Cascade Crew

Raiden · Member Joined: 10 Mar 2004 Posts: 193 Location: tacoma

Maybe some of my brothers here can point me in the right direction. I posted this on TGO and got nowhere with this topic.

At the end of my rope!

A few months ago, I was running my supercharged Z28 all out. I hit the laughing gas, but the gas was empty. The empty bottle caused a backfire when I activated the system. At the same time, actually before I did this, I had a rocker nut that was backing out and I had to re lash the rocker. I got the rocker lashed correct and then I make this run. I jump on it and then my engine made a huge detonation, so I back off and limp it homes. I pull my valve cover off and the intake push rod on the intake side ( #6) was bent. I bought a new pushrod & I put my Z back together. It started and was idling like crap and then got worse to the point it will hardly run! I’m thinking…wtf? I do a compression check and I have an even 190psi in all cylinders except for two on the other side that read 175. I pull my fuel rail and I see a few leaking injectors. I pull my heads and have a leak down test preformed, then had my heads looked at by a reputable machine shop. I had a 20% leakage on two valves; not the affected side so they lapped the two valves. Heads are fine now. Then, I replace my injectors with new injectors. I put my care back together and now, my car will still hardly hold an idle, no change at all! I’m getting 5 inches of vacume and I have to advance my timing to get it to hold an idle. I lashed my valves ½ turn past zero lash. I’ve not a clue of why I can’t get my car to idle? Current compression check is 190 in each cylinder, brand new fuel injectors and plugs. Plugs are BLACK, 5 inches of vaucme leads me to believe a huge vacume leak or something messed up in my valve train. I’m throwing no codes at all. So what will cause my vaucme to run at 5inches? And why will my car hardly hold an idle? My thoughts are leaning toward a huge vacume leak, but I’ve taken down my intake twice and have had no change in my idle and vacume issues? I put a vacume gauge to the egr and it holds 25 inches. The diaphragm does stick if I put 30 inches of vacume to the egr and that was making me think to block of the egr to see if that resolves the low vacume and no idle issue.

I don’t think one bad cam lobe or bad lifter on one half of a cylinder would cause such a drastic change in my idle and create such low vacume??? When I try to open the throttle, the car stumbles and hardly gets past 3500rpm's.

If it was a bad cam lobe or lifter, how would I check for any variances? I have a dial indicator.

I’ve a 91 Z28, roller cam and lifters, standard rocker arms, 9.5/1 compression with a paxton sn 2000 blower ( I run 9 psi boost)and a 75 shot of N20 via NX express, 30lb injectors, crane hi 6 s ignition, new cap and rotor, AFR 190 heads, slp runners.

I recenty put my intake on with an egr block off plate incase my egr is the problem.

Help…please

Dewey316 · Posted: Mon Sep 10, 2007 3:17 pm Post subject:

You might go through and relash things, if you had a valve stuck open, that might cause some problems. Running that rich just screams vacuum leak to me.

Twilightoptics · Posted: Mon Sep 10, 2007 3:21 pm Post subject:

Check vacuum lines. With a backfire as large as you say you easily could have fried the brake booster, or your fuel pressure regulator, or your IAC motor, etc. Anything vacuum was attached too. I'd start there.

You might think about new plugs too. If you hit the n20 and the bottle was empty, you dumped ALOT of raw fuel in there and may have fouled one.

Definitely start w/ vacuum

Raiden · Member Joined: 10 Mar 2004 Posts: 193 Location: tacoma

Brake booster! I'm gonna have to check that!!! I"m taking my girls, wife and duaghter to Disney land after shift tomorrow. I put brand new plugs in my Z, checked my IAC which works as I pulled the IAC and watched it as I jump the A and B ports. I pulled my fuel psi regualtor and inspected the diaphram and it looks perfect and my fuel system holds 43psi for a long time. I though my injectors were bad and it was leaking at the manifold where the injectors seat. I purchased brand new 30lb injectors and that was not the problem either. I lashed my valves twice and it's not the lash as each valve is exactly lashed 1/2 turn after zero lash.

My thoughts from here are checking the brake booster for vacume and pluging the vacume line to see if I can see any difference in my idle/vacume issue. Also, new O2 sensor. I have put my egr block off plate on just incase it was leaking from the egr....but I doubt it was leaking there since the egr was holding 30inches of vacume.

Great comments everyone...thanks a ton!!! I can't wait to get back home and work on my POS! Sad

Twilightoptics · Posted: Mon Sep 10, 2007 4:31 pm Post subject:

Don't worry about the O2 right now. If it wont hold an idle cold, the o2 isn't even being looked at, at that time so it's something else.

Raiden · Member Joined: 10 Mar 2004 Posts: 193 Location: tacoma

I forgot to add, after I tore the intake down the last time, I looked into the port for cylinder no 1 and there was fuel puddled in the chamber of the head. Sure seems like a vacume leak. I had planned on changing the O2 sensor anyway, jsut incase. He11, I've spend so much freaking money on this pit, what's another 70$.

Dewey316 · Posted: Mon Sep 10, 2007 4:39 pm Post subject:

since you know you are only pulling 5" of vacuum, that has to be the reason. Unless you have a radical cam in there, you should be getting quite a bit more than that.

BigDaddyVu · Posted: Mon Sep 10, 2007 4:44 pm Post subject:

pull the lifter from the bent push rod and see how easy if it comes out. you might have damaged the check valve in the lifter when it bottomed out or mushroomed the bottom of it.

Raiden · Member Joined: 10 Mar 2004 Posts: 193 Location: tacoma

BigDaddyVu,

I suspected something like that may of happened. However, My compression check is solid! 190 psi in each cylinder. I wish I would not have put my intake back on yesterday. I should have inspected that lifter. When I lashed my valves, I backed it off till it started clacking loud, then went to zero and 1/2 turn past zero. That rocker seemed no different that the other's.

Dannng! Wish I would have pulled that lifter! Evil or Very Mad

Sellmanb · Member Joined: 30 Nov 2004 Posts: 727 Location: Tigard, OR

One bad lifter would cause one dead cylinder. One dead cylinder will not (on a V8 atleast) cause a lack of idle and 5" of vacuum. You'd have to be missing on like 3 cylinders for that.

That's a massive vacuum leak. Take the vacuum line off the intake that goes to the booster and plug it. See if idle quality changes. Start from the outside before you rip apart the top end of the motor again.

Raiden · Member Joined: 10 Mar 2004 Posts: 193 Location: tacoma

Yea, I was thinking the exact same thing, just forgot to post it on my last reply. I too thought, man, one lifter could not cause the darn engine to have 5inches of vacume. Taking the intake apart again is my last resort. I'm tired of working on the darn thing! Bashy Bashy

I'll keep ya all posted when I put it togheter next week. Thanks for the replies and keep m coming! Just trying to get this thing running again. I miss driving it, especially since I have only 20 miles on my new rear tires Crying or Very sad

Dewey316 · Posted: Mon Sep 10, 2007 7:06 pm Post subject:

being a roller cam, I would think if it broke, it would break and you would know. I am talking out of my arse there, and don't know, but just thinking of the work.

I would follow the vacuum leak route, and see what you can find. I would also check the line to the map sensor. If you have a scan tool, you might just see what the map sensor is reading.

As for the rear tires. I don't image those last long behind that motor. Burnout

BigDaddyVu · Posted: Mon Sep 10, 2007 8:56 pm Post subject:

you adjust your valves while the engine is running? i was told not to. in shop while the engine is off and the lifters are charged you adjust them while rotating the rods until there is enough drag and then turn them in a half a turn doing only the ones are closed and then turn the crank 360 and do the rest. doing this makes it your lifters more even and getting the full cam profile usage. but that what i was told. i used to adjust them while the engine is running.

did you check your rocker stud if its pulled up? did you also check if your rocker or valve stem if its out of wack? something was interferring or failed in you valve train rods don't just bend like that. unless you pulled a stud or bottom out your lifter.

Twilightoptics · Posted: Mon Sep 10, 2007 9:01 pm Post subject:

BigDaddyVu · Posted: Mon Sep 10, 2007 9:02 pm Post subject:

Actually was it a back fire or was it detonation? detonation can crack heads, back fire can screw up map sensors, MAFs, PVR, and Jets. depending what induction your using.

alloy · Posted: Mon Sep 10, 2007 9:02 pm Post subject:

BigDaddyVu · Posted: Mon Sep 10, 2007 9:11 pm Post subject:

Twilightoptics · Posted: Mon Sep 10, 2007 9:30 pm Post subject:

BigDaddyVu · Posted: Mon Sep 10, 2007 9:41 pm Post subject:

the impression i got he wasn't running a big cam. but thank you for making it clear.

Twilightoptics · Posted: Mon Sep 10, 2007 9:45 pm Post subject:

I guess I assumed with AFR 190's, SLP Runners, super charger etc.... that a cam would have been in there somewhere. Either way, still go IOEC to be safe.

It's imperative with a Solid cam like mine.