frustrating hesitation [Archive] - MX-5 Miata Forum (2024)

MX-5 Miata Forum > NA/NB (1990-2005) Miata > NA (1990-1997) General Discussion > frustrating hesitation

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My 94 Miata seems to have problems with hesitation especially when it's been raining. Lately it's rained everyday in GA and it's driving me nuts. Thought for sure it was just the plugs and wires so I changed both last night. After doing the plugs and wires it ran great so I was very pleased until I drove it again today. I did wash the car (not the engine) this morning. I let the water flow freely over the car when I wash (rather than a strong spray with hand or nozzle). The cat was replaced a few months ago and I thought that perhaps some of the old cat was stuck in the muffler but the symptoms don't seem to support that idea as the car runs great when the weather is dry for a few days. I've also tried a hair dryer in the sparkplug wells. I used dielectric grease when installing the plugs as well. hmmm... anyone have any ideas?

Open the hood and check the engine while its running at night ,you might see some arcing from a defective wire some where, make sure you do this when its very humid as that seems to be when it happens,good luck

That was a good idea. It's raining out tonight so I just tried it but didn't see anything. My 11 year old son had a good time revving up the engine though. ;)

Ok, I'm reviving this thread because unfortunately I still have this problem. I've used some Techron and I really thought it had cured the hesitation. I actually used another brand of fuel injection cleaner before the Techron. I thought the first injection cleaner cured the problem as the car ran fantastic for a few weeks. When the hesitations reappeared I gave the Techron a shot thinking maybe it was a better brand and would be the final cure. Unfortunately the problem still occasionally comes back to mess up my piece of mind. One day it'll run great. Next day maybe not. The car has just crossed the 100,000 mile mark. I have no maintainance records so I figure it's time for a oil change, oil filter, fuel filter, and maybe the dreaded expensive timing and water pump change. Any advice on what to look for will be appreciated.

Oh, I just wanted to mention that I think the humidity may have just been a red herring. I don't think it has anything to do with the problem. (I could be wrong).

PLUG WIRES

PLUG WIRES

You never mentioned what brand wires you originally put in when the problem first surfaced. Some wires just don't seem to work right on the Miata even when new. The popular opinion is that the NGK blues work the best for the money invested. There are others that work well, but generally cost more money.

ngk plugs and wires. I know it's the first thing to check so lets just say been there done that.

Bill, thanks for the advice. The wires and plugs (NGK)were changed but the problem returned a few days later. Last Saturday I had to drive three hours to play a gig and the car ran very rough part of the way back home and then ran okay the last hour back. It made me very nervous in rush hour traffic especially in sections where there was no place to pull over in case the car conked out. Yesterday I drove my daughter to her school two hours away (took part of snake run up here in N. Georgia) The car ran perfectly all the way up and back. I'll search for that ground screw and tighten it up. My only problem is it's hard to tell if it gets fixed or not as it's been know to work perfect for two weeks straight and then the problem resurfaces again.

Coil pack?