Misfiring After Warmup

[eclipsepunx]

Ok I have asked this before and searched and everybody contributes it to bad plugs/wires or boost leak. I really need to figure out this problem because I want to drive my car.

Car runs awesome when cold but when it warms up it starts missing on acceleration and if I try to give it some gas it will backfire occasionally. Like it starts running so bad that I can't drive it because it has no power. Here it what I have done so far and i'm running out of cash so I really need to narrow it down so I can only get the part I need.

Changed plugs- twice bkr6e's and bkr6e's v-power gapped at .48-.50
changed wires - twice
compression - 165,165,170,165
changed cam sensor
cleaned TB and IAC
coil test good
fuel pump clicks on every time

Now the car did sit awhile (about a year) during my build. I swapped engine and trans. Timing is good. Idles good around 800-900 rpm's. So i figured it was bad gas although I drained the tank prior to build. I just can't figure it out because it confuses me that it only happens when at operating temp. I was gonna change the fuel filter but I figured if it were that it would happen all the time instead of just while warm. I have also heard that it may be a clogged cat but it looks like all I have is a resonator underneath. Doesn't look like any cat i've ever seen anyway. I have driven this car probably only 30 miles in 2 years! I love it but I am really about to get rid of it if I can't figure this out. Serious help only please and thanks for reading all of this.

 

[eclipsepunx]

I will try that. It makes sense because that is kind of what it feels like. But I got plugs the first time and after driving it only a few times to the store and back they were white. Could they still blow out if i'm lean?

 

[bullettdsm]

Hmm....O2 or coolant sensor?

MB

 

[eclipsepunx]

What should my O2 read at idle. I tested it and it was getting like .02. That is with the car not running. I thought any reading is a good reading. And it looks good as far as appearance. I know that doesn't mean much but... and my temp gauge works so I didn't even think about that but how do I test it and what should it read?

 

[96TurboGS]

I don't know if measuring the voltage on a 02 sensor is going to tell you if its bad or not. If you had an oscilloscope you could measure the wavelengths or just replace it with a new one to see a change. 0 is rich 1 is lean, you should see it advancing from 0 slowly to 1. I know I was seeing something like .6-.7 when engine/02 was warmed up. Telling us the voltage with the engine off doesn't tell us anything, you have to have it heated to get an accurate reading. Do you have any CEL's? Have you checked ohm/voltage specs on all the sensors (map, tps, iat,clt, ect)? I know having a logger solved most of my problems.

Edit: i just seen you had a 95 ecu, hmm

 

[jd420a1995]

ok this may sound crazy i change my battey and my wireing harnest by the egr hose the wireing got hot and my car started blowing coil pack it sound like what my car was doing i had to change my wireing harnest check that wireing harnest by the battey and egr hose get back to me

 

[eclipsepunx]

Harness is tucked neatly out of the way. And there is no cel. I wish there were. This seems like a problem that would definitely throw one. I tried to keydance to see if any codes were stored and got nothing.

 

[jd420a1995]

ok be sure my looked fine too untill i cracked it open and seen the wires

 

[eclipsepunx]

i'm leaning toward the O2 sensor. It has all the symptoms except my idle is ok. It will be a few weeks before I can get one so I will post back results. Feel free to give more advice in that time period.

 

[rstchris]

The coolant sensor that goes to the gauge is not the same one that goes to the ecu. Hook up a scan tool and check out what the sensors are doing.

 

[eclipsepunx]

Ok but what am I testing for? Voltage? Resistance? What should it read?

 

[chemillion]

it could be a cracked piston that spreads when warm

 

[eclipsepunx]

Why would you say that? And it's a new engine. Been like this since the day I started it up.

 

[chemillion]

i know someone that had the same problem it was a hair line crack and every time his motor got warm he would lose power just throwing in an idea

 

[chiuchimu]

You said you changed wires twice.

Did it solve the problem temperately the first time? Else, why change the second time?

Reason is, I had a car with bad distributor, it kept burning out the spark plug wire. it ate serveral sets of wires before I wised up.

 

[Zardoz]

You state that the coil tests good. Is that when cold or hot or both? And even if the resistance is within spec there's still the slim chance the coil is misfiring (need an ignition scope to see it). I take it you're getting misfire codes. If they are for cylinders 1 and 4 or 2 and 3 then I'd really suspect a bad coil.

 

[eclipsepunx]

I changed the wires twice because the first time they were used wires but were suppose to be good so just to make sure.


Coil is testing good hot and cold. And i'm not getting any codes. Anybody know why i wouldn't get codes from this? It is a pretty bad misfire.

 

[eclipsepunx]

The more I thought about it the more I started liking this coil theory so I went to my local pull a part and got a couple of coils to test out. So when I get home from work today I will test this out and hopefully it will work. Wish me luck.

I also got a (non-eprom)ecu that was laying around out of a 97 gst spyder if anyone is interested.

 

[rush2252]

It sounds like Crank sensor or coil. Possibly CAM sensor. I worked on a 95 avenger 420a it would do the same. It ended up being a CAM sensor after it FINALLY threw a CEL.

Coils can act the same way as well. Whenever they heat up they begin to breakdown and you will notice issues. Whenever it cuts out does the CEL flash off and on?? This indicates a dead cylinder. It definately sounds electrical due to the fact it acts up only when warm.


Kolby

A failing crank sensor wont throw a code either. It will just begin to have intermitent signal issues to the cam and coil.

 

[eclipsepunx]

I already replaced the cam sensor. I got from work today and was ready to put on the new coil and noticed that someone stole my brand new tires off my carport! So I was too upset to take it for a drive. I filed a report with the cops and i'm hoping that i get lucky seems how no tire store in town sells those tires. Wtf is wrong with people?

 

[96TurboGS]

Simply buying a Chilton's / Haynes manual and probing the sensors for the correct values would be your best bet. I believe for the 95's your fuel filter should be located on the firewall, it wouldn't be a bad idea to change it if you haven't in the past 60k or so miles. If it's misfiring you're probably running lean from either lack of fuel to the rail or a faulty ecu (highly unlikely but possible if everything else checks out) or a sensor giving a false reading. Buy a fuel pressure tester either online or the store and place it on your fuel rail test port and let us know what you see. You're looking for something like ~47-50 psi. Also, Cleaning your injectors and fuel pump filter along with running gas treatment wouldn't hurt.

 

[eclipsepunx]

Well finally drove it today and it still does it. By the time I got back home from a 5 minute drive the idle started searching and it seemed like it was gonna die. It didn't but it was pretty crappy. This sucks because when I first drive it it pulls hard and i'm thinking to myself " this car is awesome" but a few minutes later i'm like "you piece of shit." And I can't buy parts I don't need. I'm poor so I need to try to narrow it down.

 

[Zardoz]

Sorry to hear about your tires being stolen. I hope they catch whoever did it.

How is the car running at Wide Open Throttle (WOT)? At WOT the computer should switch back to open loop like when the engine is cold? If it's doing one thing in open loop and another in closed loop that might help narrow things down.

You said in an earlier post that your plugs were white after only a few trips. This sounds lean. Take a look at this site and see what plugs best match what you're seeing and let us know. Keep in mind that your plugs don't have as many miles on them as the ones in the pictures.

Reading Spark Plugs Healthy Spark Plug Photo

If what you're seeing with your plugs doesn't jive with what you are getting from your O2 readings and it run better at WOT (ie when the computer reverts back to open loop) then it probably is the O2 sensor.