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

[vacuum 6]

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[yullose]

Overly advanced would cause detonation down low if anything. There woudl be lower bmep as the rpm increased advancing

I'm not at all concerned about the cam timing... I know it's good and I had a degree wheel on it to see where it was installed previously. Of course I didn't bother to write anything down... (It was 3 months ago) but I remember it was within a degree or two of what the cam card wanted... so I left it where it was.

At this point, I can only assume it's an injector problem...

Driving around, the car runs like a million bucks... put the pedal to the floor and it runs clean up to 5000-ish, then feels like it's dropping a cylinder or cylinders... not completely shutting down, but sputtering in and out. (Like a rev-limiter)
This seems to be when the KR occurs and it noses over...

I guess if I had a bum injector, it would go lean in that cylinder, create knock (race fuel or not) and lay-down on that cylinder... It would also make the wideband go wacky (like we saw in the beginning) due to lean-pockets passing thru the downpipe.

Does that make any sense ?

 

[yullose]

Another question I had was...

Is there ANY way to back-flush or clean injectors at home on the workbench without having to ship them out ???

I thought about putting them in the fuel rail upside-down and cranking the motor.

 

[86WH1turbo]

I still think its the valve springs. Maybe you should contact Comp and see what they say about the pressures you are running.

 

[yullose]

I had beehive springs on the iron heads with this cam... and 6200 was smooth as silk. It actually wanted to go higher if I let it.

What kind of pressures do the single beehives make ?

(Bison has mine now)


Here is the cam card:

 

[TurboBuRick]

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?

 

[86WH1turbo]

I dont know the spring pressures for single beehives. You might want to give Dan at DLS Engineering a call or Comp. My cam is a little bigger than yours and I know mine are double springs with 420-425 open pressure.

I know there are a number of guys here that like the beehives but my engine builder really didnt want to put those on mine. Probably just a preference thing.

 

[bison]

I had beehive springs on the iron heads with this cam... and 6200 was smooth as silk. It actually wanted to go higher if I let it.

What kind of pressures do the single beehives make ?

(Bison has mine now)


Here is the cam card:

Ill check a few of them next week if you want

 

[ttypewhite]

turn down the boost and remove the wire to your knock sensor and see if it passes the 5200 - 5300 rpm level. Having good fuel in the car as insurance would not be a bad thing.
Has your TPSensor been set properly? is it getting proper voltage under load?
Have you played with spark plug gap?
Double check on the valve springs pressures to make sure what you asked for you received.
Did you also varify that your fuel pressure isn't dropping off while this problem is happening?

 

[Dabigguy]

I know you said you checked the compression, but did you do a leak down test? Higher RPM usually equals higher boost. Maybe the head gasket only leaks at higher boost/RPM levels?

I know you said the heads were assembled by a reputable company, but what day of the week were they assembled, on a Monday? The assembler may have had too many brewskis over the weekend and wasn't on his game, it happens.

A valve spring could be bad from the factory or the inner spring may be broken. I'd check it out.

Trust, but verify!!

 

[bison]

Try another set of plugs. This has worked for me at least 5 times over the years when i knew the ones in there were good.

 

[Eticket]

1) have you checked the reluctor wheel inside the cam sensor to make sure it's not broken or loose?

2) have you tried swapping plug wires? I'm not sure how you test them to be good. I had brand new wires (brand not mentioned) that were bad and kept me at 5000 rpm or so. Realized the problem when I got shocked just touching around the wire/coil pack area with the engine running.

I can't see this being a mechanical problem.

 

[Alky V6]

Eticket brings up something that I fought with at one time. My ignition system under high load would break up from high tension leakage if the dielectric grease in the spark plug wire boots was inadequate or not there. And,... I have to make sure both ends are greased. Not just one end or the other.
You could have crossfiring occurring too. Make sure there is adequate separation of the high tension leads.

 

[yullose]

I checked all my wires (MSD 8.5) with the Fluke... and they are anywhere from 70-100 ohms.

I'll try another set of plugs and see if it helps.

Anyone know what else is compatible with the Autolite AR3935's ?

Nobody around here keeps Autolite racing plugs on the shelf... so if I can find something stocked at Autozone, it would be a big help.

I've moved the gaps from .035" down to .030" and didn't notice any difference.

I have two other sets of plug wires here I could throw on and try just for schitzengiggles.

And, to update... I took the car out to Maple Grove tonight for Friday night grudge racing... not to race it, but just to put some miles on it. It ran beautiful and without any problems. (never got into any boost though)
I put the baby seat in the back and drove out there with my 3yr old boy... It was his first visit to the dragstrip and he was lovin it.

 

[yullose]

Ill check a few of them next week if you want

Don't go out of your way to do it... If you get them apart and happen to look at the springs, I'd be curious to know what they are...

 

[yullose]

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?

Actually, I DO have a Caspers cap on it at the moment, but the problems were there prior to installing it.

 

[yullose]

Try another set of plugs. This has worked for me at least 5 times over the years when i knew the ones in there were good.

Hmm... that never even crossed my mind. They came right out of the box, got gapped and installed. They have been in the motor from the day I started it.


I sure hope another set of plugs DOESN'T fix the problem... because that would be really embarrassing.

 

[Alky V6]

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

 

[yullose]

1) have you checked the reluctor wheel inside the cam sensor to make sure it's not broken or loose?

2) have you tried swapping plug wires? I'm not sure how you test them to be good. I had brand new wires (brand not mentioned) that were bad and kept me at 5000 rpm or so. Realized the problem when I got shocked just touching around the wire/coil pack area with the engine running.

I can't see this being a mechanical problem.

The cam sensor is brand new... and I even have a spare new one to try if needed.

I will swap another set of wires on it tomorrow, and maybe try to hunt for a set of off the shelf plugs to use...

An educated guess tells me this is some kind of ignition problem, just by the way it feels... It feels like it's dropping and firing cylinders at 5200.
I keep thinking about the injectors too... but if they were bad, wouldn't it run crappy at all RPM's ?
On the way home tonight it was smooth as butter up to 4000, under very light throttle and boost. I didn't romp on it at all cuz I had my kid in the backseat.

To describe the problem as best as I can... it feels like a very soft rev-limiter hitting at the same RPM every time... cutting in/out... and it will keep doing it for as long as my foot is on the floor.

 

[yullose]

Eticket brings up something that I fought with at one time. My ignition system under high load would break up from high tension leakage if the dielectric grease in the spark plug wire boots was inadequate or not there. And,... I have to make sure both ends are greased. Not just one end or the other.
You could have crossfiring occurring too. Make sure there is adequate separation of the high tension leads.

More good points to consider...

I will swap around some wires, and move/space them apart more...