Motor won't rev over 5200-5300rpm... WTF???

[yullose]

Nothing wrong with gapping down to .023". That's what I use. It's very good at controlling secondary leakage.

I never even considered running them that tight... I've always run them .035-.030". I'll try closing them up some more...

These AR3935's also have the back-cut ground strap... any issues you are aware of with them ?

I have a new set of colder AR3934's, but only 5 of them are good. One came out of the box defective... with the center electrode recessed way too far.

I need to look online for a number cross-reference to see if I can find something stocked at the local Autozone.

 

[phillyvader]

I'm about out of ideas now.

I've been screwing with this car for 2 weeks now and still have the same problem.

5200-5300 the motor falls on its face and sputters... like a soft-touch rev control hits it.

I've gone over EVERYTHING.

Cam sensor re-adjusted/confirmed dead-on.

Crank sensor replaced - gapped at .025".

Brand new AC Delco coilpack and module.

MSD wires are good.

Autolite AR3935 spark plugs.

Tried multiple chips.

Brand new A1000 fuel pump.

Brand new Magnafuel regulator.

All grounds and ground wires have been checked and doublechecked.

Compression checked - all 6 between 145-155lbs.

I'm running Sunoco 112 leaded race fuel + straight meth

I've tried both alky and race chips, with and without meth injection.

I've had cronic KR problems too... and I wonder if it's related to the valvetrain. I was getting 15 degrees KR just free-revving in the driveway... I went over all the valves and tightened them another 1/4 turn. That helped a little, but not completely.
When I adjusted the valves, I set to zero lash, then another 1/2 turn. After the re-adjustment, they are now at 3/4 turn in from zero.


I'm starting to wonder if this is a mechanical problem now.

Before replacing the entire top-end of my motor, it would rev clean up to 6200 no problem. That was with ported irons, beehive springs, stock rockers and 214/.548 hydraulic roller.

The changes I made were:

TA SI aluminum heads, complete with their springs.
Springs are: 140lbs on the seat and 325lbs @ .584 lift
1.65 T&D roller rockers... (increasing lift from .548 to .584)
Champion aftermarket intake & plenum

I'm not running an RJC plate... (yet)

So that leads me to two possible conclusions...

A) The 1.65 rockers are too much for my cam/lifter combo and are collapsing the lifters at high RPM.

B) The Champion intake & plenum have airflow distribution issues and need the RJC plate between them.


A few things I HAVEN'T tried yet:

1) Replacing the ECM (I only own this one with modded drivers for the 83's)
2) Replacing/inspecting the injectors (they worked fine in the old combo)
3) Tightening the valve lash even more...


Any other suggestions ??? I just don't know WTF to do... and I'm running out of ideas.

Here are two PL files from this morning...

The 2nd one is with the knock sensor unplugged, just for comparison. It made NO difference whatsoever.

Think it may just be the knock sensor?? That would explain the knock retard and backfiring.

 

[Alky V6]

I never even considered running them that tight... I've always run them .035-.030". I'll try closing them up some more...

These AR3935's also have the back-cut ground strap... any issues you are aware of with them ?

I have a new set of colder AR3934's, but only 5 of them are good. One came out of the box defective... with the center electrode recessed way too far.

I need to look online for a number cross-reference to see if I can find something stocked at the local Autozone.

I haven't heard anything bad about those plugs. I know some fellow n/a racers that love those plugs.
I'm presently using Champion racing plugs. The ground electrode is cut back farther than any other plug I've seen. I use a very cold one with very little porcelain exposed to the chamber. Less chance of breaking a porcelain. Us nitrous guys like less exposed porcelain and tiny ground electrodes.
I've been using the champions for quite awhile now with very good results.

 

[Jicaju]

Crank it up then unhook cam sensor take it for a test run.

 

[TurboBuRick]

crank it up then unhook cam sensor take it for a test run.

x2

Get rid of the caspers sensor. IMO It will cause issues.

 

[Eticket]

Did you say you checked the reluctor wheel? Even brand new stuff can come loose.

what's the "ar" in the plug number mean? I hope that they're not platinums. Do TA heads take something different than champions? I never had a problem with the regular autolite 103's for champions, 23's for iron heads.

I'd just about bet a steak dinner that it's ignition related. Can't see that you have any sort of exotic combo or anything.

 

[yullose]

Crank it up then unhook cam sensor take it for a test run.

Tried that yesterday after the valve adjustment and again today after the RJC power plate install. Didn't make a bit of difference.

I did finally hear what sounded like an exhaust shield/tranny line rattle under the car tonight when pulling back in the driveway... so that may be a possible source of KR.

Another notable issue...

On my 15-20 minute drive tonight... I finally felt the TCC lockup... only it did it all by itself, without flipping the manual switch. It locked up around 55-60 in 3rd and 4th just light throttle cruising down the highway.
(It was actually 'kinda cool to be at highway speed, motor spinning just over an idle.)
I could have sworn the TT chip has it turned off... so I must have a wire grounded someplace, that isn't supposed to be.

 

[yullose]

Did you say you checked the reluctor wheel? Even brand new stuff can come loose.

what's the "ar" in the plug number mean? I hope that they're not platinums. Do TA heads take something different than champions? I never had a problem with the regular autolite 103's for champions, 23's for iron heads.

I'd just about bet a steak dinner that it's ignition related. Can't see that you have any sort of exotic combo or anything.

Nope, nothing exotic... and everything is pretty basic off the shelf stuff.

The cam sensor is fine... I've had my hands on it several times... and even spent alot of meticulous time setting it exactly to factory specs.

I'm 100% sure the cam sensor and crank sensor are spot-on and dead nuts where they belong. The only components of the ignition system that haven't been replaced in the last week are the plugs and wires...

I believe the "AR" stands for "Autolite Racing"

I have another set here, but one is defective... so I still need to figure out what Autozone or Napa might have on the shelf that will work with these heads.

 

[DailyDrifter]

ECM swap ? Will and unmodded ECM drive my 83's ? (I have a spare unmodded ECM here to try)

I seriously doubt your ECM is the problem, I always see people putting ECM's in cars and the problem still exists after the new one is put in.

Eticket has a good point about the ignition. Take the car out and get it up to temp, then ohm out the coil pack while its still hot. Sometimes they ohm out good when cold but once they heat up the problem starts.

 

[yullose]

Now HERE is something I just found very interesting...

I used my Fluke to check resistance on all three sets of plug wires I have here for the car...

The set that are currently on the car are made by MSD and are the "Super Conductor" wires.

They all check out with LESS than 100 ohms each.

A set of Delco Premium wires all check out around 6500-7500 ohms each.

A set of junk Magnecor wires all show 5000-5500 ohms each.

I'm wondering if the MSD wires are copper core... or if the low resistance is creating RF interference with the ECM... which was relocated to just behind the pass cylinder head, on the inside of my AC delete plate.
It's literally within 8-12 inches of the #6 sparkplug, on the other side of the firewall.
Maybe the Autolite racing plugs are non-resistor ? maybe that could be a source of interference ???

Tomorrow I will put the higher resistance AC Delco wires on the car and take it for a ride... before changing plugs.

ECM location:

 

[DailyDrifter]

I've never done it but supposidly you can wrap wire around an electrical component to block radio interfearance, just ground both ends of the wire. I know some speaker wire has it. Dont know if it will work but worth a shot if you want to test it. BTW sorry for the lack of spelling but its late and i'm tired . Did you try to swapping out wires?

 

[yullose]

Did you try to swapping out wires?

I just put the AC Delco wires on it a few minutes ago... but it's now 130 in the morning... and the wife & kids are in bed.

She'll have my ass if I take the car out now and wake everybody up.

 

[DailyDrifter]

I just put the AC Delco wires on it a few minutes ago... but it's now 130 in the morning... and the wife & kids are in bed.

She'll have my ass if I take the car out now and wake everybody up.

Well its the weekend, everyone should get up bright and early . Just put a blow-up doll in the bed with your wife

 

[Alky V6]

I just put the AC Delco wires on it a few minutes ago... but it's now 130 in the morning... and the wife & kids are in bed.

She'll have my ass if I take the car out now and wake everybody up.

LOL. A hard core car guy. I love it. Take the darn car out. Your fan club is waiting for an answer.

 

[KevinB]

The un modded ecm will work for a test. You just should not use it primarily.


Your not running a stupid caspers cam sensor cap, are you?


Have you tried running in limp mode?

Whats wrong with the Casper's cap?

I'm having very similar issues with my car. Just spent 12+ hours at the track today (friday) and put a ton of runs trying to figure my car out. I have a Caspers cap on the car. Unlike ullose, I have a Gen7 and a solid roller. The car is very inconsistent in the way it breaks up too. One pass it will go to 6400 rpms, next run it will pop and bang at 4K. My issue seemed to pop up over night.

Sorry to steal your thread yullose but I think our problems might be similar. Tomorrow I am going to trace all wiring. So far I have had 3 coil pack/modules on the car, replaced crank sensor, compression is ok, have yet to check springs, replaced wires and plugs many times too along with wideband 02 and fuel pressure is ok.

 

[yullose]

Whats wrong with the Casper's cap?

I'm having very similar issues with my car. Just spent 12+ hours at the track today (friday) and put a ton of runs trying to figure my car out. I have a Caspers cap on the car. Unlike ullose, I have a Gen7 and a solid roller. The car is very inconsistent in the way it breaks up too. One pass it will go to 6400 rpms, next run it will pop and bang at 4K. My issue seemed to pop up over night.

Sorry to steal your thread yullose but I think our problems might be similar. Tomorrow I am going to trace all wiring. So far I have had 3 coil pack/modules on the car, replaced crank sensor, compression is ok, have yet to check springs, replaced wires and plugs many times too along with wideband 02 and fuel pressure is ok.

Hey, the more info we can churn up, the better...

I'm really starting to lean toward the possibility of electrical interference... and here's why.

1) I moved my ECM off the kick panel and on to the firewall... putting it much closer to the coil, module, plugs and wires... where there is a $hitload of electrical activity.

2) My MSD wires are VERY low resistance (less than 100 ohms) which compare to copper/solid core wires... generally not recommended for sensitive electronics, from what I understand.

3) My new TA heads take a specific sparkplug... which of course is a "NON-resistor" type racing plug... again, not generally good for sensitive electronics.


I can remember back in the good old days when Accel super coils and copper core wires were popular. You couldn't listen to a radio within 20ft of a car running those things due to static/electrical/RF interference. Remember the old 60's Vette's ? They had stainless sheilds around the distributor, coil and wires right at the firewall because of interference.


Anyways... my a$$ is dragging now... so anymore work will need to wait 'till tomorrow.

I think tomorrow I will pull the ECM off the firewall and jam it back in the kick panel... just to get it further away from the ignition system.

I also want to see if I can find a comparable RESISTOR style sparkplug to the AR3935's / AR3934's and/or the NGK R5671A-7's & 8's.

I think a set of quiet wires, resistor plugs (if I can find a set) and moving the ECM may just do the trick. (In theory at least)

 

[KevinB]

Let us know. I will hopefully get something done on mine too tomorrow. I am very interested in this caspers cap thing right now. I'm beat also...left the house at 7:30 am and just got back in after 1:30 AM.

 

[Alky V6]

If the MSD wires are spiral wound, which seems to be real popular these days, the low resistance could be right. The spiral wound wires are supposed to prevent EMI, and some do have a low resistance. If the wires are solid core, that is most likely your problem.

I've run non-resistor plugs with spiral wound wires with no interference problems. With an Electromotive system, that's saying a lot. But,... I found that it is very, very important that I do not use the dielectric grease sparingly on the wire boots.

Do not take the use of dielectric grease lightly!!! It took me 3 months of frustration before the simple use of dielectric grease on all boots of the high tension leads made me a believer.

 

[KevinB]

If the MSD wires are spiral wound, which seems to be real popular these days, the low resistance could be right. The spiral wound wires are supposed to prevent EMI, and some do have a low resistance. If the wires are solid core, that is most likely your problem.

I've run non-resistor plugs with spiral wound wires with no interference problems. With an Electromotive system, that's saying a lot. But,... I found that it is very, very important that I do not use the dielectric grease sparingly on the wire boots.

Do not take the use of dielectric grease lightly!!! It took me 3 months of frustration before the simple use of dielectric grease on all boots of the high tension leads made me a believer.

My wires are dry right now. We keep coming back to an ignition issue.....you got me thinking on this!! What were your problems?

 

[yullose]

I'll have to go on MSD's website and see if I can find info on the superconductor wires...

It may very well be just an issue with (like you said) electrical leakage past the boots... OR... my ECM is now too close to the coilpack. I hate to give up my MSD wires... they are they only ones that fit and look nice on the motor.

The AC Delco wires look like a bunch of spaghetti.

The other thing that comes to mind is... these aluminum heads have the sparkplugs buried so deep... it's a very short path to ground if you have a leaky plug boot.

I actually had to turn down the OD on one of my 5/8 sockets just to get the plugs in and out without getting the socket jammed in the hole.