This is my first post... hope it is not too lacking of info.
My 89 244 has just started this odd, what I would call a pulsing at driving speed . What happens is at 30+ mph, the engine speed drops from normal to about half of normal RPM and then returns to normal RPM - so I lose power -hard to drive too.
This occurs at a very even timing - about once per second for the full cycle - Normal RPM - Half Normal RPM - Normal RPM (in one second). So, that's why I call it pulsing since it is so precise in it's timing.
What I am trying to say is about once per second the RPM level falls and returns to normal.
This does not occur at idle
I can shut the car off for a few moments and then drive it and the problem goes away. It can happen to the car cold or hot, at anytime , no relation to heat.
I disconnected the AMM and the problem went away , but poor start off acceleration . Left the AMM unplugged a day and the problem did not return. Plugged the AMM in and it took 2 days for the problem to return.
Also my idle speed is higher than normal at about 900-1000 RPM.
I don't get it.
First - let me say that this is the most entertaining and informative post I've read through in quite some time! BTW, I'm putting my wife's retired '98 S90 back together - the forum posts for that model are neither entertaining or very informative -- more to do with nasty stains on floor mats and the like.
But I too have a '93 245 which, this week, has developed a problem which may be CPS in the end. It starts easily, idles roughly and continues to miss here or there until it's good and hot. Then things settle in and no problems from that point on. I was thinking maybe an ignition coil with a circuit that is flexing with temperature, but I'll be sure to have a look at the CPS as well. Is this thing sitting on top of the flywheel bell housing?
Welcome to the Brickboard. That is a good first post. You gave the symptoms you have noticed and what you've done so far. I don't think anyone could ask for more.
If you can actually see the tachometer needle drop by half every second you are loosing ignition pulses 50% of the time.
If I had this problem, I would swap the coil first. It is the easiest component to swap for troubleshooting by substitution: Do you have spares to swap?
If not, get a resistance reading on the primary side and the secondary side before you drive the car. Drive the car until the problem develops and check the resistance immediately, as soon as you can get the hood open. I think you will find a significant change; probably on the primary side.
If the coil is not the culprit work backward through the circuit. Ignition Amp, Ignition Control Unit, Crankshaft Position Sensor. If you need help checking these, check the FAQ and post back for help.
I cannot explain why disconnecting the AMM had any effect on this problem. Maybe someone else can explain that and can help better than I can. At the very least this bumps your post back to the top of the list. ;-)
High idle is always associated with excess air. It can be the Idle Air Bypass stuck open (or commanded open) or the throttle plate held open. But it is usually a vacuum leak. Closely inspect every inch of the intake tract behind the AMM.
If not the coil, I would be very much interested to know what does remedy the ignition problem. Please post the fix when you find it.
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Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 53 year old fat man. ;-)
Thanks for your response.
Of course today no oscillation in the RPM's, so I did not check the coil.
I don't have a spare but I will check the resistance of the primary and secondary windings on the next failure.
I read the FAQ's but did not find any info on testing the ignition amplifier.
From what I read in Mitchell ,it supplies the ground for the coil as directed by the ignition computer. Don't have one of the amps either to substitute and it looks like Bosch is a bit pricey to test with a new unit.
I have seen some aftermarket ignition amps (for half the price)with large heat sinks - Chinese stuff. I wonder if anyone has had any experience good or bad with this stuff? I see FCP and others have been selling these Asian products for quite some time. I think my purple urethane bushing were from Asia.
One thought I had was whether the Fuel Injection computer could be causing this problem for whatever reason??
I will report back with whatever I come up with.
Thanks
I would heartily agree with sdewolfe - your post has all the information needed to begin a thread here. Makes it a pleasure.
If the problem is indeed ignition, my first suspect would not be the coil, but the crank position sensor (CPS) whose cable is known to disintegrate and short out. This could be affected by engine torque as well as an AMM hose, both parts physically tying the motor to the body. Check your OBD codes, and wiggle the CPS wire while idling. If no effect, move on from ignition.
Another possible explanation for the pulsation is a split in the AMM hose or either of the two smaller hoses connected where it meets the throttle body. The torque of the motor will open the split, depriving the AMM of its ability to measure the intake air, resulting in fuel being reduced. The torque will then drop and the cycle repeats.
Disconnecting the AMM causes the computer to ignore air flow as a means of determining fuel, and use only RPM - another reason to discount a primary ignition problem.
The clue you gave with the RPM dropping to half actually excludes your coil and primary ignition system, when factored with the problem going away when the AMM is electrically disconnected. The tach would go to zero if you lost ignition primary, but maybe go to half if fuel was suddenly cut off while the motor is driving an automatic transmission.
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Art Benstein near Baltimore
Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you're a mile away and you have their shoes.
Thanks for your response.
Of course, since the responses I have received the problem has not
occurred again and procrastinating I have done nothing, waiting for a better time to start chasing my tail - when -
my wife decides to drive the 240 to go shopping -
I get a call( all after the fact) telling me that the 240 died in the middle of the road, a man stopped to help , wiggled a "wire " and the car started.
What wire I asked - "I don't know " replied my dear wife.
I asked - Did you watch the man when he was doing whatever to the car under the hood?-
"No" replied my dear wife.
I asked - Did the man tell you what he did?-
"No" replied my dear wife.
I asked - Did you ask the man what he did?-
"No" replied my dear wife.
Then - Indignant disdain came loudly over the phone with her shot across my bow - "I don't know what he did". "Good bye. " Click. Phone goes dead.
Frustration with Volvo electrical and women.
I'll tell anyway, so you can see yours wins: I finished swapping rear springs and shocks in #4 daughter's 91. Ran it out of the garage, and up the driveway, noticing it lost power twice going up the drive. In the street, it worked well once again and continued on a short test drive.
Shook my head and turned it back over to the owner with a warning to "watch it". How lame. Didn't even pull the codes. Two days later (and 20 some miles) it quit on her about 5 miles away. I met her, found the code set for the CPS and wiggled the wire to verify it was indeed. Figured I could limp it back home, but got chicken at the highway intersection, and drove it back to a safe spot along the lane. Went home to fetch a replacement CPS and installed it at the roadside.
Great story ! : )
That's a good looking cable on the sensor. Volvo made really good
wiring harnesses .
That looks like I am guessing my CPS might look like when I get it out.
I know that the section just after the connector on mine looks like yours , where I have taped it up with friction tape.
Didn't think the CPS would cause the car to die ??
I guess though if the CPS shorts or stops sending a pulse train
to the ignition computer, then I have a dead car.
Maybe that's the wire the "man wiggled".
I can't think of much under the hood that someone could "wiggle"
to get the darn thing running again - ? - coil input and ground wires, module wires and CPS wire, maybe TPS wires. ....
Sure wish I knew.
I will just have to start going through each item , CPS first.
The "wiggle" is the key. I think many denizens of the board will concur that this is how they've diagnosed the bad CPS harness, by moving it to one side or another and securing it there temporarily with anything. Often the harness at the exact point it enters the top of the CPS casing is the issue. In one such instance, while spread prone across the top of the engine with my wife driving it around the parking lot, I could get the car to start and stop with amazing regularity just by wiggling the harness to the CPS. One does need to find someplace to hold on though. And I would not suggest exceeding 2 mph!
DS
Yes indeed, my wife has endured 25 years of such wayward auto enthusiasm with hardly a complaint. Now if I could just teach her the finer points of towing with a cable....
Good idea .
Well, though after my conversation with my wife today I might get a friend
who isn't upset with me to do the driving. My dear wife might accidentally
slam on the brake and then accidentally hit the accelerator and then accidentally run my *** over.
I know the jacket on the CPS is gone up top, so I am guessing the rest is toast
including the part inside the 3 pin connector.
I'll give it try with a less emotional driver.
The CPS on a 240 is a highly known failure, and yes, that is your problem... 99% certain. Unfortunately, on the BB we like to gripe about such "common things", but wait, the original sensor was designed for a 10 year life in order to minimize nasty environmental stuff in the local dump! It lasted twice as long as it was designed to do, I call that design margin beauty... downright perfection!
Compare that to a 93 Jeep Cherokee, 60K mile warranty from the factory. At 65K miles, she started dieing while making left turns through intersections. Three tows to the shop, the first two were $200 each with a "no problem found" result. On the third failure, I got ticked off and went into the shop area to start "wiggling" wires with it idling. Amazingly, when I grabbed the perfectly good looking CPS harness, the engine died! The mechanic shook his head in disbelief. The shop manager came over and I told him they owed me $400 and a free CPS due to the inconvenience of the failures and the risk it exposed me to. No problem "Sir" it's taken care of! Sold that sucker of a nice looking well maintained Jeep two months later... Why? Simple, the OBD diagnostics didn't even know what the problem was! A bad design!
jorrell
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92 245 284K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!
Yes, I agree , that 20 years is a long time for the cable on the CPS to last.
So, I tried the wiggle and pull and wiggle on the CPS cable and could not get the car to do anything wrong of course.!
I cleared all of the old OBD codes hoping I would get codes of some use on the next failure.
Sure enough I got a no start . Took 3 tries to get it to start and set the check engine light with-
2-1-3 Throttle switch full load setting faulty or grounding short
2-2-3 Signal missing to/from idle air control valve
2-3-1 Fuel trim (lambda control) too lean or too rich at part load ...
but nothing that points to the crank position sensor.
The loss of power at driving speed has not occurred again.
Now the dead in middle of road or won't start condition has begun.
I am going to check the TPS , don't know what else to do.
I'm hoping I don't have a really hard to find electrical wiring problem.
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