Okay I've been having very intermittent, random misfire on usually cyl 4. Sometimes it's 4 and 5, and rarely 4, 5 and 6. I normally clear the codes and drive on doing random fixes when I have time. It's been happening for the last year usually when freezing temperatures always when the mode is OPEN loop (ie no O2, and other sensors, being used yet).

I've done random things in attempt to fix like swap coils, new plugs, cleaned PVC, iacv, , replaced the MAP, replaced egr, cleaned the Idle air bypss valves, and seafoam. All those help to some degree especially the MAP & idle air bypass. In particular I noticed before the MAP and Idle air bypass fix my cold idle was about 200-300rpm lower than normal.

Since then I rarely get any misfire except the other week after I ran some fuel injector cleaner thru the tank. So I figured I was not clear of my misfire woes. Figure the fuel injector cleaner lowered the octane just a tad.

Today as another task to help alleviate the problem, I am in the middle of adjusting the valves. Just when I had everything opened up I realized the cyl 4 is furthest from the fuel pump followed by 5, then by 6. So my theory now is fuel delivery the issue rather than a clogged injector. What do you think?

I've got 103k miles.

 

If any thing a fuel injector or ECU issue (seeing you replaced plugs and coils)

 

Okay since I have the cylinder head still off, I'll run out and get 3 injectors for 4, 5, and 6. I'm tempted just to do #4 due to cash flow issues, but I'd feel like an idiot if #5 and #6 cropped back up.

I'm reading the service manual now and didn't know there was a loosening sequence for things. The engine was cold, do you think any warpage may occur?

Also the gaskets, do you think I need to replace as suggested by the service manual? They look good still. Can they be cleaned or anything?

Thanks!

 

before you rip it all apart
When you say you SWAPPED the coils- did you buy 1 new coil and try it on each cylinder- resetting the ecu each time

 

Codes are clues- not diagnosis, and not to be cleared because the CEL bothers you

 

no i did the swap method. when 4, 5, and 6 where more common a yr ago winter, i swapped 1 and 4, 2 and 5, and 6 and 3.

i've been clearing them and fixing as i get free time. now it doesn't go off unless i degrade my fuel slightly like add injector cleaner. and it's only cyl 4 that acts up.

if i didn't reset it all the time i would not have seen a pattern in the freeze data. the big clue is it only happens w/ engine cold and in OPEN loop. So i've only changed/cleaned items that are active in open loop (except for the egr because i didn't see the pattern a yr ago). this is why i'm in the middle of adjusting my valves and yeah it's all ripped apart right now.

 

You mean you just moved the coils around and didnt buy one new one and move that one around?

 

correct

 

you have accomplished nothing- as you know

One or more coils has a problem, and you keep moving it around like a naughty priest~

Try buying 1 new coil- get the codes read to have an idea which ones to try it on to start with, reset ecu- test- move new coil to next cylinder, reset ecu- test- move new coil to next cylinder reset repeat as needed until problem coil found

With all this- I would seafoam it good too- once the coil is found- going to be loaded up on the weak cylinder
Injector failure is pretty rare- codes can mislead you

 

Wouldn't swapping coils move the misfire? That's what I've based my assumption on. Also, I am guessing that a "weak" coil would produce a lower voltage for the spark and the misfire would be more random, we'll actually when there was a lot of fuel to burn. Would this be under idle or heavy acceleration?

I guess one question is how accurate is the ecu in determining which cyl is having a misfire? Can it by off by 1 cyl or something?

Anyhow, I finished adjusting my valve and cyl 4, 5, and 6 was a little tight on the exhaust. Not sure they were out of spec enough to cause my problems.

How about dirty causing poor spray pattern?

I did buy 3 injectors but maybe I'll just replace just cyl 4 since I have it open. I read sleeperblues latest post and he mentioned that the dealer replaced the "front three" and he's happy. Not sure they were just selling him injectors or if there is something mysterious with the "front three" ie. 4, 5, and 6.

If this doesn't work I'll try the new coil and rotate...

Anyhow here is my freeze data from the latest p0304 in case it's helpful:

tps 9.4
rpm 992
load 48.2
map 14.5
coolant 72
iat 48
lt fuel % 0.8
st fuel % 0
mph 5
sys1 open
sys2 n/a

 

If it gives a code of multi cyl misfires its usually just 1 bad coil- but the car throws several codes because its not certain whats wrong
Sometimes it is the cyl listed on the codes= sometimes its not!

Since its not an exact science on the codes you have to get a known good fresh new coil and try it as descibed before--
this is the common part failure a month or 2 after a plug change too- if mishandled even slightly- the coil is damaged internally and fails soon after

Injectors are easily cleaned with a bottle of Redline SI-1 fuel cleaner or a can of seafoam in 1/2 tank of gas
Seafoam the intake vac port to clean off the loaded up pistons and valves
that alone solves many problems. tune up in a can- when a code is not already there

 

Trying to figure how I can test my injectors. If I energized the fuel rail, then placed each injector in a cup, and manually pulsed each one with 12 volts would that give me a poor man's test. I will then be able to see the spray pattern and check for any leaks. Seems easy/crazy?

I guess I can go a step further and remove the "bad" ones and soak the nozzle in 100% seafoam/carb cleaner and keep it open (with 12 vdc), allowing the solution to enter the injector. Would it hurt the injector if I kept them open for say an hour? or are they designed for quick pulses and I would fry them?

 

how do you know if you misfired? will the engine act different?

 

It will run rough. Your check engine light will go on with code P030x where x *might* (as i am learning now) be the cyl your misfiring on.

 

and your car will start shaking. i just had one of my coils go out on me.

 

A pro shop is needed to properly test and adjust the injectors if needed
and its a specialty job- not a regular shop job
Needs flow bench to test before and after rates and amounts

Dont screw with whats allright- go fix the real problem!

 

yeah when i pulled out the fuel rail i realized they were just pressure fit w/ an o ring so if i did energize the rail they would leak or even act like a projectile and shoot out.

i wound up replacing the front 3 injectors.... i was going to just replace 4 since that was the problem child but since the others were staring at me I gave in and did 5 & 6.

have it buttoned back up and relearned my idle. all seems good for now.... i still have the injector cleaner in this tank so we'll see if the CEL comes back.

 

drive it 100 miles and check for codes- even without a CEL

 

The best thing is to buy one new coil as mentioned previously, then swap. Make sure that you have the new plugs properly torqued. Also you mentioned replacing the EGR....did you check the passageways for obstruction ? Just a shot in the wind !

 

Yeah EGR isn't a variable in my misfire case (usually idline engine cold - fuel sys OPEN). I didn't figure out till later that this was my misfire condition.

Yeah my ports were partially clogged. Prob about 20% typically but one was 45%. Cleaned everything out pretty good.

 

you removed the intake manifold assembly and cleaned it thru the egr ports and intake runners?

EGR blockage will mess with idle, the valve itself is probably ok- its the passages inside the intake manifold that need to be well cleaned every 75k miles or so

 

When the engine is COLD the egr is open- recirculating some exhaust gasses to heat the manifold and speed engine warming- then it can get on the lean fuel circuit faster

 

OH okay thanks for clearing that up.

Anyhow I think it *might* be okay now. I had about 100miles on the tank w/ fuel injector cleaner (and about 200miles on fresh 93 octane gas) and the temps were similar so it should have set the code if it were still bad. Read the codes but mine doesn't do pending codes so there wasn't anything there. I used an ELM w/ EasyODB.

Won't really know for sure till next winter because it happens more during subzero temp.

 

shoot i can't edit the post after 5mins... anyhow i meant to say, that 100m w/ the injector cleaner should have set the code. with virgin gas it doesn't set it unless it's subzero.

 

are you still getting misfire code?

 

no, CEL light is off and scanner shows no codes.

 

I don't think this is correct. Egr is typically inactive until closed loop operation, usually around 180 deg F. Also not at idle, even when fully warmed up.

 

you're right- I misexplained-
when its dead cold its not operating- there are temp sensors in the system so the extra carbon loaded full rich fuel mixture is not allowed to gunk up the egr ports with carbon--which the TL has a problem with anyway!

Once it has SOME temp-( I dont have a number) then it kicks in, except a full throttle or idle-no load conditions where the mix might cause idle problems or stalling