3.3L. Intermittent, brief stall

From the description of a slight bogging during acceleration, I would suspect either a fuel delivery problem (clogged fuel filter or fuel pump starting to fail) or more likely, bad ignition wires or plugs. Ignition wires seem to fail fairly frequently on the 3.3L engine and you do not indicate how old they are so I'd start there if they are over 5 years/50K miles old. Does the engine also backfire at all when you accelerate after this occurs?

I would doubt it is a sensor since no code was set. Good luck

Bob

Check the fuel pressure as recommended, but another problem that can cause a hiccup during acceleration is a bad throttle position sensor, and it won't ALWAYS set a code. Cam or crank sensors, at least in my experience, tend to either cause a complete shut-down or a longer duration cut-out. And the cam sensor will definitely set a code, not always the crank sensor though.

Bob Shuman wrote:

Thanks for all the help. The plug wires, and fuel system components are all original from it's Sep 1992 assembly. The TPS was replaced two years ago to correct a surging problem at idle. The fuel filter was replaced then too. Looks like a lot of things to check.

It does not backfire during acceleration.

-KM

One last and simple thing you might wish to check are the battery connections. Check to be sure they are clean and tight and that the clamps are in good condition.

It does not backfire during acceleration.

-KM

When were the plugs last changed/checked?

I would pull one of the front plugs and check it with a plug gap tool. If the plug gap is significantly off then replace ALL plugs. A larger plug gap can throw off ignition timing.

Ted

I don't understand that. Can you explain?

Larger gap means the firing voltage must be higher before the spark happens - when the mag field is collapsing in the coil as the field collapses the voltage is rising in proportion - it isn't an instantaneous thing - it takes slightly longer to reach trigger voltage.

I've observed with a timing light on my MC engine (which has electronic ignition, but manually adjusted timing) the timing marks changing position after simply re-gapping the plugs. Now, maybe a modern engine computer can compensate for this....

Ted

I would have thought the rise time of the coil output would be extremely fast, and therefore the delta T extremely small, relative to the motion of the engine - but that was an assumption on my part.

Let's do some Googling and some math: I found that it is accepted that coil output rise time is typically 50 to 100 microseconds. At 6000 rpm, the crank rotates a full revolution every 10 milliseconds. That's a degree of crank rotation every 28 useconds, or a degree of distributor rotation every 46 useconds. Lets say a gap change could give a delta T of 1/10 of total rise time, so we're talking less than a degree of distributor timing change, about a degree of crank timing change. To be honest, I don't know if what we traditionally talk about as degrees relative to TDC is crank or distributor rotation - probably crank, but thats a guess.

Anyway - so - there is some measurable effect (assuming my assumptions, like 1/10 of total rise time delta T, and that I didn't make any mistakes in my calculations) on the order of a degree or so. The better the ignition (faster rise time), the less that effect. And - yes - I think you're right, a modern engine would definitely compensate for that since it controls timing based on the effects of ignition (like knock). If that's the case, then it's a moot point.

Would the hotter spark resulting from the wider gap (higher firing voltage) offset that with faster pressure build? All the ad copy for the rip-off devices on the internet would lead you to believe that. Not sure if it's true or not (I want to say not, but that's an uneducated guess).

Related to the OP's original problem and your comment about plug gap: Excessively high plug gap puts undue stress on the coil insulation and can cause coil failure (insulation punch thru and/or carbon tracking) for the reason you cited: higher voltage before the spark gets initiated. That's why you don't fire a coil without its output either being grounded or going thru an appropriate spark gap.

Ah, that also depends on HOW it's compensating.

It's been my observation that plug gap doesen't wear equally in the engine - after wear, in some cylinders the plug gap is larger than others. If the compensation is of an average of the change...

Ted

Then that would simply be an argument for changing the plugs before significant wear (which would create those differences) occurs and accurately gapping them initially.