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Car was running fine. Pulled into a parking lot and stopped car. Realized I needed to move slightly and started up again, didn't want to run, stumbling had to keep foot on gas. Moved car and stopped it, came back a few minutes later and started up OK and ran fine. Later in the day picked up a friend at airport and thought car seemed to be surging very slightly. Drove for an hour and a half and check engine light came on but car was still running OK although it felt like it was surging slightly at highway speed. When I stopped felt like idle was a bit high. Got home and checked codes 2-3-2 & 2-2-1. Cleared codes and started up cold and immediately got 2-3-1 & 2-2-1 which now re-occur starting cold or warm. The Oxygen Sensor is showing a bouncing voltage in correct range on my digital voltmeter. Cleaned throttle body and Idle Air Control and can't find any vacuum leaks but problem persists. What should I check next?
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You might want to check the fuel pressure. It almost sounds like the pump is not delivering as required. A quick pressure check can at least get you looking in the right direction. I like to rig the pressure gauge in a way that I can monitor the it while driving - like going up hill with my foot heavy on the throttle.
--
Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)
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OK I'm a little stumped here. I replaced the in-tank pump which was dead. I had to replace the fuel sender as well because it was so rusted the metal return line broke off while trying to remove the rubber return line. Replaced the fuel filter as well while I was at it. Suspect it was original to the car as one of the fuel pump/filter tray bolts was shiny under it's complete coating of undercoating. 250,000 miles on a filter and main pump??? I guess so. Anyways the car is now running without throwing any codes. However the idle seems high, 1400 RPM in neutral and the car wants to coast much faster than before. However if I stomp on the gas it seems to run out of oomph and be unable to accelerate after a couple of seconds. The oxygen sensor is quickly oscillating back and forth from about .1V to .8v when I check it at idle.
When the in-tank pump was dead the car was having no problem accelerating on the highway so what's up now? The only thing I can think of as a restriction is maybe not having pressed the filter sock tightly enough onto the in-tank pump. Could this cause a fuel starvation problem at higher speed?
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Hi,
From I can tell, from my obscure end of the world, you are chasing a red bouncing ball but in this case it is probably red rust.
Getting rid of those pumps and filter is probably the answer or should have been. You have to be careful and keep those hoses from getting dirt inside them. A speck of dirt can kill a main pump. There are rollers in there just like a roller bearing. But you are up and running so that’s a very good sign you did good.
I need to ask about the fuel pressure regulator.
It might be just as old as the other stuff. Do you have any ideas on this?
It’s possible that it may be bypassing too much gas back to the fuel tank so the fuel volume/pressure is too low at high speed. Age of the FPR and the new pumps might cause them not to play well with the other one now? Just a thought.
Under acceleration the FPR is suppose to hold back fuel from going to the gas tank so the injectors get more fuel. This is a vacuum operated device and does the above when there is less vacuum because the throttle got opened and more air rushed in.
The lack of vacuum or more air pressure allows the diaphragm to move against the spring the check ball get closed down.
When the engine get all the air it needs the vacuum returns and opens the check ball to drop the pressure back to normal spray pattern with less fuel.
The normal status for the FPR, with the engine off, is that check ball stays closed holding rest pressure on the injectors for the next restart. This makes for a quicker start.
If you find that it takes a longer time to crank the engine to start, especially after an overnight stoppage, the FPR can be the number one cause for that symptom.
A rough running start in the morning can be to a diaphragm leakage into the intake manifold until the fuel is burn off!
On the nineties cars they have an ECU pre-prime mode that makes the engine start faster but if the FPR has leaked gas into the intake it still will run rough upon start up.
The symptoms can be the same if one injectors leaks over night too. Even though there are four injectors versus one FPR it is rare that it’s one injector but not impossible!
FPR’s have been sited for many more failures.
As far as getting up to 1400 rpm idle the engine should not be able to get that much AIR past the throttle plate. Look for a problem there or a vacuum line off.
The idle air control motor has to be sealed to the two hoses that go to it.
All those hoses under the manifold have to be hook up to the flame trap and on top of the intake manifold.
An Oil Swollen hose or spilts on the underside that you cannot see will bite you.
Any of those hose openings is going to behind the throttle plate. That in turn is Uncontrollable Air!
I Hope this post puts you to snooping in the right places or for any future symptoms.
Phil
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Thanks. I think I'm going to have to try and do a propane test to see if I can find an intake manifold leak or something. Unfortunately I have no way of checking the fuel pressure. Turns out I was wrong about not throwing codes any more. When I checked it again today it is still showing a 2-3-2 although there is no longer a Check Engine Light. The in-tank pump seems to have taken care of that. I don't think it's the FPR because it has always started on the first turn of the key and it doesn't run rough at all, just fast. It is still trying to surge when driving down the street. I ran the O2 sensor test and pulling(and plugging) the vacuum off the FPR sets it rich and a vacuum leak sets it lean. Hooked up the sensor bounces nicely back and forth from around .2V to around .8V. Like you say the high idle should be from un-metered air getting in somewhere but I've been over all the hoses and can't find anything.
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Yes, check for an intake manifold leak. No noise yet? Normally you can hear them with a stethoscope or hose.
As an aside, the Bosch main fuel pumps are very robust. They can last the life of the car. Sold my 240 with 300k and original main pump. My 850 had over 250k on its Bosch pump when I sold it recently.
Oh, inspect the main pump's check valve. Doesn't sound like a problem there but still worth a look.
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Propane test didn't show any manifold leakage. However today I decided to try an experiment. I removed the IAC hose from the intake manifold and also for access the cabin vacuum line & PVC vacuum line. When I start the car and then block the IAC port into the manifold the idle will drop to what seems like a normal level. The only air moving would seem to be through those two vacuum ports and maybe a little leakage around my finger. I suspect my IAC is at fault which might also explain the surging if it is opening and closing a little bit while driving. Does that sound like a reasonable guess?
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You might try removing the IAC valve, clean it out and test it with 12 volts to see if it opens and closes.
Dan
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Already had the IAC out and cleaned it making sure it moved smoothly but hadn't tested it so took it out again. Ohms out at ~8 ohms as per spec and responds to 12 V by slamming open. Oddly enough the car seems to be running a little better as I can hear the RPM drop slightly a couple of seconds after starting. Decided to take it for a test drive and the surging and wanting to pull seems to be gone. It's still throwing a 2-3-2 code so I decided to look at the O2 sensor signal again and now it is not fluctuating but sitting about .7 to .8V which would indicate a slightly rich condition if I'm not mistaken.
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Forgot to ask a question about the IAC as my previous experience was with the 3-wire style and this one is 2-wire. Is the window supposed to close completely when it is not activated? Mine stays open about 1/16" or so.
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Yes that's normal, did you clean the throttle body and flame trap/ PCV system?
Dan
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Yes I cleaned the throttle body and did the blow test on the PCV line. Lots of back pressure with the oil filler cap on, no back pressure with the oil filler cap off.
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Try first measuring the rest voltage from the AMM. On a 92 that's the red/white wire leaving the AMM connector you can reach by peeling back the boot. Measure it with key on engine stalled.
Then clean the connector on the AMM side, inspecting the harness side. Exercise it some (reseating it) to wear through any light oxidation layer. Do the same with the two grounds at the fuel rail mounting screws.
Next reset the ECU by momentarily lifting fuse 6 clearing both the codes stored and any adaptive trim.
Repeat the measurement of rest voltage, which is the AMM's output signal to see if anything changed by the cleaning you did.
This might be your lucky day, but there's no really good substitute for measuring fuel pressure, even though I describe the same all the time based on the likelihood of having an intact FPR. Doesn't your '92's rail have a Shrader fitting? I ask, not suggesting how to attach a gauge, but from curiosity that you haven't mentioned it.
--
Art Benstein near Baltimore
Bad decisions make good stories.
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OK that made some sort of difference. How long does the ECU take to 'learn'? Nothing else I've done since the pump and filter have really changed anything. Re-seating AMM/MAF connector several times made no difference in the voltage(about 1.35V). Not surprising as I had already had connector off a couple of times and had AMM/MAF out and cleaned it. Cleaned grounds as suggested and reset ECU. When I started the car it was trying to set a low idle but I kept having to stab the gas to keep it running until it had been going for a few minutes. It was surging about 3 or 4 times in a 5 second period. Took it for a test drive of a few blocks as I had somewhere I had to be and it would run smoothly at higher RPM under load. At a stop light it wouldn't stall but it would be surging. No tach in car but it sounded like it was trying to idle at normal RPM. Parked and came out again when car was cold. Again it had trouble not stalling while trying to idle after startup. After driving again it is able to start without trying to stall but put a tach on it back in garage and idle has returned to around 1200RPM. Checked O2 sensor as well and it is again not fluctuating but sitting about .08V. That's twice now I've seen it sitting and not fluctuating although all the other times I checked it there was normal behaviour.
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Sounds to me like your car is exhibiting normal limp-home behavior, after the ecu has given up on matching the air/fuel ratio to the information provided by its senses (temperature, air mass, oxygen in the exhaust, rpm). From my experience and others' the adaptive trim works in about 10 miles of driving, but it can take even less than that to give up on faulty inputs, causing limp-home rich running.
If you repeat the reset routine, you can verify for yourself. It doesn't tell you what the trouble is, of course. Could be anything from a leaky fuel pressure regulator to holes in the exhaust system. I've found 1.4V as about the "floor" for AMM operation in the -016, but this is just a series of anecdote. If you don't find a fuel pressure problem or trouble with the coolant temperature sensor, you might want to locate another AMM to try. They do go South. And its hard to say for sure except by substituting another of known performance.
--
Art Benstein near Baltimore
If you have a lot of tension and you get a headache, do what it says on the aspirin bottle:
"Take two Aspirin" and "Keep away from children"
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Bought a fuel pressure tester but of course it doesn't fit due to the bizarre angle the schraeder valve is mounted to the fuel rail. Have ordered a 90degree tire stem extender as I can't find anyone in this town with stock. Should finally be able to test the fuel pressure in another week or so.
Not sure about the 1.4v minimum for MAF sensor as have read elsewhere 1.0V. As a test I disconnected hose into MAF and blew into MAF thru a piece of tubing to see reaction. Barely breathing into tube was causing rapid elevation of voltage reading. As an further experiment I reconnected MAF, reset ECU via fuse 6 and started car while observing output of O2 sensor. Ran until car was warm and voltage never went above 0.08v which would I believe indicate extremely lean. This is I think the third time I have observed incorrect readings although every other time it was oscillating in normal fashion and when I specifically tested for lean and rich conditions it responded accordingly. Am I correct in assuming that once the ECU goes into limp-home mode it will stay there until reset. If the O2 sensor is intermittent it could have forced limp-home and then when I was checking things it would have looked fine.
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Getting a secure connection to that pressure test point on the 92- rail without the expensive and possibly NLA Volvo adapter has been a challenge for which I've not yet read a satisfactory solution. Many have questioned the use of right-angle tire adapters and other fittings designed for folks with dual wheels and trucks, but none yet have given us a supplier and part number for a solution proven to work. You could be the first!
We have one Volvo in our fleet with that Schrader, but long ago I'd cobbled an adapter to the 14mm flare rail feed fitting, so I, personally, have no need of one to fit the tap.
Interesting you see lean now, because limp home setting is purposely rich to keep the engine from damage. May be your fuel pressure is faltering. Certainly sensors can be intermittent, or more likely, wiring damaged. And if it was absolutely accurate, what you said, about the voltage never going above 0.08V, then your oxygen sensor wiring is shorted to ground. It should start out cold at 0.5V and, within 20 to 30 seconds begin to rise or fall, because the stoich point is marked by a low current originating in the ECU. Check the heater by measuring its resistance warm and as it cools.
Of course you're not sure about the 1.4V, but I'm confident our AMMs in LH2.4 would not work at all if all it saw was 1.0V resting output. There are many example posts on this forum where someone attempted to use "MAF Cleaner" to clean the hot wire AMM and ruined it somehow. Many more than say it helped. I can't tell you how they did it. I've not made that mistake yet to learn from it.
I've not seen an AMM that would not respond. A simple tweak of the corrugated hose will do what you did blowing through a tubing, but the offset and gain have to result in a match withing tens of millivolts to the airflow being measured. The rest voltage is just a clue to the offset. You won't be able to recognize a working AMM using a multimeter.
"Am I correct in assuming that once the ECU goes into limp-home mode it will stay there until reset."
Good question. In my experience it depended on what forced the mode. I've also seen that it can be reset by using the long-press code reset for some causes, while others needed the power reset (fuse 6 in yours). The 113 code is the best example I can recall for that behavior. I wouldn't assume.
--
Art Benstein near Baltimore
I know a guy who's addicted to brake fluid, but he says he can stop any time.
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Well the slow boat from China finally arrived and I got my 45 degree and 90 degree valve stem extenders. Tried the 45degree today and it worked great showing 35 pounds of fuel pressure. I don't think it likely matters where you buy them from but this is where I got mine https://www.tmart.com/search.html?typeid=&q=90+degree+tire+stem
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Thanks for your help Art and everyone else too. Looks like it was the AMM/MAF. There don't seem to be any local wrecking yards with Volvos in them anymore. Had a great one 40 minutes away for years but it is now gone. Found a guy wrecking a 1989 740GL just 20 minutes from my house and seemed like it would have same AMM so went and had a look and it was the same unit. Brought it home and plugged it in and got 1.49V static so installed and car now seems to be running normally. Still haven't got the adapter to do fuel pressure test but will report back on results when I finally get it.
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Thanks Art. I'd wondered if it might be in limp-home mode from something I read elsewhere but it didn't seem to have other usual symptoms. Apart from the one time the day this all started the car has never had a problem starting on the first crank. That's also why I don't suspect the FPR. I am hoping to get a pressure tester in the next day or so. My car does have the schrader valve in the fuel line but oddly enough none of my auto shop teacher buddies have a pressure tester either.
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Did the blow test on PCV hose. Lots of back pressure until oil cap loosened. Still haven't been able to get next to a fuel pressure tester. However I did put a vacuum guage on the line to the Fuel Pressure Rugulator and with the engine running at about 1500RPM it was showing 20 inches. Does that sound about right to anyone?
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A worthwhile investment:
https://www.harborfreight.com/fuel-injection-pump-tester-62623.html
--
Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)
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Thanks Chris. I didn't think it likely that it was a pressure issue as it had lots of power on the highway. Just checked though and the in-tank pump does not appear to be running. Getting ready to pull it now.
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