Daniel6718

it backfires through exhaust...
history car sat for 3 years i built a cam only lt1 for it...cc306 tune rockers longtubes ewp ect
car wouldent initially start(put a fresh tank of gas in it premium)
jumped the injectors with 12v and they call came to life...then it had a dead o2 so i got a new ac delco got the car inspected ect great...put about 25 miles on it then gave it to the customer...now he brings it back 150 miles later its poping through the exhaust...randomly

on my scanner it reads bank 1 sh term fuel trim is 25% bank 2 is 0%...so for some reason bank 1 is dumping 25 % more fuel...off idle the car is perfect...

checked for vac leaks...o2 move fast and from 80-900 swapped them from side to side and its great...also changed the injectors from 1 side to the other sprayed carb cleaner all over the intake no leaks...removed and blocked pcv, its a 96 and has no misfire counts...(i did unplug injectors 1 by 1 and still didnt get any missfire counts...any help?

Guest47904

First, did removing the clips from the injectors cause the engine to run rougher at every clip? Or was there no change at some or one of them?

Could someone have jumped out the CKP with a resistor or the like?

I believe you have an ignition issue where it's firing occasionally. Fuel is building up in a cylinder and then eventually gets lit and fires.

Pulling the plugs can start you in the right direction. Look for one that is sooted up more than others.

Also try using an inductive timing light on each plug wire while it's running to look for a flash pattern that indicates a plug doesn't fire occasionally while the problem is occurring.

Daniel6718

kool ill do that...and no all the injector clips didnt make it run rough...at one point i had 5 off...complete driver side and 1 pasenger and it was iskeig the same...it seems at low rpn it has a miss above about 2k its fine smoother but down on power...

im not sure what you mean about the cpk/resistor? he said nobod has touched it since i built the car...im goana try the timing light thing...noid light thing...and pulling the plugs and rail and look to make sure everything looks normal

Daniel6718

meant to say only thing i noticed out of place was the iac is 80-85 at idle? thought it was supposed to be about 40 at idle?

HardcoreRM125

If its a cold idle, it could read higher.

Also, FWIW - I have unplugged injector clips and had it make no difference. It really really freaked me out? I still don't understand it. I went, 1 at a time, unclipping each of the 8 cylinders (individually) and clipping them back in with no noticeable difference. It scares you to think how unnoticeable a dead cylinder could be...

Daniel6718

this one has a dead cylinder but the exhaust temps are almost identicle within 200 of eachother with a pretty even spread...i think its ignition...i put new msd wires but i just noticed i put the old plugs back in it...so im goana do new plugs, then timing light to check them our...then a cap and rotor...

whitehooptie

I've seen plenty of crossed plug wires cause the exact same problem.

Daniel6718

you and me both...but car was fone for the first 150 miles...no poping and pulled great to 7k

Guest47904

Alright help me out here. I got one thing I want to know. You said you have no misfire counts and I inadvertently asked if your CKP was bypassed. Just now I noticed in your signature that you have a 94!!!!

A 94, if that is what you have, does not have a CKP and can not monitor misfires. Thus that is why you don't have any. So you gots a 94 or not?

Second, are you saying you "ran" the engine with all the drivers side and 1 of the passenger side injector clips off?????? And noticed no change in the idle???

If you pull an injector clip and no change occurs to the idle, obviously you have a dead cylinder.

I will reserve judgment on the capacity of an engine to run with dead cylinders for later

And oh yeah explain the customer and if you feel like it the "3 years".

whitehooptie

His car is a 94. Not the car he sold.

As far as the injector "clips", those are the clips that hold the pigtail on the injector itself. The pigtail is the end part of the wires on the harness. Correct?

I haven't run the clips in my car in over 5 years. I do in one because the pigtail will not stay on the injector.

whitehooptie

Just thought about it too, how does the ground strap from the driver side between the ABS block and the cruise control look on both ends? I know my from years of moving around had partially busted off and gave me all sorts of problems.

HardcoreRM125

Whitehooptie - Yea the clips hold the pigtail to the injector. On a cammed car, it gets pretty tough to hear/feel a difference with just one pigtail disconnected.

Daniel6718

got it guys the metal "anchor" looking piece of the rotor has 2 plastic pieces stick through it and they are melted...the outside one broke/melted and caused the anchor to move and have too much clearence i supposed to make the spark to the cap

they need to make a rotor with that piece screwed to it

whitehooptie

I had a similar incident years ago. Don't know what happened but the rotor melted about 1 pole off. So instead of it firing on 1, it was firing 2 even though it thought it was firing 1.