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Discussion Starter · #1 ·
Thanks for all the suggestions and thoughts on my earlier post regarding the injested MAF screen retainer. I screwed off this afternoon, replaced the 52 with a 45, cleaned out the IC and was back at the strip tonight. Still had same problem. After changing out fuel rail & injectors, ecm, coil pack/mod./wires, plugs, fuel filter, turbo, chips and every other possible thing, I've still got the same problem.

Hit 12 to 15 pounds of boost, the knock retard goes to 21 to 30 degrees and car falls flat on it's face. EGT's in the low 1300's and 02's in the .830 area. It's clearly not detenation.

For kicks, I stabbed the accelerator in park bringing the RPM's up to around 5000 a couple of times. I get 30 degrees of retard in park (no load)! I run nothing less than 114 octane gas and several of us run our cars from the same drum so I know it's not dirty or contaminated fuel.

Keeping a close eye on my EGT's and 02's, and deliberately running richer than normal, I pulled the wire off the Knock Sensor. The car ran through the gears better than I could ever remember. Changed the knock sensor and wired it back up. Same problem as before. Pulled the wire off the new sensor and the car screamed.

I'm starting the think this 218/218 flat tappet cam I just put in is so loud the knock sensor thinks the racket is detonation. Anyone out there with this cam that has had similar problems?




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[This message has been edited by Jack Evers (edited November 22, 2001).]
 

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Jack,


Lets eliminate a few things before we condemn the cam.

Did this problem arise immediately after the cam was installed ? If not, and the motor does not sound any louder then right after the install, the cam probably is not the issue.

Let's eliminate a possible ground problem first. With a set of small sized jumper cables, connect one wire from one side of the intake manifold to the chassis. The ground nut on the firewall is a good contact.
Then take the other wire and connect it from the other side of the intake manifold to the frame. Make sure a connections are secure.
Then go out for a blast. If the problem goes away, it's a ground problem somewhere.

Next, swap in a spark control module (ESC) from another T/R. The very rarily go bad, but we had a bad one in the shop recently.

The crank sensor could cause a problem like this as can a loose harmonic balancer.

The cam sensor might also be the cause.

Lastly, more than once, we had false knock problems coming from the IC shield on a CAS V4. It seems that the sway bar was contacting and vibrating the shield under quick acceleration. The cure was to enlarge the sway bar hole in the shield and also wrap a piece of heater hose around the bar, just in case.

If the motor is misfiring while you are monitoring 02 volts (another value of having DS onboard) 02 voltage mv's are useless and innacurate.
Each time a misfires occurs under load internal recoil or whiplash occurs and something starts to weaken or get damaged inside the motor. The head gasket if you are lucky.

Good luck.


Ron

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Ron Joseph
'87 GN, [email protected], Red's chip, guidance, and it's more streetable than stock....

Ron's Custom Auto
Merkel Performance Engines
305 S. Michigan Ave.
Kenilworth, NJ 07033
1-800-718-7667
Website <ronscustomauto.com>
Ron <[email protected]>
Paul <[email protected]



Paul Joseph, Repair Shop Mgr.
Jack Merkel, Engine Shop Mgr.
Tony Burda, Repair Shop Tech
Jack Trotte, Repair Shop Tech
Mike Wade, Repair Shop Tech
Eli Caraballo, Engine Shop Supr.
Steve Meza, Engine Shop Tech
Terri Nicinski, Secretary & Office Mgr.

"Janis builttransmissions on the shelf"
"Complete, in-house engine machining and building"
"Cylinder head o-ringing"
"Complete engine rebuild kits"
"T/R crate motors available soon"
"All billet and roller trans. internals in stock"
"Custom roll-bar installations"
 

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Discussion Starter · #3 ·
Thank you, Ron. I'll check these things out.

Interestingly, while I've been fighting this problem for some time, I did run four back to back 11.4's in Vegas (4500 ft density altitude) the 10th of this month without noticeable KR. Fifth run it was back to it's old self (spitting, sputtering, very high KR even at low boost).



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As Ron said above and also check if the TV cable or injector harness is tapping the knock sensor or a broken motor or tranny mount. I know Eric (1QuickV6) Has that cam with no problems.

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Originally posted by Jack Evers:
Thank you, Ron. I'll check these things out.

Interestingly, while I've been fighting this problem for some time, I did run four back to back 11.4's in Vegas (4500 ft density altitude) the 10th of this month without noticeable KR. Fifth run it was back to it's old self (spitting, sputtering, very high KR even at low boost).

Jack


In that Nick installed, set up, and checked for proper lash, I'd still bet the cam is not the issue. He can install a cam in my car anytime.


But, are you running roller rockers or the factory style? If roller rockers, it doesen't take much for them to be out of adjustment much to make enough noise to set off the knock sensor. At idle you might not hear anything, but bump the RPMs, with or without a load on, and the noises can begin.
If the factory style, I'm sure Nick used Mike T's billet shafts and etc. that even more makes me not think cam.
If not, look for a bent shaft, worn or bent rocker or a loose retaining button.

A good test for determining faster ramp cam noise is the following:

With the hood down, motor warm, at idle you should not or barely hear any valve train noise. Same goes from inside the car with the windows closed.
Then quickly snap the throttle listening for excessive noise on the RPM's upward movement and also the post downward RPM drop. Do this in park and also, carefully, in gear. Listen from both the top of the engine compartment and also underneath the car. Listen for any drastic increase in valve train noise.


Another area to check is for a possible cracked flex-plate or fly-wheel. A cracked one can make various noises, intermittantly or at inconsistant times, either under load orout of gear. The bad part is that, sometimes, it's impossible to see or detect the crack unless the trans. is backed out of the way for closer inspection.


I'd love to see a couple DS files when this condition is occuring.
It's possible some clues might be in them.


Although I refrain from hammering a cold motor, can you determine if this condition exists only when the motor is warm or when cold also?

Ron

[This message has been edited by RonsAuto (edited November 22, 2001).]

[This message has been edited by RonsAuto (edited November 22, 2001).]

[This message has been edited by RonsAuto (edited November 22, 2001).]
 

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Discussion Starter · #7 ·
Originally posted by Steve Wood:
You replace the rockershafts, ever? My 221 deg cam did that...actually peaked around 2800-3000. It got a lot better when I put new shafts on it but still did it a little.

I dialed the ME kr lockout up to 41 mph and hid the problem as it did not drop far enuf back on shifts to fall into the rpm range again.
Steve/Ron...I've got Mike T's HD rocker shafts with factory rocker arms. Lifter noise at idle not much greater than factory cam. I guess it's prolly not the cam as (I mentioned in earlier post), car made four strong back-to-back runs in Vegas and then reverted to it's former problems. The problem seems to be intermittant. Ron, I did jumper the grounds and that's not the problem. The coil module was swapped out earlier.

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Originally posted by Steve Wood:
Disconnect the cam sensor.

A good initial preliminary test, but not necessarily conclusive.
We have found the cam sensor to be probably the least understood T/R sensor and, as time goes by, we are still learning about them and their effect on T/R performance. Part of the reason is a cam sensor is more of a critical factor in a turbo motor needing more of and more accurate doses of fuel. We have experienced cases wherein the disconnect test readily condemned the cam sensor and it's replacement solved the problem. In other disconnect tests, the car, either, ran the same or worse.

After the cam sensor disconnect test is deemed inconclusive, we then loosen the hold down bolt and orient it to varying and different positions within the reluctor window. If this leads us nowhere, we simply swap in a new one, if for nothing more than posterity. More than once, the problems were solved and we still are not sure why.

Having available, one each of, every T/R control part and sensor in the shop, on rare occasions, has made us look smart.


Have you tried swapping in a known good ECM ?


Ron



------------------
Ron Joseph
'87 GN, [email protected], Red's chip, guidance, and it's more streetable than stock....

Ron's Custom Auto
Merkel Performance Engines
305 S. Michigan Ave.
Kenilworth, NJ 07033
1-800-718-7667
Website <ronscustomauto.com>
Ron <[email protected]>
Paul <[email protected]



Paul Joseph, Repair Shop Mgr.
Jack Merkel, Engine Shop Mgr.
Tony Burda, Repair Shop Tech
Jack Trotte, Repair Shop Tech
Mike Wade, Repair Shop Tech
Eli Caraballo, Engine Shop Supr.
Steve Meza, Engine Shop Tech
Terri Nicinski, Secretary & Office Mgr.

"Janis builttransmissions on the shelf"
"Complete, in-house engine machining and building"
"Cylinder head o-ringing"
"Complete engine rebuild kits"
"T/R crate motors available soon"
"All billet and roller trans. internals in stock"
"Custom roll-bar installations"
 

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I posted domething about this on the other board a while back.It was about CS timing and how it affected fueling and performance.Seemed the guys who posted back to the thread liked to adjust the setting away from factory for the bigger cams.I'm not sure how much or which way,but it seemed there was some advantages to altering from the factory settings.One thing I did bring up was wear[axial and radial or thrust washer and bushings] of the CS.Before you go ahead and change the CS,you might want to pull it and check it for wear.If the bushings are worn or there's too much endplay,you can either by a new CS or get a Mr Gasket[I think] thrust washer kit for setting endplay on GM HEI distributors.I would set the endplay to around .015"-.020",retime it,and see if that helps.The way I look at it,a Cs is a Cs,as long as they are both functioning properly.Since the drive for the CS is helically cut,it stands to reason that too much endplay would alter the timing adjustment,allowing the shaft to climb in the housing,and hence changing the timing from the initial setting.Maybe that's why Ron's changing CS's worked out even though both units in the repair appeared to function normally when originally set correctly.The only other thing that might affect the CS is the pick up in the cap screwing up as the signal pulses increased in frequency[saturation of the pickup].You could find this with an oscilliscope,by probing the signal lead and watching the trace as the rpms rose.Hope that helps you out.

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[This message has been edited by The Radius Kid (edited November 23, 2001).]
 

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Take the top of the cam sensor off and check that the screw that holds the reluctor ring isn't loose.
You didn't set the cam sensor 180 out when you put the cam in did you.
 

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Discussion Starter · #13 ·
The suggestions made by you guys have been very helpful and I think we've found the problem. The rear coil pack bolt, the one that sits on a "U" shaped bracket straddling the knock sensor was missing. While the front two bolt held the coil seemingly solid on the motor, at RPM the missing third bolt allowed the coil to bounce just enough to feel like detenation to the knock sensor. Replaced the missing bolt, hooked the knock sensor back up and things are back to normal. The little subtleties of these cars are mind boggling.


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Glad to see it was something simple.

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