MY engine prollums

[uglyota]

97 GMC, 350 vortec, 4L60e, 4x4
lately when I start it, it revs to like 1500 and stays there for a half a minute or so...also doesn't drop back down to idle at a stop as quickly as it should. Same deal when I put it into gear from park...it kinda revs up for ten or fifteen seconds...like I'm powerbraking.

I'm thinking I may just need to clean the TB. Any ideas?

[Jackasic]

have you replaced the intake manifold gaskets? they go bad at 100k.

[uglyota]

I believe I can speak for Jerry as well as myself when I say "that's not very funny"

;)

[cntryboy1865]

clean the throttle body, my brothers truck did the same thing, and that was the problem

[Jackasic]

what? it is a known problem on vortec's. they develop a vacume at 100k.

[jerryg79]

I believe I can speak for Jerry as well as myself when I say "that's not very funny"

;)

I'd say that its not an intake problem an intake problem would be that it runs for 15 minutes and then runs like **** till it dont run at all.....eventually it dont run at all permanently :flipoff2: :flipoff2: :flipoff2: :flipoff2:

[agjohn02]

my first guesses would be a sticking IACM (idle air control motor) or a bad VSS (vehicle speed sensor). my lt1 had the same problems at first and i cant remeber what exactly fixed it. im still not running a vss so i think it was the iacm.

[jerryg79]

Damn i'm dumb, I have the scanner for our motor, bring it over on Thurs night and we'll hook it up. Give me a call on thurs. 713-857-7150

[uglyota]

kewl, thanks...engine light's not on though...could it still be throwing a code?

with the truck turned off and cold, if I work the throttle linkages at the TB, it kinda hesitates for a sec before dropping all the way closed. I'm pretty sure that's it.

I may devote a day and $24 to replacing the intake gaskets here pretty soon...just in case...I would think that if it was so common, Chevy would eventually do a recall on them :confused:

iacm sounds valid too, John...how much $$$ are those?

[agjohn02]

$60 at oreilly's. mess with the linkage first though. sounds like your problem. if that doesnt do it replace the iacm but keep it clean so you can return it if it doesnt work. not that id ever do something like that...

[uglyota]

thanks boyz...
does anybody know if I can still get codes if the "check engine" light isn't on?

[BigRedFord04]

OBDII (`96 and newer) should store codes.

[uglyota]

thx

[uglyota]

even if I've run the battery dead 2x in 2 weeks? :D

[jerryg79]

I'm home now if you wanna check it out, i'll only be here prob. till tomm. or sat. It'd be easiest if you have a laptop, otherwise i have to drag my whole computer outside.

Let me know.

[uglyota]

sorry man, ran out of time last night
you around today? Will your deal tell me anything more than Vatozone's will?

[jerryg79]

yeah in theory it should. Alot of those scanners only tell you things related to emissions problems, mine is the same one they would use at the dealer. I'll be around most likely...if not you can just borrow it and use it at your leisure

[uglyota]

okay my truck decided to start acting like a little b1tch last night.
drove around doing some errands, parked it for about 2 hours, started it back up and the Service Engine Soon light was flashing, running like sh1t, and backfiring. Parked, looked at the manual and it said that if the SES light is flashing, it's probably an miss or an emissions problem, ease off the gas, drive it to a dealer etc, so I looked under the hood and made sure all the plugs were in, wires connected and tight, etc. Started back up, drove to Advance (found out they don't have a code reader, but I got some fuses for my other non-functional vehicle), drove home and parked it. Running like chit the whole time, mostly below 1500-2000 rpms, seems to run fine above that.
It's been about 50k since my last tuneup, so I'm thinking I'll pull the codes, then do plugs, wires, cap/rotor and see if it fixes anything. Since it runs fine at higher RPMs I'm worried it may be an ignition module problem...like the electronic advance isn't working right, but I'm hoping it's just a plug or a wire.
Any ideas?
Jerry you gonna be around tonight? :D

[fbronco86]

okay my truck decided to start acting like a little b1tch last night.
drove around doing some errands, parked it for about 2 hours, started it back up and the Service Engine Soon light was flashing, running like sh1t, and backfiring. Parked, looked at the manual and it said that if the SES light is flashing, it's probably an miss or an emissions problem, ease off the gas, drive it to a dealer etc, so I looked under the hood and made sure all the plugs were in, wires connected and tight, etc. Started back up, drove to Advance (found out they don't have a code reader, but I got some fuses for my other non-functional vehicle), drove home and parked it. Running like chit the whole time, mostly below 1500-2000 rpms, seems to run fine above that.
It's been about 50k since my last tuneup, so I'm thinking I'll pull the codes, then do plugs, wires, cap/rotor and see if it fixes anything. Since it runs fine at higher RPMs I'm worried it may be an ignition module problem...like the electronic advance isn't working right, but I'm hoping it's just a plug or a wire.
Any ideas?
Jerry you gonna be around tonight? :D


If it was me i would change the intake manifold gasket

[jerryg79]

Jerry you gonna be around tonight? :D

Yeah bring it over i'll be around, i'll borrow a laptop

[uglyota]

cool man, thanx
amberbock?

[jerryg79]

cool man, thanx
amberbock?

sho 'nuff

804 San Benito

713-857-7150

m/25/tx horny

[JB]

My old 98 had the intake gaskets done under warranty at like 34k. At work, we usually do one of these a week, so it is a pretty common problem.

I would suggest a tuneup and "top engine" type cleaning after you get teh codes.

[mark]

My guess is that you have a vacuum leak. You can try the old carb cleaner test. That is spray carb cleaner around the intake, vacuum hoses etc. If you have a leak you will hear it stumble when it sucks in carb cleaner. I just fixed a vacuum leak in the old CJ by plugging in a disconnected vacuum hose. Mine was large enough that it wouldn't idle at all and the computer was indicating an overly lean condition at idle.

Start simple and work towards the expensive.

-Mark

[jerryg79]

Survey Says - 02 sensor - about 15 codes

[mark]

Fascinating. It shouldn’t have any symptoms with a bad O2 sensor until it goes into closed loop mode at approximately 140 degrees F. It sounds like you were having issues at start-up.

Is it a single sensor out of range issue (you have 4 O2 sensors, you know)? Is it a rich or lean too long issue? Is it upstream or downstream of one of the cats? Are you getting codes from the sensors both upstream and downstream of the cats? Well anyway, make sure you get to the root cause of the O2 sensor failure. A failed sensor is one thing. Having all the sensors tell you the same thing usually means they are picking up a symptom of a larger problem. If you are getting codes from the sensors downstream of the cats only, you probably have ruined the cats. Cats fail from an overly rich condition over a period of time. Sensors usually fail due to being clogged (overly rich) or contaminated (non compatible RTV).

-Mark

[uglyota]

bank 2 heated oxygen sensor 1
also a "misfire detected"
yeah it seems to be messing up almost immediately on startup, but I have been having problems with one sensor for several years, throws a "bad O2 sensor" code under heavy load, mtn driving, etc, I just didn't know which one it was (the chevy dealership in Fort Collins said their computer wouldn't tell them which it was, they just had to start replacing them at $65/hr plus parts :rolleyes: )
It's backfiring, so I'm still thinking it's running rich
It also feels to me like it's skipping a cylinder regularly, like I've got a dead cylinder, i.e. a bad plug/plug wire. Anybody know how many ohms a plug wire's supposed to read?

[mark]

Do you have a detonation issue or poor fuel economy?

Heated O2 sensor 1 indicates an upstream O2 sensor. The cat is probably OK then. This would be an ignition problem. A bad plug wire is a good guess. I would look at the plugs on that side of the engine and narrow it down to the offending cylinder. As the engine uses a CPI system, It most likely is not a stuck injector. With the misfiring, I would suspect ignition, plug or wire as well.

So the OBDII scanner is not indicating which way the sensor is failing? My guess is rich as well.

Oh, a plug wire should read approx. 1200ohms per foot of impedance.

-Mark

[Jackasic]

he's back and in full "mark-the-mobil-mechanic" form :D

[mark]

It's a slow day at work, muck like your day Jackassic. And its “Mark the Psychic Mechanic."

[uglyota]

Do you have a detonation issue or poor fuel economy?

Heated O2 sensor 1 indicates an upstream O2 sensor. The cat is probably OK then. This would be an ignition problem. A bad plug wire is a good guess. I would look at the plugs on that side of the engine and narrow it down to the offending cylinder. As the engine uses a CPI system, It most likely is not a stuck injector. With the misfiring, I would suspect ignition, plug or wire as well.

So the OBDII scanner is not indicating which way the sensor is failing? My guess is rich as well.

Oh, a plug wire should read approx. 1200ohms per foot of impedance.

-Mark
sweet thx
yeah hope it's not a stuck injector...apparently those are $350 :eek:
don't remember seeing which way the sensor was failing...that must be what the voltage readings were for.

[Fredo]

It's a slow day at work, muck like your day Jackassic. And its “Mark the Psychic Mechanic."

I'm having a slow day too so I'll add my opinion. From the sounds of it, I'm going to go ahead and say your intake gaskets might be the culprit. From the high idle, it sounds like it might be a vacuum leak, then again, it might be a gummed up IAC sensor. Like Mark said, check the cheap stuff before going after the expensive parts. Also, you talking about the o2 sensor problem reminded me of something. We had that happen on Dragula right before we found the intake coolant leak. Turns out the coolant coming through that side's exhaust was keeping that o2 from heating up, causing fuel economy and drivability to go down the crapper and finally killing the sensor. Also, about two days after I replaced the intake gaskets, the rear o2 sensor on that side of the motor died. I pulled that one and it was rusted much like the other o2 that had failed. So if your o2 sensor failed, and your idle is high, I would definitely suspect the intake gaskets. Keep an eye on the coolant level and make sure the motor isn't drinking it.

[uglyota]

So if your o2 sensor failed, and your idle is high, I would definitely suspect the intake gaskets. Keep an eye on the coolant level and make sure the motor isn't drinking it.
idles low and rough, almost like it's gonna stall out.
hasn't drank a drop of coolant since replacing water pump ~ a year ago.
Thanks again guys...

[Fredo]

97 GMC, 350 vortec, 4L60e, 4x4
lately when I start it, it revs to like 1500 and stays there for a half a minute or so...also doesn't drop back down to idle at a stop as quickly as it should. Same deal when I put it into gear from park...it kinda revs up for ten or fifteen seconds...like I'm powerbraking.

I'm thinking I may just need to clean the TB. Any ideas?

That right there is why I thought you said it was idling high. :confused: So it's actually idling low?

[uglyota]

That right there is why I thought you said it was idling high. :confused: So it's actually idling low?
that was old, fixed itself :D
...maybe I should have started a new thread for this one
yeah it's idling at 5-600rpms. Still suspect a vacuum leak? I'll hit it with the 'pane just to make sure

[Sharpe]

The dealership...pffff. My 97 Z71 has been showin a check engine light for the last few months and a non-dealership shop told us it was one of the o2 sensors but they didnt know which. With 4 of them at like $65 apiece, I'd like to know which one it is before I start replacing them. The truck runs great in its current condition so we dont have any plans on replacing them.

[Fredo]

If it throws an o2 sensor code, it tells you which one it is. Like if it says, Bank 1 Sensor 1....it's the driver's side pre cat sensor. Bank 2 would be passenger side, and sensor 2 would be a post converter sensor. Make sense?

[jerryg79]

If it throws an o2 sensor code, it tells you which one it is. Like if it says, Bank 1 Sensor 1....it's the driver's side pre cat sensor. Bank 2 would be passenger side, and sensor 2 would be a post converter sensor. Make sense?

The problem with the code reader I have is that it is so complicated. It wont just come out and say what is wrong. It gives you information in excruciating detail like voltages, different readings etc., that mean nothing to someone such as erik or myself. It did give the bank 2 sensor 1 thing and me and erik got on the web and surmised which one we thought it was.

If you change the o2 sensor and it is rusted like Fredo said we can change the intake gasket over here sometime if you want.

Also did the check engine light come back on after we cleared the codes? If not that probably means that the 02 sensor is no the only problem.

[uglyota]

The problem with the code reader I have is that it is so complicated. It wont just come out and say what is wrong. It gives you information in excruciating detail like voltages, different readings etc., that mean nothing to someone such as erik or myself. It did give the bank 2 sensor 1 thing and me and erik got on the web and surmised which one we thought it was.

If you change the o2 sensor and it is rusted like Fredo said we can change the intake gasket over here sometime if you want.

Also did the check engine light come back on after we cleared the codes? If not that probably means that the 02 sensor is no the only problem.
Yeah based on what Mark said I bet the voltage readings it gives help tell you whether it's running lean or not. I'll pull that sucka out tonight and see what the verdict is...hopefully not rusted :(
thanks for the offer
oh yeah the check engine light came back on as I was pulling out of the driveway, but not flashing

[Fredo]

Yeah based on what Mark said I bet the voltage readings it gives help tell you whether it's running lean or not. I'll pull that sucka out tonight and see what the verdict is...hopefully not rusted :(
thanks for the offer
oh yeah the check engine light came back on as I was pulling out of the driveway, but not flashing

Well, it might be slightly rusted even from the moisture in the exhaust, but I'm talking a ****load of rust...like scaly...then you've got a problem.

[mark]

Usually they come out sooty. They might have a bit of ash at the tip. If the soot has blocked all the holes in the sensor, then you have to get a new one. The scanner will tell you a lot. If the voltage is zero, or does not move, then it may be a sensor or wiring problem. Another problem you may have is if the heated element not functioning. In that case, the sensor would not get warm enough to operate given its location. But given your drivability problems after a cold start, I'd look elsewhere before replacing the sensor.

Oh, voltage on an O2 sensor is between 0 and 1V at the sensor. Most ECU's run the signal through a 5V amp so at the computer it should read between 0 and 5V.

If the sensor is operating normally, the scan tool will show the voltage fluctuating after the engine warms up and the ECU goes into closed loop operation. The proper operating mixture of 14.7:1 under moderate load will result in a mid range voltage reading from the O2 sensor. But you should see rapid cross counts as the mixture crosses from rich to lean rapidly.

On a side note, here is an interesting way to test the sensor's function outside the vehicle:

With a digital voltage meter, hook the black and red wires (usually) to the meter. The additional grey wires (4 wire heated sensor) are for the heater and are not connected. Using an open flame from a propane torch or gas stove, heat up the sensor. After a few seconds move the sensor in and out of the flame. Out of the flame it should read zero (lean state) in the flame it should read near 1V (rich state).

To test the heater, hook the grey wires up to a 12V source. Polarity is not important. Within a few seconds you should feel the sensor warming up. If not, the heater is bad.

-Mark

[uglyota]

Okay guys, thanks for the help on this...

First of all, I recommend Kwik Car for anything you could possibly need fixed on your vehicle. Very honest, nice guys, and very knowledgeable.

Second, I would recommend against Car Doc. Those guys took my $45 and told me to fix all the things that I had told them were wrong with it, but were not causing my problem :rolleyes:

Third, I found that Bosch spark plugs are not hot enough for GM products and will throw an O2 code under heavy load (advice came with my $30 diagnostics from Kwik Car)...this was not my problem

Fourth, if anybody knows who sabotaged my truck, it's worth a case of the beer of your choice (as well as a portion of settlement, if this is legal) if you can prove who did it and will testify for me.

YOU DON'T &^#* WITH ANOTHER MAN'S AUTOMOBILE!

[jerryg79]

YOU DON'T &^#* WITH ANOTHER MAN'S AUTOMOBILE!

What the hell happened?

[uglyota]

it was something really simple and stupid (and that I should have caught while I was trying to diagnose it), but something that could not have happened without someone doing it on purpose.

[agjohn02]

thats way too vague...

[uglyota]

yeah I know :D

[Graystroke]

missing spark plug wire? plugs wired wrong?

[agjohn02]

did someone rearrange your wires for you?

[uglyota]

good job guys, now find out who did it and I'll hook you up

[bburris]

Maybe you messed up when replacing them? Just a thought...

[Sharpe]

Yah the first time I replaced the cap and rotor on my burb I got confused and put the plug wires all on backwards. Made really funny noises when I tried to start it up. I do agree that Bosch plugs are junk. I have them in my burb right now and it makes a really wierd chattering sound sometimeand I've been told they could be the cause. I am going to replace them with AC Delcos as soon as I can afford it. Does Napa sell the Delco plugs?

[bburris]

Car Quest does

[agjohn02]

isnt this on your chevy? how'd they get to them? from underneath?

[uglyota]

okay my truck decided to start acting like a little b1tch last night.
drove around doing some errands, parked it for about 2 hours, started it back up and the Service Engine Soon light was flashing, running like sh1t, and backfiring. Parked, looked at the manual and it said that if the SES light is flashing, it's probably an miss or an emissions problem, ease off the gas, drive it to a dealer etc, so I looked under the hood and made sure all the plugs were in, wires connected and tight, etc. Started back up, drove to Advance (found out they don't have a code reader, but I got some fuses for my other non-functional vehicle), drove home and parked it. Running like chit the whole time, mostly below 1500-2000 rpms, seems to run fine above that.
It's been about 50k since my last tuneup, so I'm thinking I'll pull the codes, then do plugs, wires, cap/rotor and see if it fixes anything. Since it runs fine at higher RPMs I'm worried it may be an ignition module problem...like the electronic advance isn't working right, but I'm hoping it's just a plug or a wire.
Any ideas?
Jerry you gonna be around tonight? :D
Did it all by itself, anyone ever hear of spark plug wires rearranging themselves? When I did the wires I replaced them one at a time. I guess someone popped the hood from the outside...wouldn't be too hard if you own one or know what you're doing.

[Jackasic]

it was aliens working with the CIA.

[uglyota]

dude I had this dream that aliens came and probed me last night
http://gerdlievens.tripod.com/cartman.jpg