Missfire.. Help

[Vsho93]

So as the title implies I have a misfire,

I caught it at the exact minute my flex pipe breaks , I think it's exhaust so I have a custom cat-back installed, now I get the car back and it sounds means as **** but still misfiring.

Today I replaced the DIS, Coil Pack, Spark Plugs, Wires but nothing.... except that the wires I replaced because they were arcing fiercely so I suspect a ground issue. Any suggestions where to start?

Btw: I get all my new parts for free ( except for exhaust ) so I have no issues replacing them, minus the time wasted changing them and not having that be the issue.

 

[LJRuddy]

Check the ground strap that is on the passenger rear on the intake manifold. That ground strap is key. Also, make sure those DIS bolts are tight and the crossover tube on the intake has both bolts tightened well.


Any codes being thrown?

 

[ilikepoultry]

check ALL of your engine grounds
i had the exact same thing happen to my 91 and it turned out to be bad engine grounds... pretty much every single one
you could also try the CKPS or the ICRM
i'd try engine grounds, because if one is bad, it won't get better on its own and it sounds exactly like my problem
i replaced literally the entire ignition system, along with the wiring harnesses and a few... other... things, including the PCM
i'd say engine grounds

 

[Vsho93]

car ran idle for 10 minutes to see if code shows up but car is passing,ground strap is good DIS bolts are new and tight , cross over checks out, where are all the other grounds, I'm assuming one is connected to the coil pack?

 

[Vsho93]

almost forgot , left the car off for about 6 hours turn it on and it idles fine, press the gas and everything fine, about 3 minutes later starts to miss again.
I tried to record but my camera phone doesn't like my new exhaust so I won't be able to post a vid.

 

[LJRuddy]

I am uncertain as to where the other engine grounds are. The one that I would think would be the usual cause is that rear ground strap that I mentioned before.... Heres a bump so someone else could inform us all where the other grounds are located.


Another idea that poped into my head as a random thought was the coil pack. Perhaps it runs fine until it heats up which would then cause the misfire? Never heard of this happening before but it might make sense. Only way that i can think of testing for a bad coil pack (as i think aloud here) would be to find which cylinder(s) are misfiring. The coil pack fires 2 cylinders at the same time so if there is 2 cylinders that are misfiring at the same time, perhaps it might be the coil pack...


Im sure this idea will get shot down but its all this tired mind can think of at 2 in the morning

 

[Vsho93]

The car doesn't want to start anymore, could also be a bad starter or crank sensor so this I decided to recheck for codes if the car starts... this is what came up when I finally got it going:

koeo

111 - System checks OK
111 - System checks OK
111 - System checks OK
111 - System checks OK




koer

216 - (M) Primary circuit failure - ignition coil 2 - Ignition Systems
167 - (R) No Throttle Position sensor change in "goose" test (must get at least 25% rotation) - TPS
222 - (M) IDM open or high or right coil pack failure - Ignition Systems
116 - (O,R) Engine Coolant (ECT) sensor out of range - ECT
157 - (R,M) Mass Air Flow signal is/was low or grounded - MAF
225 - (R) Knock sensor not tested (ignore if not pinging) - KS






cylinder balance test


30 - Problem with cylinder 3
30 - Problem with cylinder 3





Anyways I got a new starter in the trunk, maf was replaced recently, and I also recently replaced the coil pack twice to be certain I even tested them ( lied to my boss and told them they failed so he would exchange them anyways ) any suggestions?

 

[hawkeye18]

My goodness, that's a lot of codes.

216 suggests a bad coil pack, but if you've replaced it twice already, then that ain't it. I would tend to think at this point that you've got a bad wiring harness.

I just discovered that the TPS, KS, and ECT all go through a common connector; C133. It's right below the throttle body; check to see if it's unplugged or corroded. If the MAF, TPS, and ECT are all bad, I'm amazed that the car runs at all. The car really depends on the MAF and TPS to figure out what RPM you're at/commanding.

Anyway, start with that, since I doubt your TPS, MAF, and ECT are all bad at once. Also, check the PCM connector for pushed pins, and check the DIS connector for good contact; the IDM is the Ignition Diagnostic Monitor from the DIS to the PCM to tell the PCM what coil the DIS is firing and when.

Cylnder 3 is the back right cylinder. That sounds like a completely different problem, since all the ignition problems point to the front bank of cylinders...

 

[SHOZ123]

I've seen the silicone gasket on the coil pack connector if not properly inserted would prevent the primary harness plug from not seating right and cause a miss.

 

[Vsho93]

I believe that the maf is an old stored code since it was replaced and at that time the car did not run properly due to failing and I also forgot to hit the pedal on time so that could explain the tps code, I will be checking the connector next, just weird cause I come back hours later and she starts up runs fine until I rev up, then she misses again.

 

[SeanMc]

When I couldn't figure out my problem, I ended having to replace the wiring harness. It wasn't fun, but it was what had to be done. Car runs like a champ now.

 

[Vsho93]

Just checked the connectors and everything is fine I even removed the silicone in the coil. When I started it ran fine for 5 minutes then it started missing after I hit the gas I shut it down and it would not start, I'm seriously considering changing the crank sensor.

 

[ilikepoultry]

it sounds like it could be
some of the engine grounds that were bad on mine were actually just wire wrapped around another inside some insulation
believe it or not, the outer wire corrodes and the inner doesn't, which was why they were replaced

as for the crank sensor
i replaced mine a total of four times
the first time it was bad
the second time the one they gave me was bad
the third time it didn't get screwed down tight enough and got caught
and the fourth time it wasn't gapped to the engine, just to a recommended gap
everyone's engine is different, so just keep that in mind
i had a guy i know do mine, and it turned out mine needed a gap of about .005" to be optimal, however Ford and SHOPP say .030"

 

[Vsho93]

I'll give the grounds another go but still haven't been able to find them all, even with my subscription to alldata

*edit *


Thanks to my Boss for finding the ground locations , I will post them here but will not be able to check until the morning.

Here they are:

Ground Locations

G100 Lower LH front of engine
G101 Top LH side of upper radiator support
G102 Top RH side of safety wall
G103 Center of LH front fender apron
G104 Front of RH front fender apron, behind G106
G105 Top front of engine
G106 Top front of RH front fender apron
G107 Front of LH front fender apron
G108 LH side of upper radiator support
G200 Behind RH side of I/P, below glove box
G201 Behind lower center of I/P, above warning chime module
G2O3 Behind lower center of I/P, near warning chime module
G205 Behind lower center of I/P near warning chime module
G301 At LH front door sill
G400 (Sedan) Center rear of trunk, on latch brace
G400 (Wagon) LH rear corner of cargo area
G402 (Sedan) RH front of trunk, near trunk lid hinge
G402 (Wagon) RH rear corner of cargo area
G403 (Sedan) Below center of rear package tray, on vertical brace, near amplifier
G403 (Wagon) In rear of LH rear quarter panel, near amplifier

 

[Vsho93]

checked the grounds and they are fine, I was going to pull the crank sensor but thought I'd run the codes again this time the list was smaller

koeo

111 - System checks OK
111 - System checks OK

stored code

122 - (O,M) TP low (possibly grounded or open circuit) - TPS
122 - (O,M) TP low (possibly grounded or open circuit) - TPS

koer

116 - (O,R) Engine Coolant (ECT) sensor out of range - ECT
(sensor looks worn so I will replace it tomorrow or later today if possible )

cylinder balance test


30 - Problem with cylinder 3



on the balance test when the car shut down 3 it ran way better, when it turned 3 back on it missed again. I now believe the crank sensor could very well be fine as well as the ignition system but am suspecting injector 3 could be the culprit, has anyone run into any issues similar where it turned out to be the injector?

 

[hawkeye18]

it has happened before. Injectors have a life span too! It's very little effort beyond pulling the intake to get the injectors off. I would recommend having all 6 cleaned and flow balanced at a shop for ultimate sleep-at-night-comfort.

 

[SHOZ123]

I was wondering about this and asked a couple of FI cleaner/flow balance places this question.

If I send in 8 FIs (for the V8) and two are not flowing as good as the rest then what? Should I send in 10?

Got no direct answers other than the fact most FIs once cleaned, rebuilt and tested are usually all very close together in actual performance.

 

[Vsho93]

sending my car to dealer , turns out we don't stock the injector so can get the hook up on it ( unfortunate ) anyways I was going to have the injectors cleaned to see if anything changes, was hoping for some insight on it or should I just fork up the money for a new injector.

 

[dpsutphin]

I had a similar problem. Turned out to connector to the TPS. One wire had gotten a little loose inside the connector. The wire would pull loose with engine movement and cause the car to die, and then not start for while.

Try having someone wiggle those wires while cranking the car, or while it is running. Just a shot in the dark, but can't hurt to try, and it's a cheap fix if that is what it is.

Good Luck.

 

[Vsho93]

Did not take the car to dealer , instead I took the intake off and am installing one of the 6 injectors I got for free, thanks to my guy for looking out will have it installed sometime tomorrow will let you guys know if it solves the problem.

btw I did however have a friend of mine who works for midas check the car out , injector 3 is infact not working properly after pulling the intake off the pig tail was not holding down properly due to the clips being broken off but even after we go it plugged in it was still causing the miss, hopefully one of these injectors work ( since their used but can't really complain ) thanks to everyone for your quick replies