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Just like the title says. For anyone wanting to know, the saga of my car's troubles can be found with a simple search, but the basic gist is that I have one last demon to slay before I give up and take her to a shop.
I recently replaced a bunch of hoses that looked like they may be suspect, and the car ran a little better for a while. Now, the hesitation whenever I accelerate from a full stop has gotten to be a full almost-stall. It starts just fine and idles smoothly. When I have to accelerate from a full stop, it coughs, belches, and stumbles before finally zooming, unless I touch the gas pedal like it's made of heirloom porcelain, and then I putt-putt through the intersection like Mr. Magoo. It's gotten to where I'm almost a road hazard and I need to fix this before I get creamed the next time I go down the freeway on-ramp heading to work.
My attention has moved to the Throttle Position Sensor switch (one of the last parts I haven't replaced). A curious thing happened after I did the diagnostic on it recommended by the Bentley Manual:
- Rotate the throttle all the way open.
- Press the Diagnostic Unit button for 2 seconds twice and wait for the LED to start flashing
- Rotate the throttle all the way closed
According to the Bentley Manual (and others) If the switch is bad, the LED on the Diagnostic Unit should flash, but if it's good, it should display a 3-3-3 code.
I get a 3-3-2.
I can't find anything anywhere about what that means, and I don't want to drop 75 bucks on YET ANOTHER part that won't make a difference.
Any ideas? I've replaced everything I can think of BUT that switch. Is it most likely the culprit? Or should I start looking at the Fuel Injection system? Or...
Sounds like MAFS problem to me, (Mass Air Flow Sensor)... Unfortunately, no easy way to test it, plugging in another one is the way I do it.
Another possibility is the fuel pump getting tired.
Don't rely on the OBD system too much, it's wrong or inadequate often.
3-3-2 is actually an OK indication for the TPS at idle.
Check the throttle position switch by turning the throttle pivot wheel slightly from within the engine compartment. The LED should go out and then flash code 3-3-4 which indicates proper operation of the TPS. If no code is flashed and the lamp keeps flashing, the TPS is faulty.
After the tests, the LED should keep flashing.
Remove the ignition coil center lead and crank the starter motor; the engine will not start but it will turn over. The LED should go out, then flash 1-4-1 for the RPM sensor. If no code is flashed and the lamp keeps flashing, the RPM sensor is faulty. Reinstall the coil lead and turn the ignition key ON to KPII.
Install the cable into socket 2 for fuel injection-related tests.
Press the button two times for >1 and <3 seconds each. The LED lamp should flash.
Activate the following sensors. If the LED diagnostic code shown (note: this is not a fault code) is present then the sensor or component is OK:
TPS OK in full load position (when throttle is moved from full load) 3-3-3
TPS OK in idle position (when throttle is moved from idle) 3-3-2
I hope it's not the MAF, I don't want to spend another $200 to be disappointed again.
Both fuel pumps are brand-new; maybe a year old or so.
I rely on the OBD system because I have no other recourse; I don't know any genius Volvo mechanics, and although I can turn a wrench pretty good, I'm no Mr. Fixit. Although I suspect I'll know quite a lot before this is over...
I tried all the diagnostics you mentioned, but I get 3-3-2 for the first one (TPS OK in full load position) instead of 3-3-3. The next two are OK.
Here's another idea: The knock sensor was the culprit a few posts ago, but that only helped marginally. How dangerous would it be to unplug the knock sensor, or un-bolt it from the block, just to do a jaunt around the neighborhood and see how that goes? That would eliminate the knock sensor as a factor if I still get hesitation. Then I'd be looking at why my engine is knocking when I'm now filling it with higher-octane fuel (it's been a few months now) and I've replaced all the hoses that I suspected were bad.
I realize I may be grasping at straws, but I'm getting desperate...
So I was thinking about it again, and it seems strange that doing the first TPS test would give me the 'success' code for the second test. That tells me that while the switch isn't completely bad (flashing LED after test), it's detecting that I'm going from Low to High when actually I'm going from High to Low. As soon as I realized that, I went ahead and ordered a new TPS. I've already thrown enough money at this car, what's another $70? We'll see tomorrow after the part shows up at the O'Reilly store...
OK, I got a new Throttle Position Switch on there; not a pretty task as I did not take the throttle body off to do the job. Next time (if there is one), I will. I did the tests and got the same codes, so that was a bit disappointing, but I took it for a test drive just to see if anything had improved.
The car drives MUCH better. NO hesitation at the infamous intersection or the freeway on-ramp, but later on I do notice a bit of hesitancy, especially if facing uphill. This is with a full tank or not, and I've checked and re-checked both fuel pumps, so it's not that. I have replaced all the hoses that could have had a vacuum leak, so I'm confident that is taken care of. By the way it behaves, I'm wondering if the Throttle Body itself is worn at the bushings, letting extra air in. I've had problems years ago with a '73 VW Super Beetle that the carburetor needed new bushings, and I eventually just bought a new carb. So now I'm wondering if the problem solved by a new TPS was not the switch itself, but the rubber O-ring was worn, letting air in at the bushing on that side. Can a Throttle Body be rebuilt with new bushings or seals? Or is a new TB in order? Or not?
Yes. New cap, rotor, wires, and plugs. I've pulled the plugs and they all show that slightly tan-ish coating that I always see as "normal" on all the spark plug inspection charts. I pulled the cap recently and nothing looked unusual.
I pulled the codes and still getting the 2-3-1 code consistently so there's still a vacuum leak. O2 sensor is new (well, a year or two old or so).
New TPS didn't fully solve the problem, and I started to notice that there were "sweet spots" in the accelerator travel where I'd have to kind of tap/pump the accelerator before pulling out into an intersection to make sure I had enough 'get-go' before actually pulling out, else I'd cough, stumble, and wheeze through the intersection. Embarassing. That made me think there was some problem with the bushing. I looked up diagrams on Volvopartswebstore.com (handy resource, that), and found my problem.
Where the throttle flapper shaft pokes out of the throttle body, behind the throttle lever and spring, there is a little formed rubber seal. Part #419568. It's only $6 USD at most places (though the shipping was highway robbery) and it arrived last week. I finally got a break in the weather, took the nut off the front of the shaft, pulled off the throttle lever and spring, and dug out the old seal with a hook & pick set. It crumbled as it came out, and was hard as a piece of plastic, not the supple rubber it was supposed to be. I swabbed out the hole where it goes, put the new one in, buttoned up everything, pulled the battery cable for a half hour to reset the codes, and went for a test drive.
Night. And. Day.
No more hesitations, stumbles, or wheezing through the intersection. No more having to stomp it to the floor to get up to speed on the on-ramp. No more car hesitating and almost dying before pulling up the hill where my house is. 1-1-1 code on the diagnostic afterwards.
I guess tomorrow morning will be the 'acid test' as it was always worse in the mornings, but I actually have hope now. I'll report back with results...
OK, solved the acceleration problem, now it's randomly dying when stopped. Like at a traffic light, or waiting to turn onto a busy intersection, but not every day. My wife drove it one day and it died on her 3 times. I drove it the next day with no problems. I drove it this morning, and it died on the way in the gate at work. I don't get the high idle when parking though, so that's a good thing, but it's not idling very smoothly. WTH?
You know the funny hose that sticks up off the intake manifold and it's got a flat check valve on it? Just looking over the engine for bad hoses yesterday, I got a thought to take the thin hose off the end of it while the car was idling. The idle got smoother. WTH? And when I press the accelerator when driving, I can hear the hiss of the vacuum tank from under the dash. I hope I don't have to replace that thing...
Codes are 3-2-2 and 2-3-2. The MAF is different from the one that was originally in the car. The old one had a wire strung on a fork kinda doodad, and this one has what looks like a circuit board in a wind tunnel, maybe that's why I get the 3-2-2 error, and I should hunt down a wire-type? IAC is new, MAF is new, O2 sensor is new, main air intake accordian hose is new, bunch of other hoses new, but not all, maybe I should replace the hoses connecting to the IAC and the flame trap? I just don't know...
Hissing noise from under the dash upon acceleration or when you shut the car off indicates the black/white vacuum check valve isn't working. Easy thing to check. Just remove it and try blowing air through one end and then the other. It should only go one way (into the intake). If it doesn't it's a fairly cheap and easy fix.
Any idea what that part number is? I can't find it in my Bentley manual, and the closest I can find is IPD's part number 105628 or 244973. If I look up the OE part number elsewhere, it's called a "brake pressure check valve", but IPD makes it clear it's for the vacuum system between the engine and the vacuum tank. Are they interchangeable? Here's what I'm looking at:
I understand I'm only looking for the plastic bit in between the hose ends, but maybe those need replacing too...
i had a lot of vacuum leaks behind the dash so i just capped that line off. the climate control system 'should' default to defrost.
i turned my vents manually. however, i don't have the issues of stalling you describe....
that is indeed a vacuum check valve, the black-n-white thing in the middle of that stack of hoses. there's normally one of htose between the intake manifold larger vacuum line and the brake booster, and maybe another or maybe a T off the same one going to the dashboard HVAC control stuff.
My brake booster has a right-angle check valve at the junction where the hose connects to the booster body. I contacted IPD to ask if the part they called a "Climate Control Vacuum Check Valve" was indeed the same as the part in my picture, and if it was interchangeable with the check valve found on many booster hoses. They confirmed both, so I ordered one. We'll see how it works when it arrives.
It has arrived, and the old one won't come off the little bit of hose, so I'm going to go down to O'Reilly and get a 3/8" I.D. bit of hose. Hopefully they have one that's for high heat applications. The bit of rubber on the other end is OK, but I'd like to source a new one. Anybody have any ideas of the part number for that? It's a short bit of rubber that's ~9mm I.D. on one end, and a 2mm or 3mm hole on the other end for the vacuum pipe elbow to stick in there by friction. I can't find anything in the Bentley manual about it, and Volvopartswebstore doesn't have give any clues either.
I forgot to do the airflow test on the old one, so I tried it just now and it seems to block air one-way just fine. I'll see how she does with a new one...
You have to improvise on the hose. At this point these kinds of parts are NLA, if they ever were, from Volvo. But if the old valve is OK, then leave it alone, not much to it, it either blocks air one way or it doesn't...
You have to improvise on the hose. At this point these kinds of parts are NLA, if they ever were, from Volvo.
Gotcha. The old one seems to still grip OK, I'll probably stick a low-grip hose clamp on there eventually just in case.
But if the old valve is OK, then leave it alone, not much to it, it either blocks air one way or it doesn't...
Well, I already bought the new one, and the symptoms seem to point to a bad valve no matter what my testing revealed, so I carry on...
I bought a piece of 3/8" (close enough to 9mm) I.D. heater hose from O'Reilly, so it should be OK with the heat, and it fit pretty snug so I'm happy with that. I cleared the codes and took my wife out for a test drive in town so there's lots of stop-and-go, parked it a couple of times to take in a park and a beach, went up a very steep hill to put some stress on it (which it tackled handily) and got back home after about an hour. No more hissing under the dash, and the air direction flaps work fine, so I'm happy about that. I read the codes and the only one that showed up is that damned 3-2-2, but at least it isn't throwing the "lean or rich" code anymore, so I think I got the leaks handled now. I'll give it another week or two to settle in and see how she does.
OK, I replaced the MAF because I suspected I simply had the wrong type, even though the part number matches. The engine function got worse; cough and sputter and nearly dying every time I try to accelerate from a stop, but a few seconds later, it's hustling down the street as if nothing had happened. I no longer get the MAF hot-wire burnoff error though, and I get 2-3-2 pretty consistently now. I read some more, and watched a few videos, and came to the conclusion that maybe my fuel injectors needed new O-rings. Bought O-ring set, replaced O-rings, spacers, and caps. Cleaned out the pits where the injectors fit in the engine; they were filthy. Replaced injectors and buttoned everything back down. The symptoms still have not cleared up, but now none random or intermittent, these happen EVERY time. I clear the codes and go driving:
- When I'm driving on the freeway, I press the accelerator to get into a passing lane to get around a slow-moving truck. The car slows down as if it's bogging, then slowly picks up speed.
- When driving around town, and I'm stopped at an intersection, when I press the accelerator to go, the car shudders and coughs, then suddenly picks up speed quickly. Kinda like the car is clearing its throat before saying "vrooooommm!"
And still the 2-3-2 when I get home. There's gotta be an air leak somewhere, but where? I'm going to pull out all the hoses I previously checked as good and see if I can find any holes.
Hesitation at acceleration - it's getting worse
