Ok, guys I need to get a couple heads together. I have no hair left to tear out. This one's kicking my butt.

1988 244, M47. Totally stock save for a nice GT steering wheel center I found for it and recently a set of 14" GT wheels.

This car has had an ongoing problem with loss of power when accelerating, and severe bucking until you're rolling on level ground at a good speed in 3rd gear... and it's getting worse!

I've been trying various things for months now and the owner has been committed to fixing it, driving it very little and trying to avoid hills due to the power issue. It's bad and I'm close to pushing it into the river. No, I am seriously going to fight this one out because I *HAVE* to know what's doing it.

Here's a similar post about a similar car:
http://www.brickboard.com/RWD/volvo/1085620/220/240/260/280/1986_240_bucks_taking_stick_shift.html

The items mentioned in this are exactly what I've been going after, and were primary things mentioned to me as guesses from a host of other local Volvo mechanics.

Here's what I've done to go after this problem (and it persists):

New fuel pressure regulator (old one was just about rusted out anyway)
Intake manifold gasket
Inspect intake boot from AMM to TB (no cracks)
Clean throttle body
Replace AMM with another one that ran fine on an 88 745 (neither made a difference in either car)
Replace fuel filter
Replace hoses to flame trap (the one to the breather box was spectacularly bad and the big one to intake was falling off, no change when fixed)
Tuneup: plugs/cap/rotor twice
Check timing*

Known issues still to be resolved:
Trailing arm bushings are bad. Shot, blown right out. That's some of the bucking, I know. Torque rod bushings were replaced a year ago. They were typically cracked but not failed. The car actually feels just fine riding down the highway, but I know that contributes.

Clutch is tough to get a proper adjustment but does not slip... I suspect a pressure plate going bad contributing to some drag that makes reverse crunch a bit when engaged, but getting going, the bucking is NOT from engaging the clutch. You can release it gently, get moving, and then as you give it gas, it begins to buck and jerk BADLY.

In any case, the engine seems to have NO power when trying to accelerate beyond a very moderate rate. It revs just fine, sounds strong in fact when revved in neutral.

* I am tearing down the timing covers tomorrow AM to make sure the cam has not jumped a tooth. It would be nice to find it off a tooth but I find it hard to believe, given that it starts, idles, revs so nicely. I have to verify it though.

Open to any suggestions, thanks Brickboard!

--Rob Bareiss, New London, CT:: 90 745T, 90 745GL M47, 92 244 M47, 89 244GLT Turbo

My 1st 240 started bucking and losing power to the point it would barely make it up a hill 1 week after I bought it. Knowing absolutely nothing about EFI I was pissed and thought I wasted a hundred bucks, I dumped a can of fuel injector cleanerin it and it did nothing, then out of anger I beat the ever living dog snot out of it trying to kill it and then it started getting better and then ended up running mint. I think the cat was plugged or a ring was stuck and wailing on it end up fixing it. Ended up driving that beater for 7 years and did nothing to it less one oil change.


81 Bertone intercooled turbo , 92 940 turbo wagon, 84 (300k) dl wagon mint, 88 DL sedan 5 speed, 90 DL sedan, 85 GL sedan, 89 5 speed dl wagon (winter beater)

I would bet on air/fuel problems rather than electrical. I had the exact same symptoms on the 83 (LH 2.0) and it was a cracked intake duct between the AMM and throttle body - but you've checked that. Have you put a vacuum gauge on it? Should show about 18-20 inches at idle, if there are no leaks, ign. timing is right, valve clearances OK, etc.

If it passed a smog test recently, it's hard to see how the O2 sensor could be bad - maybe a little "lazy" due to crud buildup, but worth checking as others have said.

On my old Dodge Caravan, intermittent bucking and stalling, accompanied by no power on acceleration stymied our local garage who were excellent tech's. They finally took the van for a week, put a fuel pressure gauge on it and handed it over to one of their guys as a daily driver. Sure enough, when it began acting up, the fuel pressure was bouncing around. New pump, problem gone. An intermittent supply of electricity to a perfectly good pump could have the same effect. Try wiring an ammeter in series with the pump circuit and see if it fluctuates when the bucking starts.

If there is a dodgy connection somewhere, the ammeter may swing wildly as the pump demand requires more amps under acceleration, and the bad connection won't supply them. If it just shows a small drop in amps, this may indicate a restriction in flow - either on the suction or discharge side.

Cautionary note: as an old pal on the MGB board says - "when you have found one problem, don't assume that you have found ALL the problems".

Good luck!
--
Bob (son's 81-244GL B21F/M46; dtr's 94-940 B230FD; my 83-244DL B23F/M46, 89-745(LT1 V8), and 98-S90; and four old motorcycles)

Had a bad cat that would shift on hills and acceleration blocking the exhaust just enough to buck. Hit it and check for rattles.

Sock filter in tank? These can get pretty crappy, fall apart and restrict flow.

Internally swollen or deteriorated fuel line to filter?

A fuel pressure check does not necessarily indicate adequate fuel volume.

You may be getting a weak spark at the plug. Supposedly a bad ignition coil could do it.

Also check your total resistance (ign wire, plug wire, plug). Try to keep it below 12(? I think I read that somewhere, mine's around 8)kohm.
--
1980 245 Canadian B21A with SU carb but electronic ignition and M46 trans in Brampton, Ont.

Have you checked the fuel pressure? When the main pump went on my 760, the car would eventually only idle (and it would do that just fine), but would stall when trying to drive it.

I haven't. It's on my list to get done as part of this troubleshooting. I don't have a complete setup right now for fuel pressure testing. I had the pieces to allow a gauge to sneak out the back of the hood so you could read indication as you drive, but I no longer have that setup. Wish they put a schrader valve on the fuel rail like on some 940's.

--Rob

Do you have a tach? IF so, what's the tach doing when the car is bucking and jerking?

Also, bad motor mounts can torque the engine on acceleration which can warp the clutch and/or pressure plate.

No, of course, why would Volvo put a tach in a 5-speed car? That would be silly.

I've actually been considering installing one in her dash just for the troubleshooting of this issue. Probably should do that soon. I wish I had a small one I could pop into one of the side pods.

The trans mount is brand new, and the other two mounts look fine to me. I did think maybe excess engine movement pulling on a harness or vacuum line could be doing it but no such luck. Wouldn't be surprised to find a broken mount one of these days. The bucking can be really severe.

Thanks,
--Rob

Any luck Rob?

You've gotten a heckuva lot of good advice. I've not much to add other than to place my bet. It's either poor fuel pressure or a bad ground/electrical connection (perhaps even a connection behind the dash). Or maybe loose element in the cat... I guess I'm not much of a gambler. How do the spark plugs read?

I have a small tach that you are perfectly welcome to borrow. It's in an automatic car so it's usefulness is limited. I also have a fuel pressure gauge to offer, but it's not much use without a schraeder valve.

-Will

Rob,

Does this lack of power happen cold as well as warm?
--
Art Benstein near Baltimore

The short fortune-teller who escaped from prison was a small medium at large.

Hi Art (haven't said hi to ya in a while!)

The loss of power may not happen, or be diminished, right at first, but with one trip around the block, it's warmed up enough to happen continuously, every start except for the most gentle.

I've been reading through a couple of the other posts on this subject, and all seem to be similar- I *never* encountered this stuff with cars at the dealership when I worked there (when we saw a 240 as every other car). It's weird, its as if the newer fuels are compounding minor problems that these cars have always tolerated until now.

I've always thought of the LH 2.2 system as damn near bulletproof but lately it's making me wonder. Granted we're talking about 20-year old fuel injection components, so what do we really expect.

I may have left out a couple of other issues. The fuel pump, I found when replacing the filter yesterday, is an aftermarket one with the attendant hacked wires and replaced terminals- the guy actually spliced in extra length to the cables, and made my filter job easier that way. Thanks, I guess.

Also we did some work on this car back in June when it needed to pass emissions, and got caught up with, of all things a VIN # problem in the state's computer, so I paid more attention to the awful paperwork issue than the technical details. The AMM was adjusted then to bring CO up a bit and NOx down and the ignition timing was retarded and then advanced after passing the test. It's right on 12° now or it was when I checked it last.

I'm thinking of going after the O2 sensor, the AMM again, a full check for vacuum leaks, Techron for the fuel injectors, and then finally addressing the rear end bushings. I built myself a bushing tool finally! Doesn't hurt that we have an assortment of pipe fittings handy at work. All nice stainless steel!

I was supposed to go after the timing belt today but with a very long night shift, I needed to sleep this morning much more than I needed to tear apart a B230. Hopefully tomorrow.

All thoughts on this beast appreciated.

--Rob

Hi Rob,

I have the sense it is fuel delivery, but that's probably colored by my notions of what is wrong with mine, and never myself actually having experience with power loss resulting from a weak spark. The AMM might have degraded to the lean side, but I'd think you'd have hard starting too, even with the temperature adjusted enrichment.

Also, I'm time and again tempted to have a fuel pressure gauge I can see while driving. As much as I've searched for affordable transducers, the best deal I can find is the Auto Meter package (egauges.com for example) starting around $200. That's a chunk of change for diagnostic certainty.


--
Art Benstein near Baltimore

He often broke into song because he couldn't find the key.

Howdy Art,

...tempted to have a fuel pressure gauge I can see while driving.

I haven't tried this so I have no idea whether the diaphragm would stand up to fuel chemistry but, wouldn't a 5 Bar sending unit and oil pressure gauge work?

--
Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 52 year old fat man. ;-)

Yes, thought of it, but of course all of mine are installed on a block and the yards I visit don't have any these days. And the overriding nay is the thought I could be standing over the remains of a good carbecue with someone from the fire department saying "you did what???".

The thing about taking readings of fuel pressure, is it is like blood pressure. When you get the meter out you're not likely to be seeing it under stress. As long as there's the correct pressure, the volume of flow is adequate. If the flow is inadequate, the pressure will drop below the regulated value as soon as the injectors require more than the flow can supply. It is a pretty good indication the filter is not a suspect item if you can hear plenty of fuel coursing through the return line. But the pump's performance can change in a (ah) heartbeat. That's when it would be helpful to be watching the gauge.

I noticed in some of my searching, there are cars nowadays using a fuel pressure sensor (piezo type) to provide feedback regulation under control of the computer. The pump is actually modulated to vary the pressure. But these cars are not likely to show up in the pick-n-pulls yet.
--
Art Benstein near Baltimore

It may be that your sole purpose in life is simply be kind to others.

"And the overriding nay is the thought I could be standing over the remains of a good carbecue with someone from the fire department saying "you did what???"."

That certainly conjures an image. :-0

If I ever get a 100psi gauge setup I will try it. I'll let you know if I have to call the VFD.

My 2006 Kawasaki 650 has a pump that is regulated at the tank; there is only a supply line, no return line. According to the shop manual it holds a constant 36PSI. I haven't investigated the technology. It may be computer controlled. I suspect though it is spring and check valve controlled.

Now you have my curiousity up about remote pressure monitoring. I will have to do some reading...

--sd

A few random things to consider -
- shoot a timing light at the crank pulley, and blip the throttle. There should be smooth advance or retard with engine vacuum (this one has the ignition module on the passenger side, with the vacuum line to it, right? My '88 did) If the timing mark jumps erratically, suspect failed rubber in the harmonic damper ("dampener" to some). Make sure the vacuum line to the ignition module isn't cracked or plugged.
- this one's a long shot, but if you're pulling power the engine is reacting by moving in the roll axis against the engine mounts. Any chance that wiring is being compromised (stretched, grounded?) by that motion?
- if you have a good digital multimeter, run the test leads from the O2 sensor wire and ground into the car so you as passenger can observe the O2 sensor output as the car is driven. Problems in fuel delivery might show up this way.
- likewise, clip the DMM leads to the battery and observe the system voltage as the car is driven. Could be revealing.
- check ALL the grounds - battery to block & the intake manifold ground in particular, for integrity and low resistance.
- with the engine off, grab the exhaust pipe downstream of the cat and shake it laterally. Any loose sounds from inside the cat? A failed core can shift and block the exhaust outlet, but this kills power (short of stalling the engine) rather than making it buck.

From first-hand experience, a jumped tooth or 2 on the timing belt just limits power and doesn't cause bucking. Just won't rev like normal, under load or even in neutral. I doubt that's the problem.

From 2500 miles distant (but a former resident of Litchfield Co.) the seat of my pants says there's an electrical power interruption - either to fuel pumps, ECU, or ignition, in descending order of likelihood.

Press on, Rob!

--
In God We Trust. Everyone else, keep your hands where I can see them.

Thanks, Smitty--

I don't think the bucking really is 100% the symptom of the engine problem, whatever its nature is. I think the bucking is a result of rubber-banding of the suspension, driveline, and rear axle as a whole system. With bad TAB's, I think it magnifies what would otherwise be a hesitation or shudder.

I didn't note that I have recently replaced the trans mount on this car to help alleviate the jerking... didn't really help though the old mount felt like jello, all inflated and soft with oil.

Also, the car has a brand new cat, as of June, when it was replaced to lower NOx numbers for state emissions test. Emissions numbers came in nice and clean but only with somewhat retarded timing.

I was actually thinking that the harmonic balancer may have separated, giving me bogus timing info. I will check it tomorrow when I take a look at the belt. It has about 20000 on it I think since I did the timing belt. I hope I didn't screw it up, that would be embarrassing but at least we will know.

Will post back with results.

--Rob

Check out post below At "power loss and bucking when warm" by NOCKENWELLENRAD on Sat. Nov. 29 14:10

Do you have a idea of what the condition is of the gas tank and the pump in the tank.

You may have a quantity problem due to a bad tank pump. Especially under acceleration or going up hill on less than a half tank of gas. Dirty or plugged sock filter from possible rust in tank. Did you cut open the filter you replaced?

You mention that this might be someone else's car. Could they may be a miser and not kept the tank full enough to keep out condensation. Old gas?

If this is not the case. I want to blame the a AMM but you said that was rule out.

The 0-2 sensor and AMM are electronic mixture buddies. The FPR is outside of the computer. It would be hard pressed for it to cause the bucking.

If a combination condition exists of a "sluggish sensor" and or erratic fuel pump volume/pressure. The computer would try to compensate switching to rich with longer pluses and shorter pluses for to get lean. Air flow tumbles in the AMM. The cycle begins to repeat.

The engine begins oscillating because the AMM is doing its job!

Change to a known good single wire sensor. Cheaper! If no better. Then check the fuel supply.

I want to bet on fuel supply for the load/acceleration!

Happy Hunting but you may want to wear a warm cap for your head!

Thanks, machine man--

I haven't gotten into the tank, mainly because I'm afraid to in a car this old. The main pump does not strain, growl, or warble, and the car always starts immediately regardless of how much fuel is in it.

The owner was driving it regularly on the highway about an hour a day, until recently when she started school in town and now drives a lot less. The bucking has been happening since summer. She bought the car from me, and lives right downstairs, so it's been under my advice since she's had it. It's never abused, at least not since it was rescued from its prior owner who took some liberties with proper maintenance techniques. In any case, she's been keeping the tank full and it hasn't made any difference.

I didn't cut open the filter, but it did not pass any fuel out the outlet port when disconnected. The inlet side of it poured out, the whole volume of the filter was full of gas. Obviously it was passing some fuel when under pressure, as the did start and run ok.

I may try another AMM just to be sure what's going on with it. It doesn't ever stall, which is what I associate with a bad AMM- an 87 I had would stall under acceleration, just cut right off, if you accelerated hard for 10-30 seconds, and it was due to a bad connection actually at the AMM. Upon restart it would be fine until you accelerated hard again. This car is not like that one.

Thanks,
--Rob

Thanks for the reply.

Now that you cleared up some of the tank possibilities like old gas and rust. That leaves the in tank pump system.

Reading some of the other post that you have gotten it is still out there. I like the one abut jumping the fuse. It may work if you can hear it from the bottom of the tank or an ear at the filler neck. I've used a hose and ear trick there. When the tank is full its going to be pretty quiet!

As far as the filter draining. Thats normal because the filter paper is very fine and gas will sit on one side. If it had drained out a lot there would be a hole in the medium. I was curious about knowing if there was pump roller debris from the main pump or trash.

I read some real long shots in the mix of posts. I remembered one too!

It is, check the injector clips. The prongs of the injector and up inside snap on housing. I brighten the prongs with a gritty finger nail file. I spray the clips with T.V. tuner cleaner or contact restorer. They work on the ECU, grounding the circuit. A approximately 5 volt pulsed circuit. Corrosion is a bigger deal at these levels. Oh! Mine was the very rear injector too! Coincidence? Maybe the hood leaks. Always the rear something, I don't know.

You may want to skip this but...

The reason I suggest this is that after buying a used '86 that still had a Volvo warranty. Later the rear muffler fell off, the tail gate lock sometimes failed to unlock and it developed a miss under load. Especially going up entrance ramps to freeways. It lost power.

The dealer Volvo mechanics claimed it was "a" platinum spark plug. They were against them and only recommended their plugs. Wanted to sell me only the one plug. Weird!
I said if you change one why wouldn't you change them all for your reasons. I fell for it!

They charged me for a tune up diagnosis and the plugs. Not warranted. I paid for the muffler via the tune up! Plus the tail gate was to intermittent for them to find to fix excuse!

This was the second time since '78 a dealer screwed me. It was the last time anyone has ever touched any of my many vehicles.

On the way back 40 miles home it did the same thing! I was hot but didn't even want to deal with the dealer again! I mean never now.

Later. One thing at a time I got it. Now you got it. A long shot!

Well, it starts right up and runs fine at idle and once it's going down the road (level ground), and other than an occasional miss that I've heard, I have no reason to suspect it. I will check wiring to it and make sure it isn't abraded or possibly grounding against anything.

--Rob

Can you check the O2 sensor output to see if it's too lean? Probably you could even do this while driving with some long leads to a meter in the car.
Everything points to a lean condition under load, it would be good to verify that.

--
84 242Ti IPD bars&springs, 89 745 16v M46 IPD bars, 89 744 16v M46 IPD bars, 90 745 AW70, 91 245SE AW70 IPD bars, 93 245 CLassic M47

This is not related to the fuel level in the tank, right, not a situation of a broken up fuel pick up hose?

The only time I have experienced bucking in our Volvos it was fuel related- once running out of gas and another time a perforated pickup hose.

Might this be a fuel delivery problem? Intake pump functioning?

Randy

Thanks Randy-

It occurs regardless of tank level. I was thinking of the possible problems with the in-tank pump and pickup hoses, but I guess if it was leaking there, a full tank ought to make it better. Today's tests after filter replacement were with a nearly-full tank, and there was no significant improvement. It did seem a little stronger but only went from maybe "horrible" to "bad". The filter was definitely old and seemed to be pretty well clogged.

I do not at all relish the idea of diving into a 20 yr old tank to go after a possible bad pickup- it's likely to need a new sender even if nothing else is wrong.

A fuel pressure test is next though, I haven't done one yet.

--Rob

Have you checked the intank pump function?

If you pull the prepump fuse out and apply 12v to the right side of that holder the prepump should run. I have never heard of a bucking condition caused by a non functioning prepump but if it doesn't work you might want to consider it.

Randy

do you happen to have an extra set of properly functioning fuel injectors you can do a swap?

i have had similar troubles which were caused by bad injectors.

you might also try and swap in a known good ecu

I only have a set of injectors from an 89 hanging around. I don't think they're the same (LH 2.4).

I could probably scare up a set though. Maybe a good time to replace injector seals too?

Thanks
--Rob

You mentioned plugs/cap/rotor. How about them old ignition wires?
--
1986 Volvo 245

Hello Rob:
check wiring to crank position sender. Had a mysterious no-start for several weeks until I realized I had installed the CPS crooked.
Just my 2 centavos.
el raidman

Thanks Raidman, and good to talk to you.

This one's a LH 2.2 car though, distributor triggered: no crank sensor. Dist seems to be fine, and I can adjust the timing through its range easily. (They're often frozen in place.)

--Rob

I had similar symptoms on my '89 and traced it to a bad O2 sensor.

Hi there,

I'm curious about your O2 sensor leaning out the '89 so much it wouldn't pull hills. Were you able to change or forestall the symptoms by resetting the computer? Did it complain with code 113?

I know Rob's is an 88 and not adaptive, so I'd "lean" more toward a delivery problem on his neighbor's.
--
Art Benstein near Baltimore

Acupuncture is a jab well done.

Thanks, that's something I haven't checked out yet. I really didn't think that any of the fuel injection sensors (O2, temp sensor) would make such a huge difference but at this point I'm willing to try just about anything.

I wonder if disconnecting the O2 will help at all.

--Rob

Just disconnecting usually makes car have a tremendous loss of power especially on hills. You want to make sure the car is able to breathe,exhaust wise. no clogged or broken cats,mufflers.

I've had similar symptoms with different problems. My project car came timed at 0. Once I re-timed it -12 the car would take the hills where as before it barely had power and wouldn't accelerate on them. I have had bucking. Two things I remember. Once was a hole in the hose to the in tank pump but of coarse the half tank gave that away. The other was a bad connection to a chrysler distributor which I got rid of. Every time I went up a hill the wiring would move and the connection would loosen making it really buck. I've also recently solved another bucking problem with a vacuum leak at one of the nipples on the intake manifold. One of the extras next to the Idle control valve hose and flame trap vacuum hose. The .15 cent cap really solved the hesitation and cutting out problem I had. I replaced one TAB this week and that helped with the clunk sound and feeling that the rear axle was loose. Not a fun job although I expect the other side to be much easier now that I've got the order of bolts down. My car still has problems until it drives a couple miles then they go away, like stalling or loss of power.

Don't under estimate the effects of a vacuum leak is what I most recently learned.
Distributor wiring harness damage?
I know once when I washed the engine the 25 amp fuse got messed up but before it died the car ran crappy with missing and bucking.

Anyways thought I might throw in a couple ideas.