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Hello
I have 1992 940 230fd + automatic.
Ive owned this car about 6 months now. First months consumption was about 24mpg / 9.5 liters per 100km. That was highway and city 70/30.
After that it has been going to worser. Now its about 19.6 mpg / 12 liters per 100km and same driving style and routes. Even 100% highway mpg was 24. I had 940 with same technic 5 years ago and it took 30mpg highway.
Brakes are ok, allmost all new, plugs, wires, rotor, o2 sensor, air filter etc new. Car has idled, started and drived good all the time it just rises consumption. No header or exhaust pipe leaks also, i cleaned maf which was already clean. Pulsair valves were fault but blocking that no effect. No vacuum leaks and also new intake manifold gasket just for fun
No fault codes, automatic works great and tcc also.
Thermostat is new and works, i have new ecu temp sensor at garage but replaced yet because no symptoms for that either
Im very astonished what is going on????
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I double checked fuel lines and also replaced fuel filter and clamps.
Checked brakes and no problem. Also fault codes again, no. Only 1-1-1.
This makes me sad. Also checked odo/trip for fault readings but no.
Also seems like fuel gauge drops faster than ever. I see newest consumptions at weekend when i refill
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Have you check/ replace the computer temp.sensor.?
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Not yet. Thats next but its pretty bad place. Good cold and hot starts wont give suspects for ect but i replace it anyways.
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How about these volvos cold start and "choke". What should be cold engine idle at colder temps? I now realized that mine runs allways about 800rpm no matter what, wont rise 1000 or up even cold
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Dear volvomies,
Hope you're well. As northern hemisphere winter has begun, a B230F/FD should idle at 500-700 RPM. Idle speed of 800 RPM is "high" and 1,000 RPM is abnormal.
I suspect the engine coolant temperature (ECT) sensor. If the ECT fails, the engine control module (engine computer) "thinks" the engine is cold, so supplies extra fuel all the time, rather than just for the few minutes until the coolant reaches normal temperature, i.e., 87-92⁰C.
If you have "small" hands, you can reach under the intake manifold's runners (tubes) to detach the ECT sensor's wiring harness connector, and use an open-end wrench (spanner) to loosen the sensor. You can then remove the sensor with your fingers and put in the replacement with your fingers until it is snug. A quarter-turn (90⁰) will make it leak-proof. The ECT's wiring harness connector can only be installed one way.
Hope this helps.
Yours faithfully,
Spook
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Ect showed 290 and 136 values. So they arent same like measuring guide says. I drived 30miles before measuring so engine was hot. 290 is about 80-90c but 136 is near 110c value
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Now got new ect, wasnt that bad to change that it looked.
Now hot engine 189 and 190so its now good.
Checked FPR again with vacuum pump, no leak. At hot engine idle pulling vacuum hose out of FPR (and blocked with finger) didnt effected to idle.
Looked again gargo area hatch to fuel tank, no leaks there either bone dry places covered with dry dust.
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And also checked maf 3 pin voltage at idle and there was 2.49. Ive been read that 2.3v is correct, is my maf bad? Voltage rised when i pressed throttle
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Today new measurings with two different multimeters. Gived 2.44v at idle but it jumped 2.45-2.46v several times yesterday was steady 2.3v
Ignition on engine off gived 1.48v and internet says should be 1.4v
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Dear volvomies,
Hope you're well. According to the Volvo pocket data booklet - Cars (700,850, 900) 1991-1996 /900, p. 31], the resistance values for the Engine Coolant Temperature sensor are:
-10⁰ C = 8260 Ω -- 10560 Ω
+20⁰ C = 2280 Ω -- 2720 Ω
+80⁰ C = 290 Ω -- 364 Ω
For the Mass Air Inflow Sensor, the resistance between connectors 2 and 3 should be
2.5 - 4.0 Ω .
Hope this helps.
Yours faithfully,
Spook
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i got 2.9 ohms between 2 and 3.
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Dear volvomies,
Hope you're well. The 2.9 Ohm reading suggests the Mass Airflow Sensor is OK.
Hope this helps.
Stay Well!!
Yours faithfully,
Spook
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How about votls which vary for specifed?
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Dear volvomies,
Hope you're well and stay so. For the engine coolant temperature sensor, Volvo provides no data as to voltage. Volvo does provide data as to resistance. From this I infer that resistance is the key to knowing if the sensor is OK or not and that voltage is not.
Hope this helps.
Stay well!!
Yours faithfully,
Spook
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Yes i talked to ohms with ect and my ohms are okay now with ect.
Engine hot with old sensor: 290 and 136ohms. New 189 and 190ohms.
I also tested maf: 2.9ohms.
But there is also maf 3 pin tests with voltage. They say that 2.3volts at idle is what you see at working maf, i got 2.49volts. But how accurate and sure this voltage test is?
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I was going to link to the ipdown.net site to refer to the images below, but it is currently down. Luckily I had downloaded the images previously.
This is of the LH 2.4 system, which I believe your 1992 940 will have (6-pin MAF connector, the LH 3.1 will have a 4 pin connector).
The coolant sensor signal (ECT) starts at around 2.6 V cold and drops to around 0.35-0.4 V when the engine is warm. You can measure this on pin 13 of the ECU connector (for which you need to take its sleeve off first).
It says that on pin 7 of the ECU connector (coming from the MAF aka AMM), there should be a voltage of approximately 2.3 V with the engine idling, as you wrote. 1.4 V with ignition on but engine off.
A while ago, I measured exactly 2.3 V on mine with the engine idling at 750 rpm.
You are reading 0.2 V higher than that, so first question: is your engine idling 750 rpm?
If it idles higher, more air is drawn in and it is logical that there will be a higher voltage.
If it idles at 750 rpm, then I'd say the 0.2 V over reading might be significant.
The LH system uses a hot wire to determine airflow. This wire has a non linear resistance. At low revs, this resistance changes a lot while at high revs the resistance changes little. So at idle that difference will have much more impact than at high revs.
So back to my question: what was the idle rpm when you measured the 2.49 V?
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Those pics are big help, thanx!
I only had original rpm meter so i cant say 100% sure is it 750rpm but it is close if i look needle. Its half way to 1000rpm and 500rpm.
I had engine off also 1.48-1.49volts so its also then little bit high but ≈ this symbol means approx?
Maybe that helps if you got 2.3 at 750rpm, what would be reading at 1000rpm? Is full throttle somewhat 4-5volts or more?
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Yes, that symbol means approximately.
I did not measure at different rpms, just at idle, but since you seem to have an offset at no load, it's likely that at higher revs it will also measure somewhat higher. So that may not be an issue, the ECU probably takes that into account.
Given that you measured the resistance of the AMM wire within spec (i.e. 2.5-4.0 Ohms) AND that you cleaned the wire AND that your spark plugs don't show black soot deposits after the 20,000 km change interval, I'd say the engine is not running too rich.
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If its not running rich but mpg is bad, then one option is running lean? But no bog bo lag nothing symptoms about driveability or idle.
Idle is little bit unstable but i mean very bery very fine movement at needle. What i remember those engines arent running fine like straight six engines for example.
It wont humb rise or lower idle at any situations.
One option is still ect. With new one i drived only 20% off tank and 80% with old. Mpg at yesterdays fuelup was 18.8 and 90% highway :(
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I don't see how running lean would increase fuel consumption. Besides, there is not that much variation from 1 part of fuel to 14.7 parts of air possible in a gasoline engine.
If the mix gets too rich or too lean, the ECU will throw a DTC (diagnostic trouble code or fault code). When my FPR had failed enough to occasionally cause a DTC, it was 1-1-3.
My engine doesn't idle perfectly either, besides, a really steady idle of a straight four probably means it's very low on compression.
If the fuel mix isn't the problem, then there MUST be some other reason for your increasing fuel consumption.
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Then its still big mystery :( This is slow just wait next fuelup and check consumption again.
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It might help your cause to start a new thread. In the new thread summarize where you are at now. You might receive new and helpful feedback.
--
Will I buy another Volvo??? We'll see....
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ECU temp sensor ? Can you do a fuel system pressure test ? Need to make sure the system running pressure is correct. Just checking the vacuum of the FPR isn't enough. Diagnostics doesn't code the FPR.
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Got new ecu sensor, old was reading little bit wrong
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Yes, indeed.
I have had a fuel pressure regulator fail on me in my previous 245. It was a process that took years, and only in the very end did I get issues related to it.
Black spark plugs already told me that the engine was running a little too rich.
That must have hurt fuel economy.
My current 245 suffered a small leak of coolant into one cylinder. After replacement I got roughly 1 km per litre (~2.4 mpg) better fuel economy.
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my plugs were/are clean so so....
need to buy fuel pressure tester
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Addition: I meant to wrtite "after replacement of the head gasket". But that wasn't entirely correct either as the head itself had to be replaced as well because of badly corroded water channels.
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is that resistance engine or power on or power off?
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Dear Volvomies,
Hope you're well. The sensor need not be installed. Thus, if you want to test a brand new sensor, put the sensor's tip in water at the specified temperature. If the resistance reading matches that specified, then the sensor is in good order.
Because there's so little room to work under the intake manifold's runners (tubes), it should be easier to remove the in-service sensor and test it.
If the sensor is the factory-original, it doesn't owe you even a centime. Having removed it, I'd replace even if it is still in good working order. Keep the removed item as a spare part.
Hope this helps.
Stay well!!
Yours faithfully,
Spook
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I got 700rpm too 800 was just quess :) So no fast idle at factory so thats ok then. Rpm is 1000 and 500 half way minus pointer width
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You 1992 940 has a Schrader valve on the fuel rail used to check pressure.
Not a Turbo, yes?
You blocked the Pulsair ports? Can you do that and pass emissions inspection?
Do you have EGR? Pulsair is sometimes included with EGR.
So you have Bosch fuel injection. Your 1992 940 should also include on board diagnostic to check for engine control faults, typically attributed to emissions sensor or device faults.
https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm
Read more in the FAQ
My guess is that the fuel pressure regulator (FPR) may be failing. The FPR can get stuck and not return fuel pressure to normal. When you want to go fast, and press down on the fuel pedal, the air intake port manifold vacuum lessens causing the vacuum controlled FPR to reduce fuel volume passing through it, raising fuel pressure at the fuel injectors. The FPR can fail in a few ways. One way is the vacuum diagram is punctured and fuel passes through the vacuum line imnto the air intake. Yet you'd smell fuel in the engine bay.
--
Beh.
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N/A yes, egr is functioning and its independent system. Pulsair blocking was must do because exhaust gases went thru wrong way.
I inspected FPR with vacuum gauge and it keeps pressure when vacuum is on so diagram is at least fine.
Ive got no fault codes at all i checked all ignition and injection etc codes and zero nada.
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I meant the fuel pressure in the fuel rail using the Schrader valve on the fuel rail.
You can vary fuel rail pressure by using a vacuum pump with gauge.
If you have no fault codes ... such imbalance, lean or rich, could set an OBD fault code in socket 2 (fuel injection) and socket 6 (ignition).
There exist ways to replace the engine coolant senor engine control uses without having to remove the air intake manifold port. (Unless the gasket is original as the air intake port gasket tends to embrittle and shrink, causing air intake vacuum leaks.
Any exhaust leaks? Engine cold, some dish detergent in a spray bottle, and spray cold exhaust unions from the exhaust manifold gasket to the header pipe out to the catalytic converter input?
The header pipe out to the catalytic converter in union is closest to the header pipe support bracket that hangs off to bell housing bolts. If the header pipe out to the catalytic converter in union leaks exhaust, ambient outdoor air can be sucked in. A working oxygen sensor encounters the air, and engine coltr sets a fault code and enriches the fuel to air ratio.
Yet you have no fault codes.
Is the catalytic converter original? If your 1992 940 has been running in a lean or rich fuel to air ratio, the catalytic converter can fail and become clogged. A clogged catalytic converter may not set fault codes immediately, yet will make running the engine and driving it, as the exhaust is partially or worse clogged, so accelerating, or trying to, may cause the engine to 'bog'.
A throttle position switch (TPS) can begin to fail yet engine control is forgiving and not set a fault code. The TPS can fail a few ways. The way TPS to fail is engine idle control remains on interferes with pressing the gas pedal, so the engine stumbles or bogs.
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Beh.
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Yes i have to measure fuel pressure from railbbut first i need fuel pressure gauge.
Ive already replaced ect sensor, old gived hot engine 130 and 290, new 190 and 189.
No exhaust leaks, flange gaskets, manifold gaskets all new
Is there some specific voltage for tps sensor at idle?
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I'm unsure the voltage. The TPS is merely a switch.
FAQ TPS entry (copy and past URL):
https://www.brickboard.com/FAQ/700-900/EngineSensors.htm#ThrottlePositionSwitch
Wiring diagrams:
http://www.v8volvo.se/mekartips/volvo/index.html
How old is your catalytic convertor?
--
Beh.
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Catalytic is old i think but i do emission test month after buying and readings was good. I dont think it has gone so fast bad? Emission test time consumption were okay but month after it began to rise.
I measured maf, didnt get helper. I but screwdriver between throttle cable roll at engine. About 3100rpm maf gived 3.077 volts. Is that okay? Pretty small increase of idle ≈750rpm 2.5volt reading
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Catalytic is old i think but i do emission test month after buying and readings was good. I dont think it has gone so fast bad? Emission test time consumption were okay but month after it began to rise.
I measured maf, didnt get helper. I but screwdriver between throttle cable roll at engine. About 3100rpm maf gived 3.077 volts. Is that okay? Pretty small increase of idle ≈750rpm 2.5volt reading
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I have a 93 940 & similaR bad mpg,,,I justr replaced the banjo fitting,,,it had corroded w age,,, I found them on youtube,,b a machinist in New hampshire
makes them../,theyre $10 plus shipping,,,
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Fuel pump/filter banjo fitting or what?
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Dear volvomies,
Hope you're well. Have you checked for a fuel leak? If the car lives (or lived) where salt is used to melt snow/ice, an under-body fuel fitting - corroded - could leak fuel. While the car's moving, the air stream will evaporate the gasoline, so you will not see any sign of a leak.
To find a gas leak, inspect the metal fittings at either end of the fuel filter. Wrap them in clean, white paper towel and tape the towel into place. Drive the car. If there's a leak at one of these fittings, the white paper towel will be discolored by the leaking fuel.
A gas tank leak is not likely unless caused by road-hazard damage: these Volvos' fuel tanks are plastic, about 6.5mm (1/4" thick).
Another possibility is that the transmission fluid is worn-out. Does the car climb hills smoothly or does it seem sluggish when climbing hills?
Pull out the transmission dipstick and wipe off the fluid with a clean white paper towel.. Fresh automatic transmission fluid (ATF) is a clear, rosy pink. If the ATF is dark red - or worse, even brown or black - the ATF needs to be replaced.
See this site's FAQs for how to flush-out the old ATF. If available in your area, Mobil 1 synthetic ATF is a good choice. Otherwise, any "Type F" (Dexron/Mercon) ATF will work properly.
Hope this helps.
Yours faithfully,
Spook
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Fuel hoses are good, i checked all at bottom of car and upside of tank when i renewed tank straps couple months ago.
Transmission works great and torque converter lock also. I flushed tranny after i bought car because old oil were 40k drived but pretty fine.
Im sorry im not native english speaker so i cant write that polite and nice that you did but thank you for very warm message :)
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Dear Volvomies,
Hope you're well. Your English is fine: many native-born speakers should do as well as You do!
Pull the oil dipstick and smell the oil. Your nose will tell you if there's gasoline in the oil.
If an injector get stuck in the "open" position, gasoline is burned inefficiently or not at all. That will cause fuel use to rise.
Gasoline enters the oil supply because it gets past the piston rings. If the oil does not smell like gasoline, then the injectors work property.
Have you inspected the fuel rail, especially the end caps?
Hope this helps.
Yours faithfully,
Spook
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Fuel rail ok, no gasoline smell in oil. I tested injectors today while i ultrasonic cleaned these and all fine. I did test before cleaning to be a sure what is starting point.
No drip or leak at all. Fine spray pattern.
Only maf is question but what ive read or own experience they do idle or driving harshness/problems.
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Hi,
I've not had a 940. Does the fuel door open from the interior ? If not, do you have a locking cap ?
Peter
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Dear maplebones,
Hope you're well. On 940s sold in North America, the fuel filler door is not secured.
While the taxes make motor fuels far more costly in Europe than they are in the U.S., oil prices have recently been depressed by the plunge in travel thanks to COVID-19.
Hope this helps.
Yours faithfully,
Spook
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Check to see if your O2 sensor shows voltage swing. I never trust new to be working.
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o2 showed about 200-900mv range running up down, i did vacuum leak and then voltage was 200mv so seems to being ok?
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Check the function of your air filter box heater flap control if your preheater hose is still attached.
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no preheater hose, air coming outside
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My header that I got for my 940 is defective becuase when I go to tighten the connection to the cat back is seems to just stay loose & thyat where the excess air comes in that affects the oxy sensor,,Maybe yours is the same?I m gonna see if my mechanic
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I had no preheater hose on my 90 240DL with the similar b230f engine. Didn’t affect the gas mileage on my car. Just a rougher idle when cold.
With automatic transmission that car got low 20’s in town and 26-28 mpg on the highway. Remember once I got 30 mpg on the highway and I was thrilled! As I recall, 240’s are at least 200lbs lighter than 940’s.
I suggest double-checking your brake calipers. Make sure they are not sticking or “dragging”. Stuck calipers can be hard to notice and will affect your gas mileage,
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Will I buy another Volvo??? We'll see....
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Calipers are fine because i checked those after i bought car and rear has whole new calipers.
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Ok i check. Its oe bosch because aftermarkets are proofly poor.
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Check the function of your New O2 sensor......How old is the fuel filter ? Pour and bottle of "Chevron Techron " into half a tank of fuel. It cleans the injector so you spray pattern is correct. Get a fuel pressure check done to make sure there is No leaky injectors.
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I had old o2 sensor until last fuel up so it didnt make difference. Old was original and ive seen many tired old o2 sensors without check engine light but that was miss.
I dont have fuel pressure gauge but ive tested regulator with vacuum pump and it works.
Today removed injectors, clean and nice pattern so they arent my fault. Spark plugs also clean and like they should be.
Fuel filter is one year old but i have new so must replace that also.
Also checked vacuums with vacuum gauge. Steady 22hg at idle.
I have same tyres and angles etc nothing has changed. When i bought car front brake guide pins was rusted and front brakes were stuck. Still car was more economy than now.
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Hi,
Other than obvious reasons for low mpg like fuel leaks and blocked catalytic converter, the front suspension plays the most important role. Tyre wear, improper inflation, alignment (this include inner/outer tie rods wear) should be checked. These happen gradually over time.
The OE tyre for 940 is Michelin MXV4 plus (from Volvo publication) but these are discontinued. Look for low rolling resistance Michelins if you're in the market.
Less than obvious reasons for low mpg are low quality fuel (try using different gas), partially blocked PCV system (blowby gases restrict piston movement - this doesn't always translate to oil seal leaks), old battery (slow to charge causing longer load on alternator), dirty fuel injectors (relates to fuel quality) and old differential fluid.
Lastly do Italian tune-ups once in a while. Find an open straight clear road ie highway and drive in 2nd gear with 4500 to 5000 RPM in 3 to 5 minutes. Speed about 45-50MPH. Helps to clear the injectors and carbon deposits.
Regards,
Amarin
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