I've been trying to figure out what is wrong with my 1986 Volvo 740 GLE with the B230F with the M46 gearbox.

So, it would always misfire in the rain until it warmed up. Ran like that during some heavy rain for a few days, then it was dry. During start up it would idle around 1.1K and the revs would go up and down, almost sounding like a diesel engine as well. This happens when it's been sitting for a while and is cold. When it is warm, it will idle around 800-900 RPM and not make that diesel-like idle sound. It still doesn't sound normal, however. While driving through it doesn't feel right. In gear around a corner at low RPM under load, it will misfire.

So, I replaced the spark plugs, wires, and installed a new distributor cap. The contact points on the old one were pretty dirty. I also cleaned the MAF to be safe.

Still runs rough and idles poorly. Last night while coming to a stop I stalled twice. Would push the clutch in, RPMs would drop, and it would die. This would happen approx. half the time when I would come to a complete stop.

I'm not sure what to try next. I tested the fuel injector O-rings by spraying WD-40 around them while it was idling rough to see if there was a leak and nothing changed. I can sometimes smell fuel in the engine bay when I manually open the throttle.

Any guesses on what to try next? Just filled up with 91-octane (the only available non-ethanol fuel) and put some seafoam in the tank to clean the injectors.

Thank you in advance.

 

Update: Drove it around a bit this morning. It stalled four times when I would come to a stop. The RPMs would drop when I put the clutch in and it would die.

After sitting for a day in below-freezing temps, it took like 20 seconds to start. Starter was going (replaced over the summer), took a sec for the gauge lights to light up, then it started. Any ideas?

 

Could this be the Hall sensor? When I replaced the distributor cap, I noticed that I could move the wires that connect to it. Couldn't see the actual connector due to it being on the back of the engine, but I didn't try to mess with it too much, knowing how much of a pain it is to replace.

 

Bump, any ideas?

 

Can hear a faint hissing somewhere, don't know what line. My guess is the little piece where two hoses (one large before the TB and one small after on the manifold) come together on a piece that connects to the engine block on cylinder No. 3. Any idea what that could be?

 

Any idea what this part is (on block by cylinder No.2 I believe)? Wires are pretty corroded; could it cause the engine to run rich/misfire?



Anyone know what this wire is/goes to? Wondering if it's a ground for something.

 

Ground strap, goes under a valve cover nut...
The other wire is to temp gauge.
Find those air leaks and fix them! That could be your problem.
The Hall Sensor can cause those stalls.

 

Getting some ether to try and find the leak today. Not what I want to hear about the hall sensor though. Thank you!

 

Sprayed an entire can of ether around the manifold and nothing. Hit every hose after the MAF and nothing. No surge or change in the way it idled.

Attached that ground cable to the cam cover nut and stud, and that fixed the engine interference that I could hear when I had the AM radio on.

Back to square one.

 

Just look/listen for air hissing, not too many hoses under there.

 

that 2 pin temp sensor is the one the ICU and ECU use to decide on the mixture and timing, and yes, open circuit certainly would cause 'way too rich' on a warm engine as the ECU/ICU would think the engine is extremely cold.

 

Would a bad sensor/connection cause my engine temperature gauge to not work (it's been working fine)?

 

the dashboard temp gauge is on its own sensor, a single pin one. so no, the ECU,ICU coolant temp sensor (or wiring) could be bad, while the dash gauge could still work.

 

So, after playing around and trying to diagnose things, I started researching the fuel system online. Found a video that showed a bad fuel pressure regulator on a 240 and how to diagnose one. Smelled fuel in the hose that was connected to my intake manifold.

Just got the new part from FCP Euro today, installed it in about 15 mins, and voila! Runs perfect now. Just have to give it an oil change after all those misfires/stalling issues I had prior.