No luck with misfire... >:(

[monkeydude3]

well I'm really startin to think this is fuel related.

I took all four plugs out, cleaned them, cleaned the wire contacts and everything and put them back in. Here's the kicker, plug #3 (3rd from the crank pulley) looked to be running leaner than the other three, like they were all greyish and this one was a lighter grey.


when i put the plugs back in, I fired it up. Always to check if i fixed it I brake torque it in drive and hold it at 1500 rpm. I did this, for about 10 seconds it was smooth as silk, and then like a light switch it started misfiring again.

I really think I have an injector issue or something... would someone be able to tell me how the fuel system works on this setup? Like injector wise, and what's an easy way to check them on this car. It's obd1 and I have no access to diagnostic computers so it's kinda gonna have to be back yard style. Tonight I'm gonna buy a bottle of cleaner and fill up my gas, and run another tank through it with cleaner and see what happens.

Any input please let me know! Thanks


George

[MRX]

only thing going through my mind was injectors. May just have to swap out other ones to find out if it is or not. Theres plenty of ppl here that would be able to sell you some for cheap...including me if i can find them. There's no real way to test out the injectors without pulling them completely out and getting them flowed and tested.

[monkeydude3]

now i described how it went from smooth to misfire like a light switch while hodling at 1500 rpm in brake torque.

coudl this be just a dirty injector... or is it more likely that one is bad..

at any case... what would the going price for those be on here... oye

[MRX]

probably like $20 total. Could be clogged or bad. But you already tried cleaners. I'd just buy others since its real cheap and easy to replace. Could even be distributor timing

[monkeydude3]

so $20 per injector, or $20 for four?

Well i ran some seafoam t hrough this tank of gas... i'm gonna buy a bottle of cleaner th is afternoon and fill my tank with it and fresh fuel and after that next tank of gas i'll see wher ei'm at, but the way it went from smooth to misfire points directly at an injector

[MRX]

$20 for all of them put together. Talk to the turbo guys they'd probably give em' up for shipping costs and a happy meal.

[F22-GURU]

I know I'm coming in late on this one but have you actually checked for any Vacuum Leaks around the Injectors or Intake Manifold. The symptoms you explain sound like a classic case of a Vacuum Leak or Valve Timing Problem.
Just checking for Vacuum at the Hoses will not eliminate a Vacuum Leak as the cause.
Get a spray bottle with water in it and spray around each Injector at the Manifold. Also Spray around the Gasket between the Manifold and Cylinder Head.
If the engine stumbles it will be leaking where you sprayed.
Recheck your E.G.R Valve and make sure it is not sticking open slightly.
Also check the PCV Valve.
Another simple test is to connect up a Vacuum Gauge to a constant vacuum source (not ported) and observe the Needle.
Many a fault can be diagnosed with a basic vacuum gauge.
Have you checked the Compression or done a Cylinder Leak Down Test?
Just a couple of suggestions for you.
Cheers
Geoff

[Otto]

^^^ I need to get compression and vacuum testers.
Sorry, nothing useful to add. All already been said.

[monkeydude3]

no have not done any mechanical checks of the engine yet. When I pulled the plugs, there was no trace of anything odd on the tips... all were grey, no oil or nothing. But I mean other than those exact conditions (warmed up, 1500 rpm, light load) it runs smooth as a nut. No stumbles, plenty of pull to redline, etc etc. Idles great. I tried spraying the carb cleaner at many vacuum lines, checked all over to no avail.

however... you just reminded me to check the injector seal themselves and spray the cleaner there.

So my stumble could be caused by either an injector vacuum leak, or an intake manifold leak? Hm....

thing is... I think I'm gonna put this problem , or fixing it, on hold... because yeah it's about 10 degrees average here outside and I am real busy with school, movin in and getting into firefightin.

THanks for the info everyone... i can't wait to get at it with this one and get it runnin better. oye

George

[monkeydude3]

well so today I let it warm up until it started misfiring under the load with throttle, let it sit and idle a few mins, and then I started sprayin carb cleaner around. I tried around each injector, and at every place i could along the entire intake, from the head/manifold back. No where causeda sputter, stumble, rev, etc etc, had no effect on it. So I don't think it's pulling it in.

I think it's pretty safe to say I got a turd injector??


George

[monkeydude3]

well I've run two tankfuls of injector cleaner through it and it's still there.


I have a few CB7 owning friends here and one of them showed me this piece on the front of the intake manifold near the throttle body, and he said there is some sort of screen/filter in there that gums up and can cause my problem? I have no picture of it but it's held in by two bolts and has two hoses going to it...

I'm gonna take that apart and clean it out soon and see what that gets me


George

[monkeydude3]

okay I found this thread....

http://www.cb7tuner.com/vbb/showthre...hlight=misfire

read through it, and now I'm thoroughly confused. I don't know if I should go after the EGR ports or the O2... because it only does this thing once the car is warmed up, I'm liable to lean towards the 02.... but then again....

Is there any way to check as if it's one or the other? This thread describes the exact issue I have been having..

EDIT: Would I be better off just blocking off my EGR? Because this car is a beater, not worth sinkin a lot of money and time into tearin apart the egr ports (and I don't really want to, got enough other crap to do) Am I gonna harm anything by blocking off the EGR?

George

[monkeydude3]

well I blocked off the EGR and it runs smooth as a nut. We'll leave it like this for now

[Otto]

Glad ya figured it out. Maybe not a actual fix, but what the hell. Least you know where to go if you decide to fix it.

[monkeydude3]

Yeah, I cannot justify cleanin those ports out, it looks pretty involved and for a 221000 mile beater I just can't do it. Not when my main car needs a headswap.... that's where I'm puttin my time

It runs fine for now! haha