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12340987 · 06-04-2010, 01:05 PM

I'm visiting Seattle and am 300 miles away from my tools and my car isn't running right. Lately it has been getting 22 MPG highway and way less than 18 city. Of course, I take a trip and while getting gas I notice the idle starts loping. I can hear a weird "puff" sound from the exhaust when it hits that cylinder.

A while ago I replaced the plugs, wires and a bad injector. It was some time after that my mileage started to tank. I pulled the front bank of injectors/plugs one by one but didn't find a bad cylinder. And the same for the back, but I couldn't reach all the injectors.

Ignition? I'm just a little worried because I'm out here toolless and alone, and this is not the time to have engine trouble just before I move. I am seriously hoping a plug went bad, or the wire's not making contact or something else simple, because I need to be able to get around, so any suggestions are appreciated. Can a bad headgasket or valve cause this stuff?

I actually have a 93 lexus es300, so it's a camry v6.

LittleWhiteBubble · 06-04-2010, 01:34 PM

Are you getting spark at all cylinders? I'd say there's a good chance it's a spark or injector problem at one cylinder. Totally different vehicle, but on my f150 I had a problem where the exhaust was doing what I described as hiccupping. It felt like it was sucking in rather than out when one of the cylinders was firing. I found out my number one injector wire had been cut and crimped back by the previous owner and it had come undone. It made my truck run terrible and my mileage dropped like a brick out the window. This sounds similar to your problem, so I would be suspect of an injector before I went looking for a stuck valve or something else internal. You said you can't pull the back set of injectors out, but can you unplug the connections? If so, try just unplugging them one at a time and see if the idle changes. If unplugging one doesn't change anything, then there you go.

12340987 · 06-09-2010, 04:17 PM

Turned out to be an exhaust leak... Removed every spark plug wire and they all make a considerable difference.
But I wonder, could one of the injectors be stuck on? How would I tell?

chronoti · 06-09-2010, 05:04 PM

screw driver touched on each injector and use it like a stethoscope to hear the ticking

12340987 · 06-09-2010, 11:52 PM

Doh. I even have a mechanics stethoscope. Injectors were fine. The PCV valve was rattling like crazy, even though I replaced it just a few months ago. I could blow through it both ways so it must have been bad. I notice even on the new one I can kinda blow through... Fram sucks.

I wonder if that will give me the 10MPG I'm missing?

***fenixus*** · 06-10-2010, 12:29 AM

have you tried doing an injector balance test ? you would need a scan tool for live fuel trims monitoring while unplugging each injector alone on running engine and writing down the fuel trims after each got unplugged.
once you find the dirty one you will see that base line fuel trims do not change much (because ECU already compensated for it initially).

you can always try chevron techron fuel system cleaner in gas tank. if it makes the difference at all you will know that problem may be narrowed down to this sub-system. if not then it's probably elsewhere.

don't use fram filters on anything, it's a piece of shit. if you need any filters from store get them from Napa or dealer.

12340987 · 06-10-2010, 06:44 PM

Cool. Would I be able to see fuel trims on an ODBI car?

I used some generic fuel system cleaner, but not sure if it did anything because of the aforementioned problems.

***fenixus*** · 06-10-2010, 07:17 PM

nah ... obd-I

no live monitoring (as far as i know). forget the fuel injector balance test then.

chevron techron makes a very good fuel system cleaner (get 20oz bottle), did it many times with quite good results. lucas makes one too, but never tried it. some people say Gumout Regane is good too (i didn't feel anything changed). others are questionable and probably only a placebo effect.

LittleWhiteBubble · 06-11-2010, 07:54 AM

Could be a timing issue

12340987 · 06-12-2010, 03:18 AM

So last year I leaned out my AFM by 3 clicks but never advanced the timing, could that be a culprit? I figured it could only improve mileage. Everybody else does it...

Man, I really need to do the timing, but you have to remove so much crap to get to the timing marks on the 3vz.

12340987 · 06-16-2010, 05:40 PM

My loping idle came back. Exact same really low puffing noise from the tailpipe. I have spark on all 6 cylinders. I listened to each injector with a stethoscope, and while #2 seemed weak, they were all firing. I notice front bank is ticking way too loudly, which I dismissed as common on the 3vz-fe. This only happens on a hot engine and isn't really noticeable when I increase rev it up by a couple 100RPM.

I will have to check again, but I pulled the plugs on the front and it seemed like #2 and #4 were lighter in color than #6, with a few white granules on the electrodes.

Also, it takes me like 5-7 cranks to start it on a cold engine. 1-2 when it's hot.

Head Gasket? Bad valve? Adjust valves? Fuel filter? FPR? Low idle?

carsrus · 06-16-2010, 07:21 PM

Is it burning oil or coolant out the exhaust?

Could be a clogged cat.

12340987 · 06-16-2010, 10:55 PM

I think it might be burning or leaking coolant. My PCV valve was bad and seems to have been spewing oil into the intake. The oil looks fine, it doesn't overheat, but I see white smoke when it's cold. I am not so sure because I thought it could be condensation. It goes away when warm.

There has been a weird humming/rattling noise that les schwab can't figure out. They said they checked the cat and everything and that they didn't hear anything. I haven't had those other signs of a clogged cat, like lack of power.

AlmightyCamry777 · 07-05-2010, 05:08 PM

so 12340987 did you find out what it was? Loping is usually caused by ignition not fuel.
BUT Its possible the injectors could be worn out and still function.
To start with the easy things first, does this engine have a distributor and rotor? If so change them -
-i'd do a compression check, at least on the front 3 cylinders.
-Also look at the plugs, they might tell you a whole lot, normal is tan or light gray, anything else indicates a problem.
-maybe your valves are sticking, run some marvel mystery oil in the crankcase for a few thousand miles and see if that helps

12340987 · 07-05-2010, 05:34 PM

Quote:

Originally Posted by AlmightyCamry777

so 12340987 did you find out what it was? Loping is usually caused by ignition not fuel.
BUT Its possible the injectors could be worn out and still function.
To start with the easy things first, does this engine have a distributor and rotor? If so change them -
-i'd do a compression check, at least on the front 3 cylinders.
-Also look at the plugs, they might tell you a whole lot, normal is tan or light gray, anything else indicates a problem.
-maybe your valves are sticking, run some marvel mystery oil in the crankcase for a few thousand miles and see if that helps

Nope. Don't know what's going on. I changed the cap, rotor, plugs and wires last year. I think I need to do a compression test... How can I check if my cat is clogged?
I don't know about the rear bank but one of the exhaust valve shims on cyl 6 needs adjusting.
One thing I notice is that my gas mileage seems better with the first 1/2 of the tank. If I fill it up at the 1/2 way mark I get 25mpg, if I go until E I get 22, is that some sort of sign?