ_Expanded_Index_Version/
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I've seen some mechs hookup a shop vac to the exhaust on "blow". Then move forward towards the engine and listen for hissing.
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Post Back. That's whats makes this forum work.
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I'd replace the intake mani gasket, just as a matter of course.
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That hesitation sounds, to me, like a symptom of intake leaks somewhere.
Symptoms of intake leaks include:
rough idle
high idle (not necessarily over 800)
off-mixture (too rich usually - which can cause high HC)
Maybe there could be a leaky exhaust gasket contributing to the problem?
I don't think a failing fuel pump is responsible. There's a little variance in the FPRs and 3psi doesn't seem noteworthy. 10psi definitely is. In fact, I think the turbo cars had 3-5psi higher ratings than NA cars.
HC basically means unburned fuel. Check over your ignition system (cap, rotor, plugs (condition and gap), wires). I would also run some injector cleaner.
I think CO is a result of a rich mixture too. More O2 going in would give you more CO2 and less CO.
Hmmm, way out in left field maybe a leaking fuel or cold start injector could be at issue.
Good Luck!
PS If you're in CA, you can get one-time assistance of up to $500 towards a shop diagnosis and repair. I used mine to buy a $400 sensor from a dealer because I couldn't find one from a 92 in any yards.
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