Federal VX 26mpg
 

Hey all! I'd like to start by saying I've been reading many posts on this forum for the past couple weeks and have been really impressed by the knowledge and determination to follow a problem to the end that I've seen by a huge number of members on here.

On to my problem, I purchased my 92 federal VX a couple of weeks ago and got a great deal(or so I thought) on it because the previous owner said the car had a horrible stumble/hesitation and that it wasn't "burning all of the gas" aka it was running rich. I test drove the car and sure enough it bucked horribly but the check engine light was on and I knew that would most likely hold the answer to my problem. I the car home and checked the code, it was for engine coolant temp. I initially thought it was the t stat as the lower radiator hose never got hot but after replacing it I found that the lower hose still wasn't getting hot. I then proceeded to look online and found that vx's run cool enough that the heater core provides sufficient cooling and that the radiator is rarely used for cooling. I then went back to the basics, what measures the coolant temp? turns out the connector for the coolant temp sensor had come de-pinned, most likely from someone trying to disconnect it improperly. so I repined it and the light went away and it's been driving great ever since.

however, I went to have an emissions test performed and the VX failed due to high HC at idle, cruise, and slightly elevated CO at cruise. the HC measured somewhere around 700ppm at idle with an allowable 400ppm. I went home and replaced the improper champion plugs with the proper NGK zrf4f-11's, and reset ignition timing, it was slightly advanced. I have yet to return for my retest as I've already burned through 1 tank of gas in 252 miles.

I'm getting 26mpg and it smells like I'm running rich but the old plugs looked ok and the new plugs still look good after 75 miles. I just put a new oem distributor cap on tonight, I'm considering buying an oem o2 sensor as I'm not 100% sure the one in there now is stock and I have yet to check it with a dvm. any thoughts? thanks

Did you ever figure this out? It almost sounds like the same problem I'm having with my D15Z1(VX engine)

Yes and no. I ended up having to pay for an emissions waiver because I found out my catalytic converter is gutted so it does absolutely nothing for emissions. I also reset my cam timing and ignition timing, did a valve adjustment, cleaned my egr valve and tested my o2 sensor. The final time I did an emissions test I almost passed. everything cleaned up and passed with the exception of HC which ended up at 502 ppm.

I still believe something is slightly off because I'm only averaging about 42 mpg mixed city/highway and that's staying in lean burn damn near all the time, I have an MPGuino and pay attention to it quite often. I'm not sure if this mileage is just a combo of cold weather(long warm up times) and not having proper tire alignment or if its something engine related. I'll be doing an injector cleaning this weekend to see if that helps.

Wow, thanks for the quick reply!

Let us know how that injector cleaning goes.

Was the cat replaced? Perhaps the gutted one isn't creating enough back pressure?

These cars also rely heavily on EGR...make sure the EGR valve is clean and functioning properly.