s2racer

i know the proper gap on new plugs is supposed to be 0.7 mm, and the plugs are supposed to be properly gapped from the factory, but the box each plug is in says they're gapped at 0.8mm (0.032"). any thoughts about this? the vendor was not particularly helpful. my gap measuring tool is not the wire type, so i haven't been able to verify the gap out of the box.

marc

timothymoffat

Bump. Been thinking about this lately as a friend did a full major service on his car over the winter (belts, plugs, wires, caps, rotors etc). Car ran great until the end of a long trip a few weeks back. Filled up with Chevron 94 and car started idling rough and "chugging" to life on cold starts. Car seems fine once off idle but I'm wondering about plug gap. The Bosch box does say .8mm. Do these plugs need to be gapped? Could a bad tank of fuel have this effect?

timothymoffat

Anyone?

timothymoffat

Hmmmm......

syzygy

Tim, I suspect it's likely just the gas. Maybe a recent fill of the station's tanks stirred up some sediment or other crap. If it was running fine before the fill, then that's my guess.

rsr91128

Tim,

I don't believe some of what is in this book but I agree with what he says about the plug gap. Somebody believed it enough to publish it so he must know more than me.

Sorry for the pic, scanner was giving me fits finally gave up and took a picture instead.

I agree that it is not real likely to be plug gap is the problem but I have heard of stranger things.

timothymoffat

^^^Interesting and comforting read. Didn't even think about gap when doing the plugs on the 97 in the spring.

I've been leaning towards the idea of a bad tank of gas as well. My 97 took on roughly 1/2 tank from the same station and did have some rough starts afterwards but all seems well now. The car in question took a full tank (close to 60L) and that may be the difference. Time will tell.

Steve Weiner-Rennsport Systems

Tim,

No need or reason to regap the plugs as they come in the box. Just install them as they are.

Its not uncommon to get a contaminated load of gas and one of the biggest causes is filling the tank during or shortly after the filling station was replentished by the tanker truck. Each time the station gets a "refill", any dirt, rust or condensation (water) get stirred up and it takes about an hour to settle down so the raised pickup inside the tank pumps nice clean fuel.

I've been burned by this one myself and honestly, its difficult to know when the tanker just left. I found my fuel filter to be almost completely obstructed but the fix was easy in this case.

Make sure the ignition system is in perfect condition before looking at the fuel system.

IXLR8

But each pump has a filter cartridge. Its that long cylinder alongside the pump. I know I've seen them. I'll check at the next fill-up. We at least had them on our aviation gas pumps.

Garth S

Filtration doesn't do much of a job in capturing water .... when a car runs rough following a fill up, one can reasonably assume excessive moisture: while water will eventually coalesce into drops & collect at tank bottom, the sure fire way to eliminate it is to pour a ounce or two of isopropyl alcohol into the tank ( or 'gas line antifreeze'). The alcohol azeotropes with water and gasoline, allowing the contaminant to be burned off without notice - or detection .... leaving a nice, dry tank.

This is also good preventative maintenance for the fuel tank, as there is always water collection as the air space above the tank 'breathes' .... and allows moisture to condense and collect.

In the worst case, as Steve mentioned, stirred up particulate ( rust, etc) is very effectively captured by the filters .... and will not bother performance until the point that flow to the injectors is effected.

IXLR8

Which is why we always stored/parked our aircraft with the gas tanks fully topped up.

timothymoffat

Thanks Steve W, it's just one of those things that makes you rethink EVERYTHING you've done recently. Bases on my car's more speedy recovery and the fact that it took substantially less fuel than the "troubled" car, the "bad fuel" seems to be the guilty party.

PS: I guess we got an answer to the OP's question in a round about way.

Steve Weiner-Rennsport Systems

Thats NOT a filter,..............thats the Federally-mandated dry break valve that prevents a major spill if someone drives off with the nozzle in the tank.

I've not seen any gas station that had filters in 30+ years,.... . The old AMOCO stations here had them but thats a LONG time ago,....Av gas is a totally different deal,...