RRC in need of Help, elemental disco mike various other smart people

[p76rangie]

I would still be checking for leaks, hoses off, etc, on the intake manifold.

[Dr Lobster]

Originally Posted by p76rangie

I would still be checking for leaks, hoses off, etc, on the intake manifold.

I was going to mention loss of air due to the low vacuum, but thought that it had already been ruled out.

A MAF sensor with an intake leak (anywhere from the airfilter box to the intake manifold gasket and beyond) would cause these symptoms as well. A crack in the head where the intake manifold connects would cause this as well. Cooking mentioned a problem with overheating, and I've seen cylinder heads crack/warp after numerous overheats, but that was only after the waterpump had crapped out/warped first.

Is the intake manifold in good shape??? What about the gaskets?? Intake hose before/after the MAF sensor?? Does the airfilter can seal correctly around the airfilter?? A loss of metered air will cause bucking, low vacuum, air/fuel ratio problems and so on, but, like I said before, I thought this was ruled out.

[ArmyRover]

the vac lines weren't brand new but were in better shape than mine. His af box is missing but it does have the end plate sealed tightly against the filter and maf.

[Dr Lobster]

Man, this problem is a serious ghost.

Keep at it. There has to be a logical sollution to this somewhere.

[MysteryTheatre]

HUMMM.... something that would cause both a lean condition and a lack of vacuum... the most obvious answer : a split vacuum hose or bad connection to the fuel pressure regulator. did some monkey unhook the vacuum advance hose to the distributor and accidently reconnect it to the back side of the diaphram instead of the front? HAHAAA!!! that would cause some bucking as well as a variety of overheating and performance problems. everything hose and connection on the ram housing must be carefully inspected. remember any vacuum leak also causes a lean condition because un-metered air is entering the
engine and leaning out the mix. Lean=Hot. Yup you got a vacuum leak somewhere!!!!

[Elemental]

Just how good did you look at timing?

Including, but not limited to, proper firing order, both Centrifical/Vaccum advance functioning...

I would be giving this distributor a good hard look.

[p76rangie]

Of the standard tests that determine the motors general condition, it would appear that low vacuum is the only one reading abnormal. A cracked header tank cannot cause low vacuum.
The Vacuum advance on the distributor only has an impact when at cruise. It appears that the thing is mainly playing up under load. So the vacuum advance is not likely to be the issue.

The low vacuum will cause the motor to get the incorrect air/fuel mixture and therefore could be causing the overheating and lean running.

Therefore, what I have been suggesting for the last few weeks is that you put a vacuum guage on it and don't stop checking things until it reads somewhere near normal. As also suggested, you check the intake manifold is bolted down correctly and that there is no leaks at the gasket.

[apbtpetey]

I am still wondering how it is running after he made sure all his spark plug wires are attached. Not having them all attached would cause problems as well. When they were not all attached it would cause poor running issues under load as well. After reattaching them I would take a hard look at what is causing the low vac and also be looking at things like the distributor and timing, but first and foremost those plug wires need to attached correctly.

[MysteryTheatre]

a couple more thoughts :
getting a low vacuum reading from high performance cams is real common. a Centripetal Advance Distributor is a good option matched for racing /high performance set up. Lastly You could have a mouse nest in your exhaust pipe. but someone needs to see if the timing is advancing thats your next step.

[RUGDRVR]

Was it bucking at speed? I have had a similar problem and it was an O2 sensor. However the car never stopped running it just ran very rough and had problems at speed.

[cookingwithfat]

Boy, I am a doink... so sorry everyone, I could have sworn I posted the latest information here.

So, my friend Brandt and I went to put in new injectors. (I know I know.. but we figured it would be good experience for us and could get the nay sayers off our backs.) So while under there we noticed a few things, but the big one is this: the hose that comes out of the back of the MAF was so loose it was obviously not creating any kind of seal at all. I tightened it up, and took it for a ride. This time it ran right up the hill, went all over with very little trouble. A little bucking when I suddenly removed my foot from the gas... and I am not sure why that is.

But it is still running real hot. Not as hot as before... which is why we drove it past where we had gone before, but still I felt I had to constantly be looking at the after market gauge so be sure I did not head off into the red. Now, that being said, the factory temp gauge says everything is fine, but they are known to not work.

So, it still idles rough and is getting hot fast. I couldn't take it through the rockies just yet, but we have made progress, and I am learning a lot.

[ArmyRover]

Good job on finding that loose connection Dave. Keep it up one thing at a time.

[Kevin88RRC]

What temp does the gauge read? Are the fans working properly? How bout your radiator?

For the idle, I would clean the MAF and check the settings on the MAF & TPS.

[MysteryTheatre]

it took five pages of posts and a bucket load of trial and error parts and months now in time to find a loose intake duct!!!! wow!!!! unbelievable.

[cookingwithfat]

Well mystery - and others - it is not that simple. Things have gotten better, they are not fixed. The truck is still running hot and can not really be used for more than driving around town. My post was to point out that progress has been made.

Further, things that this thread and the one before have solved include - bleeding the cooling system (something I didn't know how to do before), replacing the vacuum hose to the dizzy (things that I did not know the first thing about before ), tightning up the hose from the MAF (I did not know what the MAF was before) fixing the plugs at the dizzy - good thing I stumbled on that, and would not have were it not for this post - and soon the replacement of the injectors - which is a major job for a guy like me, but I feel much better about undertaking it with my friend Brandt because of this post. So, before we go dismissing these months of posting etc, I hope everyone knows that this whole process is bringing me along nicely and I am grateful for everyones patience.