The other day I was leaving work and when I started the car up, it had a bad miss at idle. WHen I took off to leave, it was making a knocking sound. Sounds like a loud spark knock and I am convinced that this is what it is. The sound is coming from the driveres side of the motor and it only happens when the motor has somewhat if a load on it (ie, accelerating moderately)

Any ideas on what it could be? I changed the rotor and did a visual on the cap(looked OK but cant rule it out).

This knock almost sounds like a bottom end problem, but the oil pressure is great and it also sounds a lot like spark knock/detonation.

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L98, 3.27 9-bolt, Hooker shorty headers, custom 2.5inch Y-pipe, no cat, 3inch 2chamber flowmaster, JET AFPR, Ported MAF, Best ET: 13.86 @100mph. 1.99 60'
17 inch ROH "ZS" wheels. 17x8.5(front) and 17x9.5 (rear). Firestone Firehawk SZ50s. 245/45/zr17s and 275/40/zr17s. T56

On the way... Radar Blue 89 Formula, T56, Ram Jet 430, Ram Air, 17inch ROHs.

 

What is your base degree set at? What kind of gas do you run?
Any type of "aftermarket" chip? Custom chip?
How many miles on the lower end? And I'm sure your hard on the car correct?


Brendan

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1987 IROC-Z L98,SR,EB 6085's,LPE 219/219 SR Cam, Crane 1.6RR, EB TPI Base, 58mm TB, Stock T5, 30lb SVO, AFPR, K&N, EB TES, Catco Cat, 3" Borla Cat-Back, Accel cap,rotor,distro/other crap, Aluminum DS, 94 Disk Rear, Adjustable Prop Valve, Precision 3.73 Gears, Weld in Sub-Frame Connectors, Hotchkis LCA's, KYB Shocks/Struts, Poly Bushings all over the place, Moog Upper/Lower Ball joints and Tie Rods ends/Idler Arm, Big stereo, 730SD Conversion.

To see the ROC, Check out the webpage Here

 

I'd say check all your ignition components first, base timing, cap, rotor, wires (replace) plugs etc. Maybe regap your plugs.

I've got a knock that I've had for months past 4300 rpms that I just can't get rid of so i know your pain

good luck

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1985 IROC-Z
TPI 305, 700R4 with shift kit, richmond 3.73's, auburn pro series posi, crane compucam 2030, ported plenum, gutted air boxes, all the little insignificant stuff.

 

My base timing is set at 8 degrees. Yes I am hard on the motor. It has 36K on the rebuild. I run 91 octane gas. This is not like detonation ive had in the past. Before it would only occur when the timing was up too high and you were at WOT in like 3rd or 4th gear. Now, its in any gear with a minimal load on the engine. And it feels like it has lost 200 horsepower too. I could swear it sounds like something in the bottom end, but like I said, my oil pressure is real good and it also has a terrible miss. What the heck is this and how do I take care of it?

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L98, 3.27 9-bolt, Hooker shorty headers, custom 2.5inch Y-pipe, no cat, 3inch 2chamber flowmaster, JET AFPR, Ported MAF, Best ET: 13.86 @100mph. 1.99 60'
17 inch ROH "ZS" wheels. 17x8.5(front) and 17x9.5 (rear). Firestone Firehawk SZ50s. 245/45/zr17s and 275/40/zr17s. T56

On the way... Radar Blue 89 Formula, T56, Ram Jet 430, Ram Air, 17inch ROHs.

 

dude i no your pain same thing on my car last night i tried out g tech and couldn't even finish the q -mile it skipped so bad that i thought the engine was going to blow it must be the timing or some bad gas

 

Have you popped the hood yet? Check all the plug wires, make sure none have burnt on the headers. Make sure you're getting spark at all cylinders.

If ingition checks out, you may want to pull the valve cover and make sure everything on top is still attached, no broken spring, etc.

You could just have an exhaust leak, setting off the knock sensor and retarding the timing.

Just ideas, difficult to guess at sounds on the 'net.

 

I took the drivers side valve cover off and readjusted the rocker arms. I thought that I may have had one that was clattering. Wasnt it. All the plug wires are good. Not even close to the headers. I think I may have a problem with the cap although it did look fine.

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L98, 3.27 9-bolt, Hooker shorty headers, custom 2.5inch Y-pipe, no cat, 3inch 2chamber flowmaster, JET AFPR, Ported MAF, Best ET: 13.86 @100mph. 1.99 60'
17 inch ROH "ZS" wheels. 17x8.5(front) and 17x9.5 (rear). Firestone Firehawk SZ50s. 245/45/zr17s and 275/40/zr17s. T56

On the way... Radar Blue 89 Formula, T56, Ram Jet 430, Ram Air, 17inch ROHs.

[This message has been edited by FormulaJoe (edited August 16, 2001).]

 

maybe we are getting bad gas because me new 19k mile motor just started doing this, it has ran spark knock free for 18.5k miles. it is doing exactly what you described

 

You said you check your wires and they're fine not near headers.Check to make sure they are fully pushed on to the plug.I had this one wire that wouldn't stay on the plug.The first time it happen I took it to the garge and paid $40 for them to put it on the diagnostic machince and say "you had a plug wire off" It eventually did it again,but to look at it you colud never tell.It's worth a shot at least it will only cost you a minute or two

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1991 1LE Z28 355cu 5SPD (ORIGINALLY 305 BEST E.T. 14.186@99.86mph)NO PASSES ON 355 YET.MINI RAM INTAKE,AFR 190 HEADS,10.23:1cr 24# SVO INJECTORS,BBK 52mmTB,AFPR
FULL ROLLER MOTOR,1.6 rockers MSD 6AL
AUTOMETER A/F GAGUE MARCH PULLEYS,HEDDMEN HEADERS 3IN EXH NO CATS FLOWMASTER,POWER TRAX NO-SLIP LOCKER,3:42 GEARS,LAKEWOOD LOWER CONTROL ARMS HOTCHIKS STRUTTOWER BRACE,COMPETTION ENG.SUBFRAME CONNECTORS
MALLORY TACH W/SHIFT LITE
BLACK, TINTED WINDOWS, TAIL LIGHT COVERS BIG BLOCK COWL INDUCTION HOOD,SHAVED DOOR HANDLES

67RS 327cu 92K ORIG MILES.NEWER GM HEADS HEADERS,650 HOLLEY CARB,CAM, 350 TURBO TRANS W/SHIFT KIT&COOLER 12 BOLT POSI 3.73'S MUTLILEAF SPRINGS
NEW VINYLROOF&CARPET, COWL HOOD,HIDE AWAY HEAD LITES,

 

I dropped a new distributor, distributor cap, and ignition coil in it this morning out of my other car and it did nothing. Problem still there. I wonder if I dont have a valve spring broken? That knocking sound might be a backfire in the intake? That oculd explain the miss that I have as well. Just an idea. Im not ruling anything out at this point. Any other ideas?

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L98, 3.27 9-bolt, Hooker shorty headers, custom 2.5inch Y-pipe, no cat, 3inch 2chamber flowmaster, JET AFPR, Ported MAF, Best ET: 13.86 @100mph. 1.99 60'
17 inch ROH "ZS" wheels. 17x8.5(front) and 17x9.5 (rear). Firestone Firehawk SZ50s. 245/45/zr17s and 275/40/zr17s. T56

On the way... Radar Blue 89 Formula, T56, Ram Jet 430, Ram Air, 17inch ROHs.

 

check for coolant leaking in one of the end cylinders. i just had the same thing on a corvette at the shop. #2 cylinder was getting coolant from across the intake gasket. it did not leak anywhere else.

 

Joe, i live in Okla also ,work at a dealermand have been seeing lots of fuel contamination problems latly! Try to get a fuel sample and see what it looks like

 

I ran the rest of the fuel out of the tank and filled it back up with some 93 octane. It made no difference. I have no clue as to what the heck is going on. Anybody have an idea?

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L98, 3.27 9-bolt, Hooker shorty headers, custom 2.5inch Y-pipe, no cat, 3inch 2chamber flowmaster, JET AFPR, Ported MAF, Best ET: 13.86 @100mph. 1.99 60'
17 inch ROH "ZS" wheels. 17x8.5(front) and 17x9.5 (rear). Firestone Firehawk SZ50s. 245/45/zr17s and 275/40/zr17s. T56

On the way... Radar Blue 89 Formula, T56, Ram Jet 430, Ram Air, 17inch ROHs.

 

A lot of people seem to think I have a valve spring broken. I think im going to change the springs. They have 150K on them. Others say the motor may have jumped time. I dont know what it is for sure, but all I can do is start replacing stuff I guess.

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L98, 3.27 9-bolt, Hooker shorty headers, custom 2.5inch Y-pipe, no cat, 3inch 2chamber flowmaster, JET AFPR, Ported MAF, Best ET: 13.86 @100mph. 1.99 60'
17 inch ROH "ZS" wheels. 17x8.5(front) and 17x9.5 (rear). Firestone Firehawk SZ50s. 245/45/zr17s and 275/40/zr17s. T56

On the way... Radar Blue 89 Formula, T56, Ram Jet 430, Ram Air, 17inch ROHs.

 

i think it may be 9bolts on your rear end

 

I think I may have a lifter that is bad (collapsed?). Where can I get a set of OEM style roller lifters without paying an arm and a leg?

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L98, 3.27 9-bolt, Hooker shorty headers, custom 2.5inch Y-pipe, no cat, 3inch 2chamber flowmaster, JET AFPR, Ported MAF, Best ET: 13.86 @100mph. 1.99 60'
17 inch ROH "ZS" wheels. 17x8.5(front) and 17x9.5 (rear). Firestone Firehawk SZ50s. 245/45/zr17s and 275/40/zr17s. T56

On the way... Radar Blue 89 Formula, T56, Ram Jet 430, Ram Air, 17inch ROHs.