SilentBounty

I have a few issues with this truck after finishing the job and I think they may be related as to why this problem is happening. The problem is that I can start the truck up and it idles right and stuff but the second I touch the accelerator it drops to 0 RPM and the check engine light flashes really fast. Sometimes it idles back up, other times it works fine enough to drive it around, but mostly it just dies.

The issues I think may have something to do with it are:

*the crosspiece leaks bad on both heads because 3 out of 6 nuts are stripped and I have yet to buy new ones yet.

*Smoke comes from the oil filler cap if I take it off. I think it's because I oiled the cam and top of the head really good while putting them in.

*It for sure has a bad ground. I can't start the truck without making a ground to the frame with a jumper cable.

*the EGR Vacuum Modulator has one of the two hose nipples broken off on the side that has two. I stuck it back inside but obviously it hasn't sealed right. I honestly think this may be the problem because it uses hoses that come from the throttle body and TPS but I don't entirely know what the modulator does so I can't say.

This is just a beater truck that I tried to fix the heads on so I haven't spent too much time at once working on it but I wanted some opinions on what I could try. Thanks!

Terrys87

iTrader: (1)

[Quote]*the crosspiece leaks bad on both heads because 3 out of 6 nuts are stripped and I have yet to buy new ones yet. [Quote]

I am assuming this is the 3.0 maybe someone that knows that motor better can help.

SilentBounty

Yes it is a 3.0 v6 (3vze) I forgot to mention that haha.

millball

You listed multiple issues that you know it has.

Why don't you address those problems first and then decide where to go next.

You may find that you have fixed it.

mtrdrms

Have you checked the code (s)? It should point you in the right direction.

SilentBounty

It doesn't display a check engine light when running so I didn't think it would have codes. I haven't tried jumping the ports to check but I will as soon as I get back to working on her!

thook

Bad grounding is going mess up everything. EFI simply won't work right; ignition, fuel/spark timing, ECU voltage/signal input, etc. Get that fixed, first. Then, like millball said, see what's next.

SilentBounty

I highly suspected grounding. I'll make some new grounds/ clean up the old ones tomorrow morning and see what that does. Thank you!

SilentBounty

Ok I sanding all the ground spots to bare metal and made a new body to negative ground and it no longer has issues starting every time haha. I also fixed the exhaust leaks with new nuts on the studs. I siliconed the nipple on the egr vacuum modulator and all the lines running off of it are sucking/blowing so it must be working. Still no luck on the issue though. I'm now suspecting either a leaking intake pipe or the TPS being out of whack.

I undid all the lines to the egr and sucked/blowed on them all with no noticeable change to the motor at idle so I doubt it is the issue. I also sprayed carb cleaner around the intake pipe and noticed no change to rpm so I don't think it is leaking but it still could be.

I will test the TPS tomorrow weather permitting. It has no issues on a cold start though with the higher rpms but it still dies if you hit the gas faster than it likes. I also tried checking the check engine light but when i put the jumper in and turned the key it just kept flashing with no noticeable variance to it. I counted sixty consecutive flashes at the same pace before I decided it may not be working properly.

Does anybody have any idea what this could be yet?

thook

A uniform CEL flash means there's no codes stored. No reason to suspect it's malfunctioning from that alone.

The modulator simply routes vacuum to the EGR from the throttle body depending the on the angle/position of the throttle plate. If you were to look inside the TB you'll see little holes that correspond to the EGR ports (among others). Apart from the this, the modulator has no real mechanical function. But, whatever malfunction may be occurring in the EGR system, it is not causing your problem.

I'd suggest following the troubleshooting guide for diagnosis. Run down the list in order of numbered relevance for "engine stalling"..

http://personal.utulsa.edu/~nathan-b...63troubles.pdf

Also, make sure you're getting proper and consistent voltage to the ECU. In fact, you might even want to start here...

http://personal.utulsa.edu/~nathan-b...e/102engin.pdf

SilentBounty

Thank you for the helpful links! Honestly reading through the probable causes, dying on acceleration's number 1 cause is the volume air flow circuit. The intake pipe is really dry rotted and it looks like a huge chunk is missing and there's no way it could seal properly all the way, especially at higher rpms or quick intakes. Could this make the VAFM readings throw off and kill the engine?

SilentBounty

There is a very prominent hiss when the engine is running and it seems to follow the upper intake pipe if you move the pipe to various spots on the intake. The fuel pressure regulator also hisses when just the key is on but I think its just the pressure of the fuel coming through the return line. Could this be an issue too? I know fuel pressure was another probable cause. If the pressure was wrong though the motor wouldn't idle right?

skypilot

iTrader: (1)

Any un-metered air into the engine will screw it up just like you are seeing.

SilentBounty

That reinforces my idea that its the pipe then. It was pretty bad dry rotted. I'll see if I can come up with a pipe from a buddy or "borrow" one from oreilleys. That way I can tell what the issue is and if it's not I can still get my money back! Haha

thook

Even if it's not "the issue"....though it very well may be, it is an issue. A big one. You should really fix that. Search the forum for intake mod, if you need some way to fix it simply and perhaps more economically.

No, it won't throw the readings off as far as the VAFM is concerned. IOW's, if it's working right, the voltage the ECU sees will still be correct as the meter plate moves. The problem is that it's intake air that's not metered and a huge vacuum loss. Manifold pressure will drop. The ECU will detect it if the O2 system is working right, but the ECU can only adequately compensate for so much extra oxygen in the exhaust and only during closed loop operation. Minor fluctuations, really. So, as skypilot said, it's going to screw things up.

Also, hissing is quite synonymous with a vacuum leak. And, the sound with the FPR is normal. It makes that sound as fuel pressure builds.

jbtvt

O'Reilly's won't have that. Saved this link for myself. $35 new (no dry rot like another used one!), vs over a hundred from the dealers -
Check fit yourself.

You could also have a busted diaphram in the FPR if you're hearing unusual noise from it. Run the checks in the FSM on it if the intake tube doesn't solve things.

thook

Again, a "hissing" noise at the FPR is normal.... whether it's good or bad. But, if the diaphragm is leaking as jbtvt validly mentions, there will be fuel in the vac line attached to the top of the regulator. So, just to say....easy check.

SilentBounty

Ok guys an update, I fixed the air intake pipe. I got the dorman one jbtvt linked through O'Reilly's. I knew I could get that exact one because I work there hahaha. Employee discount ftw! Sadly the intake pipe wasn't the problem. The hiss is still there now. I can not for the life of me figure out where it is for sure. Could the intake manifold gasket be leaking or the intake chamber gasket on top of it? It now sounds more towards the center near the firewall.

Something interesting I noticed too is that the fuel pressure regulator doesn't seem to care if there's vacuum on it or not. I plugged the nipple on it, blew in it, sucked on it, nothing ever changed. Everything stayed constant. I haven't really had more than an hour to work on it at once though so I haven't done the serious tests on readings but that's food for thought.

And when you say it will compensate for extra air in the exhaust, could a leak upstream of the o2 sensors on the pipe cause what I'm seeing? I'm fairly certain I fixed them but I can always try again if another leak I didn't get could cause it.

jbtvt

Your exhaust is pressurized, I've never seen a leak affect 02 readings. I believe Thook was referring to intake leaks which are under negative pressure and suck in extra 02 throwing off the mix and sensors.

Among other methods, you can check for vacuum leaks by running an unlit propane torch around all the fittings. The propane will burn if sucked in so the engine will idle up when you're near a vacuum leak. I prefer visual checks but if the previous owner ripped a gasket you can't really see that by eye.

SilentBounty

Alright I'll break out the torch when I work on her next and run it around stuff to see where the leak is. If I find the hiss source that way maybe I'll know what to do to fix it then! Hopefully I put the intake manifold gasket on right when I was putting the motor back together...haha.