Can't rev above 3K RPM, and no power

[fishead]

OK, here's the story. Thanks for reading, sorry its going to be so long.

 

I bought this '90 Pathfinder SE-V6 a few months ago, and put only 3 days insurance on it so I could change the timing belt (260,000KM just want to be safe). I was super careful to make sure I did it right, and took my time. Once I was done, I noticed that it was REALLY gutless. So, I changed all the cheap stuff: Sparkies, fuel filter, air filter, cap, rotor, wires. No improvement. Searching the forums, everyone says "exhaust manifold". I put this off as long as I could, then finally bit the bullet, borrowed a short drill, and called up some buds. 5 broken studs, and we fixed the manifolds. I expected an immediate improvement, but didn't get it. More research tells me that maybe my O2 sensor gave up in frustration. Where I work, we share a parking lot with a fairly reputable mechanic shop. They borrow stuff off us sometimes, and vice versa. Short story, I trust the guys. They said "don't just go replacing stuff. Bring it in, and we'll give you a deal on reading the codes and testing the exhaust." (they said they would only charge for the codes, but throw in the exhaust test). So, they scan the codes, and find nothing. He takes it for a spin, and confirms "severly gutless". He tests the exhaust, and confirms copious amounts of raw fuel, and will definitely fail emissions testing in December. OK, why? MAF sensor? Because he is a mechanic shop, he ordered up a MAF sensor and swapped it in. No difference. Cat? He pulled off the Cat, and said it looks fine. Timing? Knowing that I did it, and I am not a mechanic, (he gave me advice when I did it originally), he pulled off the top cover and confirmed that I have it bang on. Distributor off a tooth? He put a light on it and tweaked the timing. He also tested EGR, temp sensors, throttle position sensor, everything he could think of.

 

He sent me home on Friday and suggested I do a compression test. On the way home, I could not rev above 3K RPM, and have NO power. I have a fairly long commute through the city, and was a little worried about someone getting angry, but managed OK. So, fearing the worst, I did a compression test on Saturday. My lowest reading is 130PSI, and my highest is 160PSI (I have no idea how a "compression ratio" is calculated). OK, so my compression isn't perfectly even, but why the problems? Something the mechanic did is causing it to run worse then before, but what? I think that tomorrow I will see if I can get my cat off and check for blockages downstream or something.

 

If anyone can give me advice, I would REALLY appreciate it. Just now I finished confirming my timing belt, and tweaking the timing myself. I have it bang on 15 deg. One other thing. I am still a few thousand KM away from my next scheduled oil change, and already the oil is BLACK. I noticed that right from when I first got the truck that the oil goes black real early. The antifreeze was a nice brite Kool-aid green as well. Mmm that stuff looks tastey. And the neighbours dog that barks all night... just kidding.

 

Thanks everyone.

 

chris.

 

(long time lurker here, I love this site)

[Slick]

well.. you should read my threads.. lol.. broken piston and or head gasket come to mind first.

if he tweaked the distributor, that could have been it or knocked a vaccum line off.

some pathys don't run good bang on the timing marks. some like 14 degrees, some like 15.... and so on....

 

does it smoke a bit on start up? run like ass? sound like it's perhaps not running on all 6?

 

 

^^my owee.

 

ALSO....... did the mechanic mess with the spark plugs, wires or anything around there?

does it feel like it's starving for fuel? have you checked to make sure all the vaccum lines and sensors are plugged in?

Edited September 4, 2006 by Slick

[fishead]

I actually read that thread, but was still unsure. Broken piston/headgasket... wouldn't my compression suck?

 

It runs/idles perfect until you hit about 3K RPM. Then it totally bogs down and you can smell raw fuel out the butt end.

 

I pulled each plug one at a time while doing my compression test. They were pretty black. In the past, I have always found a loss of low end with bad plugs.

 

From what I can see, everything is plugged in tightly. I will check more thoroughly tomorrow.

 

Doesn't smoke on startup. Actually, it runs quite well on startup.

 

Maybe I should just put a sparkplug in the tailpipe to burn off all the extra fuel and leave it actually thinking about this... if I do, there WILL be pictures for you.

[Slick]

I actually read that thread, but was still unsure. Broken piston/headgasket... wouldn't my compression suck?

 

It runs/idles perfect until you hit about 3K RPM. Then it totally bogs down and you can smell raw fuel out the butt end.

 

I pulled each plug one at a time while doing my compression test. They were pretty black. In the past, I have always found a loss of low end with bad plugs.

 

From what I can see, everything is plugged in tightly. I will check more thoroughly tomorrow.

 

Doesn't smoke on startup. Actually, it runs quite well on startup.

 

Maybe I should just put a sparkplug in the tailpipe to burn off all the extra fuel and leave it actually thinking about this... if I do, there WILL be pictures for you.

no. all my compression was still in the 100's.. but more than 20 off the rest on piston #4.. the broken piston........

[Precise1]

I'd check your vacuum advance first.

 

I seem to remember compression "spec" being something like 160 psi and fairly tightly grouped (10 %) ? Still 130-160 is not terrible (Chiltons manual agrees), and should not produce the effect you are describing.

 

Fuel filter ? Probably not.

Injector/fuel pressure issue ? Could be...

 

B

[fishead]

OK, so far this morning I have checked all the wiring I could reach, and pulled at all the vacuum hoses, but nothing changes. I pulled the exhaust off after my cat, and it looks like lots of exhaust is coming out, but doesn't make a difference. Just for good luck I am gonna pull out the air filter...

 

Thanks for the advice guys, but I am just running out of ideas.

[Precise1]

Hmm, try running the ECU codes again. Did you check the vacuum advance unit ? Throttle position sensor ? Seems engine control related to me...

What changes might be made at 3000 rpm ? Does it run fine then immediately blubber at exactly 3k or does it start at 2800 and get worse until 3100 ? You get the idea...

 

Only 20 psi difference with a broken piston !?!

 

B

[fishead]

I can't find any vacuum advance. It seems to be all electronic ('90 VG30E). My haynes manual says that the timing is not adjustable...

 

It runs fine until I rev it up. It hits a certain RPM, then totally bogs and the RPM drops.

 

I pulled the throttle position sensor off, doesn't seem to be that.

 

Thanks for the ideas. Just gonna go pull some more stuff off.

[fishead]

I was just messing with it, and notice quite a bit of water dripping out of the exhaust. I have it pulled out behind the Cat to see if there was a blockage (I should pull it apart behind the Y pipe next, eh?) and there is a substantial drip coming out of the opening. There is also a drip out the end of the tail pipe.

 

I know water is one of the byproducts of combustion, but how much? It doesn't smell like gas, and isn't slippery. Haven't tasted it... yet.

 

If it looks like my engine has substantial internal damage, there are plenty of local engines available for less then the price of a rebuild. Then I could rebuild this one in my garage.

[jj big shoe]

My 87 wouldn't rev past 3k either when I bought it because the drivers side cam was one tooth off. It would run fine until 3k RPM then just flat had no power. I know you checked it but it sounds like the same thing mine did.

[Mr. Pickles]

I'd stop throwing parts and guesses at it and go back to square 1 at this point. You changed the T belt and immediately had problems? Go back to the T belt, and start from scratch.

[Guest Thumper]

Raw fuel and can't go past 3 grand, sounds to me you're in safe mode. I do remember when mine did it,it was a little orange sensor down by the passenger side kick panel and the one wire was broke and just touching. Which was what thru the ECU into safe mode. While it was in safe mode it did not through any codes. But since all trucks are different in the way they run this is just something you could check. And hopefully fix your problem.

 

 

This is all my advice for tonight since my wife is typing this and I keep changing my wording and ticking her off a little.... Good luck if I think of anything tomorrow I'll post it.

 

By the way OPPS this was Speedys advice but of course Thumper typing Guess he doesn't know how to sign in hahaha

Edited September 5, 2006 by Thumper

[speedy]

Another thing to check is ohm's between the ECU and the injectors, if you don't have Zero ohm's then you have a break in the wire or resistence which would through it into safe mode and not let you go above 3 grand. Hope this helps also, it was another problem I had before when I had changed my plugs and had moved some wires around.

[fishead]

Thanks for the advice guys.

 

I just took it for a burn on the highway and threw in some top grade fuel. Doesn't seem too much different. I will try some of this tomorrow.

 

T-Belt... yeah, I figured the same. My mechanic checked, then I checked. Looks pretty perfect. I tightened it a little bit, no difference.

[Slick]

..

 

Only 20 psi difference with a broken piston !?! 

 

B

you remember my numbers B? yah.. piston was broke enuff to lower compression. but not enuff to cause an obvious miss..... then the slight smoking started... and that.. was the head gasket...... she gave little to no signs.... btu you saw the pics

 

 

and i had the uber drip of water from the exhaust.......

Edited September 5, 2006 by Slick

[zonianbrat]

My guess is head gasket or broken piston. The water drippage sounds like gasket. Even though the oil is black it still could be gasket. My camaro had a bad head gasket and I ahd no power and tons of water out the exhaust. I first called my pops because it was running like crap and the ecu did not know what to do so at idle it would rev up to 3000 rpm then down to 500 then up and down etc. As soon as I told my dad about the water he said check the oil, I did and it looked normal but still I had a bad gasket and two pistons were gone. (yeah the motor was fubar)

[94extreme]

My 87 wouldn't rev past 3k either when I bought it because the drivers side cam was one tooth off. It would run fine until 3k RPM then just flat had no power. I know you checked it but it sounds like the same thing mine did.

I'd stop throwing parts and guesses at it and go back to square 1 at this point.  You changed the T belt and immediately had problems?  Go back to the T belt, and start from scratch.

that's my guess too although having a tad large difference in compression doesn't sound all that good either. did you wet the cylinders and try again?

 

i'd still bet on a tooth or two off. easy to miss and it will do exactly what you're saying your truck is doing.

[fishead]

No, pretty sure it is not off a tooth. Like I said, it has been checked a few times. I agree that you can't be too careful, but I am pretty sure it isn't off.

 

Last night when I took it for a burn on the highway, I noticed the oil pressure light come on a couple times when I had the clutch in.

 

I did wet the low cylinder a bit, and it didn't make a difference.

 

I am on my lunch break right now, so I am going to run across the street and talk to my mechanic. I will keep you guys posted as I find stuff out.

 

Chris.

[94extreme]

we're not reading you say specificaly that you counted the teeth on the t-belt between the 3 sprokets.

 

what were all the other compression readings? can you list them all?

 

are you loosing any coolant?

 

start the motor and open where you put in oil. sucking? blowing? neither?

 

at one place you said you maybe running rich. you don't mention any smells nor blakish/blueish exhaust.. are you sure about it being rich??

[88pathoffroad]

Check the MAF sensor wiring. Check the TPS wiring. Pull the MAF and make sure it didn't break when it was reinstalled. Run the ECU error codes again, if it's in safe mode it'll have a code stored for something.

[Precise1]

I can't find any vacuum advance.

 

Yeah, neither can I... Was stuck in Z24 mode, but when I looked today, I realised there is no vacuum unit. Sorry.

 

B

[fishead]

My mechanic finally found the problem. Crapalytic Crapverter.

 

That's the short version.

 

Long version:

 

First. Bought the truck, drove it once, then parked it because I couldn't afford insurance on 3 cars and had a beater Escort plus wife's car. Changed the T-belt, then put the escort up for sale. Sold escort, insured Pathfinder and drove it. Once I was driving it for a bit, I figured it was gutless (mostly after first offroad trip after crawling up some pretty steep hills). So, I changed everything affordable, no help. Everone online says my leaking manifold was to blame. Fixed that, LOTSA power... for 1.5 tanks of gas, then it starts again. Take to mechanic. He is pretty busy, so looks at it when he can and tries lots of things. First he checks the Cat, looks good. He can't get timing quite right, we look at T-belt. Weekend comes, I take it home, but it gets WAY worse on the way home. Test compression, then un-burry T-belt and confirm with marks behind pulleys and TDC #1. I notice Rotor not pointing to the dot, and I can't get it to point to the dot. Pull it out, and MAKE it point to the dot. I set timing to 15º BTDC. No noticeable difference. Today, Mechanic swaps ECU, and a bunch of other junk. End of the day, he says to me "I bet you dropped a paper towell in the manifold when you fixed that". I am crapping bullets. He was ready to kick my (|) if he found it was my fault!!! So, he disconnects the "Y" pipe, and it revs up FAST. It is a pig to pull off, so I told him that I was gonna catch the train home and see him tomorrow. The train station is across the tracks from his shop. I got to the platform, and yelled across the tracks "So?" and shrugged. He yelled back "It was the Cat, not your fault". I yelled back "So you don't have to kick my ass?". He shrugged.

 

So, tomorrow it will be done.

 

I had previously (like last Thursday, a couple days into it) asked what the bill was going to be so far, and he said "we don't work like that. We will wait till we fix it".

 

You know what they say, a good mechanic is worth his weight in gold. I am not unhappy that it took so long to figure it out, I will judge him on how he bills me. I was a robotics technician for 4 years, and know that a simple problem can elude you for a LONG time. It isn't until you find the solution that you can really see how simple it is. But I traded that in for building navigational cameras. Same crap, just a MUCH larger commute. Next week I have a 5,000km Commute.

 

Thanks everyone, I appreciate all your help.

[QuismO]

sweet...at least you know what the prob is now! even better, it's getting fixed. and EVEN better, you have more new parts installed that you won't have to replace in the near future =P

[fishead]

Wow, I have PILES of power now! A combination of timing prolly off, exhaust manifolds leaking, and bad cat have been plauging me since I owned the beast. For the first time ever, I can use 5th gear!

 

I knew there was always a problem, but you can only do what your budget allows I guess.

 

Total bill was about $750 (Canadian). The high flow Cat they threw in was $350. That's about $400 labour. Considering their rate is $80 an hour, they are only billing me for 5 hours which I know is WAY less time then they put into it. Prolly helps that I am fixing the autopilot for his boat.

 

Next project? Oil relocation, or building a new center console. Man I hate that console that I have. No place to put my coffee!!! WHAT were they thinking?

[QuismO]

haha sweet. man that 5th gear must've been teasing you all of this time =P