I thought I had solved my problems in my last thread, but I have new ones, so I thought I'd make a new thread.
After doing some work on my car that involved a new Idle Air Control Valve and Mass Air Flow sensor, I cleared codes and did a test drive which went well. After the test drive, I checked the codes and got 1-1-1.
Now we're a couple weeks into it, and I notice that when I try to accelerate onto the freeway or turn into traffic from a full stop, the engine will simply not accelerate until I stomp the accelerator or flip the overdrive switch to force the car into a lower gear. I initially suspected the vacuum system, as it turned up a 2-3-1 code later. This weekend, I took off the long corrugated hose off and checked it for pinholes, tears, or breaks. Shining light inside didn't show anything, and filling it with water didn't reveal any leaks, so I put it back on the car. I checked the other hoses for cracks or degradation, but everything looks fine. I ran the engine and squirted brake cleaner around but nothing affected the idle, so I concluded there was no leakage that I could find.
So, what else could do this? I remember when I did the head gasket job, I noticed the distributor was a few degrees off of the timing mark. I moved it back directly over the timing mark and made sure everything else lined up Top Dead Center. Now I'm wondering if that was not the right thing to do. I don't have a timing light, and don't really want to spend the money to get a new one right now. I'm good with electronics, so I looked up how to build a DIY timing light, but discovered I don't have the parts to build one, so is there a way to get the timing right without one? Or am I barking up the wrong tree?

 

With the ignition system you have on timing is set by the computer using the signal from the crank position sensor. Moving the distributor does not have any effect on the timing. On my first 240 ('89) I hooked up the timing light to and moved the distributor and watched that it had no effect whatsoever to the timing.

So are you now throwing the 2-3-1 code?

 

Yes, that is the only code I get now.

 

The 2-3-1 code is related to the computer not liking the readings from the oxygen sensor for the conditions it's reading from the AMM. Has your oxygen sensor been replaced? How is your gas mileage?

Having exhaust leaks upstream of the oxygen sensor can be read by the computer as a too-lean condition. When you have this type of condition your gas mileage will suffer as well. However, when I had leaks like that I never had the ECU throw a code.

 

Oxygen sensor replaced sometime last year, and I got a new Catalytic Converter to go with it; the old one was completely burned out.

I accidentally let my battery run down yesterday, so EVERYTHING got reset. The car runs much better and the only code I'm getting is 3-2-2. I checked the EZK codes, but I just get 1-1-1, so everything's good with the ignition system. I'll check the codes every day for the next few days, hopefully it stays that way.

 

Codes are still good, I get a 3-2-2 every now and again, but no lean/rich warnings, which is good. 5 out of 7 days I have 1-1-1 when I get home. Sweet!

Back to the engine hesitating; I had to deal with what I thought was a new Head Gasket leak, but turned out to be the Heater Core inlet hose left loose on the Head fitting. While I was digging around in there, I took the liberty of also double-checking whether my timing was dead center. What I discovered was that I have TWO timing marks on my Intermediate Sprocket, and I think I used the wrong one the last time I was in there. Well, I figured out which one was the factory mark and set it true, which put the Rotor a bit cockeyed from the mark on the Distributor rim like the last time I was in there and attempted to "correct" it. I buttoned everything up and disconnected the battery for 10 minutes to make sure everything reset and took her for a spin. I detected a slight hesitation accelerating from about 3 of the 10 or 15 stops I made, and it got better as I drove. Could that have been the culprit all along?

 

I doubt it. When I first purchased my '90 240 (used of course) it had a problem with hard starts when cold. Once running it ran fine and never had any problems starting when it was cold. I finally chased it down to a mis-timed half-shaft. The rotor in the distributor was off by quite a bit. Basically it was arcing within the distributor quite a bit leaving all kinds carbon marks inside the distributor cap. However, it really did not affect the running of the engine other than the hard starts.

 

Still getting hesitation at some stops, not all, and pretty often going down the freeway on-ramp, I try to accelerate slowly to get up to freeway speed without punching it, but it just doesn't go. Like it almost bogs, but that's not the right description; I press on the gas and the car kinda goes "UUUMMMMMM" like it's busy thinking about my request to go faster for a second or so, then all of a sudden it does, but gosh darn it, not when I WANT it to.
Incidentally, I replaced the exhaust yesterday; everything after the Catalytic converter to the tail is now squeaky new. This car has never been quieter...
I cleared the codes and took it for a test drive to make sure I'd tightened all the clamps to the necessary tightness. Nothing fell off, so I figure I did good. Did a 2-mile loop on the freeway, then about 5 miles worth of stop-n-go town traffic back to my house. 1-1-1. Sweet!

 

I can't remember back to the start of your thread but did you check the functioning of your in-tank pump?

 

I replaced the Tank Pump and the Main Pump a few months after I got the car about three years ago because the car just wouldn't start one day. I figured out a year later that it was quite probably the main fuse in the engine bay, but that's another story. Anyways, basically I have two brand new fuel pumps and they work beautifully. Just after reading your comment, I slid under the car, pulled the fuel line intake off the Main Pump, and hit my jumper wire (alligator clips on some heavy speaker wire connected to a hand-held switch) from Fuse #6 to the right side of Fuse bay #4. Fuel poured out of the line into my catch-bucket strong and fast, so it ain't my Tank Pump.

 

OK, I've lost a lot of sleep looking at what this may be, and I finally stumbled on something. The Knock Sensor.
See here:
https://www.brickboard.com/RWD/volvo...tle_lh_24.html
here:
https://www.brickboard.com/RWD/volvo...diagnosis.html
and here:
https://www.volvoclub.org.uk/faq/EngineSensors.html (scroll down to the "Knock Sensor" section).
In the third link, it mentions that a failed Knock Sensor will throw codes, but the poster at the first link noted that no codes were thrown, but the car had "flat acceleration", which sounds exactly like what I'm experiencing.
The Bentley Manual doesn't mention the Knock Sensor at all, as far as I can find, which is disappointing.

Thoughts?

 

Well, I done did it. Puttered down to O'Reilly and asked after my order of a new Knock Sensor, brought it home and installed after letting the engine cool down a bit. I disconnected the battery before doing the work, so the system and all the codes were clear before I took it for a test drive. It was disappointing at first, stumbling through the first two cross-street stops, but got better the longer I drove. Even at that, it was MUCH better. It may have stumbled for a moment before going through the main intersection down the street from my house, but at least it didn't craaaawwwwlll through like it did last time. Hitting the on-ramp, I was doing the speed limit within 50 feet after the turn. Previously, it would putter halfway down the on-ramp before finally figuring out that speed was necessary. Hopefully that was all it needed. I'll keep driving and report back.

 

in your post #1 you said you replaced the MAF - do you recall what brand the replacement was?

 

Genuine Volvo. I spent the extra money for it because I wanted it to be as reliable as possible. If that wasn't available I would have went with a Bosch unit, and on a budget I'll get Delphi, but nothing else.

 

UPDATE: My wife took the car this morning for some grocery shopping, and she gave a good report afterwards; a very small hesitation going up the hill to her first destination, but nothing after that. Thumbs crossed.

 

LH 2.4 does a little learning the first few runs after the battery has been disconnected, but it shouldn't be so much as to make a noticeable difference in drivability, its more like fine tuning the mixture so it can anticipate the Ox sensor readings.

 

Well, whatever is happening, a new Knock Sensor made a world of difference. I'm still a little paranoid, so I agonize over every little stumble. I went out with my wife to pick up a Craigslist deal, and had to wind through downtown with its infinite array of stop signs and cross-streets and back-alley accesses, but the car performed admirably. I swear, if I keep going like this, I'm going to end up with a new car. "I got it one piece at a time / and it cost me every dime..." (apologies to Mr. Cash).

 

Its curious that the bad knock sensor didn'tt throw any OBD blink codes.




if you drive these things hard, they really shoudl ahve premium gas or they will ping and retard under various high load conditions, like hot weather, climbing a long grade with a load and the throttle flat out.

the B230FT turbos need premium pretty much all the time unless you baby them.

.

 

Interesting. I looked up "1990 volvo 240 fuel octane" and got a range of opinions from "If you don't have problems with 87 octane, keep using it" to "Volvo says use high octane, period." A quick glance at the Owner's Manual confirms that they specify 91 (R+M)/2 fuel, with 87 as the minimum. According to WA state fuel standards, I should be getting no less than 87 from the Regular, and no less than 92 from the Premium

Indeed, the symptoms of knock from a too-low fuel octane match what I've experienced, and I've noticed under certain conditions they have come back after I replaced the knock sensor. There is an intersection up the street from my house that is on a very slight grade, and I always try to gun through it with a left turn because the light is notoriously short. Two days ago, my car started with the "putter through the intersection, then zoom down to the on-ramp" chicanery it was doing before. I'll try filling up with Premium at my next fill-up (due in a day or two, so it'll be soon) and see what happens.

 

my 92 turbo 740 definitely wanted premium. my 87 non-turbo was OK with regular under most conditions