Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - '94 Civic VX stumbles/hesitates in limp mode only when hot

vxmike · 09-13-2014, 07:31 PM

Hello everyone,

I'm the longtime owner of a '94 Civic VX that I purchased with 118K miles in 2003 now sitting at 218K as my daily driver. Best car I've ever owned as I've hypermiled to 60+mpg routinely on the freeway (best tank ever 73). Up until last week I've only had to perform basic routine maintenance and never had a "problem". Since I've moved to Detroit with uneven roads, bad ethanol fuel, and cold temps it's been difficult to keep a handle on the mpg but I've been doing an average of 45mpg with 80% highway driving. I can't even lean burn 1/3 the year in the sub-freezing temps since my commute is only 15 minutes.

Last week suddenly the VX began stumbling and hesitating badly especially on acceleration. I know there's a million threads about the VX stumbling and hesitating when the O2 sensor fails, and I don't want to be that idiot who doesn't search. Thus far I've performed the follow diagnoses and experiments:

1) Unplugged O2 and EGR sensors and reset ECU to rule out a problem with lean burn. While in limp mode it drives OK while cold but once the car reaches full temp the stumbling and hesitation returns on acceleration. It's particularly bad if I drive for a while, stop somewhere then go somewhere else. On acceleration it just feels "stuck" until something finally "gives" and lets me go.

2) I checked the PCV valve and grommet and both appear pristine.

3) I did a Seafoam treatment (fuel and vaccuum feed) with no noted effects yet. No Seafoam in the oil though, since I don't want to potentially dislodge things that could be helping me after twenty years

4) There was a horrible rattle coming from underneath the car when I idle that has mostly gone away. Bad Cat? I don't worry too much with exhaust maintenance since everything rusts here anyways.

5) I've had the common jumpy idle syndrome for a couple years that has suddenly resolved itself without intervention. It never bothered me too much since I rarely idle on my commute.

Can anyone help with ideas for other areas to look at? I'll buy a wideband O2 sensor if necessary but it seems there is another problem. This issue developed suddenly without warning, but I've driven ~100 miles in limp mode so far without it getting better or worse. This VX is 100% stock, and the engine and trans are otherwise strong. I'd like to take this VX to its 25th birthday.

Thanks in advance if anyone can provide suggestions.

Not really interested in taking this car to a mechanic who likely won't understand the lean burn system anyways.

09-13-2014, 07:31 PM	#1 (permalink)
vxmike EcoModding Lurker Join Date: Sep 2014 Location: Detroit, MI Posts: 5 Thanks: 0 Thanked 0 Times in 0 Posts	'94 Civic VX stumbles/hesitates in limp mode only when hot Hello everyone, I'm the longtime owner of a '94 Civic VX that I purchased with 118K miles in 2003 now sitting at 218K as my daily driver. Best car I've ever owned as I've hypermiled to 60+mpg routinely on the freeway (best tank ever 73). Up until last week I've only had to perform basic routine maintenance and never had a "problem". Since I've moved to Detroit with uneven roads, bad ethanol fuel, and cold temps it's been difficult to keep a handle on the mpg but I've been doing an average of 45mpg with 80% highway driving. I can't even lean burn 1/3 the year in the sub-freezing temps since my commute is only 15 minutes. Last week suddenly the VX began stumbling and hesitating badly especially on acceleration. I know there's a million threads about the VX stumbling and hesitating when the O2 sensor fails, and I don't want to be that idiot who doesn't search. Thus far I've performed the follow diagnoses and experiments: 1) Unplugged O2 and EGR sensors and reset ECU to rule out a problem with lean burn. While in limp mode it drives OK while cold but once the car reaches full temp the stumbling and hesitation returns on acceleration. It's particularly bad if I drive for a while, stop somewhere then go somewhere else. On acceleration it just feels "stuck" until something finally "gives" and lets me go. 2) I checked the PCV valve and grommet and both appear pristine. 3) I did a Seafoam treatment (fuel and vaccuum feed) with no noted effects yet. No Seafoam in the oil though, since I don't want to potentially dislodge things that could be helping me after twenty years 4) There was a horrible rattle coming from underneath the car when I idle that has mostly gone away. Bad Cat? I don't worry too much with exhaust maintenance since everything rusts here anyways. 5) I've had the common jumpy idle syndrome for a couple years that has suddenly resolved itself without intervention. It never bothered me too much since I rarely idle on my commute. Can anyone help with ideas for other areas to look at? I'll buy a wideband O2 sensor if necessary but it seems there is another problem. This issue developed suddenly without warning, but I've driven ~100 miles in limp mode so far without it getting better or worse. This VX is 100% stock, and the engine and trans are otherwise strong. I'd like to take this VX to its 25th birthday. Thanks in advance if anyone can provide suggestions. Not really interested in taking this car to a mechanic who likely won't understand the lean burn system anyways.