240 GLT idle problem

[GPZ900R]

Hi folks - I've owned a 1988 240GLT auto for many years - it has been regularly serviced and generally reliable. B230E engine.

One problem we have at the moment is difficult idling.

When in "park" or "neutral" the car idles correctly. However when shifted into "drive" or "reverse" the idle speed drops significantly and immediately becomes very lumpy, trying to cut out. It stalls frequently at idle and low revs, when you're trying to pull away from a junction etc.

I thought this might be an intake air leak, but can't find one. I'm now suspecting a fuel delivery problem, as it wouldn't fire up last night, but don't see why that would be affected by changing from neutral into a gear. It fired up fine this morning.

When driving at 10 - 15mph and above the car is fine - its just a problem at low revs.

Any help/advice greatly appreciated - I don't want to send it to the knackers yard just yet.
cheers

[billofdurham]

Welcome to Matthew's Volvo Site.

When you engage D or R the engine will always 'dip' a little. However, it shouldn't cut out.

Things to check for erratic idling:

Accelerator linkage operates correctly.
All air and fuel hose connections.
Idle air regulation valve.
Fuel pressure.
Fuel injectors.
Coolant temperature sensor.
Air mass meter.
Throttle valve housing is clean.
Initial opening of throttle valve.
Throttle position sensor adjustment.

THis should get you started. Keep us updated.

Bill.

[GPZ900R]

Current postion as follows:

Accelerator linkage operates correctly.
yes ok

All air and fuel hose connections.
yes ok

Idle air regulation valve.
replaced yesterday - no change

Fuel pressure.
unchecked so far

Fuel injectors.
Cleaned and new seals fitted

Coolant temperature sensor.
Unchecked - where is this? Although as the problem exists when engine both hot and cold I would have thought not the culprit.

Air mass meter.
Yes ok

Throttle valve housing is clean.
Yes ok

Initial opening of throttle valve.
yes OK

Throttle position sensor adjustment.
Not sure about this - where is it?

Engine still very "lumpy" and stalls easily when put in gear. Idles OK in park/neutral. Currently have it idling at 1000RPM (using adjuster screw under inlet manifold) to reduce stalling, I know thats high but at least it makes the car drivable in short term until I get it fixed. If I set the idle lower it will simply stall as soon as put into gear.
Tank fuel pump, accumulator, fuel distributer replaced within the last few years, not that that necessarily proves them ok. I suspect the Fuel Pressure Regulator - how would I check this?

Thanks for advice so far
Cheers
Iain

[billofdurham]

Coolant temperature sensor.
Unchecked - where is this? Although as the problem exists when engine both hot and cold I would have thought not the culprit.

The coolant temp sensor is located in the cylinder head or engine block or on some 240s in the intake manifold. It provides the ECU with an engine temp signal. If the signal is absent the ECU will assume the temp is 68F (20C) at all times. So it is possible to have the fault appear across the board. Is your temp gauge showing normal?

Throttle position sensor adjustment.
Not sure about this - where is it?

It is on the throttle body. Open the throttle slightly and listen. A click should be heard as soon as the throttle is opened (indicating the idle switch has opened). Adjust if a click is not heard.
To adjust: Loosen the retaining screws using 3mm Allen key. Turn the switch clockwise slightly, then anti-clockwise until a click is heard. Tighten the screws and check.

I suspect the Fuel Pressure Regulator - how would I check this?

You need a fuel pressure gauge connected between the fuel line and the injection manifold. Switch on the ignition to activate the fuel pump. Pressure should be 36psi.
If the pressure is too low, pinch off the fuel return line and recheck. If the pressure rises quickly the pump and lines are working OK. Replace the pressure regulator and recheck.
If the pressure rises slowly the fuel filters or lines are blocked. If the pressure does not rise at all the pump is defective.

It is a pity you are on the West coast as I am heading for the East coast for 10 days from tomorrow. I could have brought these tips but it always rains on me on the West so I steer clear.

Bill.

[GPZ900R]

Thanks for that help.

Problem now solved - I checked the spark plug gap and all were way outside limits Must have skipped that during last service.

Regapped them and hey presto - normal service is resumed

Its always the simple things that catch you (well, me) out. I could have sworn that was a fuel delivery problem. Engine running fine now at 210,000 miles