I used to only have this problem when the engine was cold but it's been slowly getting worse.

While under moderate throttle in one of the higher gears (3-5) I have a single misfire at approximately 1750rpm. It's very consistent and repeatable and tends to occur more often under load (going up an incline).

The cold engine version (on days that are 50° F or lower) has this same problem at 1750, but also has a barrier at 3000 that feels almost like a rev limiter. Once the engine is warmed up the rev limiter problem goes away but the 1750 issue stays.

I used to think this was an injector problem in that they're old and when they weren't warmed up they weren't able to cycle fast enough. I suppose it could still be a problem, but the single misfire/stutter at 1750 doesn't make sense.

Is there anything that happens around this range in the air/fuel mapping? For instance on my RX-7 (yes, very different) there can be a stutter around 3750 because the secondary injectors kick in.

Any help is appreciated. The car is a 97 LX four door with 195K. I've used a handful of Techron fuel system cleaners the past 50k miles but I don't notice a difference in this particular problem with them. The ignitor and coil were replaced about 16 months ago.

 

Wednesday morning bump.

 

How old are the plugs, wires, cap, and rotor?

Any CEL codes?

 

X2

It could also be your injectors. It you haven't done a tune up in a long time or run injector cleaner. I would start with that first

 

Plugs are about 12 months/20k miles. Wires twice that. No CEL codes since the cylinders were re-ringed last year. Before that I had low compression, huge oil loss, and constant ping CELs for cylinders 2 and 3. The problem exists through plug changes, but I can't say that it does through wire changes.

They've had injector cleaner with no noticeable difference. I don't know if the injectors are original but if they are, at 195K and given this car's history, they are likely crapping out regardless.

 

Does the CEL work?

 

It was replaced a few months before the rebuild and yes. It had been "missing" prior to that, a testament to the car's previous owners.

 

Monday bump.

 

REPLACE CAP AND ROTOR ..... why are u ignoring that one as it usually is the most critical and over looked... they asked you about cap and rotor changes not just plug and wires

 

I must have missed that. The cap and rotor are the same age as the wires. I'll change them out though I guess.

 

just take the cap off and use a flate screwdriver and clean the little brass points that the rotor hit and the end of the rotor and see if the missfire improves ... if so swapping the cap and rotor should take care of the problem.....

 

I checked the cap and it was pretty damn filthy. Scraped it off and for the first mile or so things seemed better. Then they got MUCH worse where if I was applying any throttle under load below 2000rpm the car would flat out lurch and bog down.

Since mucking with those parts exacerbated the problem, I figured replacing them would alleviate it. I said screw it and just bought a new cap and rotor and it seems most, if not all is well in the world again. It also appears that I was wrong about previously changing them.

Moral of the story: just because you think you did something doesn't mean you actually did.

 

glad you fixed the problem..... i was pretty certain the cap and rotor was your problem... glad u came back to let everyone know the cap and rotor fixed the problem

 

After changing the cap, rotor, and plugs I'm getting a different problem. For the past week I've had hard cold starts. It takes about three times longer than it used to starting up the engine when it's not warmed up.

Also, it smells like unburnt fuel all around my card afterwards. I thought I got a tank of bad gas with too much water in it but it hasn't gone away yet.

Have I mentioned that I hate my car?

 

Check for CEL codes again.

 

Curious what spark plugs you are using. Please don't say champion- they're horrible about gas fouling.

 

Well the funny thing is that I'm not getting one right now. I did however get one yesterday (Monday):

I thought I might not have the sparkplugs fully seated because when I installed them, the head was hot. So I reseated them in a cold engine and then went to do my grocery shopping. It took forever to start, but I hoped it may have been because I just reseated the plugs.

Then Sunday I went out to check and make sure the car would start for this week, because I'm worried the ignitor or coil is going down again. Took forever to start like it has been, but it started. I turned off the motor after about 15 seconds of running (big mistake).

So yesterday (Monday) I go out to start the car for work and it bogs like crazy after it turns on. It was lumpy and burbling, flashing the CEL but after about 30 seconds (time enough for the excess fuel to get out, I assume) it ran fine. I believe I flooded the cylinders Sunday having only run it for a few seconds.

I didn't check the CEL because I figured it was the knock sensors (like when it used to gobble up oil) and reset it instead. Haven't had it come on since.

I'll check it though in a couple of minutes on my break.

NGK ZFR5F-11. I wonder if I need to go back and recheck the gap.

 

The next time the CEL turns on, pull over and leave the engine running while you jump the service connector. Don't pass up diagnostic opportunities that may help solve problems.

 

I just checked it (even though it isn't coming on while I have these starting problems) and nothing.

I did notice though that the replacement cap and rotor were the aluminum kind instead of brass, and although I haven't had problems with them in the past, is that a possible cause for the increased time to ignition?

 

Are your grounds corroded? This can put a higher load on ignition

 

Well the only one I can think of from the power steering to the front of the engine bay isn't. I can try to look at the others.

The bit that confuses me is that even when I had the old corroded to hell cap on it started up swiftly.

 

You might have damadged the little spring in the distributor that pokes out when the cap is off. It contacts into the little pocket terminal visible when cap is off.

 

did you reset ignition timing with a timing light?

 

Strangely yesterday afternoon it fired up fine. Then this morning it was in between normal and too long.

I'll check the spring in the distributor and the timing this week. I didn't check the timing with the cap change.