FEOA Forums banner
1 - 8 of 8 Posts

·
Registered
Joined
·
475 Posts
Discussion Starter · #1 ·
I have a 91 LX that jsut started to sprout a missfire. Ive head this car for awhile but havnt drove it all the time. it has 132k miles but it runs great otherwise. The missfire just started happeneing when it got cold here, and when i say cold i mean 15-20 below zero. Ive replaced the spark plugs 2 months ago so i doubt it could be that, but i will check them anyways. In WI we are having issues with reformulated fuel causing problems with injectors and even on cars that have only 6,000 miles. Its been mainly happeneing with GM vehicles but for is up there to. I am wondering if one of my injectors is intermittinly sticking. Its dosnt missfire all teh time, when its cold it will do it here and there evreey couple of seconds at idle. When its warm it wont do it at idle but if a hold a constant speed around 60 mph or so i can feel it surge and buck very lightly but i do notice i will loose speed gradually untill i push done on the accelerator a bit. Im not sure where to start, coudl be an injector, TPS, MAP, MAF. IABV. Any one have this sort of problem before?
 

·
Registered
Joined
·
2,709 Posts
Yes, my sister's festiva has been having a very similar problem. I dunno if the gasoline recently has just been bad nationwide.

I haven't noticed a difference in my 12A rotary engine in my RX-7, but then again... it also has a compression ratio of like 4:1 and it's carbureted.

From my carb experience, it usually means that you're running too lean if you get some sputtering when you're driving at constant throttle. If you're surging, is usually means you're running too rich.

What is likely the problem in your case if you're both surging and sputtering is that your ECU is in open loop mode. When it's in open loop mode, it basically tries to achieve stoichometric fuel mix by dithering between lean and rich. The cause of open loop is either

1. You're at idle
2. You're above 40% throttle position (not sure on the % for escorts)
3. The o2 sensor is sending an out of domain voltage

Chances are it's the 3rd, which means that your o2 sensor hasn't gotten to operating temp, or your o2 sensor is dead.


If could be a thousand other things, but from your story, it sounds like that's it.
 

·
Registered
Joined
·
475 Posts
Discussion Starter · #3 ·
Ive never had a problem with my RX-7s either and i have 3 of them. Its just with the scort. I replced the O2 sensor this summer but i still have the old one and it seemed fine, just replced it cause i didnt know when it was replced last. I also have an air/fuel ratio gauge in the scort and it seems to jump from lean to normal all the time except when im above half throttle crusing above 60 then its one bar in the rich to 2 bars in the rich when its floored. The O2 sensor is heated to it shouldnt take more than 30 seconds to get to normal operating temp but i will try and put the old one back in. If its nto the O2 then what else might be causing it. Ok What are all teh sensors or valve that contribute to teh fuel ratio? TPS, IAC, MAF, MAP, IAT, am i forgetting any? This is really bothering me because its not only affecting my gas milage but its a pain in the ass having to drive a car when i know somethigns wrong.
 

·
Registered
Joined
·
2,371 Posts
I have been having a "surging" problem like Siragan mentioned, and if this problem is only occuring at low temps then it is prolly the O2 sensor not being up to temp, if I let my 93 get up to normal temp the problem goes away, if that's not happening then check the other two options, but try letting it warm up before you give it the throttle, I notice the problem at 45%+ of the throttle.
 

·
Registered
Joined
·
475 Posts
Discussion Starter · #6 ·
I have it prety much narrowed down to either Map sensor or IAC. I have a Air/Fuel ratio gauge and it shows a lean condition when im staying at a constant speed at 60 to 65 mph. If i hit the gas the gauge jumps to normal but when i hold a constant speed and the engien is not under muc of a load it goes back to lean and thats when it surges and bucks but its very soft. I also noticed that the onyl time the gauge shows a constant reading is when im floored or close to it then it shows a slighty rich condition but other than that the gauge jumps around constantly from extremely lean to normal. As for the missfire at idle it happens all the time cold or warm in gear or out. Im thinking that it has to be either the MAP, IAC or MAF. Was also thinking ti could be the fuel pressure regulator but then it shoudl being doing it all the time not only at a certain rpm and speed.
 
1 - 8 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top