To put the following questions about the Volvo B230F engine temperature sensors in perspective, I am troubleshooting a rather severe engine idling and warm up problem. Basically, the engine starts OK. This is in moderate summer temperatures between 70 and 100 degF. After about 90 to 120 seconds the engine starts choking, rattling and responds to throttle pumps as though its gasping for life. I can keep the engine running in this horrible condition, without completely stalling, for about 3-4 minutes, by rhythmically pumping the gas pedal with short strokes. Then, with a few back fires and a little bit of rumbling, the engine runs as well as it ever had before this problem started, which is pretty normal for a 244. My 244 is a 1989 sedan with B230F, Bosch LH-2.4, & auto trans, completely stock.
Any members with a similar problem in the past? I'd much appreciate your solution.

I'm trying to troubleshoot the problem methodically, and have suspected the temperature sensor(s) are involved in it. (This based on Youtube videos, forum topics, and reading various aftermarket repair manuals (including the big Bentley blue book.)
My basic question is how many engine temperature sensors does my 1989 B230F engine have? The implication from reading the manuals, and looking on parts vendor sites (like IPD Volvo) that there are two: One for the dash gauge and one for the "EFI" (electronic fuel injection)
.
However, when I consult the 1989-specific wiring schematic in the Bentley blue book, there are at least four:
The first is identified as component 221 ("Temperature Sender"). It is shown in sector L4 of the schematic, and appears to have two wires connected to it.
The second is identified as component 96 ("Thermal Time Switch,start injector"). It is shown in sector B1 of the schematic. In the schematic it appears to have two wire connections and a connection to it body (presumably a ground connection via the engine block). It makes a connection in the schematic to the Cold Start Injector (comp #95).
The third is identified as component 153 ("Temperature Sensor"). It appears in schematic sector N5, has two connections, and is somehow associated with component 151 ("Relay, temperature sensor").
The fourth is identified in the schematic as component 58 ("Temperature Sender") appearing in sector D1 of the schematic. It seems to connect directly to the dash temperature gauge (comp #70, in sector D2). This one is easy to see on the engine (under the intake manifold, about mid-block).

There is a temp sensor mentioned in the various blogs and videos I have referred to, which is located under the intake manifold near cylinder #3, and barely visible without a mirror or video snooper. Which of the other three temperature sensors is this one? 221, 96, or 153?
My big question is which one of these sensors is used by the LH2.4 EFI computer to determine the idling and running characteristics of the engine (e.g. injector pulse time, ignition dwell and timing, etc)? Component 58 seems to be dedicated to the dash gauge, which leaves the other three as candidates.
IPD-USA Volvo, and other parts vendors, market two temperature sensors. One has a single push-on terminal and is obviously the dash gauge sensor (Comp #58). The other one they market has two terminals and is designated as for the "EFI". (E.g. IPD's part number 126002 (Coolant Temperature Sensor for Fuel Injection). Is this component 221, 96, or 153?

Without getting too much into the nitty gritty of electrically testing these sensors (basically resistance testing with a DMM), the graph shown as Figure 10 on Page 412-12 of the Bentley blue book is labeled "Coolant temperature sensor resistance vs temperature". Does anyone know which of the four sensors described above this chart is referring too?

In summary, my question here is how do I identify these four different temperature sensors in terms of:
A) location on the engine?
B) relationship to engine performance, specifically fuel and ignition adjustments by the ECU.
C). After-market parts nomenclature or part number.

Any knowledgeable help is much appreciated.
Thank You for enduring my lengthy explanation and questions!

 

Unplug your O2 sensor with the car running - make sure it still runs and drives ok. If it does, leave it unplugged and let the car cool down. Try starting the car the next day and see if you still have the problem.

The o2 sensor signal is ignored by the ECU for the first minute or so because the sensor has to heat up to X degrees to give an accurate signal. When the signal is accepted a bad/old/damaged/coated/broken sensor will give the wrong signal and make the car run bad until it heats up completely. Have replaced many (years ago!) for that symptom.

Answering your temp sensor question if you see two sensors on the head the one closest to the front is for the temp gauge. The temp sensor for the fuel system might be a 1346030, hard to get to, and is black plastic. Have replaced about 75 of those - usually because they were melted during an overheating event, but a couple were replaced for poor running.

 

there are two temp sensors, one is for the dashboard gauge, and the other actually has two sensors in it, and is for both the ICU and ECU, and controls the ignition timing, and fuel injection.

 

hoonk,
This is great info. I tested the O2 sensor after the car got into its OK running mode, for heater resistance ( within spec) and the actual sensor voltage (around 0.5 volts). Still there could be a reason (e.g. lack of heater drive current) that the sensor is not heating correctly.
You say to disconnect the O2 sensor "with the car running". Does this somehow fool the ECU into retaining the last good sensor reading, or similar? I did not know about this test. I will try it.

There seems to be a common consensus about the two temp sensors under the intake manifold. (one for dash gauge, one for EFI) However, do you know anything about the other two temperature sensors I mention in my original post? I am beginning to suspect the Volvo schematics may cover several different vehicle types and country/state related options. So that, these other two other sensors are "phantom" components which appear in the schematic but are not actually used in my specific vehicle for whatever reason. Has that been you experiece?

Thanks for your help. Much appreciated.

 

Voltage readings (unplugged) from a front non-wide band O2 sensor should be 0-1.2 volts. Usually .2-.8 volts when running. On an oscilloscope it's a sine wave, constantly fluctuating from .2-.8. Voltmeters just flash high and low numbers if they can sample quick enough.

The O2 sensor just fine tunes the mixture so the Cat converter operates most efficiently. The engines normally run fine without them - in fact some earlier Volvo's ran worse with the O2 connected. Disconnect while running and make sure the car drives normally is to not inject a possible other problem into the mix. (maybe the car has a weak AMM or something else that is being masked by the O2 sensor)

Temp sensors I just looked up in VIDA for your year and engine. If you want a free accurate Factory parts catalog - there are easily found downloads of the stolen/hacked Volvo service/parts/diagnostic software called 2014d.(thats the year and edition (d) -) There is limited info for 240's but a complete parts catalog is there. Swedespeed has a download in their "OBD, CANBUS" forum. You need Win7 pro to run it. (others have work arounds for that if Win7 pro is a problem)

 

Thanks Hoonk, you are obviously very experienced with these problems and diagnoses.
Do you think running my B230F engine with the LH2.4 without the O2 sensor for an extensive period of time (say one week for 100 miles) damage the catalytic converter? Will the converter ever get damaged without the O2 sensor, even if run indefinitely?
Thanks
Joe

 

The LH2.4 lambda system has more dynamic range than earlier versions... with a disconnected O2 sensor, it will intentionally run on the too rich side of things (too lean can burn out pistons), and this will lower your fuel economy and eventually clog up your catalytic converter. its fine to disconnect it for a short period for testing purposes but I would get it working correctly for the long run.

 

I agree - the earlier cars (78-84, cis and lh) we much more forgiving - and had idle mixture adjustments. The O2 sensor was almost like an add on.

However is there anything left in your converter anymore? By this time the catalyst should have broken up and blown out the tailpipe.

 

the converter on our 1987 lasted to about 2010 or 2012, and at least 400K miles, before we had to replace it to pass California smog.

 

Hi hoonk,

How do you tell if the catalytic converter has been "blown out" - meaning, I guess, the platinum screen element has disintegrated.? (This happened to a previous Volvo I owned a while back.) Will the LH-2.4 with a good O2 sensor still work correctly with a blown converter? No doubt it would fail the state emissions test ( here in Pennsylvania the emission requirements are decreased according to the age of the vehicle, but it still must meet some minimum level.)

I have very good repair records from the prior own back to 2014, no mention of the converter being replaced. Although the car is 30+ years old, it only has around 125K on it. I'm thinking the converter condition is more dependent on mileage and proper engine operation than age?
Thanks,
Joe

 

Hi pierce,
Thanks for you knowledge and advice. I definitely intend to get it working correctly. Just wanted to have some idea how easy it was to permanently wreck the thing.

How do you tell if you have a clogged converter? Is there a way to unclog it, if it is?
Thanks,
Joe

 

Unbolt the front of the converter and look in it - is there a ceramic honeycomb?

LH will work fine w/out a converter. All the converter does is reduce pollution - and don't get me wrong - that is a good thing. LH might work fine w/out a converter and a O2 sensor - it's a 2x year old car - how much do you want to spend on it? It's a volvo w/ 86 horsepower, will it make a difference if it has 89 HP?

Look at the converter - the factory ones are large with a volvo part #, the aftermarket are tiny, that's why they are 1/8 the price, there's no platinum in them.

 

I believe LH 2.4 B230F was rated at 115 horsepower, something like that. enough to get a 240 sedan cruising at 100MPH, even if you won't win any drag races.

 

Years ago my 16 year old son proudly announced he had gotten his 84 240 up to 86 mph - a few years later I told him that I had intentionally adjusted the throttle plate so it would not open all the way.

 

a few years ago my then 25-ish son said he managed to get our 1990 Mercedes 260E (300E2.6) up to 125 or something, flat out and he ran out of Nevada long-straight-road. hah hah. said the car was solid at that speed.

now he's driving his *own* 2008 BMW 535xi AWD wagon. And he's currently living in Nevada again, so I don't doubt he's taken it up close to its 155 MPH governor limited speed. I took it for a half hour spin on the mountain roads around here, and it goes around corners like its on rails and effortlessly accelerated to 100 on a short stretch of a 55 MPH mountain road.

 

This is a follow-up to my original post of mid-Sept, 2020 in which I was mostly interested in how to identify the temperature sensor which controls the EFI operation. That inquiry was prompted by a very rough idling problem which I described in that original post. Since then a number of developments have occurred, and I have a few more questions and puzzles for the very knowledgeable contributors to this forum, and particularly who were kind enough to answer my first post.

What I learned about the EFI temperature sensor: First, Impossible to see from the top of the engine, well hidden under the intake manifold. I couldn't even find it by passing my smartphone under the manifold to make a video of that area. Second, the sensor is in spec. I performed the basic resistance test of the sensor by accessing it at the ECU connector , which is under the passenger side trim panel under the glove box. It checks out right on spec for "warm" operation, so I assumed it would likely be OK at hot temperature when the engine is running. I made the resistance reading as prescribed, and also took the block temperature (with a thermocouple meter) in the area of the intake manifold, as close to the temperature sensor as I could figure out. Then I took this info to the resistance-temperature charts given in the blue book and the Volvo Factory Repair manual (green) for the LH2.4 system. My tentative conclusion was that the sensor was fine and not the cause of the rough idling problem.

So, back to the rough idle problem. Again the engine started fine, ran pretty good for about 2 minutes, then went into a very rough idle phase for about 2-3 minutes in which it sounded like it was either "gasping for air" or starved for fuel, accompanied by certain amount of sporadic, mild backfiring. I could keep the engine running (just barely) during this phase by gently pumping the gas pedal by an inch or so up and down and rhythmically. After 2-3 minutes the engine would begin to run more and more normally, and final all was fine. No running driving problems at all. When I cut the ignition at the end of the trip, an immediate restart did not elicit the rough idle episode. However, if the car sat for 10-15 minutes or longer, I had to go thru the same "nursing" routine to get past the rough idle episode.

I tried many tests, maintenance procedures, and experiments to determine the cause of the problem. Most made no perceptible improvement, or difference, in the problem at all. Except for the following two. Perhaps the experienced members of the forum can shed light on these.

A. I completely disconnected the charcoal canister from the intake manifold. I removed both hoses and blocked the manifold ports where they connected to prevent a manifold air leak. This made an immediate noticeable improvement, so I left it disconnected. But the problem was still present to a lesser degree. I'm suspecting the purge valve on the charcoal cannister is defective, Or, the charcoal is somehow contaminated with something (maybe water?) that is being drawn into the engine when the purge value opens. Any ideas from the members?

B. While replacing the FI pressure regulator with a "known good" used unit ( i had it from a prior Volvo 940), and just on a whim, I blew compressed air into the fuel return hose to see if I could hear it gurgle in the tank (which I did). From what I understood about the return line, it simply runs back into the fuel tank without passing thru any valves, filters, etc. I figured it wouldn't hurt anything, and could possibly verify that it wasn't clogged in some way. Voila!!! That cured the problem and it hasn't returned since (several weeks now). What is this indicative of? Have there been past cases of the return line getting clogged? Can the return line deteriorate on the inside and block fuel flow? Is it possible there was something in the fuel tank that I dislodged with the air blast? (Debris, a piece that broke off something in the tank and effectively blocked the return, or impeded return gas flow?

I have one additional question related to the fuel lines between the tank and the engine. I've consulted a number of repair manuals (blue book included) and on-line sources. However I am unclear as to the composition of these lines. It seems from the descriptions that the return line is at least partially metal, with transitions to rubber line at the tank end and the engine end. Is the supply line (high pressure) between the filter and engine also partially metal as well, or is it completely nylon for its whole run? Further, is the hose that connects to the entry of the fuel rail at the swivel fitting, a section of the same continuous hose that runs all the way back to the outer pump & filter assembly? (In removing this hose to take a fuel pressure reading, it seems somewhat stiff. Is this hose normally flexible enough to withstand being carefully curved to accommodate connection to my pressure gauge? Or is it known to be brittle?)

In conclusion, it's good that I "fixed" the rough idle problem. However, I suspect I may have just postponed a re-occurrence of the problem(s). Should I be looking to replace that return line? What to do about the charcoal cannister in the long term?

Thanks in advance for any advice and/or explanations.

Joe