'90 Festiva - Sputters and Dies When Warm

[MrSamNC]

Hey guys, I tried searching and the chatbox first, so I'm here now.

Helping my brother on his 1990 Festiva 5-speed.

The car will sputter and die when it gets up to operating temperature. He changed the fuel pump last year, so it's new-ish. When this first happened he thought there was bad gas from a local station. Poured a can of octane booster and Heet into the car. Still had the issue. He has also changed the fuel filter. He also just put on a new set of plug wires.

I checked all electrical connectors, vacuum lines, and such. Everything looked fine.

I suspected the TPS (next to the throttle body/butterfly valve area), but unplugging it made no difference in the vehicle's performance.

Thoughts?

[hot4dl8ly]

Does it restart right away or does it have to cool down before it will restart ? Are you losing spark or fuel pressure. (post should be in repair help section)

[MrSamNC]

From my brother: "I will start up for half a second if you hold the gas pedal down but dies again when you let off."

[Studebaker]

Need to carry a spare spark plug with you. When it starts acting up check for spark.

Go ahead and replace the cap and rotor.

[blueoval]

have you done compression test? oil and coolant both clean

[MrSamNC]

He replaced the cap & rotor recently. Good idea on spare plug to check. I'll do that. We've not checked compression.

So this begs the question... what frequently goes wrong with these engines to cause this? What overall causes do you guys have in mind that this could be?

He's told me that in the rain, the car would loose power when driving and he was told (by previous owner... a "kid") that the distributor cap would get water in it that it needed a gasket? I've never heard of this.

I am mechanically inclined and do all my own repairs on my cars, but this not being my car and me not being familiar with them, I'm turning to you guys for knowledge.

(Side note: My avatar is a festiva I owned years ago. I only owned it for a few months before getting rid of it -- too many issues with rust.)

Thanks!!

[firebush357]

Water on the distributor will cause arching/misfiring. You can try some RTV on the gasket to see if that would help.

As far as your original question, try disconnecting the Engine Coolant Temp sensor on the back side of the engine.

[Rick the Quick]

My '88 was sensitive to water. I found it to be like an old point ignition car. Don't pressure wash without carrying a can of WD40 to spray under the cap and wires. I once owned an MG that was sensitive to water. I used a tennis ball and fabricated a water proof seal for the cap. Here is what Toyota used on their '86 Hilux pick ups. I'm not sure you are having problems with the cap and rotor but when you mention losing power in the rain it sure sounds like an ignition related problem being caused by moisture. I would not waste any time on checking the compression. If the problem was low compression it would be a constant problem. Not a problem that was related to rain. Good luck!

[hot4dl8ly]

Sounds like a Vane Airflow meter concern, if its sticking this can happen.

[MrSamNC]

Hey guys, I know I hate finding a thread where the OP never replied if the suggestions fixed their issue so I wanted to follow-up with what (appears to have) fixed the issue for us.

Overall we think replacing the coolant temp sensor (located near the intake manifold, on the firewall side of the engine) fixed the issue of the random dying.

As for the issues when driving in the rain: putting some black RTV on the cap and sealing it good (while also leaving a weep hole) seems to have fixed that issue.

Thanks a ton for your help!!!

[needragr]

So troublshooting a new to me 93 with similar issues. Ran fine for .5 hr or so then starts loosing power. No PU from low gear off idle speed. Like starving for gas. Eventually wont drive. Idles but cannot get under way. Smells ...hot. If turned off for a period of time, will drive again.. rinse & repeat.
From the solution provided above what is the causation ? Why would the coolant temp sensor affect power/ running?