'97 5.7 Vortec- Fuel Meter body problems. Upgrade?
 

Greetings!

I just recently picked up a really nice 97 suburban with 179,000 miles for a decent price with the knowledge that the engine needs work.

What the symptoms are is a miss / backfire issue. No matter what RPM the engine is at there is a miss to it, almost like a spark plug wire is switched (they're not, I checked). It also bogs down really bad when you step on the gas, blowing black smoke out with a heavy gas smell in the cab.

Also when starting it cranks really slow for about half a second (like it has a dead battery) and then fires up just fine. I've been told this could be some sort of timing issue, but as these engines are self adjusting, I'm not sure what that issue is...

Error codes say 5 and 7 cylinder misfire.

It's had new wires, new distributor, new dist. cap, new plugs, the seal under the top intake manifold (the one the covers the spider / poppet system) replaced, injector cleaner run through the fuel and fuel filter replaced.

I haven't checked the fuel pressure yet.

Using instructions from this thread, I've pulled the upper air intake manifold off to reveal a pretty serious fuel leak from the injector fuel hoses running to #5 and 7 cylinders.

My question to you elite GM gods here is if I should replace the injectors as well while I'm under here? I've already ordered a new spider, but I just heard there is a newer system without the poppets that works better. Does anyone know about this system and if it's worth it?

I want this thing running good and reliably, but in these hard economic times need to spend my money wisely!

Any ideas from others who have done this stuff are more than welcomed!

Thanks!

bronzebogen

Also I forgot to mention that I suspect the mechanic who replaced the seal on the air intake manifold didn't do a great job because one of the bolts holding the spider bracket down is missing (Lordy! Could it have gone down into the engine? Methinks I would know if it did, but could that cause a similar problem?)

Also, has anyone seen a schematic on which spider / poppet hose goes to which injector? The mechanic could have gotten them mixed up too for all I know...

You shouldn't need a schematic, the intake manifold is labeled with each cylinder number and so is the injector block where the injectors out of it. It's as simple as putting #1 to #1, #2 to #2, etc....it sounds more like the mechanic didn't get them all seated properly.

As far as your comment about the missing bolt, I would recommend a compression test on all cylinders to make sure that you don't have any lurking surprises......

Yeah, after pulling the injection body out I found the numbers- after cleaning off all the soot! There was a LOT of it in there...

I also found, after cleaning, that there is only one bolt that holds the fuel injection body bracket, the other hole isn't threaded and just has a prong that fits in it to keep it steady. I'm wonder if the bracket wasn't made to be a little loose?

The compression is good on all cylinders.

I also found that the previous owner installed a new crankshaft position sensor.

There was evidence of gas leaking out of the number 5 & 7 injectors / injector hoses, so instead of getting a body and a couple injectors I decided to replace the whole shebang and bought the updated injection body without the poppets. It should be in today and I'll post my findings after installing it.

Thanks for the advice!

Well, installed the new spider fuel meter today and have the SAME problem! Small backfires, black smoke out the tailpipe when you rev it up and the RPMs are on the way down. Rough running. Missing a little bit.

Fuel pump sounds like it's working, but I don't have a fuel meter to check pressure.

Only other things I can think of are the ECM or possibly bad fuel pump!

Anyone have any other ideas? Please?

Thanks!

One thing that I'm noticing is that you haven't mentioned any trouble codes.....do you have a code scanner - is it showing a check engine light?

I had a similar situation with my wife's Tahoe and it was a bad EGR valve ($200 for one of those - ouch). The other thing that I think of is making sure that the cam timing was properly set when the mechanic did his work. That will definitely have a negative effect if it is out very far.

There are many other simple things to check for, but these are the ones that stood out in my efforts.
I'd also check to make sure that all of the electrical connectors have been returned to their proper location - especially the vacuum sensor beside the coil, it's hard to see and easily overlooked.

Hang in there!!!!

DarylH,

No, I don't have a code scanner unfortunately. The truck is at the dealer right now though and they're not finding the problem either! Error codes are multiple misfires moving from cylinder to cylinder.

CEL is not on.

I'm normally not a "throw parts at it and see if it'll fix it" kind of guy, but from all the forum posts I've been reading they all seemed to point to the spider injection system... I'm glad I replaced it anyway, but it sure wasn't the problem! It came with a new fuel pressure regulator.

SP wires are good.
Fuel pressure is reading from 55-65 psi.
Mechanic says EGR valve is good.
They tried installing a new entire distributor and setting the timing (that's what you're talking about when you mention cam timing right?), still no change
The hoses are hooked up to the vacuum sensor and all the plugs are plugged in that I can see.

I'm starting to think it's the ECM or the wiring harness. Think that's a reasonable conjecture? :P

So an update on my problem:

Dealer can't seem to find the issue!

Found that the only cylinders misfiring are on the drivers side (1, 3, 5 & 7).

So I've read a little more and now I'm wondering about the lower intake gaskets. They were changed about a month ago. Previous owner *said* that this problem wasn't there before they were changed, but I can't think of why he'd want to change them if there wasn't an issue...

I hear that if the intake gasket is installed wrong or if it wears out it can cause these symptoms.

One way to check and see if this is the issue is to plug up the holes in the valve covers and run the engine while checking for vacuum at the dipstick. If there is vacuum, you have an intake gasket leak!

Going to check that now...

This thing WILL get fixed!

Doesn't appear to have any vacuum leaks from the lower intake gasket as I couldn't get any vacuum from the dipstick with the valve cover breather holes plugged.

So that ain't it!

That leaves the 'puter or the wiring harness... :( Or perhaps there's a leak under the EGR valve? When I replaced the spider I had to take the valve off and didnt' notice that it had a gasket there. Wonder if that could be causing the issue?

As you can see, I'm pretty much guessing now... Trying to hang in there, but getting pretty frustrated! I've worked on Mercedes for years and have never had a problem this hard to track down!

I'd start back at the simple stuff - compression check, vacuum leaks, cap/wires/plugs. I know that the ignition stuff is new, but it never hurts to verify things before pouring more $$$ into things that don't need attention.
The tough part with the computer is that doesn't have any way to tell you this type of stuff - so it gives vague codes.

I can't rule out the ECM, but it seems odd that it is ONLY on the left bank of the engine.......

A couple of other thoughts - follow the wiring harness for the crank position sensor and the cam position sensor (distributor) and make sure that there's no issues with that either (in2pro brought that one up when I was struggling with our Tahoe) and you might take a look at the O2 sensor for the left side of the engine and make sure that there's not a problem or perhaps it needs to be replaced.

Hopefully one of the pros will chime in with additional suggestions.

Meantime, I will keep checking to see if I can help.

It took me 2 weeks to track down my issue, so don't give up!!