94 940 N/A Hot Or Cold - Hard Start, Rough Idle

[Pacerdonfl]

Hello, I am fairly new to the forum. Thanks for any comments.
I have had a 940 NT for a couple of years, hardly driving it. It always has had a hard start and rough idle, whether warm or cold. A bit easier to start when warmed up, but still cranks longer than it should need to - and idle is rough hot or cold.

When it does start cold (engine cold - I live in Florida), it will bang and shake away for 2-3 (sounds like on 1 or 2 cyl's) minutes and then finally "smoothe out" to a rough idle. It takes 5 more minutes before I can accelerate without stalling. After about 5 minutes, it still idles a bit rough, but once out of idle, runs and accelerates beautifully.

Had intake manifold leaking and replaced that - helped a bunch, but still very hard start when "cold" and always rough shaky idle.

I have replaced many sensors...I have "cleaned" the idle air control valve, replaced the temp sensor under the intake manifold on driver's side, new crankshaft position sensor, new exterior fuel pump and filter, anti-knock sensor, new intake manifold gasket, new distributor rotor, cap, new spark plug wires and spark plugs.

I have not changed the MAF and MAP sensors, but did try and "clean" the MAF.
The oxygen sensor "looks" like it was changed soon before I got the car (2 yrs ago)...

The CEL is on, but I don't know how to check codes???

Any ideas would be greatly appreciated.

Thank you,

/Don

[93Regina]

MAF and MAP sensors

Got a picture of that MAP sensor? I'm not aware of Volvo using a MAF and MAP sensor on redblock engines.

If you have a MAF sensor (AMM in Bosch speak), then you have LH 2.4

If you have a MAP sensor, then you have Rex-I/Regina.

So, we need to find out what you got.

[Pacerdonfl]

Thanks so much...will send pic tonight. I believe its a Regina...Here is a picture of the same item as on my car - Mass Air Flow Sensor

[93Regina]

I believe its a Regina...

Nupe, it would be a Bosch system, as in LH 2.4

Well now, your temp sensor, do you have a part number on the invoice? Make sure its plugged in.

[Pacerdonfl]

I think I changed the temperature GAUGE sensor ..... will get ignition/fuel engine temp sensor tomorrow.

Must be it - it's been running very rich at start and idle...

Thank you!

[93Regina]

The CEL is on, but I don't know how to check codes?

I've never done it, but

1. Volvo 240 Self Diagnostic Tests

2. Fuel Injection and Ignition Diagnostic Procedures in Bosch LH-Jetronic 2.4+, Regina, and EZK 116/REX 1

I'm beginning to wonder if there is a leaking injector. I've never tried fitting a tire-pressure gauge on fuel-rail's Schrader valve. When engine is cold, turn key on for three seconds, then turn it off, and repeat once more. Then see if tire-pressure gauge will fit on Schrader valve. If so, take a pressure reading, then another one in 5 minutes. You might place a cloth on-top in case fuel is sprayed.

If auto supply has a Ford 90' Fuel Inj Adapter, this will work; sometimes, there is no charge to use it

[Pacerdonfl]

Leaky injector makes sense - when I turn to key on (not start) and hear the fuel pump pump up, then cut off. If I turn the key off and back on again, it pumps up again. So it seems that as quickly as I turn the key off and back on, the pressure has gone down to initiate the pump.

Anyone know a good way to find out which injector would be leaking (if only one?)...

Thank you!

/Don

[93Regina]

Anyone know a good way to find out which injector would be leaking (if only one?)...

Like spark plugs, you pull the connector, one at a time when running at idle.

But, either use a tire pressure gauge, or get a loaner/rented fuel tester from local auto supply, and test pressure when engine is cold.

Fuel pressure regulator could be faulty also.

Myself, I'd pull the whole rail out, and turn key on with a cold engine. Get 4 new injector o-rings when re-installing.