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#1 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() Hi guys,
I have a problem with my 760GLE, aw71, 88, equipped with lpg - the automatic trans is shifting down too early, (because) engine lacks power. List of things I have changed: Ignition: new sparks, spark wires, distributor cap, distributor rotor, both knock sensors, checked coil - both primary and secondary impedance ok, cleaned connection between body and power stage, tested with another ignition ecu, all connectors cleaned. Fuel system: new bosch o2 sensor, new fuel pressure regulator, new coolant temperature sensor, new thermostat, tested with another fuel ecu, tested with another air mass sensor. Intake: Throttle body cleaned, idle valve cleaned, also tested with another one, cleaned crank case ventilation, TPS sensor work fine, throttle and kickdown cable are adjusted correctly, checked for vacuum leaks. And of course all filters, oil, .... Valves has been adjusted. I have installed led diode to the O2 test port - and it toggles (so mixture is correct, not too lean or rich). Idle is smooth, no disturbances or surging. But the diagnostic diode I have installed toggles twice when rpm/s are over 2000, and this is code for engine knocking. But engine is NOT knocking. At 2500 and higher, it doesn't toggles anymore, but as soon as I return to 2000+-300, it starts again. My opinion is that the transmission shift down too early because it "feels" engine has no more power at the higher gear, but I don't now too much about transmissions. This prematurely shifting is both on lpg and gasoline. My last chance is, that the fuel injectors are leaking (when running on lpg, the injectors are disconnected, but the fuel pumps are still running - to keep the system pressurized). But can it create a sound like engine knocking? ![]()
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Volvo 740 Turbo B204GT 1991 >project thread< It's the oversteer that scares passengers. It's the understeer that scares the driver. lazy PRV engine? Check >this< out |
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#2 |
Board Member
Join Date: Mar 2006
Location: Virginia Beach, VA
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![]() If you lock into 1st gear, does it still lack power? Is there any point when it transitions from having very little power, to suddenly 'full' power, while your foot is on the gas?
__________________
----- 1970 Volvo 164 M400, Virgos, Dual Webers, and A/C?! Someone else's project now! ----- 1990 Volvo 745GL 278k Miles No turbo, automatic. Regina with T cam. Too much traction. Dead and gone! ----- New to me as of May 2018 1992 Volvo 240 275k+ miles Auto, LH2.4, and the unlimited traction cheat. Catching it up on neglected maintenance. ----- |
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#3 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() On 1st gear, it seems to me as it doesn't lacks power. Also on full throttle (kickdown), it seems to me as accelerating well, but I am not 100% sure with that as I am living with this issue too long. Between these two situation, engine power is pretty bad.
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#4 |
Board Member
Join Date: Mar 2006
Location: Virginia Beach, VA
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![]() This sounds very similar to when I had two ignition issues: Spark plugs gapped too wide, and a spark plug wire loose. Car would miss at idle (not a symptom in your case), and miss all the way up to about 1800 rpm, when it seemed to "wake up" and give full power.
If you put the car in park and rev to about 1500, will it hold at that speed, or does it fluctuate? You mentioned you tested the coil- do you have a spare that you know works well in another car? I don't have any experience with the V6's, so I don't know if it uses just a standard Bosch coil or not. |
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#5 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() The sparks plugs are new, and it was also bad with the old ones...
Spark wires are new, the same was with the old ones... There are no problems with idle speed even if it is 800 or 1500... The coil is standard Bosch, it can be defective although both impedances are ok? Some kind of leakage when operating? I can use coil from friend's car for test. |
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#6 |
Board Member
Join Date: Mar 2006
Location: Virginia Beach, VA
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![]() Sorry, you can disregard my idea about the coil.
Another thread (with a vaguely similar issue) I replied to made me think of one more thing. Though you said you checked for vacuum leaks, that doesn't rule out vacuum blockages. Is there a vacuum line running to your distributor or ignition controller? If so, has it been replaced in recent memory? |
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#7 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() No, to the distributor leads just the spark wires and coil wire.
Ignition controller - you mean the ecu? There is just one big electrical connector connected to it, no hoses. |
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#8 |
Board Member
Join Date: Mar 2006
Location: Virginia Beach, VA
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![]() I give up
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#9 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() What about the knocking? When it is detected, the ignition timing is retarded so the engine has no power. But what can cause the knocking, I rerouted the wires from the alternator and also installed ferrite cores to the knock sensor wires, but it does not help - so it is probably not caused by electrical interferences, but by mechanical...?
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#10 |
FWDFTW
Join Date: Jul 2003
Location: Waxhaw, NC
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![]() Piston slap can look like knock.
I think you should kill the fuel pumps when you are running on LPG. This will extend the life of the pumps. It doesn't take long at all to prime the system once the relay is activated.
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DD: 2004 S60 on copper Pegs Current project: 2004 V70 T5M |
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#11 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() Switching off the pumps is scheduled work, I am just waiting to better weather...
But can the leaking injector(s) cause some signal like knocking? Ad the piston slap - if it is the cause - what is the piston slapping into? |
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#12 |
Board Member
Join Date: Mar 2009
Location: Jefferson City, MO
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![]() Have you done a compression check?
__________________
Robert http://www.volvowiringdiagrams.com/ 82 244DL, 2004 S60R AWD, 2008 S40 GF's Had: 77 242 DL, 80 242 DL, 82 245 DL, 89 740 GL, 94 850T, 95 850 GL, and a 02 S60 2.4T |
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#13 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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#14 |
Board Member
Join Date: Mar 2006
Location: Virginia Beach, VA
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![]() Does disconnecting the knock sensors improve the issue?
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#15 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() Hmm, when knock sensors are disconnected, ignition ecu knows it is disconnected or faulty and retards the timing all the time...so, no, it doesn't improve the issue.
Last edited by tomasss; 03-06-2010 at 03:39 PM.. |
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#16 |
Board Member
Join Date: Jan 2010
Location: Finland
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![]() On your own risk, of course, you could try bolting the knock-sensors off, leave the connnectors attached but just unbolt them and tape to some hose or something?
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#17 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() No, this is not the way. The ecu expects some kind of signal coming from the sensors, when I unbolt them from engine block, ecu is signalizing faulty sensors.
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#18 |
Board Member
Join Date: Jan 2010
Location: Finland
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![]() OK, that just worked with a bit older model EZK, as the sensor that was attached to the block died, I just put another one hanging in there so I got the missing 30hp back till I got back home to replace the original one.
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#19 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() Well, I can try to hack the sensitivity by adding some soft shim under the knock sensors, but this is not good solution
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#20 |
Board Member
Join Date: Mar 2009
Location: Jefferson City, MO
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![]() I think they are suggesting this only to see if the computer is pulling timing. If it is then you will know it is a detonation problem.
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#21 |
Board Member
Join Date: Feb 2008
Location: LongBeach,ca
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![]() sounds like the fuel filter is clogged up to me i noticed you didnt mention this as one of the things you replaced?
also you ever had the fuel injectors flow benched/cleaned and checked for spray pattern? just looked at your main post and noticed you are on LPG i dont think your car can run properly on this alternative fuel and you might try and run standard gasoline and see how it runs
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1998 volvo v70xc awd current project almost done 5000,00 later 1988 volvo744 Ti B230FT stock for now 212,000 miles ice cold A/C-R12 new Garrett turbocharger stock wheels with 205/60/R15 yokohama YK580(still driveable after being rearended. ouch |
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#22 |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() All filters -> fuel filter, air filter, engine oil filter, transmission oil filter
![]() These issues are the same both on lpg and gasoline - that's why I think problem is somewhere in ignition... |
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#23 |
Board Member
Join Date: Jun 2006
Location: SE USA
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![]() Did you replace the ignition wires with genuine Bougicord/Volvo wires? Is the ignition timing adjustable on the B280F? If so, is it correct?
__________________
The BMW said "I am the ultimate driving machine!" and the Volvo wagon said "Oh really?" |
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#24 | |
former PRVert
Join Date: Oct 2008
Location: Leuven, Belgium
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![]() Quote:
The timing is not adjustable, it is fully controlled by the ignition ecu. |
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#25 | |
Board Member
Join Date: Jan 2010
Location: Finland
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![]() Quote:
Have you tried any other similar vehicle? Might be rare model though... But the 760 b280f+aw me and my buddy have, isnt actually a rocket either, even that it also shifts a bit early downwards. |
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