Anybody wanna troubleshoot a sputter/miss???

[redgtxdi]

A little background. (1995 Toyota Corolla) Pinhole in upper rad hose a few weeks ago. Until it finally started spewing enough coolant for me to notice, it would stutter miserably and have no idea why leaking hose would cause that. (???)

Next, after fixed all was fine. Now, lately it's been doing a very slight version of the same stutter at low rpm. No coolant leaks anywhere. One day I pulled all the spark plugs out just to see if any fouled. Nope. Reinstalled. Thing ran good for a week. Now doing it again.

Plugs are 2yr old Denso's. Plugs, wires, cap, rotor all ditto on age. It's certainly tolerable and goes away at higher rpm, but just buggin'.

???

TIA

 

[jlee]

Plugs, wires, cap and rotor is where I'd start. I had a bogging issue with my MR2 and that solved it. You could try just plugs first - would be cheaper.

 

[exdeath]

Does it occur when flooring it at low RPM until a certain point? Check the coil also.

 

[boomerang]

An ignition problem would more than likely manifest itself at high rpm or throughout the entire rpm range. You had a coolant leak. Are you certain the cooling system is fully filled?

The next thing I'd look at is where the coolant could have possibly sprayed and damaged an electrical component. Temperature sensor, throttle position sensor, yada, yada, yada.

No check engine light?

 

[Blunc]

I disagree with most of what boomerang posted, it's a misleading generalization.

low rpm misfires are usually caused by failed/worn ignition components, however, high rpm misfires can also be caused by bad/worn ignition components...usually not the same kind of failure.

the fact that the engine ran rough when coolant got on the plug/plug wires is a no brainer, running rough when the engine is not leaking coolant on ign components is not quite a slam dunk to diagnose.

spark plugs are a consumable, I would replace the plugs first. plug wires don't go bad quite as fast as plugs but running the engine with old/worn plugs causes spark plug wire, dist cap and distributor rotor failures.

another cause for misfire can be a vacuum hose leak, maybe someone damaged or stressed a vacuum hose when replacing the bad coolant hose.

 

[exdeath]

Misfire under load that smooths out at higher RPM = coil. Runs ok when cold but starts acting up at idle when it gets hot, or intermittent depending on ambient temperature or phase of the moon = coil. It won't necessarily fail a resistance test either, which will leave you banging your head.

The mixture is hardest to ignite under load from low RPM, so ignition problems such as lack of coil energy can manifest at low RPM and be fine at high RPM.

When it's acting up, pull a plug wire and hold it close to ground with a screwdriver. You should have a nice bright thick spark jumping 1/4" to 1/2" easily. If you need to get almost touching to get it to spark, or if the spark is faint and weak or not consistent, replace the coil. Do you know if it's a CA or Federal emissions vehicle? Is the coil separate with a 5th wire on the cap, or is it built into the distributor with only 4 wires on the cap? If it's under the cap, inspect the epoxy at the base of the coil for cracks and dark spots and other signs of arcing.

What were the conditions of your cap/rotor/wires when you replaced them? If you replaced them because they were in bad shape and causing problems, it's conceivable that the coil was working extra hard to push through extra resistance all that time and it's finally taken it's toll.

Your best tool for troubleshooting ignition misfires is going to be an oscilloscope.

I'm fixated on the coil because you say all the other components are relatively new, and it goes away at high RPM. I just went through this exact scenario recently on my 95 Camry 2.2L. In my case it was intermittent and very hard to spot the occasional lack of coil ring on a scope, and the coil had acceptable resistance on both windings, but it still ended up being the coil. If you can flog it and get it to stall completely when it starts acting up, you end up with a no start condition that is much easier to troubleshoot.

 

[boomerang]

The chances of your problem not being related to your coolant leak is slim.

If you want to throw parts at the problem, replace the plugs, then the wires, then the cap and rotor and then the coil.

If you want to get at the heart of the problem, look at what was downstream of the coolant leak. What got sprayed by the leak? It's simple cause and effect. Whatever got blasted by hot coolant and steam would be my first suspect.

Obviously opinions are varying here. None of us are standing in front of your car.

 

[aleckz]

I had a stutter on my little Civic, I replaced the plugs and wires that helped a little. But mine had a small leak in the rad and over time it started to have bubbles in the system. After awhile I noticed it, along with the stuttering and pulsing low RPM's. I fixed it by replacing the rad and running the car with the radiator cap off for about 10 minutes, checking and filling every so often. I did this process with the radiator cap off a total of 3 times, just to make sure there weren't any air bubbles in the system. After the first time, the stutter had gone and the RPM's did not fluctuate. So if that is your problem, I would try to do that. Plus, it doesn't hurt to top off your fluids and check for air bubbles once an awhile.

 

[DuffmanOhYeah]

A little background. (1995 Toyota Corolla) Pinhole in upper rad hose a few weeks ago. Until it finally started spewing enough coolant for me to notice, it would stutter miserably and have no idea why leaking hose would cause that. (???)

Next, after fixed all was fine. Now, lately it's been doing a very slight version of the same stutter at low rpm. No coolant leaks anywhere. One day I pulled all the spark plugs out just to see if any fouled. Nope. Reinstalled. Thing ran good for a week. Now doing it again.

Plugs are 2yr old Denso's. Plugs, wires, cap, rotor all ditto on age. It's certainly tolerable and goes away at higher rpm, but just buggin'.

???

TIA

Is it a constant stutter or very intermittent? If intermittent, how old is your battery? Kid you not, I've seen this more times than I care to count. Usually, only one cell has gone bad, and without sufficient alternator spin, you dont have enough juice, and miss occasionally. Easy enough to check.