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Hi all,
New to the board and looking for some advice. I’ve got a new-to-me 1994 940 Turbo that I can’t get over the hump with smog check. Here are my numbers:
HC 15mph Max 59 Ave 25 Meas 55 PASS
25mph Max 34 Ave 14 Meas 41 FAIL
CO 15mph Max 0.34 Ave 0.06 Meas 0.07 PASS
25mph Max 0.32 Ave 0.05 Meas 0.05 PASS
NO 15mph Max 692 Ave 263 Meas 542 PASS
25mph Max 711 Ave 221 Meas 426 PASS
This is the second time its failed on the 25mph HC level. So far I’ve put in new plugs, plug wires, distributor cap and rotor, ignition coil, and air filter, and changed the oil and replaced the PCV box. The car drives well except for a surging/hunting idle. I checked the codes after the first fail and got a 2-3-2/Lambda Adjustment/Too rich or lean at idle. After getting the code I tested the O2 sensor and that was fine. Fuel pressure regulator checked out OK too. I pulled the MAF while the car was running and the idle smoothed out and went up a 100 rpm or so, but I don’t know what to make of that. I’ve encountered conflicting information as to what happens when the MAF signal is non-present.
After I cleared the MAF codes I cleaned the MAF with sensor cleaner. Then I checked for vacuum leaks with a propane torch and couldn’t find anything. Took the car to get tested again and failed a second time, with the above results. Today I cleaned the throttle body, it wasn’t dirty but I did the job for due diligence.
Nothing so far has fixed the idle problem, and I have a suspicion that it is tied to my problem passing smog. I’m reluctant to throw down cash for a new MAF if I’m not certain its at fault. I had no MAF codes prior to disconnecting it. Tomorrow I’m going to put some Techron in the gas at fillup and try the italian tuneup.
I’m getting frustrated, any thoughts?
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around the throttle body are 2 o rings that dry out over time on the shaft.
All the vacuum tubing should be new & tight,,
I have a 93 non turbo & I think the next thing Ill replace is the carbon canister & the lines back to the tank. another thing to try is spraaying starter fluid at any connection while running to see if the idle changes?
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Thanks for the input folks. Here’s an update on the situation.
I cleaned the idle air control valve yesterday, and replaced a small piece of vacuum tubing at the turbo. The car now idles at about 300 rpm higher, somewhat smoother. Unfortunately I didn’t start the car in between tasks so I can’t say for sure which had effect. Bad methodology.
Later today I while driving the car I had a brief no-start condition, which went away after I blipped the throttle. I took the IAC off again when I got home and cleaned it some more, checked the resistance and tested it with a 9v battery. No noticeable changes after that.
I noticed that at about 1/4 open throttle in neutral the engine still surges, and I think my next task is to do a super thorough search for vacuum leaks that I may have missed. Some research also suggested that my high HC may be due to a lean misfire, since my CO levels are fine.
Alternator checks out ok. No ignition codes, no new fuel system codes yet (I cleared the 2-3-2 after recording it).
Feel free to keep the input coming, I appreciate all the help.
Edit: Also going to readjust the idle and check the TPS. And yes, I’m in California.
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Welcome to the board!
Hunting idle in my 940 ownership usually happens after sudden braking or stopping at red light. A brief tap on accelerator pedal makes it go away. So I'd check the TPS adjustment and brake booster. How many mileage is the car? Although you have checked the O2 sensor to be ok high mileage cars may have slow to respond sensor. Bosch recommends new sensor every 100k km or about 60k miles, although practically you may stretch it to 150k km or about 100k miles before change. Its not enough just to ensure the sensor voltages do swing from 0v to 1v. Its the swiftness of the sensor to respond to any O2 change in exhaust gas (fast voltage swing) that keep the air/fuel mixture in check to ensure low HC emission.
Amarin.
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There is also this Volvo 700-900 Series FAQ, and so, hunting idle and emissions info is here and hinted at in other FAQ pages. Hunting idle may be caused by the idle control motor becoming stuck with PCV vapor condensation inside it or age, yet other causes as listed here.
https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm
As you say 'smog' test, I'll imagine you are in Cally-Forn-I-Ayyy?
High HC is a rich running condition.
If exhaust composition leaving the engine before catalytic converter input is proper, like 1.0% CO upstream of the cat when measured by a exhaust gas analyzer. Yet you state you encountered OBD socket 2 (LH 2.4 fuel, emissions) 2-3-2, so rich or lean at idle to a point engine control can no longer compensate and sets the fault code. You do know to repeat the code check until no new codes display unless you receive the 1-1-1 okee dokee red light flash? And no fault codes in socket 2, EZK116 ignition?
How did you check the oxygen sensor? Digital Multimeter (DMM) +VDC lead at the oxygen sensor at the boot and the -VDC. DMM fluctuates wildly between 0.1 and 0.9 volts DC?
Use a better DMM than this red harbor freight thing I used:
https://www.brickboard.com/RWD/volvo/1628410/220/240/260/280/oxygen_sensor_code.html
We'd all like a Fluke DMM. I'd like to work at Fluke in Everett in mighty and lovely and powerful WA-state. Cherries are in season!
Ground connection between alternator and engine block are good. Alternator power output is 14.5 or so cold and 13.8 warmed up? Poor ground / power connection and power output can lead to a rich running condition and weak spark.
You tested the spark with fuel delivery disabled on full battery charge (a good battery is in there within the duty cycle). The spark a brilliant bright blue in a darkened garage?
How old is the fuel pressure regulator? These fail in several ways-
- Stuck at fuel pressure on high as encountering a low vacuum like you are flooring it.
- Not responsive or slow to respond to low vacuum or boost as when you floor it.
- Fuel passes through the diaphragm and through the connected vacuum line in any failure state. Though you'd smell gasoline vapors a bit.
HAve you encountered an AMM / MAF fault code? A missing AMM / MAF connection or fault sets a CHECK ENGINE light and is in a fuel rich limp home mode. You'd fails emissions with a rich exhaust through idle on on run.
Engine Coolant Sensor tests out okay? These can fail also. Two sensors in one: 1 for the fuel injection and the other for ignition to change dwell (spark duration). The ECT can show a failure mode at test yet engine control won't set a fault code as it is programmatically 'forgiving' or too tolerant.
Yes, try CBs suggestion. I'm unsure whether LH-Het 2.4 enrichens fuel / air mix on boost as greatly as on prior engine control versions in the 1980 models. Turbo is harder on the cat.
Hope that helps.
--
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You had it 1st off. You unplugged the air mass meter and it ran better! They can’t code except for open ot short if it’s telling the ecm 40gm. Per Sec but it is lies and 50 gems are really going through both are plausible numbers it won’t code. Better example would be the engine coolant temp sensor. Open or short it will code but if it parameters are to measure from -55 degrees to 150 degrees, and the computer gets a number in that range , it see it as normal it may be actually be 35 degrees, but a faulty sensor is say it is 170 degrees computer believes it but the calculations will make for a hard start and bad running ( if at all) engine. By pulling the connector for the MAF the computer defaulted to a number in the middle. The car no longer is using sensor dated but a preprogrammed data set that allows it to run, but an able to adapt in real-time. But in your case the car liked the so-so fixed data then it did being given bad information. Get a different Air mass meter.
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Hi,
CB and you seem to have a very good plan there.
It’s simpler than pulling all the injectors to test spray patterns, to each other for a reference point and the fuel quantities have variables dealing with a hard or no start issue.
The engine is doing really well IMO.
A poor injector spray pattern on just one injector might cause the Lambda Sond system to correct a the faulty firing or burning of the mixture. Is always fine tuning itself very quickly.
It’s not so much with the injectors pluse width but it will try to move the ignition timing, really fast and that will shift idle speeds! Similar to a misfire in the mid stream of things!
The specific 25 MPH test point, that they are using, must or may have a purpose, with say, an EGR functionality area.
This area plays with the Lambda programming when it turns on or off.
The evaporative canister supply is an open variable.
I don know when that is allowed to open with a vacuum source signal from the throttle plate, but you cleaned that.
It should be very Low on a list of HC’s contributors anyway, especially at that speed!
I know how you feel with that rich or lean code business!
It’s like saying, your car is a Limbo star!
That’s great, but how low is that bar anyway?
Phil
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posted by
someone claiming to be CB
on
Sat Jun 8 17:44 CST 2019 [ RELATED]
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Rather than Techron get a can of BG44K
you have to find a shop that uses it to buy a can. The website will direct you to a local shop in your area.
https://www.bgprod.com/catalog/gasoline-fuel-system/bg-44k-fuel-system-cleaner/#bg-product-3
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