I have an 89 formula 5.7 tpi.
my problems started a few monthes back. evertything was great.
then i started noticing the gas mileage was getting bad. it started getting worse and worse. I used to get around 25 mpg it sliped to 16 then to 12 and finally its setteled to about 10 mpg this transpired over a couple of weeks of daily 5 mile trips.
finally about 2 weeks ago it started surging during idle. it only does it while warm though. since it has been doing this it also started puffing black smoke when i first start it. then it clears up but it runs real rich and has lost a decent seat of the pants amount of power.
Im also just now getting a code 36. I tested the burn of wire to the maf and its getting 12 volts for about 1 to 1.5 seconds so i assume that is within perameters. one strange thing though if I unplug the maf and drive it i dont loose any power it just idles a little bit rougher. but the black smoke at start up goes away.
The vacume was tested. it checked out ok. Same with the fuel pressure.

List of parts with less than 600 miles on them.
injectors, fuel pump, ecm, spark plugs, wires,

Thanks for any help you can give in advance!

 

Also another part with less than 600 miles is the O2 sensor.

 

sugestions?

thoughts?

concerns?

 

Any help?


Bump!

 

Have you checked the EGR?

I had the same problem and while I was cleaning the IAC passages, I forgot to hook up the vacuum line under the throttle body and the car ran fine until I plugged the hose back in. I replaced my EGR valve and the hard vacuum lines under the plenum (I didn't realize how brittle those thigs were) and no more running pig rich.

Scott

 

It might be your MAF sensor. You could possibly have bad relays. I wouldnt doubt it. Swap your maf relay with your fan relay and see if it helps. If not, you might need a new MAF. Thats the problem with mine right now. And im getting new relays. If that isnt the problem, Im not sure were to go from there.

 

im going to check those two things out and see....

thanks for the ideas...

 

checked all the relays they work great.
but trying to figure out a good way to test the egr.

 

since i dont have a heated o2 sensor could this be a problem with my shorty headers. maybe not letting it go into closed loop opertation?

If thats the case when i put on the headers i put a new o2 in worked great for a while but could it have went bad because of the headers and then started getting bad gas mileage later.

and if thats the case is it possible to not set of a code but still have a bad o2 sensor?