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Greetings, everyone!
The Volvo 244, an 84-family car, starts fine; however, while driving, it suddenly slows down and seems to stall before picking up speed again. This behavior occurs randomly during driving. Recently, I installed a new in-tank, stronger fuel pump (AEM-5-1000 High Flow) to address the issue, but it hasn't resolved it completely. Have cleaned throttle body, spark plugs, and air idler valve.
I would highly appreciate any tips or insights based on your experiences to help me diagnose and fix the problem. Thank you in advance!
Habiba
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Hi,
That’s a little better description of what is going on with your cars idling system.
Just because the car is coasting down the road it doesn’t mean the engine isn’t trying to idle.
Someone might think you are cornering too fast an slinging all the gas away from the tank pump causing a temporary stall. No one is going to bite on that scenario. 😎
I think you are getting enough information through your new observations that you are heading in the right direction.
The TPS has to tell the ECU that you are wanting to slow down, even though the RPMs are within a convict having the engine doing that .
Upon a correct idle click the ECU will try to idle and send a command to shut down the IAC Valve.
That’s when you describe a “time lag” of trying to bring the engine back onto power to finish your turn. At that very moment the ECU and itself in the opposite mode.
Your statement “ related to the throttle position sensor, which could be causing the throttle flap to be held in a completely closed position” is not possible.
It’s only a switch straddling a shaft but it truly has have an important job to do.
That TPS cannot be allowed to hold the throttle plate up or from cause any movements.
The foot feed cable needs to be flexible for engine movement especially behind the bracket holding it. That should be designed in.
There should be a little bit of slack over to the throttle cable spool
It can be possible that it’s sticking or hanging up but other than it has to feel to move.
The plate has to be closed entirely but must stop against an adjustable stop screw. It’s purpose is to help keep the return spring from jamming the plate into the bore of the throttle body. Under a sudden release of the gas pedal pressure it is supposed to slam shut.
You do not set idle speed with that screw except under an instructions to set the “very basic idle speed” according to a procedure in the service manuals.
Art talks about the grounding of a wire for this purpose to take the IAC out of the loop entirely.
So it should not hold the throttle plate open any but not to be down tight either.
Some call it “just touching.”
As soon as the plate wiggles upward the switch has to follow very shortly thereafter with a change or very faint click.
You can verify that the contacts are changing “state” back and forth with an ohmmeter on this year car.
That is what Art is talking about and has two ways of confirming this signal is getting to the ECU while it’s verifying good wiring. That has been mentioned before about the engine harness. His method is more of a throughput diagnostic procedure that is much like what’s on the cars of the nineties with the OBD I system. Only manually.
I believe when Art has his 1984 he shined up his eye teeth on that car to become the documentarian he is with a camera and this site and his web site.
http://cleanflametrap.com
You also cannot have any kind of a air leak behind the AMM so a make sure the accordion hose is completely air tight.
Check the volutes with a bright light on the inside and where the hoses are connecting for cracks.
At this point the TPS must sense and report to the ECU to make things idle or decelerate.
Of course, we know that shutting off the air causes that to happen for the most part.
The idle signaling point maybe a little out of sync with the throttle plate.
The ECU responds accordingly to the AMM and by closing down the IAC at the same time.
A reduction of fuel is an ECU job along with other incidentals.
LIKE if having a conversation with a black box that’s timing controlling the spark from the coil. That is beyond any driving issue you having at the moment but I do not discount wiring harness issues, ever, on this car.
The idling point is done by the IAC.
It is only affective as long as the throttle plate is holding back the major control air.
It has to be minimal amount to put the overall opening and closing range within the plates capacity inside the IAC.
It is very limited but then its only made to govern an idle air amount to begin with.
WHEN you go to slow down that initialization is caused by you, so, at that very point the ECU needs to know that idling is coming up or changing on an agenda.
You appear to have a time lag, within what I call, a “TRANSITION ZONE.”
It hinges on a very tiny air gap of the throttle plate change and the ECU knowing about it.
The plate operation is working with other tiny ports in that zone to control fuel pressure for idle or acceleration and evaporative emissions.
That’s why a throttle body helps smooth out that zone’s importance.
A gap too wide and then those get compromised, let alone exceeding the IACs working range.
I have realized that we don’t know if this is an automatic transmission or a manual?
A manual is more problematic or sensitive to making the engine dropping off into “no man’s land.” The ECU is good but it needs a “heads up”. It will get lost.
Only because the load can be more suddenly released like you are describing now.
The automatic is dragging a torque converter, so therefore, the resulting lag is not so instantaneous to let the engine stall or die but it still can in extreme cases.
I see your thread is getting a lot of good feedback as this is a recurring issue on all the 240 cars before and after this particular year.
Phil
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"You also cannot have any kind of a air leak behind the AMM so a make sure the accordion hose is completely air tight."
Phil, you remind me of another possible fault associated with "slowing down." I haven't had the experience yet, but I wonder what occurs when the brake booster check valve fails to check?
Does the stall, or near-stall occur only when braking?
--
Art Benstein near Baltimore
Always keep several get well cards on the mantel. If unexpected guests arrive, they'll think you've been sick and unable to clean.
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Hi Art,
I hadn’t thought about that in particular either.
In my experience, of only one, a check valve on the booster is necessary to build and hold vacuum in the booster quickly after the car starts. You will feel that in the pedal softening very shortly after the first few hits of the engine.
It should hold vacuum for some lengthy period after shut down as well.
A failed check valve makes for some hard to start moments due to the leaner mixture at all times.
Even right after shutting down in extreme cases.
It is of course worse with a cold engine.
I have seen those check valves get a crack around the outer edge, of the outer center disc, that you can see from the outside. Rare but they can get brittle with age as with the large hose to it.
There’s also a grommet that can become an issue. It should be rather pliable to work well.
If he has some of those symptoms, then yes, I would agree that a bad check valve could jeopardize what should be a stable running engine in to sporadic stall when using the brakes through a turn. Not so discerning at a very low speed in an automatic.
A manual shift would not provide any glide as soon as the clutch disengaged in order to grab a gear change.
He will have to meticulously or methodically sense his way through the symptoms to reveal the vehicles clues.
I think he is using three of the five commonly known senses and will solve the problem. 🤔
Luckily, In this case I will say smelling and taste can be ruled out. 🫢
But then again, Substituting into many different forums threads here and there ocan lead to needing those other two back.
We have seen recently how long that troubleshooting routine can play out to be a simple distributor cap @ 20,000 miles of use.
🤐
Phil
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Is the engine missing or just loosing power?
Is this occurring on the highway, in town or both?
Can you compensate with more throttle?
Like jwalker said, "Think fuel, ignition and air flow." Its a divide and conquer technique.
Obviously more information would help. For that you need to take measurements while the problem is happening. To do this you can run test leads, vacuum and pressure hoses through the firewall and hook up meter, test lamp, and gauges.
Proving what is happening gives more confidence in reliability.
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Sir, thank you so very much for taking the time to respond to my post.
The engine fires up really well and runs smoothly while in park. On the road, it has great power. However, when I slow down to turn left or right, the engine suddenly loses rpm, power and stumbles, then picks up again. I have already taken out the throttle and cleaned it thoroughly. I also cleaned out the idle control valve. Additionally, I just installed a new Bosch O2 sensor. I suspect that the symptom might be related to the throttle position sensor, which could be causing the throttle flap to stay in the completely closed position. I intend to replace that part to see what the outcome will be.
Kind regards,
Habib
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Dear Mr. Benstein,
Thank you so very much for taking the time to provide valuable tips and information. I immensely appreciate it. I have always enjoyed and benefited from your knowledge and Volvo experiences.
Regarding the connectors in general, I am quite meticulous to ensure they are clean. When disconnecting the battery negative, I use a wire brush to clean both the male and female connectors, making them shiny and free of any corrosion residue. Additionally, I always apply electronic connector lubricant on both sides before connecting them.
After reinstalling the throttle, I reattach the throttle switch using the two mounting screws. However, I still need to figure out the optimum position for the throttle switch.
Thank you once again for your assistance and expertise.
Kind regards,
Habib
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Kind words, Habib. Thank you. Call me Art. I'm only "Mr. Benstein" when I'm in trouble.
The throttle switch needs to be active whenever your foot is not touching the pedal. If the switch works (not internally dirty or broken) that position is when you feel a click as you open the throttle. It should not be touchy; that is you don't want to take the advice to hear it click at the slightest opening, but be sure it does with any intentional foot pressing. Its most important job is to enable idle control with your foot off the throttle, not so critical to disable it immediately when you put your foot on the pedal.
The problems happen when the switch is worn, old, and has ingested a lot of blowby oil. Then the switch can sound and feel like it works, but not make sure contact electrically.
I believe it is a good practice to use a grease that will exclude water after cleaning connectors exposed to it. Sounds like you do too.
--
Art Benstein near Baltimore
When asked what time it is: "Do you mean now?"
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I believe the throttle position switch is adjustable. You can check it with a meter or test light to see if it is working. I would not replace it unless you have the procedure for adjusting it. The Volvo "Green" shop manuals are available here: https://ozvolvo.org/archive
If you plan to keep the car I recommend downloading everything related to the 1984 200 series.
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Hello,
Unfortunately, the system does not function the way it used to, so I can't see your name.
Again, thank you so very much for the tip, and thank you for the link. I very much appreciate it.
Best regards,
Habib
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I use my car's info for my name: 1981 242DL B21F California.
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Dear Sir, thank you so very much for taking the time to respond to my post.
The engine fires up really well and runs smoothly while in park. On the road, it has great power. However, when I slow down to turn left or right, the engine suddenly loses power and stumbles, then picks up again. I have already taken out the throttle and cleaned it thoroughly. I also cleaned out the idle control valve. Additionally, I just installed a new Bosch O2 sensor. I suspect that the symptom might be related to the throttle position sensor, which could be causing the throttle flap to stay in the completely closed position. I intend to replace that part to see what the outcome will be.
Kind regards,
Habib
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Sir,
Thank you very much for your time and the tips. I really apreciate it.
Kind regards,
Habib
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If it just starts stumbling and stalling out of the blue and soon returns to normal then put on your possibility list the Hall sensor in the distributor starting to fail.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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Dear Dave,
Thank you for the suggestion. I will check into the sensor and will see if there is any issue with it.
Kind regards,
Habib
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Hi,
The thing to ponder would be a bad wire going into the distributor that powers the hall sensor that sets up the ignition timing for the engine.
The 1984 year was also a car for having an engine harness wiring issue up until 1987 or so.
The term used was “biodegradable wires” inside the sheath.
Run the engine and wiggle stuff is the only suggestion at this point.
Even check out the harness over to the black box, on the right fender, as sometimes a person may have tried to unplug that. That, in itself, is a big mistake.
They are one-time use connectors from Chrysler’s thinkers box?
Like having left hand threading wheel lug nuts in the old days.
I was very young when heard this and today I wonder, if it was only on the left side of the car?
That had to be maddening?
Imagine what other countries thought of that too.
Like if driving on the opposite side of the road, would change anything? 😳 I wonder if Chrysler even exported back then?
Whoops, I had better hush, my own entertainment rattle is really beating me up now! 😵💫
Since you say since it random, on a 1984 ….. With my 1984, I have learned to be leery of that years AMM. The previous original owner replace one and so have I now.
I’m Down two or three depending on how you count.
So now, I have a know good spare in the trunk.
The rebuilds come with lifetime a warranty but LIFE depends on the TIME of when any extinction policies are to be implemented. That’s 🤨 commercially or governmental?
That B 230 engine is made tough and solid so it’s bulletproof to make it this far.
1984 was the first or early years of the LH systems.
Since then the AMMs have changed twice on their last numbers. Going from the 001 to a 007 by 1986 with a lot less problems. But then moving on up to the 016s around 1989 with the Crank Position Sensors and a more sophisticated LH with diagnostics or a weak code teller system. The infamous CEL came into being.
The AMM could be getting weak or loosing calibration. There is no way to test them on the car and the symptoms are not quite the ones of a fail unit at this point IMO.
Usually it’s hard to startup or like to die shorter or will have no power of which we call “limp mode.”
The car could be going in and out of limp mode if the AMM is faltering in some manner.
One would have to be cautious with this “heads up symptom” but a failing AMM of the old number could be a tell. Like in a poker ♣️ of players.🫣 The word is out within the Bricks community forums.
Keep being aware and looking, as it can be a gremlin with a hideous laugh, during the most inopportune moments.
Phil
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Dear Phil,
Thank you for taking time to respond to my post in detail, I really appreciate it.
I will fallow through all teh sugestions, hoping the problem will resolve.
Kind regards,
Habib
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A few thoughts: Think fuel, ignition and air flow. Your engine needs all three.
Speaking of fuel. You probably did this already…. Change your fuel filter.
How are your fuel injectors?
Check your vacuum hoses for cracking and breakage. Replace as needed.
How are your ignition wires? Distributor cap and rotor ok?
--
Will I buy another Volvo??? We'll see....
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Dear Mr. Walker,
Thank you for your time and attention. I have completed all the tasks you mentioned, and I am looking forward to receiving the new oxygen sensor tomorrow to proceed with the replacement. While the engine generally runs well, it occasionally experiences some struggles before returning to normal. Along with replacing the oxygen sensor, I am also planning to install a new vacuum booster check valve to ensure the optimal performance of the engine.
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Hi Habib,
One more thought. Does this poor running happen only after the car is fully warmed up? If so, it could be the ignition coil. Suggest testing it before replacement.
Good luck,
JW
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Will I buy another Volvo??? We'll see....
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