This has been occuring for about a year. My normally strong running 8 valve, non turbo 740 develops a miss problem if it rains the night before I drive it. Now it is occuring after a trip to the do it yourself car wash.It always clears up after 30 minutes or so of in town driving.

I pulled the injectors one at a time recently while idling with the miss & found that #4 when pulled, did not affect the engine. I thought it was dirty & ran techron for 3 tanks of 89 octane. Next rain it came back, but this time it was #2. I think I've got a intermittent short to ground when humidity is 100%. To make matters worse, I live in Seattle.

Should I pop the hood and start misting with a spray bottle everything electrical until the miss develops, then consentrate on that component, or is there something else I should try?

Please don't tell me to Arizona.

Car recently had 50K service. Has lots of new stuff, but nothing in way of F.I....

I have had a similiar problem from old spark plug wires. It appears you have isolated your problem elsewhere, but I thought I would mention it for what it is worth.

Jim Weber

Robert:

I'm guessing that you're getting some condensation into the electrical connectors on the fuel injectors themselves. The fact that the problem goes away after you drive a bit is the tip off (the moisture evaporates as the engine heats up). I've had similar problems on LH-cars after using engine degreaser and rinsing the engine compartment with a hose. Open up the connectors (they're held together with little rectangular wire springs; you can compress them with a small screwdriver blade to get them open) and dab a bit of dielectric tune up grease (any auto parts store should have this, comes in a small tube) on each contact.

Also good advice by another poser to attend to the FI system grounds. They should be connected to the hold down bolts from the fuel rail to the intake manifold. Remove the bolts, shine up the ring connectors with some emery cloth or sandpaper, apply the dielectric grease and reassemble.

Good luck.

Dielectric grease is antithetical to conduction. The only reason it works is because there is enough voltage to overcome the resistance in the grease, and this is why you do not want to use it on the O2 sensor, as it operates below 1volt.

This is also why you do not use it on grounds. It will make the connection worse! Use OxGard (available at Lowe's, Home Depot, etc.), as it is conductive and will enhance the connection and keep it clean.

OxGard on grounds.

Dielectric grease in sensor boots (except O2).

Ed O'Briant

Ed:

Thanks for pointing this out! I was never too clear on this distinction (obviously). Now I'll have to go back and remove the dielectric grease from all my ground connections and apply Oxguard AFTER I finish with the blower motor changeout on the '87 245.

Mike,

Interesting that you mentioned cleaning the engine with degreaser & water.

I did the same thing a few months ago. I'm going to follow your recipe tomorrow & will get back with results. Dialectric grease keeps coming up in the postings. I'm convinced that it can only help in this wet part of the country.

I talked to a guy today , Doug at our local Volvo dismantler while trying to aquire a used shop manual. He asked why I wanted the manual, so I told him of the problems with with the car. We went out to the curb for a look see. He checked the codes, which were fine. Then he went to the connector near the firewall for the Tachometer wires. We surmised that due to the location below the gutter that a car wash or heavy rains could douse it. Another possibility to explore. He felt that could be part of the problem.

I guess I've got a good start on this fix now, thanks to every one who has taken the time to help me on line and at the curb.

Thanks, Robert

Robert:

Hah, tachometer wiring! Here's another one to file away in the memory banks: I once owned an old Ford Bronco, and installed an aftermarket "Sun" tachometer in it. Wasn't careful with how I ran the wire from the coil, which subsequently got pinched and grounded itself, causing a no start situation. Took me forever to figure out what was wrong with the darn thing!

In what kind of shape are the injector ground points? I'm not sure as to their location, though on the turbo cars they're on the intake.

Check all the ground junctions-by each headlight, behind both kick panels, etc. Also, how are the sensor connections?

I bought a tube of Ox-Gard and another of dielectric grease and went through my entire car, cleaning every ground I could find and 'sealing' them with the Ox-Gard. The dielectric grease keeps the sensor boots and their connections trouble free. I cleaned all the sensor junctions first with DeOxIt and then applied the grease to the boots (except the O2 sensor).

Even if you do find a faulty component, the above regimen will go a long way to making your car and its electronic gadgetry more stable.

Ed O'Briant

You've got the classic signs of a weak ignition part. It's very unlikely to be related to the F.I.

The top of the list is ignition wires - bad insulation or cracked/missing/poor-fitting boots.

The next on the list is a porous or cracked distributor cap. Cheap Asian knock-off parts are prone to this even if new.

Items like ignition rotor or a cracked tower on the ignition coil are next. Since you have probably changed the spark plugs at least once in the year you've had the problem, you have already eliminated a cracked spark plug insulator.

Thanks Gane & Vytas. Everything you guys pointed out is new in august except the ICU, which the dealer says is sort of noisy but servicable. The miss carries past the idle area and into 2000 - 3500 area where it kicks in on all 4. I've had it back to the dealer a couple times, but they can't get it to act up.....would not rain. They say they guarantee what they did for a year. Guess I should visit again. I would like to get this taken care of so I could switch to an independent volvo shop. So many parts were put on by the dealer. Seems at least one or two were bad. Vytas, your comment "the ECU is inside, safe and dry, right" I gotta tell you, I don't know it is. I think it's time for me to buy the late 740 & early 940 manual and start finding things.

Thanks for helping me.

Are you sure that it's your fuel injection? That is, have you checked and/or updated your ignition system? Moisture can definitely affect your ignition system, especially if it is weak at any part of it. Some or all of the spark will find an easier path to ground and will not cross the plug gap in the cylinder. Thus resulting in a misfire or worse, a no start condition when it's wet outside.

If it hasn't been attended to, your ignition system might be needing a new ditributor cap and rotor and/or new wires and/or new plugs. Preferably change them all at once if they're getting old. Perhaps none of this is news to you, but maybe it will help you track down your problem.

The rest of the 12V system is less likely to be grounding out with such a low potential, except perhaps inside the computers - water can affect stuff on that level; maybe it's your ICU getting water in it? The ECU is inside, safe and dry, right?

Hope this helps.

vytas