Only getting 160 miles on 25gal tank

[Sparky]

I've never had it mess my cat up on either vehicle I did it on.

Maybe lop off the cat, let it smoke, then put new one on in case you're concerned.

 

[Ziggy]

I've never had it mess my cat up on either vehicle I did it on.

Maybe lop off the cat, let it smoke, then put new one on in case you're concerned.

That's exactly what I was thinking...

 

[pcharm129]

Well, she got me back to NYC this morning without incident (whew!). Tomorrow is my BDay so i may not not get to her until after that. I had a few ABS/BRAKE lights combination flashes (which i had problems with in the past and denoted faulty/loose ABS module), and a few stalls at idle (which was not uncommon since i've been having this issue), but thats about it. Im definitely going to get the CAT checked out by the wknd.

 

[pcharm129]

Ok. So i finally got the back pressure test done. Drumroll please......0! 0 back pressure! If i didnt have this issue i'd be extatic. But alas...smh. So now im completely LOST!!! Im driving off the next cliff i see...!

 

[Tiggerr]

You have to have a serious engine problem going on, If it's not the cat. compression check and leak down test would be my next move. Something is way wonky. How does your trans "feel"? Do you notice any kind of oddities? Slippage, shifting strange, that kinda thing?

 

[pcharm129]

Mechanic just told me im throwing p0171.

Screenshot of real time reading using bluetooth obd device...

 

[Tiggerr]

That could be map sensor, O2, lots of things. If you have lean condition PCM will try to compensate with more fuel. Could be onto something with that. I'm sure someone knows these codes and electronics better than I do will chime in

 

[Texan]

P0171 System too lean (bank 1). May be a vacuum leak.
Check all vacuum hoses/connections. Loose intake manifold bolts?
Power brake booster/hose? EXT has rear HVAC. Check vacuum
operated hot water valve at fire wall, passenger side.

 

[pcharm129]

If i blow smoke into the brake booster hose, will that suffice for vacuum leak test? Or do i have to take it to mechanic with smoke machine?

 

[Texan]

If it was mine, I would pinch the brake booster hose shut with
a vacuum gauge hooked up and the engine running, and see
if that effects(increases) the vacuum.
Have you checked the fuel pressure? Has the fuel filter been
changed?

 

[pcharm129]

I'll try that. Fuel pressure and filter were done already. Im under the hood now changing the plugs. First problem i see is that the plug 1 chamber has oil in it. Covering the plug...

 

[djthumper]

Your coolant temp is a little low as well.

 

[pcharm129]

I just realized that i may have the wrong plugs in the TB. The plug i pulled is an ACDelco Iridium 41-993. But the new plugs are 41-103 (significantly longer thread column). And i have seen on a thread that 41-103 plugs are what i should be using. Could this be part of the problem?

 

[coolasice]

41-103 is correct number. 41-993 is for older blazer/jimmy and some other models. That could account for some of the problem.

 

[pcharm129]

Yeah, all are 41-993 except plug 4, which is the 41-103. I just pulled the Throttle body and its filthy. Im heading to get some tb cleaner now. Some of the plugs look terrible. One has some pinkish looking residue on the tip. A couple of the coil packs have a white powdery film on them too.I'll post some pics when i get the chance...

 

[Mooseman]

And for the oil in the plug well, that is a common problem with these engines. If it's just a little, I wouldn't worry about it. Just make sure that the coil hold down bolts are torqued properly.

 

[pcharm129]

Thanks Mooseman. But now there's ANOTHER issue...! I finished cleaning the throttle body and changing the plugs and NOW the truck is misfiring!!!😤 Its throwing p0300. I swear this thing has gremlins!!! Im beat from working on it and my friends van from 6am. Im too tired to deal with this crap right now. Going to take a nap and cool off a bit cause im P'd OFF right now. I'll definitely get those pics up as soon as i can...

 

[littleblazer]

Check the plugs on the coil packs and recheck their seating on the spark plug.

 

[pcharm129]

Check the plugs on the coil packs and recheck their seating on the spark plug.

Yeah. I was going to go over them again. Its just such a PAIN! If i do this and its still misfiring i may just tie antlers on it and shoot her...jeesh!

 

[Sparky]

It is easy to get the coil next to the plug by accident. Hopefully that's all it is.

 

[Tiggerr]

Did you do compression check while you had it apart?

 

[pcharm129]

Did you do compression check while you had it apart?

Crap! No. Honestly i forgot all about it. And i went to AutoZone twice. Could have rented the tool. I'll try and make that happen tomorrow since im going back in anyway. Thanx for reminding me.

@Sparky... Doesn't P0300 mean variable cylinder misfires? I stretched the coil pack springs a bit to ensure good contact and removed any corrosion from the contacts before i put them back in. Should i not have done that?

 

[Tiggerr]

Crap! No. Honestly i forgot all about it. And i went to AutoZone twice. Could have rented the tool. I'll try and make that happen tomorrow since im going back in anyway. Thanx for reminding me.

Lol no problem.... Relax.... Breathe

 

[Mounce]

Doesn't P0300 mean variable cylinder misfires? I stretched the coil pack springs a bit to ensure good contact and removed any corrosion from the contacts before i put them back in. Should i not have done that?

Yes, but a lot of times it throws that before it figures out which specific ones are causing the issue. A lot of times it'll figure it out and give you the specific codes as to which cylinder is misfiring.

 

[pcharm129]

As promised, here's some pics...

Threw plug 1 away before i thought to do this...


Here's the oil in the plug well covering the plug...


Coil packs with white chalky film...


Dirty throttle body...


Going to tackle compression test and misfires tomorrow. Uhhh, today.

 

[Mooseman]

The corrosion on the coil is likely due to a leaky gasket allowing water in. And I'll bet that was #4 because of where the drip edge from the firewall is located. Those plugs would have reduced the compression ratio and shielded the spark from the intake charge causing misfires. And they look like they were too hot being so clean.

 

[pcharm129]

So apparently, the pcm just needed to acclimate to the new plugs because i drove her today and the misfires are gone. I cleared the p0300 code and it didn't return. P0171 is also gone. I got the compression tester and i'll get to that tomorrow. Im also in the process of building an evap smoke machine so i'll also be getting to the vacuum test soon.

Oh. And i just did my first fill up since the plug change. So we'll see if anything changes.

 

[pcharm129]

Ok. Im trying to tackle the compression test, but i can't locate the fuel pump and fuel injector fuses. I have an EXT. Can anyone point me in the right direction with that?

 

[Mounce]

Just pull the relay?

 

[pcharm129]

Just pull the relay?

Would that be 41?

 

[Mooseman]

Should say so right in the fuse cover under the hood.

 

[pcharm129]

My compression test was positive...


And just 2 days after the plug change, plug well 1 was again filled with oil... I think i see intake manifold gasket change is in my near future...smh.

 

[Mounce]

Pressures look great. And yeah, if it's hemorrhaging oil that quick it's an issue. Better keep your eye on the oil level and keep it topped off.

 

[Sparky]

Did you try tightening the valve cover? Some people have found theirs to be loose.

 

[pcharm129]

I'll tighten them up a bit before the next time i move it. And i'll let you guys know how the mileage is looking after about a quarter tank. Thanx fellas.

 

[pcharm129]

No luck fellas. Still getting 40 miles on a quarter tank...smh.

 

[Mooseman]

You can't just go on a quarter tank. Too many variables. I find the last quarter tank goes faster. You have to go from a full tank and calculate actual MPGs.

 

[Blckshdw]

You can't just go on a quarter tank. Too many variables. I fond the last quarter tank goes faster. You have to go from a full tank and calculate actual MPGs.

For the most part, you are right, but comparatively speaking, I know my EXT runs about 30 miles per tick mark on the gauge until just under half a tank with daily surface street driving, then it starts to drop at a faster rate. So if I started seeing a consumption rate that the OPs getting, I'd be alarmed right away too. (unless I spent a ton of time idling in bumper to bumper traffic with the AC on or something)

 

[triz]

Why is the number 4 plug longer than the rest?

Your misfiring could be coming from the coil packs not being seated properly. As far as the mileage issues throwing some concentrated Chevron TechRon in your next tank full up. You could have dirty injectors.

 

[Mooseman]

If you read through the thread, the wrong plugs were in there except that one.

Now, because of the previous misfiring and wrong plugs, the cat could be plugged. Any more codes? During the plug swap, did you disconnect the battery for 30 minutes so the engine can relearn itself?