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4 Posts
Discussion Starter · #1 ·
I continue with my quest to diagnose a severe hesitation at load on a 1995 940 Turbo. If I try to accelerate with any but a light feathering of the gas pedal you get it. Also when cruising at a steady speed on the highway and you go up any kind of an incline, you get a slight rythmic hesitation.

I NOW HAVE SOME NEW EVIDENCE THAT MIGHT MEAN SOMETHING. I DISCOVERED THAT THE HESITATION GOES AWAY AT ABOUT 4,000+ RPMs! So what does that mean in my search? That is NOT a turbo hose leak? That is is NOT a fuel pump problem?

I have (by category):

Fuel Delivery:
replaced fuel filter.
filled tank with gas.
put in bottle of techron.
resoldered FI relay.
swapped fuel pump relay.
swapped fuel pressure regulator.
checked fuel pressure at rail.

swapped AMM.
swapped coil.
replaced distributor cap and rotor.
replaced plug wires.
replaced plugs.
swapped power stage.
swapped RPM sensor.
Cleaned grounds in trunk, pass, and driver. footwells, and at fuel rail.

inspected all and replaced some vacuum hoses.
inspected turbo hoses (replaced one, swapped one).
pressurized system at turbo inlet (after hearing air under intake manifold, but not finding a hose problem, I replaced intake manifold gasket).
replaced two idle motor hoses.
cleaned throttle body, with new gasket.
Swapped IAC.
Plugged intake to EGR pipe.

Checked exhaust for individual bursts (to see if blocked).
There is no black smoke from the exhaust when the hesitation happens.
There are no codes (only 1-1-1).
I then tried to replicate the problem on my 1994 940. I disconnected several air hoses off the intake manifold to create air leaks. It did not produce the same effect.
It stopped doing it at the end of a 200 miles trip and returned a day or two later.

Any ideas would be greatly appreciated.

4 Posts

Describing very precisely what happening to my 1992 960 sedan !!! I have no idea what is doing it. While the mechanic drove it was OK unfortunatelly.Of course, because all this problems occuring only sometimes , most of the time car runs well !

4 Posts
Discussion Starter · #4 ·
I checked the TPS for the click I should hear, and I did the check at the OBD-I (it did not give the exact results that it was supposed to, but the results were the same as on my other 940 T).

And I have the problem no matter whether the engine is cold or hot, so should the temp sensor come into play at all?

Volvo Guru !
5,908 Posts
If there is no singnal seen from the temp sensor it goes into a programmed setting. Which might be messing with the way the car runs.

But it is kind of hard to say what else to look at without seeing the car.

Is the engine harness in very good shape?

126 Posts

Could you please describe more about how the car runs otherwise.

Is the idle perfect?

Does it run poorly while sitting at a standstill at higher RPM's?

Have you done a compression test?

Have you had the main fuel pump replaced at any time? I have had 2 occasions where an aftermarket pump was running at the right pressure, but not providing enough fuel delivery under load.

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