c4 killing motor once warmed up

**rcblackdog** · 10-08-2009, 07:02 PM

Hiya folks!
Gotta fresh 1966 289 built to stock specs bolted to a fresh c4 built to stock specs also with a new stock converter, all from reputable shops. Problem is that once the motor and trans are up to temp the trans goes into any gear so hard that it kills the motor. It will do this regardless of what the idle is set at and the only way to keep the motor running is to feather the gas while holding the brake. It seems like the fluid (type f) is bypassing once it gets thinner, but I don't know where to look for that!

When cold everything functions great. Any suggestions would be greatly appreciated! All I can get from the trans shop is that they have never had that problem before from a c4.

**wsa111** · 10-08-2009, 07:42 PM

Possible torque converter seizing up when hot?????

I hate to see you spend $$$ to put in mercon V fluid if it is the torque converter & it sure sounds like it.

Warped valve body????

Pull the pan & see if any metal shavings in it.

**rcblackdog** · 10-08-2009, 07:48 PM

This is the second time i've had this problem with this trans and actuall thought it was the converter so I made the trans shop replace it with another new one but unfortunately it's still doing the same thing. I didn't notice any shavings when I drained it the last time but I can drain it again! It can't hurt to look. How would I know if the valve body was warped?

**steharz** · 10-08-2009, 09:58 PM

Quote:

Originally Posted by rcblackdog

This is the second time i've had this problem with this trans and actuall thought it was the converter so I made the trans shop replace it with another new one but unfortunately it's still doing the same thing. I didn't notice any shavings when I drained it the last time but I can drain it again! It can't hurt to look. How would I know if the valve body was warped?

sounds like your problem is the trans-i wouldnt be opening it up,id be taking it back and getting the company you bought it off to put it right,
opening it will probably void any warranty you might have

**Mario428** · 10-09-2009, 04:21 AM

OK let me get this straight, you are blaming the C-4 tranny because you cannot set the idle on the engine.

If the converter is fine feathering the throttle and fine when cold then it is fine.
You need to look at your idle circuit, must be fine when choke is on and you are on high idel.
Look at your idle settings and spark advance mechanisms

**Rich27028** · 10-09-2009, 04:32 AM

and find the vac leak you have--

**rcblackdog** · 10-09-2009, 05:56 AM

I'm not looking for a flame job here I'm just looking for a little assistance!

I am capable of properly setting my idle and a/f mix and as I said above, it doesn't matter what the idle is set at. The higher the idle the more likely it is to remain running however, I am not comfortable with having to stand on the brakes to stay in place. When it is in gear and running it acts like the converter is locked up. I know that's not probable on an older style converter since they didn't have that capability. Since this is the second new converter I have to lean towards ruling it out of the equation.

On a second note I have checked every possible location for a vacuum leak with every technique I could imagine and have found none. Either cold or once the motor warms up the readings stay the same. No change in idle or stalls with carb cleaner, water, trans fluid, starting fluid around intake, carb, modulator line, modulator, or dist. !!

Once again, when cold everything is great! Idle remains the same cold or hot (manual choke) goes in gear smooth as silk until it's up to temp! Could there be a pressure regulator bypassing internally once it gets warmed up?

**FEandGoingBroke** · 10-09-2009, 07:54 AM

Dudes, he said it goes into gear so hard that it's killing the engine. Friggin READ his post then come up with some answers...

AFTER it's fixed, then you can rib him a little!

I think there are some inner issues, like when it heats up the VB is warping or maybe the VB bolts are loose and need tightening...

**PaulS1950** · 10-09-2009, 06:55 PM

There is nothing in the C4 internals that would cause the engine to stall under any conditions. There has to be something wrong with the converter or the engine.

**mustangdad** · 10-24-2009, 03:42 PM

ck vac at modulator it should be the same as what ever manafold vac is and change with throttle opening ck modulator valve to make sure it is the correct one .a hole host of other things could cause symptoms valve body gaskets spacer plates by modulator valve i do mean the actual valve