Hi, everyone, my 1993 240 has always had a weird idle problem: when the car warms up, it would idle roughly as the engine shakes a lot. When it’s cold, it idles fine. I have done the jobs below:
A known well-working MAF installed
IAC cleaned
Throttle Body cleaned
sprayed brake cleaner around intake manifold and hoses after maf, no change in idle
Also, every time when I give a very very low throttle, the engine seems to stall for a moment. It also stalled in a heavy traffic when I was doing run and stop a lot. My assumption is a vacuum leak but the brake cleaner test didn’t support it.
Thanks ahead for any advice!

 

when the engine is cold the idle air valve will close allowing the mixture to be enriched so a lean condition caused by an air leak or low fuel pressure can present with a warm engine. Check pump pressure, rail pressure etc, try jumpering the fuel pump relay etc.

 

A word of caution - when some brake clean burns it creates "harmful or fatal corrosive gases such as hydrogen chloride and possibly phosgene".

Best to use carb cleaner if you value your lungs.

 

Thanks for your reply, I think it would be a good idea by checking the fuel pressure regulator first? That's the easiest solution for this by now.

 

Thanks, I actually used carb cleaner instead of brake cleaner, I remembered it wrong haha

 

What is the idle speed when warm? Have you tried simply raising the base idle?

I have seen many and replaced many fuel pressure regulators. Generally the only ones I saw that were bad - spiked the fuel pressure only when first started cold. And would flood the engine. The only way to catch the malfunction was to install a fuel pressure gauge the night before and check when first started the next day.

However, this was at least 20 years ago when there were many of those comiong into my shop so types of failures may be different now. .

 

Thanks for your reply, when warmed the rpm is around 700. I tried to raise the idle rpms but it will only smooth out when being set up to 1100+ rpms. The car is in very good condition otherwise, just the idle problem is bugging me out. Also, the fact that when giving very subtle throttle the power tends to cut for a moment makes me suspect a fuel problem more.

 

I'd be interested in how you tried to raise the idle. For the '93 240 you either have the LH 2.4 or LH 3.1 fuel injection system which has no idle adjustment.

 

Hi Forum. This is a question about procedures on a 1993 240. I am cleaning the throttle body as part of a fuel system tune up. I have removed the intake manifold, injector rail, throttle body and am cleaning all including rebuilding the injectors with filter screens, o-rings and pintle caps. My question is about the large brass valve in the throttle body, the one with 14mm base. Mine is stuck solid in the TB. I have the TB soaking in parts cleaner overnight and will try to budge it loose again tomorrow. My hope is that it is just suffering from 32 years of fuel gum and varnish. Any thoughts? This is removable, right?
Thanks to all for your tips and expertise.

 

My injection system is the LH 2.4.

 

While I am at it I will ask how to properly replace the TPS. I removed it and noted the position of the spindle with the flat side on the shaft. Plan to just put it back in same orientation. Any =tips on adjustment? hanks

 

Check out this page:

https://www.brickboard.com/FAQ/700-9...linjection.htm

Lots of procedures there - including TPS adjustment. It's for the 740/940 cars but the engine and fuel injection system is the same.

 

Thanks. I'll be busy!

 

I also have a weird idle problem on my 1992 240 5-speed. I swapped out the o2 sensor because of a running rich problem, but now it has a slightly surging idle from 700-1000 when cold.
when warm it runs a little rough, but not much surging. I unplugged the iac valve with the engine running and the idle went crazy surging really bad, when I plugged it back in the idle jumped to 1500 and stayed there, so I shut the engine off and restarted it and it was back to a slightly surging idle. I unplugged the maf sensor with the engine running and the same thing happened as with the iac valve, the idle went crazy surging badly, when I plugged the maf back in the idle jumped to 1500 and stayed there.

any thoughts?

 

No ideas about that weird problem!
But to follow up on my big PCV/intake service project i have just done testing and cleaning of my injectors. They seem to function as designed. I have now rebuilt them with the washers, o-rings, filters and caps. The aerosol spray from each once cleaned is consistent. The intake manifold is clean, all orifices and nipples too. I have a new EGR, oil separator, flame trap and return hose, new fuel hoses, vacuum hoses, gaskets, IAC valve. I have cleaned the block OK.
Now to put it all back together and see what i have. hopefully I do not end up with any of the other problems you fellows have posted here. At least none without answers.
Hope you get your answer soon 240WStick.

 

I am suspecting my problem is caused by the Fuel Injection Coolant Temp Sensor. If this would not cause these problems let me know.

It may be worth checking or replacing the sensor mentioned above, unless you already have One end to the Other.

 

Good call. Those pesky little sensors cause all kinds of issues. I'll look for your update to confirm that was your solution.
I have decided to replace all little components that are connected to the intake and PCV systems.
What can it hurt besides the wallet? Thanks

 

BTW, what is your Go-To parts source?

 

Here is a list of parts websites I use:
rockauto.com
ipdusa.com
fcpeuro.com
vp-autoparts.com
classicvolvorestoration.com
prancingmoose.com (for wiring)
swedishcarparts.com

 

Thanks. I have used Rock,IPD, FCP. Will look at the others.