LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Hesitation/idling problems/engine stutter/ and numerous others?

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Old 06-02-2011 | 05:13 AM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

Your running rich due to the 44. It's falsely indicating bank 1 is running lean. I believe it's the wires to the left O2 are burned and the signal wire is touching ground like the exhaust.

First look over the entire length of wire from the O2 on up. If you don't find anything there, switch O2s and see if the problem goes with the O2. If so it would produce a DTC64. Then you know it's the O2. If not, you know it's the wiring.

If you had a way to view the O2 signals real time, you could unplug the suspect O2 and see if the signal goes to 450. If it then did not, you know it's a wiring problem.

Last edited by Guest47904; 06-02-2011 at 05:25 AM.
Old 06-02-2011 | 06:29 PM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

Thanks I plan on doing that tmrw. But would a bad sensor and it running rich be a contributor of why my idle is still high? The TPS is replaced and the IAC yet its still idling at 2000+ and fluctuates alot.

Ill give feedback tmrw on the o2 sensors.
Old 06-02-2011 | 07:20 PM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

When ever you have a known problem and an unknown problem. You have to take care of the known problem first. You don't know what other effects fixing it will have. Don't try to reason the other problem until after you have addressed the known problem.
Old 06-02-2011 | 11:16 PM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

I wouldn't put much faith in the first scan with 32 codes..... doesn't make any sense at all.

DTC 44 indicates a lean reading on the driver's side O2 sensor. The PCM's response to that would be to add fuel, which means the long term fuel trim (LTFT, or BLM) would be ABOVE 128. 128 means the PCM's standard calculation of injector pulse width is correctly fueling the engine. A LTFT above 128 means the PCM is adding extra fuel, to compensate for a lean condition. A LTFT below 128 means the PCM is subtracting fuel to compensate for a rich condition.

There are bothe long term fuel trims, and short term fuel trims (STFT, or INT). You need to be concerned with the long terms. The STFT's normally swing to either side of 128 several times a second, as part of the PCM's strategy to maintain an average A/F ratio of 14.7:1, while swinging back and forth between slightly rich and slightly lean to allow the catalytic converter to function.

The long terms are based on the O2 sensor feedback, and are the "learned" portion of the fuel control system. To further complicate things, there are independant controls for the left and right banks of th engine, and a set of 18 cells which are subdivided to cover various combinations of RPM and engine load (MAP). You need to record the LTFT's for both left and right banks, for as many cells as you can.

If only the driver's side is running lean, you would look for things that affect only that side of the engine, like certain vacuum leaks, misfires on that bank, exhaust leaks before the O2 sensor on that bank, a leaky exhaust valve, a faulty O2 sensor or sensor wiring, etc.

For more info on what the scanner reading mean, read this:

http://www.injuneer.com/ScanMast.html

Last edited by Injuneer; 06-02-2011 at 11:19 PM.
Old 06-07-2011 | 05:31 AM
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inquiring minds want to know

Originally Posted by JGuy07
Ill give feedback tmrw on the o2 sensors.
Well???????
Old 06-09-2011 | 09:24 PM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

sorry been really busy, just started an internship with sheriffs dpt so not able to do much lately. We went to try and switch the sensors but we couldnt get them off. I couldnt even get them to budge. But lately the car has been doing a lot better it only acts up every now and then. The service engine light comes on at random times but nothing ever seems to be acting up so I assume the code 44 is still popping up. Whenever I get the money and more free time I'm going to try and go after those sensors again but at the moment i cant do much.
Old 06-10-2011 | 04:58 AM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

Try removing them while they're hot.
Old 07-20-2011 | 01:31 AM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

Ok removing while hot definitely helped. Although I'm not able to replace them yet, they were both carboned up pretty bad and the slits on the sensor were clogged. I cleaned them and put them back in until Im able to replace them.

On a different note, idk why I felt like doing this but found out it was def needed. I flushed out and cleaned the cooling system and for the first few times it was nothing but sludge and chocolate coming out....so it was very much needed. The thermostat was also sticking which I guess could have been one of the problem leading to the stuttering and bad performance. Ill keep things posted as I go, but it's gna be awhile again.
Old 08-03-2011 | 06:22 PM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

Ok guys, I'm gonna need some more input on this problem. I have just replaced the left o2 sensor which the code was previously for. Yet, after replacing the sensor the car runs even worse. I know I may still need to check the wiring but other then that I'm out of ideas.

When sitting still the rpm's jump around alot from around 1200 all the way up to 2200 or so like it's searching for an idle. The idle screw is backed all the way off though just to attempt to compensate.

I took the car out for a run to get it warmed up and put it through the paces. The car shuttered and the rpm's fluctuated a lot in all gears and rpm ranges. It's literally acting up worse then with the old o2 sensor. I still need to check the wiring from the o2 sensors on both sides and check the right o2 itself also, even though it didn't pull any codes.

So far I've been sorting through all options. I have flushed the coolant system and replaced thermostat, replaced left o2 sensor, can't locate any exhaust leaks, vacuum pressure appears fine when I checked last as well. What other options do I have? Currently I don't have my own scan tool, however I do have the FreeScan program and waiting on my obd1 usb cable so I can use it and get a better idea of what is going on. But until then, anymore help would be appreciated.

Also, could a problem with the MAP cause any of this...or any other sensors?

Last edited by JGuy07; 08-03-2011 at 07:07 PM.
Old 08-05-2011 | 04:06 PM
  #25  
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

Im not an expert, but an easy way to factor out the EGR would be to pull the hose out of the top of it. My car at one time was jerking and doing some crazy stuff. Found out the it needed a new EGR. Being short on cash at the time i unhooked it and it ran fine. Just food for thought, don't know if that would do anything for you but its quick and easy.
Old 08-08-2011 | 09:59 PM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

Yea, checking the EGR was one of the first things I did when starting to figure out what my problem was. The vacuum is fine, and the EGR valve tested ok.

I actually got the plugs/wires/opti checked out when I first bought the car and they told me everything was fine. But I think they just took my cash and didn't bother to actually get in and check everything out like I wanted them to. So still thinking it could be the opti.

I checked the wires the other day and they're 8.5mm and zip-tied pretty good and away from the exhaust and block. They aren't burnt or appear to be shorting anywhere. But this car has 170xxx + miles and I am not aware of any sort of maintenance the previous owner put into the car since I did a lot of work when I got it.

So what I need to look at further is the opti/plugs/wires etc. and maybe even the fuel pump...?

also wanted to mention I do have a small leak on the front seal, suppose this could effect the opti. There was a lot of build up on the underside of this car when I got it and I cleaned as much as I could. But, Im sure since the leakage has built up for so long it has gotten into places causing other problems....this sound like a good possibility to you all?

Last edited by JGuy07; 08-09-2011 at 06:41 PM.
Old 08-11-2011 | 12:53 AM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

*BUMP* still stuck pondering...
Old 08-11-2011 | 06:49 AM
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

Are you suggesting the wired are original?

I'd replace the wires and plugs and start from there,...
Old 08-11-2011 | 06:06 PM
  #29  
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

Well idk what original would be, but these are MSD 8.5 mm wires. Also, I plan on trying to check for corrosion and all the other stuff here soon too and testing to make sure the signals are getting to the coil/opti using shoebox's method...but from there I'm not sure what else to do but keep searching for the unknown.

**Just did a quick check of the plugs, they appear to be relatively new. They were a little dirty/sooty and when checking the gap wasn't correct. IDK how much of a difference the gap actually makes but I still have the passenger side plugs to check. But gap on the plugs wouldn't make a noticeable difference such as what i've been explaining right?

**BONUS** I've also managed to figure out where I'm leaking haha I'm pretty sure it's my intake. There was a small amount built up under the EGR Valve so I thought it was my oil sensor where the elbow connects to the block and it just builds up around where the intake connects to the block. It could still be that, but there is also some leakage around the front end of the intake on the passenger side leaking down behind the WP. Hopefully it's the intake and not heads. O.0

Last edited by JGuy07; 08-11-2011 at 08:42 PM.
Old 08-13-2011 | 12:36 AM
  #30  
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Re: Hesitation/idling problems/engine stutter/ and numerous others?

Just another note,(btw been working on this since 730pm) I looked up how to "easily" or better manage to get the passenger side plugs out. And of course there is no relatively easy method. But in searching the forums for methods I saw quite a few ppl referencing the ability to get to them from bottom and IDK how you could manage that. I pulled the alternator and even pulled the top pully wheel so I could have more work space and sit up top the engine to get good angles on the car for my FAT FOREARMS. So I am pretty envious on those who were able to access them from bottom. -__-

But, after checking the plugs they all seem in normal condition basing off of what the haynes manual says. The wires are all ziptied away from everything and not burnt or shorting. The only thing wrong with the plugs is that the gaps seemed to differentiate between .055 and .068 and I fit them back to .05 which is where I have been told/referenced by the manual as well. Basic stock engine so I assume this is the gap I need.***anymore input would be appreciated. Thanks.


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