Help! rough idle, no power, vacuum leak?

Twranger · Jun 21, 2018

Hey All,

Totally new to the TRS as a member, but I've been lurking off and on for awhile.

So here's the story, then the problem.

About a week ago I noticed it started leaking coolant from some undisclosed location at the back of the engine, seemly mostly when hot. A nice steady leak. Enough to make a puddle. I thought it was a head gasket, turns out it's super common I guess that these motors start leaking from the lower intake gasket.

So, long story short, I followed 97RangerXLT's right up on this whole process. (Thanks btw!) I did it all, including the fuel rail and injector o-rings.

Now the gosh darn thing seems to start up okay, not great, and idles okay, but a little rough. And it sounds rough if you rev it up and if you put it in gear... Forget about it. It almost stalls and has no power what so ever and sounds super rough.

Sounds like a vacuum leak right? That's what I thought. I have been checking for vacuum leaks for the last week... Among other things. The EGR tube to upper intake seemed to be leaking, replaced the o-ring (super carefully because I think I pinched the last one, hence the leak).

Oh and it did throw a P0174 (lean bank 2) code. And my scanner shows the short term fuel trim bank 2 at like 42! Whereas the bank 1 trim hovers around 0.

I'm totally stumped. I bow to the superior knowledge and wisdom of this forum. Any and all suggestions are welcome.

I'm ready to send this thing off a cliff.

Twranger · Jun 21, 2018

Oh and it seems to not be a vacuum leak, what with all my testing and probing around. Although I hear a hiss very noticeably when you shut it down.

What would seem like a vacuum leak but isn't?

I'm assuming a screwed something up with the install of everything and that it's just not some wonderful coincidence.....

Denisefwd93 · Jun 21, 2018

Everyday there seems to be new post on basically the same topic, is your exhaust or catalytic converter blocked?

Twranger said:
Oh and it seems to not be a vacuum leak, what with all my testing and probing around. Although I hear a hiss very noticeably when you shut it down.

What would seem like a vacuum leak but isn't?

I'm assuming a screwed something up with the install of everything and that it's just not some wonderful coincidence.....

Twranger · Jun 21, 2018

Haha, yeah I've read quite a few... But I guess I didn't find the right ones. I doubt that the exhaust is clogged because it ran fine before I tore it apart... Unless I did something to clog the exhaust?

Is there a post you think I should look at? I don't mean to be redundant about posting.

RonD · Jun 22, 2018

Welcome to TRS

First, Check the firing order on the Coil Pack
3 4
2 6
1 5
Front

The 5 6 4 side gets me every time

And also follow each wire to its cylinder 4, 5, and 6

Vacuum leak
Warm up engine
Unplug IAC Valve, it will close all the way, and RPMs should drop to about 500 or engine may stall, either is good it means no vacuum leaks
(cold engine will always stall if you unplug IAC Valve)

If RPMs don't drop then there is a leak
On a warm engine with IAC Valve unplugged you can spray soapy water around lower intake or ??, to see if it is sucked in, engine will stumble if it is, and all soapy water will do otherwise is clean stuff off, lol.

DO NOT use flammable sprays on warm engines to find vacuum leaks, on a cold engine it is still marginal IMO

Twranger · Jun 23, 2018

Hey Ron,

Thanks! I wish it were under better circumstances, but really... When is it?

So I did check the firing order, as I plugged it in wrong initially, and THEN checked the manual.

I did the test with the IAC. RPMs drop and it stumbles a bit and then just stays a really low idle. So I'm assuming that's good and no vacuum leaks. I also tried (on a cold engine) good old propane I couldn't find anything for a vacuum leak.

I'm just about to go out and take out the O2 sensor just to make sure it's not a clogged cat or something like that. And see it if improves anything. Is there another way to test if the exhaust is plugged up? Without taking it apart that is.

Other question: Is there a way to test to see if the driver side O2 sensor is bad?

Thank you both so much for taking the time to respond.

RonD · Jun 23, 2018

Bank 2 is drivers side and one O2 sensor could fail or its wires, but O2 sensors are not used until they get heated up above 600degF, so failing O2 shouldn't effect Cold start and running for the first 4 or 5 minutes
Also O2 sensors are "ignored" by the computer at WOT(wide open throttle), computer just pumps in "lots of gas" lol.

You can hit the road and press "pedal to the metal", if engine starts to smooth out then yes O2 sensor could be the problem

With +42 fuel trim it wouldn't be a stuck open or leaking injector on bank 2, that would show -20 or more fuel trim, and Rich code.

Misfire itself dumps unburned Oxygen into the exhaust, and O2s "read" oxygen levels so misfire will cause higher fuel trims but +42 is excessive for that.

Vacuum gauge can ID blocked up exhaust
At idle vacuum should be 18-21"
When you open throttle full vacuum should drop quickly to 0-2"
Then let throttle snap closed, vacuum should instantly come back to idle level
If it slowly comes back then exhaust blockage would be suspected

Hold engine at about 2,000rpm if vacuum starts to slowly drop then pressure is building up in exhaust system

But exhaust blockage usually won't effect idle, unless its the "banana up the tail pipe" blockage which stalls the engine and no restart, lol.

Do you have a way to test cooling system pressure?
You just did lower intake gasket, may be some coolant is leaking into cylinders 4 or 6 on drivers side, maybe pull those spark plugs and see if they look steam cleaned.

Twranger · Jun 25, 2018

So...

I checked the vacuum... 18" as idle, nice and steady, rev it up, it first hits zero and the sits around ~2". Let the throttle snap back, and the vacuum shoots right back to idle vacuum of 18". And the vacuum is very responsive with the throttle. So no exhaust blockage I'm assuming.

I also pulled plugs 4 and 6 on the drivers side and 4 (the front) is black and sooty. 6 on the other hand is is soaked with gas, which seems weird to me. Is it not firing? That would cause it to be lean right?

I guess I should take it out on the road and see if it smooths out at WOT.

Another note, if I rev it up for any amount of time it starts pop pop popping with a backfires I'm assuming.

I still don't understand.... It worked fine before I took it apart.... Grrr....

Oh and I might be wrong to some degree about the rough idle... It seems to shake more than it should at idle and the exhaust sounds really chuggy/throaty. Under the hood though it really doesn't sound rough. But boy, put it in gear and it practically stalls out.

Twranger · Jun 25, 2018

Well I'm officially a moron.... Also I need to learn to read....

Ron, thanks for telling me to actually follow the plug wires to make sure I have them right... Sorry I didn't follow that part sooner. I thought I knew which on was which, I had them labeled and everything.

So I finally followed that advice... And I had the 5 and 6 wires switched... It's amazing how well it ran like that.

So note to self... And anyone else who's doing this, pay attention to the odd configuration of the plug wires and how it's not odd on the engine, but odd on the coil pack...

Finally I can actually get some real work done and stop messing up my truck.

RonD · Jun 25, 2018

Good work

Thanks for follow up and fix

I goof up firing order all the time when I KNOW it is RIGHT, KISS applies

Denisefwd93 · Jun 25, 2018

Really, don't feel bad I've been in the HVAC business almost my whole life, every time I fix the AC on my truck another leak shows up! (Which is why I'm replacing everything about the compressor and maybe even that!)

Help! rough idle, no power, vacuum leak?

Twranger

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