My 5.5 cyl International....fixed with seafoam believe it or not

[GOT2B GM]

Update: my diagnosis skills suck

 

# 1 cylinder isn't getting FUEL.

 

I pulled the plugs wires one at a time and stuck a spark plug in the end and verified each plug is getting spark.

 

Pulled the #1 plug out (the misfiring cylinder - idle doesnt change when #1 plug wire is pulled) and the plug is dry (no fuel)

 

Dead injector on #1 I'm figuring. What else could it be? Fuel pressure is 40-45 psi.

[GOT2B GM]

Another update. Pulled the plenum and the fuel rail.

 

Ohmed out all of the injectors. Injectors 2 through 6 read 12.5 ohms spot on.

 

Injector 1 read approx 1.5 ohms

 

Swapped out injector 1 with a remanufactured injector that also had a resistance of 12.5 ohms.

 

 

Figuring I had the problem solved, I reassembled everything, only to have it missing on the # 1 cyl still.

 

 

I have spark. CPS, ICM, coils, wires and plugs are all new or tested good (ICM).

 

I even swapped spark plugs from one of the other cylinders, and pulled the plug out and grounded it to watch it spark. I definately have spark.

 

 

So now, I'm thinking whats left?

 

Fuel pressure is good (40 - 45 psi) Injector is brand new. I'm thinking a short in the injector harness. Of course the #1 cyl is on the back bank so I can't get at it with the plenum on to test if the injector is getting a signal to fire.

 

AND seeing as how its MPFI , all the injectors fire at the same time, and are fed by the same 2 wires that split off to each injector at the fuel rail.

 

So theres no tracing the harness back towards the ECM.

 

It must be damaged at some point between where the harness Y's off for the #1 injector and the injector itself.

 

I guess I'm down to pulling the plenum back off, and doing continuity tests between each injector plug, and the main plug at the ECM.

 

 

 

 

 

 

Any thoughts? Im running out of ideas.

 

 

 

[19Cutlass94]

The connector on injector #1, measure it for resistance and voltage, and compare that to the rest.

[GOT2B GM]

The only thing is, I can only get at the connector with the plenum off ......and I obviously cant run the engine with the plenum off.

 

I've already done the resistance checks. That why I was thinking a continuity test, to check for breaks or shorts in the wire.

[Robby1870]

What you've thought of so far is what I was going to suggest. Continuity test on #1 injector wires. Other than that, a clogged fuel rail?? That seems rather unlikely though.

[Crazy K]

I got zinged!!!!!! :lol: :lol: :lol: :lol:

 

At least I brought one TGP back from the brink. time to work on my cars.

 

 

you are on task. I believe that you can do continuity between the injector plugs, as they are batch injected as mentioned.

[GOT2B GM]

Thanks for the input guys.

[5speedz34]

I really haven't had a whole lot of experience with fuel injectors in these cars, not to mention wiring in general but good luck!

[GOT2B GM]

Wiring checked out fine.

 

I ended up swapping out the entire fuel rail / FPR / injector assembly from my 92 Z34 parts car just for shits.

 

Now it only sporatically misses at idle. While driving down the road it runs great.

 

I'm thinking of running a strong injector cleaner through the system and changing what looks to be the original fuel filter.

 

 

 

this car..........its a good thing I like it.

 

[Crazy K]

time to do a compression check. no ifs ands or buts.

[GOT2B GM]

I did one but the engine was cold. Its supposed to be warm. The readings for the entire rear bank was 175 -180 psi

 

the front bank varied a bit # 2 was 120. # 4 and 6 were 150 ish.

 

BUT! that was cold.

 

The suspect cylinder (#1) had great compression tho.

 

I was thinking if there was any dirt down at the bottom of the deep spark plug cavities on the LQ1, preventing the compression tester from getting a good seal, that would throw off the numbers a bit too.

[5speedz34]

If you're going to change the filter (which sounds to be orginal). Run some fuel injector cleaner through it, and seafoam the bitch. Then go from there.

[Drummer]

I call CPS too. You know you can test it at the connector at the ICM? I can give you the directions.

 

How can/do you test the CPS?

[GOT2B GM]

update:

 

3 cans of seafoam later (one in the gas, one in the crankcase and one in the intake) and shes runs like a champ!!!

 

 

No more miss, no more hesitation off of idle. Runs A1.

 

Maybe it was carboned up a bit from being a low mileage city driver?

 

I dunno.....but its fixed.

 

I call CPS too. You know you can test it at the connector at the ICM? I can give you the directions.

 

How can/do you test the CPS?

 

If your car runs, the CPS works.

[ManicMechanic]

I need to pick up another can of Seafoam...

[5speedz34]

LOL.

 

Maybe because it was a old lady's car who never drove it?

 

I call CPS too. You know you can test it at the connector at the ICM? I can give you the directions.

 

How can/do you test the CPS?

 

PM me and I can tell you directions.

[White93z34]

If your car runs, the CPS works.

 

not necessarily. I can personally vouch otherwise.

[Crazy K]

If your car runs, the CPS works.

 

not necessarily. I can personally vouch otherwise.

x2 you can actually have a working cps that gives out a poor/erratic signal.

[AWeb80]

sweet Matt!!!!

 

I split a gallon of seafoam w/ a coworker.....I got a half gallon right here in the apt...LOL

 

 

seafoam is FTW!!!!!!!!!!!!

[EviLette]

sweet Matt!!!!

 

I split a gallon of seafoam w/ a coworker.....I got a half gallon right here in the apt...LOL

 

 

seafoam is FTW!!!!!!!!!!!!

 

Agreed.

 

Threw a couple cans of seafoam into my motor when we swaped it into the Pontiac out of the Cutlass. One in crankcase, one in fuel IIRC... and the motor runs just GREAT. Couldn't be happier about it, though the rest of the job was done kind of shittily. Meh. Ya live, ya learn.

[shadow]

I am considering seafoaming my car when it starts to run rougher but its cool that it fixed your problems . All I hear are good things about seafoam. I put that chevron techron in my engine but did not notice any improvement.

[Brian P]

I wouldn't keep that oil with a whole can of seafoam in there for too long. That really thins it out. Most people do like 1/2 or even 1/3 can in there.

[Captain Ficho]

I wouldn't keep that oil with a whole can of seafoam in there for too long. That really thins it out. Most people do like 1/2 or even 1/3 can in there.

 

I believe you are supposed to change the oil out within 100 miles of the seafoaming, regardless of how much you put in.

[AWeb80]

I change my oil immediately......

[Crazy K]

I add 1/2 a quart of tranny fluid... and change it the next day after driving to work and back.

 

tranny fluid is basically what STP additive is, and many old schoolers would use tranny fluid to pour down into a carb just like we do with seafoam... with the same resultant smoke!