Help! Need to figure out miss fire issues so i can start raising turbo boost

[TuxMask-Andy]

Well here is my dilema.

My car is missing slightly at idle and cruising conditions. Does not appear to be missing at full throttle however that may be caused my higher revs tend to blend in the miss

I replaced sparkplugs, replaced wires, replaced coil pack. Still got miss fire

I did full compression and got 180 across all cylinders.

I rechecked all ground cables and they are all grounded


So what can my problem be? Cam sensor or some sensor that might be causing a miss?

[062stang]

well there are 4 basic types of misfires.
1) rich misfire
2) lean misfire
3) ignition misfire
4) mechanical misfire

looks like you can rule 3 and 4 out. check to see if a cylinder is running rich or lean by reading plugs or something. sometimes even a vacuum leek can cause a mis.

-umesh

[TuxMask-Andy]

I forgot to mention i had this problem before turbo install. I just couldn't hear it as much but now i can since i got a louder exhaust.

So im on stock injectors and stock tune at the moment so can't be a rich or lean condition.

I did check spark plugs and they all looked good. So i know its not a big miss fire just a small slight one in a way like i would need a tune up

It has to be a bad sensor or clogged injector or somethin. Engine does got 110k on it

I'll check for vacume leaks. I haven't had time to install my boost guage yet :(

[LincTex]

Do you have a wideband O2 that you can borrow from someone??

When was the last time you cleaned the little wires in the MAF?
Cleaned throttle body?
PCV valve?

......by the way, those are NOT all created equal. I tested 8 different brands/styles of PCV valves before I found ONE that can handle boost!

[Danny Baker]

Lots of luck, I have 196,000 miles on my engine and of had a miss at idle for 146,000 of those miles. At idle only. I have changed maf,injectors, plugs, plug wires, dpfe sensor, etc sensor, even added a Vortech supercharger, its not any certain cylinder I have pulled plug wires while it was running and they are all hitting. Runs great other wise. Please let us know what you find out.

[TuxMask-Andy]

Okay fixed problem.

I fixed it with by turning the egr, evap, rear o2 sensors all off thru the computer. I installed a base force induction tune. This ended up fixing my miss fires at crusing conditions.

My car runs a lot smoother. However I feel my car is 2 solid now. It has to much timing i think and im getting a pinging noise at wot. Feels like its running 87 octane and makes that ping noise.

So im gonna pull some timing out or just slap bigger injectors and retune it again.

[LincTex]

Okay fixed problem.

I fixed it with by turning the egr, evap, rear o2 sensors all off thru the computer. I installed a base force induction tune. This ended up fixing my miss fires at crusing conditions.

I would like to see you do just one at a time, to see if you could isolate which device was the problem. It would help the rest of us.

[cgrant26]

Besides a wideband O2, is there any reliable way to distinguish between too much timing and too little fuel on a detonating engine?

[Danny Baker]

Besides a wideband O2, is there any reliable way to distinguish between too much timing and too little fuel on a detonating engine?

great question.

Andy do you use SCT on your computer things?

[99cruisin]

hooray for 100 octane!!:chrisb: You can get some up the street from me at a 76 station. they have 100 at the pump and 110-114 in the back. then you won't have to pull timing yet.

[TuxMask-Andy]

great question.

Andy do you use SCT on your computer things?

Yes I use the sct software.

Good question about 2 much timing and not enough fuel if there is a way to distinguish.

I don't think there is a way to distinguish it. So i may be running lean. So i will use a wideband tonight and verify whats going on with the pinging sound. My timing is set pretty low at 12 degrees at high rpms.

I dont' know. My new tune makes the car feel more torque and aggressive. I guess i automatically assummed there was more timing. At lower rpms there is more timing but at higher rpms 4k+ the timing is lower then stock. So I will try to get to the bottom of this. Maybe my injectors are maxed out at 40 psi fuel pressure. I may need to raise fuel pressure. Maybe my maf is peg.

Well i do know that the stock 21 injectors are rated at 210 hp max at stock fuel pressure. So im quite sure i need to raise fuel pressure now. Will raise fuel pressure tonight and see if that changes anything. Kinda strange b/c i wasn't getting pinging before when i had service engine light and stock tune at 4.4 psi.

Next week i plan to put 39 cobra injectors and cobra maf. So i'll do as much testing as i can at 4.4 psi.

I do know my car is making A LOT of power at 4.4 psi.

[_J_]

Andy good to know you fix that problem,
and welcome our domino world.. :D

[LincTex]

I do know my car is making A LOT of power at 4.4 psi.

Feels like a whole 'nother car now, Huh!?!
Would like to see some dyno numbers at 4-5 psi

[taylor0987]

Andy, were you getting a misfire code or did it just feel/sound like it was misfiring? Was the car kind of bucking?

[CHADD]

hows your tps or iat sensors? those could cause it...

[jday001]

i've had this exact same problem for a really long time too. if someone can pin it down that would be awesome. i've cleaned my maf several times and checked voltages on sensors (did compression test too). i'm tempted to just start replacing sensors but i really dont wanna if i dont have to...

[jday001]

and also...very strange but i was having some EEC problems a while back and put in a 5 speed computer for the hell of it. the miss totally went away and my car idled and revved up smoother than ever. when i got the new auto computer and put it back in the misfire problem came back.

my car seems to run pretty well, just misses if i stomp on it, and sometimes it bucks at cruising speed

[taylor0987]

and also...very strange but i was having some EEC problems a while back and put in a 5 speed computer for the hell of it. the miss totally went away and my car idled and revved up smoother than ever. when i got the new auto computer and put it back in the misfire problem came back.

my car seems to run pretty well, just misses if i stomp on it, and sometimes it bucks at cruising speed
bucking at cruising speed could be too much EGR (caused by a failing DPFE). Disconnect the vac line from the EGR valve and see if you still have the bucking. http://www.v6power.net/vb/showthread.php?t=19525&highlight=bucking

[_J_]

bucking at cruising speed could be too much EGR (caused by a failing DPFE). Disconnect the vac line from the EGR valve and see if you still have the bucking. http://www.v6power.net/vb/showthread.php?t=19525&highlight=bucking


EGR cause too much problems just delete them all.

[P-feif]

Okay fixed problem.

I fixed it with by turning the egr, evap, rear o2 sensors all off thru the computer. I installed a base force induction tune. This ended up fixing my miss fires at crusing conditions.

My car runs a lot smoother. However I feel my car is 2 solid now. It has to much timing i think and im getting a pinging noise at wot. Feels like its running 87 octane and makes that ping noise.

So im gonna pull some timing out or just slap bigger injectors and retune it again.

The rear O2's won't do anything to cause a miss, all they can do is tell EEC to turn on the Check Engine light. I really doubt that the evap system would do that, you would have to have one hell of an air leak in the evap system that would allow air in without going through the MAF. If that was the case the engine would idle high. EGR is the problem. Something is causeing the EGR valve to hang open. Check the EGR circuit, that's where the problem is (that is if you are going to keep EGR on the car).

[TuxMask-Andy]

Okay guys.

Found out why my new tune on stock injectors is causing pinging. Its actually a lean air/fuel ratio my wideband is gettin 15.5 to 1 at wide open throttle. Its not even richening the air/fuel when i step on it at low rpms 2k-3k

For some odd reason the base force induction tune on my sct dealer package makes the car run leaner despite the fact that the maf curve and stock injectors is left at stock settings.

That must mean some other setting on there is causing the car to run leaner. Im guessing its when they change the load values to be above 1 ( above atmospheric pressure) it somewhat causes everything to run leaner and needs more fuel added)

Car air/fue ratio ran fine on stock pcm settings.

I will now have to modify the maf curve to richen up the air/fuel mixture.

So ya the moral of the story is. If you hear pinging. Your running lean. Even thru a P0171 and P0174 which means lean.

[TuxMask-Andy]

Okay richen up fuel curve by 25 percent. Still lean at 14.5. However im not detonating no more.

I logged in a 4.7 maf voltage in 2nd gear around 5k. Close to peggin but has not pegged.

I'll try to richen it up one more time and see if i can get the desired air/fuel. I may be making more power then my injectors can hold even with a current 60 psi fuel pressure setting.

[OrangeV6F150]

Glad your on track to figuring her out.Aren't turbos fun>?:D

[TuxMask-Andy]

Final conclusion of this thread.

I raised fuel 40 percent over base tune. Ran good air/fuel. at 4.4 psi. However it likes to lean out but still got good air/fuel 11 to 1 then leans out to 12 to 1 at high rpms. With more tuning im sure i could aggresvily tune the fuel curve more to pump more fuel so it doesn't lean out as the rpms climb

Well enough testing 4.4 psi im tired of it. I swapped to bigger 03 cobra injectors and maf. Realized the cobra maf is pegging like the stock maf so i will need to get an sct maf next. To be continued.