Car runs rich! bad MPG! tips?
 

Could anyone please gimme some hints/tips/tricks to troubleshoot this crap? My car backfires like a mother****** as soon as i step off the gas and upshift, or depress clutch and release gas. If i ease off the gas pedal, it isnt as severe. Now then, this has caused a few other things (i think the problems are related). The car has a WEIRRRRDDD idle, which i've stabilized quite a bit now... its fairly smooth, but it has its days where it idles quite rough, jumping from 750 to 1.2K RPM. This also results in HORRRRRRRRIIIBBBLLE gas mileage. I've tried different fuel types including 87(daily), 89, and 91. No such luck. As well, when the car is in neutral, and i floor it, it takes it like half a second to respond. Thats pretty sluggish from the throttle sensitivity you would expect from a rotary. I dont know if all of them are like that, but any help will be INCREDIBLY appreciated. The car has been well maintained and babied, the throttle position sensor has been set (as per the advice of www.k2rd.com), its a 1987 GXL 13B. I also have a K&N filtercharger element. Thank you for taking the time to read this.

Did you check your ignition?
New spark plugs?
New spark plug wires?
Verify the spark plugs are firing?




-Ted

Yup, timing was checked and set (even though the ecu automatically advances the timing when neccesary). Spark plugs were replaced, wires are in good shape and were replaced by previous owner not too long ago.
Lemme know what else it could be plz
i am thinking oxygen sensor... how much do those puppies cost?

How bad is your mileage?
Do you do a lot of freeway driving?&nbsp This is basically the only time the O2 sensor is used.




-Ted

bout $10CDN a day, freeway and city driving. Mostly to get to work and back, (60KM in total)... gas being $0.62 cents a liter.... i'm not sure... but thats pretty sh*tty... Thank you for replying

sounds just like my car...
 

My 87 T][ was doing the same thing, so after numerous trouble shooting (as you did) I took my car for the first (and last) time to the dealer. They performed the following for the pricey sum of 900 USD... Adjusted the MAF (Mass Air Flow Unit), replaced the TPS (Throttle Position Swtich/Sensor), replaced the O-Rings on all four injectors (my car had an external fuel smell), replaced the Oriface tube on the boost sensor and rewired a bunch of stuff (melted wires underhood). Car comes back on Monday, and I'll leave for vacation asap (Supposed to leave tomorrow morning, but car @ shop 'till monday).

I dont think i want to spend $900 to have mazda turn a few screws and write me a fat bill, like the dealer here in my city is known to do. If anyone has any ideas on how to solve this problem please let me know. The backfiring doesnt bother me, its the lack of response and the bad gas mileage that is pissing me off. Please let me know if you have any ideas on what to check next.

my car used to run that way once also though it is an N/A
but the problem was I found out the prev owner removed the tps but once I found one and put it in and adjusted it the car ran great no more backfires, bad gas milage, or crappy throtle feel

Yeah mine is N/A as well. Although, i've already adjusted the TPS and it goes from 1K to 4.5 KOHM. So no problem there. Is it possible to adjust the mass airflow sensor? Is there anything else i can check??

Those Bosch oxygen sensors run only 26bucks in Texas. Bought one sunday for the turboii to insure passing emmision insp. Passed. Salvage car returns to the hwy legally today (2500 illegal miles racked up with no insp sticker or license tag). The other advice I would give is to download the factory manual from the web, then go to the *Control Unit* section. There you will find two pages that tell you what to expect on each pin of the three plugs on the ecu with the engine running. Might give you a clue, like the air temp sensor being bad, oxygen sensor bad, water temp sw bad etc. You could look at you enging fault codes by making a simple less than 10 lite device. Instructions are on the www.fc3s.org site I believe. The manual is there also.

Cool cool :) where can i get that manual? Anyone have any other advice?
Thanks for all your help guys.

Once again, thank you for everyone's help... but the issue is still not resolved unfortunately :(
any more ideas?

as recommended by Six Rotors:

1. coolant temp sensor(although driveability would be a problem)
2. manifold air temp sensor
3. air intake temp sensor

I'm really thinking that it might be a bad TPS. Mine has pretty much the same problem, and I think it might be the TPS. I'm going to get a new one soon and see if it fixes the problem. I'll let you guys know.

-Derek

TPS's are pretty expensive, u might wanna try the junkyard first. sometimes someone has already changed a new one right before junking their vehicle...one can only hope.

my TPS is acting up as well, will need to change it soon too.

Most likely its one of your injectors stuck open. Thsi si the reason for the very bad MPG and the back firing. Fuel keeps flowing even when its not needed. Get it replaced.

U should be able to get a TPS cheap from a junkyard. How do you know its rich?

if it were a leaky injector wouldn't his engine be flooding out all the time?

btw fingers, have you done a compression test?