iamsuperbleeder

So after my exhaust, I developed an idle issue. Don't know if it's related, but I guess it could be. The issue is it lopes like I have a big cam in it; some of you may know about the post about it

https://www.yotatech.com/forums/f116...nstall-167165/

So today I bought a brand new compression tester on my way home from work. The truck's got 293k miles on it, I figure it's about time anyway

results are as follows:

Cyl 1 - 190
Cyl 2 - 180
Cyl 3 - 190
Cyl 4 - 170

Cyl 4 is kinda off... maybe related? Could that much of a drop really effect it and be noticeable the way it is and as much as it is?

The other thing I noticed were the plugs...

these are about 3k miles old btw

cyl 1-4 from left to right



cyl 1



cyl 2



cyl 3



cyl 4




Yep, white coating on all 4; pretty consistant, but cly 3 looks a little more lean than the rest. To the best of my knowledge, plugs that have turned white indicate a lean mixture, which supports what I suspected; not getting anough fuel. Now maybe this means that now the motor's getting TOO MUCH AIR FLOW and the fuel delivery cannot keep up? The motor now has a 3" intake, header, no cat, and a turbo style muffler, and the smallest exhaust tubing diameter is 2" at the pipe between the header and muffler; everything else is either 2.5" (behind the muffler and at the header collector), with the individual header tubes from each cyl being 1.5". Maybe back-pressure related? I plan to put the cat back on soon, cause the smell or horrible... we'll see if that helps out some.

I also tryed unplugging a few sencors. The TPS brings the idle up some, which I expected, but it's still really rough and almost seems like it's got a miss.

What got me really thinking is when I unplugged the temp sencor for the ECU. The check engine light came on right away, so I know the computer is at least seeing it, but unplugging it did not change the way it runs at all. Maybe getting a bad reading from it? I dunno... I'm almost out of guesses.

Absolutely NO VACCUM leak that I can find, even those that's what EVERYONE is suggesting it is. You can argue that's what it is all you want, but I pretty much soaked the intake and every vaccum line in starter fluid trying to get an idle change, and the only thing that happened is I went through 2 CANS OF STARTER FLUID, and was very light headed from the fumes in the end... O2 sencor is MAYBE 20k miles old, TPS is about 10k miles old, AFM is a used one that I put on about 20k miles ago. Now I know about the possibility about maybe needing to adjust the AFM too. I tryed that, and all I was able to do it bring the idle up a little bit. But as soon as the idle would come up and I flicked the throttle a few times, I guess maybe the ECU was getting readings from the O2 sencor, and it would bring the idle back down, and then it would run even worse Cap and rotor look brand new; they should, I replaced them 3k miles ago with the plugs. Wires are maybe 5k old, and are all in brand new condition, NGKs, and they snap good to the cap and plugs. Coil is fairly old, and I might through the extra I got here on to see what happends. But if it's fuel related, the coil, cap, and wires aren't going to have anything to do with it...

My other thought it either fuel pressure regulator or injectors themselves. I got a vaccumm gauge today too, but ran out of time, so tomorrow maybe I'll test the vaccum line to the regulator and see if that's good, and I might try to pull a vaccum on the regulator a little bit at a time and see if that changes anything. I would hate for it to be an injector, cause man what a PITA to get out...

But that's about everything I can think of. I'm pulling my hair out over this... I've just turned the idle up to about 1200 for now, cause at least that makes it not as noticeable...

Any input would be great guys, thanks!

abecedarian

did you put a vacuum gauge on the manifold like I suggested?

iamsuperbleeder

that's tomorrow's plan, if time permits... I never know with my job... I got off ON TIME today, so I was actually able to do the compression test...

out of curiosity, do you know off the top of your head what the manifold pressure is supposed to be at idle, or even around 1000 rpms? if not, I can take a peek at the FSM

abecedarian

should pull at least a constant 17-20" HG (if the gauge reads inches H2O, that's a different set of readings). If the vacuum gauge fluctuates, or 'flicks' significantly, you are either severely lacking in backpressure, you have (a) burnt valve(s) or the valves aren't adjusted properly.
any guess which is most likely?

iamsuperbleeder

well with the idle bouncing, I garantee it's gunna fluctuate a bit but we'll see

that's at idle, er right around 800rpms?

abecedarian

have to figure if the vacuum is bouncing because of the idle or if the idle is bouncing because of the vacuum

iamsuperbleeder

haha, ok

abecedarian

mentioned before that a radical cam will lower vacuum... oddly, even though it flows more air.

iamsuperbleeder

haha, oh trust me, I know that for a fact... after putting a Comp Cam Thumper 291/311 in my 82 Monte Carlo... let's just say no power brakes untill booster swap


but this 22re's got a stock cam in it, so it needs to idle smooth... damnit...

abecedarian

oh ye of little faith.... lest ye not realize that with improper overlap thou wilst not have efficient scavenging when thine cylinders are scavenged well.
Thine intake charge mayest be more than anticipated were the camshaft duration and overlap not computeth properly... and what thee experienth as richer than expected charges wilst affecteth thine rpms.

oh yeah...
did you check the valve adjustments?

iamsuperbleeder

wth?

lol

no, but I need to check those valves... maybe this weekend...

I didn't get to the vaccum test today either; a good old friend of mine (one that's actually been loyal and hung in there that's becoming less and les frequent) had a little 6lb 12oz baby today, so I visited them at the hospital for a good part of the afternoon

maybe tomorrow, we'll see