Poor fuel mileage, random Idle speeds, and no tach.

[David9er]

So the wife let me get the talon because the MPG's should be way better than my V-8 Dakota [14.6] but it is getting very poor mileage at the moment, about 10 and the A/F gauge had been constantly reading 16+ at highway speeds.

I took a quick look over the car and found the NGK plugs where improperly gaped [about .020] and they were improperly tightened, the sealing rings on the plugs had not been "crushed" and using a 1/2" drive ratchet the plugs offered no resistance to being removed, in fact I think I could have removed them by hand with just a socket an extension. This seems to have helped but its too early to tell but the A/F is improved to 12.9-15.9 but its still not as consistent as I'd like under normal highway driving. I'd like to see 14.6-14.8 consistently I'm not sure what is a normal range for this car.

As the title says the tach does not work so I can't give exact numbers but I can hear that the idle is not consistent and probably way too high so I'm sure that is not helping. I took a quick look at the steps listed here: BISS vfaq and found someone has probably done this because the cap it says not to lose is gone and the screw looks to have been poorly siliconed into place! Thankfully its not too bad because I can see the screw and remnants of the silicone like someone went back in after and tried to adjust it a second time.

I'm sure this is related somehow but given the early winter weather [50-65] the car has been difficult to fire when cold. It takes about 5 mins and about 7-10 attempts to start the engine and keep it running so I'd imagine that some lost fuel too.

I know a good tach is essential to help diagnose some of these issues so I did a search and found this was the easiest and most common fix: http://www.dsmtuners.com/forums/newbie-forum/410779-90-model-dead-tach.html so I went out to take a look at the filter and found this repair has ALREADY been done! If any one could point me to the next issue that would be helpful, Also I was considering getting an aftermarket tach but I'm not sure if that would bypass the problem of if the issue would affect that tach too

BTW the first thing I did was drop the boost down to about 5-6 psi. I imagine this is the best setting for mileage or am I missing something?

 

[DSM1G90]

Did you do the ISC reset, or test before adjusting the BISS screw - this is the most important step with setting a correct idle RPM.

Also, AWD chassis are a bit heavier than FWD chassis, thus mileage will suffer as well.

Does the CEL light come on on occasion or at all?

The previous owner wanted .020 gap so the spark wouldn't snuff out at high boost, but for everyday mild boosted driving, have them at .028 to .030.

Hard starts could point to a bad temp sensor, not a temp sending unit, which the bad sensor may not throw a CEL light....and even to a tired ECU.

I'm getting an avg of 25mpg on the freeway with my Turbo Laser to give you what is possible.

Good luck - DSM

 

[David9er]

Since the tach is not working I have not tested or done the reset yet. 25 mpgs would be the goal but for now I got to get it above 15 or the wife makes it go byebye. I have not noticed a CEL light while driving either. As for the temp sensor the one that goes to the stock gauge has been rewired to an aftermarket gauge, the previous owner said this might have something to do with it but the research I've done contradicts this.

Progress! Looks like the spark plugs did the trick. It's exactly 30 miles round trip to work and back and the talon only used an 1/8th of a tank so the math says....approximately 20 MPG! YaY! , I know it's not spectacular but it's double what it was and more importantly better than the truck!

The tach is the next thing I'd like to tackle, if anyone knows what I should do next or if an aftermarket tach would work it would appreciated