1990 960 Jerky acceleration

gmtgmt · Post by **gmtgmt** » 22 Sep 2013, 09:10

So heres the deal, i have been fighting my 960 B6304F for some time now.
I can drive normaly with the cruise on and its jerks af few times and stops, it also have intermittend accelerations problems can drive 40miles no problem then it starts to hesitate when i want to accelerate dosent matter if its from a standing still or rolling. its very innoying.
its an intermittend problem I can drive 50+ miles nothing and then its starts and goes away after 20miles and comes again.
its only when its warm.

It came sortly after i had the Transmission off for a rear main seal
I was carefull not to damage the flexplate so i dont think its here the problem is.

Car has 521.000miles.

I have read codes there are non both for the engine ecu or transmission ecu.

I have changed the following things. all brand new Volvo stuff.
MAF
sparkplugs
Intank fuel pumpe and sendering unit.
Fuel pumpe and filter under the seat.
Fuel Regulator.
Both Ignition stages.
6 New coils.
new Dave barton wiring harness for the coils.
New Crank sensor.
Throttle position sensor.

Airfilter is nice and clean K&N.

Only thing i have noticed is thats theres play in the throttle body axle shaft when i i changede the TPS sensor yesterday.

Any imput would be great

lindy8_man · Post by **lindy8_man** » 22 Sep 2013, 15:14

If it's only happening while in cruise control in engaged, then check on the following:
Cable adjustment
Leaking Vacuum Servo Diapragm - (Right of block has the throttle cable running through it)
Leaking Vacuum Tank - (Under passenger Dash)
Faulty vacuum valves - A Couple to check
Faulty Stepper Motor
Faulty Speed Sensor
Faulty Cruise Control Module.

gmtgmt · Post by **gmtgmt** » 22 Sep 2013, 22:43

its dosent matter if i use cruise or not it happens anyway but thanks

lindy8_man · Post by **lindy8_man** » 23 Sep 2013, 19:17

I would still go through and check all your vacuum connections. EVERYTHING on this car runs on vacuum. The hoses on my 98 s90 are being replaced one by one. I would look specifically to those connected to the intake, and test your tank.

1Wagon · Post by **1Wagon** » 23 Sep 2013, 20:20

Could it be the MAF?

gmtgmt · Post by **gmtgmt** » 24 Sep 2013, 13:33

All vacuum lines are replaced not long ago, no leaks.
MAF has been replace first thing i did.

Today i changed the throttle body, i have had problems with these on 960s in the past
It helped, it was not as bad as before so hope this has done the will come back in within a week with an update.

1Wagon · Post by **1Wagon** » 24 Sep 2013, 22:39

Sorry, I missed the mention of MAF in your first post.
Good luck!

danr960 · Post by **danr960** » 25 Sep 2013, 07:46

gmtgmt wrote:All vacuum lines are replaced not long ago, no leaks.
MAF has been replace first thing i did.

Today i changed the throttle body, i have had problems with these on 960s in the past
It helped, it was not as bad as before so hope this has done the will come back in within a week with an update.

Not sure if the throttle bodycould cause your problems. But if it does end up helping, maybe the throttle postition sensor is not up to specs. Since you had to unplug it and swap it to the replacement throttle body, maybe there is something electrical going on there. I have read where others have had crazy engine behavior that was the result of a faulty throttle position sensor.

If you could get your hands on a Volvo scan tool, it would be a very easy to test it. Then scan tool will report degrees of opening of the butterfly valve.

I remember also that if you have OBDi diagnostics, there is a test program where you at one stage have to depress the accelerator fully and the if the computer senses that it will move on to the next test. It is called DTM2, and is activated by the trouble code reader under the hood. It tests the TPS, PNP, RPM, a/c controller and a/c clutch. These conponents have to be activated by the person running the test.
The other test DTM3, activates a series of components in a given order, engine coolant fan, injector valves, idle control valve. This test is run automatically with no tester activation.

The way to activate these tests is to push the button with the test lead on the #2 hole, push once to read stored codes, push twice to activate DTM2, push three times to activate DTM3.

Also, a leaking intake gasket is another thought, very common, especially on the first years vehicles.

Let me know if you need further information.

DanR '94 964 387,000 miles (153,000 on the new engine)