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11 mpg and power lose,

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Old 05-05-2013, 02:38 PM   #1
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Question 11 mpg and power lose,

Did a spark test that looked good then a compression test 1,3,5 all at 180 and 2,4,6 at 150. 3.4 v6
the check engine light is on but have not got codes need to go have them checked.

Any thoughts?

my guesses are a burned up valve, bad head gasket. or bad cam timing.

not sure what to do next.

11 mpg and power lose,-imag0001.jpg
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Old 05-05-2013, 02:40 PM   #2
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Could be something like a clogged cat as well.
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Old 05-07-2013, 05:48 PM   #3
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A number of things test tps, o2, and coolant sensors first. If all are fine could be a bad injector hanging open. Clogged intake or exaught?
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Old 05-08-2013, 10:27 PM   #4
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code P0171 bank 1 to lean

and o2 sensor close loop?

just got my scan tool still learning to use it
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Old 05-08-2013, 10:35 PM   #5
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Compression looks OK.
Consistency is the key, and you're within 20% on both banks.
If you had a hosed valve or gasket, you'd have one cylinder lower than the others on the same bank.

Wouldn't make sense for the 2,4,6 cam to have slipped a tooth... belt normally slips at the smaller sprocket on the crank, and I'd imagine you'd be off more than 30psi.
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Old 05-09-2013, 06:13 AM   #6
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Ok so o2 is going into closed loop which is full enrichment because of a lean reading it sounds to me like a bad o2 or (maf?/map? Idk what they use) I'd start by cleaning the o2 and w/e sensor meters air and ohm test injectors (assuming fuel pressure is fine) if all the injectors are working re instal your clean sensors if it runs fine for a minute and then goes back to before its probably a clogged exaught and I would advise New o2s after clog is fixed. It wouldn't hurt to ohm test water temp, tps, and iat while your at it
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Old 05-09-2013, 06:14 AM   #7
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A new fuel filter wouldn't hurt either
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Old 05-09-2013, 12:43 PM   #8
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Any other codes? 02 sensors can go bad and cause similar problems. what are your mods?
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Old 05-09-2013, 12:47 PM   #9
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And you guys have it backwards. Closed loop is normal operation, it stays in open loop when 02 sensor fault codes are present, but a 0170 should let it run in closed loop still unless there's companion codes to go along with it.
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Old 05-09-2013, 02:08 PM   #10
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Sorry I had it backwards and it will also run open loop after exaught temps get over operating temperatures from it being rich
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Old 05-09-2013, 02:15 PM   #11
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I'm thinking o2 or temp sensor its reading the o2 under closed loop so its compensating dumping too much fuel because of the lean bank reading
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Old 05-09-2013, 02:16 PM   #12
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Open loop would've been full enrichment*
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Old 05-09-2013, 02:19 PM   #13
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Don't know if it has been mentioned, but did you check the EGR valve?
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Old 05-09-2013, 02:30 PM   #14
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Some one put a timing belt in it recently?
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Old 05-09-2013, 05:26 PM   #15
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Thanks for all the input. Seems I need to do a full one over on the intake and exhaust system.
I already have new o2 sensors just haven't put them in yet was waiting till I had a better idea what was going on.

As for mods I just bought this truck and not sure what all was done. The P.O. said the engine was rebuilt 20,000 miles ago didnt say by who. Not sure how true that is.

there was wiring to two switches from the cab to the engine housing but to what not sure. But it was removed.
thinking it may have been a supercharger not sure never worked with those be for. ecu could be remapped as far as I know
had a remote start that was shorting out the starter removed that and fixed the wiring.

It's got a 4 inch lift I believe 33 inch tires.

it's my Trojan horse u could say but bought it for something to do.

I'll take a bunch of pics and post.
Love the feed back I'll keep posting as thing progress.
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Old 05-10-2013, 04:12 AM   #16
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You should have a look at the cam timing. One cam is the even side the other the odd side your compression is lower on the odd side but even. If the cam timing is off it will lower the compression you can have one cam in time and the other one off this may explain why the compression is better on the even side. It can cause your lack of power and poor mileage and not set a code. O2 sensors will set an emission code if you even look at them wrong.
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Old 05-10-2013, 12:02 PM   #17
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Quote:
Originally Posted by Novatd View Post
As for mods I just bought this truck and not sure what all was done. The P.O. said the engine was rebuilt 20,000 miles ago didnt say by who.
Okay... Had we known this up front, some answers may have been different.
We were answering under the assumption that the truck used to run properly and it got worse without you making any changes to the engine.

Was it running properly when you bought it and it suddenly dropped, or has it always been like this?
I'd be inclined to agree that one cam may be out of time. Installing the timing belt is easy and it is a bonehead move to get the cams out of time, but if the "assembler" is not paying attention, it happens.
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Old 05-10-2013, 01:45 PM   #18
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That actually makes a lot of sense for the different compressions
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Old 05-10-2013, 07:42 PM   #19
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That's what I was leaning towards myself. And bone head moves seem to be a theme with this truck. The transfer case shifter was installed in the 4low position when it was actually in 2hi so it seemed as though it was a ceased transfer case. When they put a new cluch in I'm assuming. Glad I figured that one out. Don't get me started on the halfassed wiring.

looks like I got a long weekend ahead of me.

sorry should have pointed out earlier that I just got it. And no it ran this way when I bought it.

thanks again.
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Old 06-10-2013, 04:41 PM   #20
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OK i know its been a while just wanted to as much info as i could

so here is the update

replaced both O2 sensors and i had 2 missing bolts on the exhaust one for the cat and one for the up stream sensor replaced the gaskets for the cat now getting 13-14 mpg

after this all my engine codes have been fixed

now for the thing that is still got me confused so my compression test was 1,3,5 all at 180 and 2,4,6 at 150

so did a leak down test all cylinders "except 2" are between 10-15% witch is not bad as far as i Know.

OK so 2 is close to 100% loss witch makes no scene if im getting 150 compression right. now i did this cylinder five times with redoing TDC every time and it sounds like a lot of air is coming back out of the spark plug hole but it is coming out of the intake as well witch is intake value problems. but 150 compression no misfires im confused

when i was running lean i would get a random cylinder 2 misfire though.

any thoughts?

i did check the timing belt and all markers and notches lined up the 2 on the cams and the one on the crank shaft. this means its fine right?

updated i did check the cyl 2 compression again and dry is 90 and 140 to 150 wet so i know head rings are going.
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