I don't know if this qualifies for advanced tech, but I couldn't really get to much help in regular tech area.

my car has been running rough when it gets warm, and it lossoes alot of power, it will start to idle pretty rough after a little bit of driving (enough to shake me in the drivers seat and annoy me, and when I gun it, it will sound like it's breaking up but I don't think it's ignition related, and there is a great amount of loss in power...
I have scanned it with scanners and found nothing, except for once and a while I will get a lean condition code, so I just replaced the o2's and it still run the same..
I replaced the opti, plugs, wires, coil, ICM, fuel pump, 02's, fuel filter
I got rid of another problem I had before by replacing the ICM, however this problem still remains and I'm really getting sick of it (it's been going on for like 4 months).

I ran test on the fuel pressure and it's all good even when I going wot with this problem acting up, I also have ran a volume test and it's good... I checked my tps, cleaned my maf, checked vacuum.....however I still can't find it......

I had a friend Of mine scan it with his scanner which is like gm dedicated and he didn't see anything wrong, he also came for a ride with me and said he heard what I was talking about, but didn't know what it could have been because I changed everything in the ignition, and already ran some tests on it.

some people even tell that they don't think I will ever find the problem, however I don't think that is possible, because there is something that causes my car to run like this.....Can you's please give me an idea of what I should check and where I should look in order to find it....and let me know how to check these things...
because I have ran out of ideas and this really sucks

thankyou

 

What was the last change or mod you made to your car before all this started?

Rich

 

One of the problems of starting a new thread, to replace the one that got several replies on "LT1 Engine Tech" is the loss of continuity of people knowing what has been suggested in the past. I'm not sure you are gaining anything by moving this to Advanced Tech, because the same people who post here will most likely also post on LT1 Engine Tech.

Do you have a scan log available for us to review? Have you checked the injectors? Have you checked for knock retard? Have you done a compression and leakdown test? Have you checked for correct valve adjustment? Have you checked the Opti harness connectors - both of them - for corrosion? Is it possible you have a plug wire running too close to and in parallel with the knock sensor wire or the Opti harness wires? Checked for faulty O2 extensions? Checked for a leaking EGR valve?

Have you done a "search" for "stumble".... I recall several threads on LT1 Engine Tech that went on for a long period of time, and ended up with the resolution of the problem being posted?

 

this problem just stated happening one day I don't even remember if I realized it at first, I am going to check with a vacuum gauge today to see if I have any sticking valves or anything, I don't see how compression could cause an intermitent type of problem like this, I didn't see any signs of corrosion on any of the harnesses when I checked them out so I would assume they are not the problem..I have never heard of a plug wire running to close to the opti causing anything bad, and wouldn't the knock sensor put a code or something....the injectors I have not yet checked, wut would be a good way to check those
and I have done many, many searches regarding my problem and I never see anyone with the same problem as me (If you know of one that sounds similiar to mine then please let me know, it would be alot easier)

thankyou

 

From what I am reading from your post...sounds like its egr proplem or a converter proplem. Check top see if the exhaust is really hot coming out and it might have weak pressure. If so your converter is clogged...Also disconnect the egr and drive is and see if it goes away.

 

Trust me, that can be a real problem, and no the knock sensor would not show a code for high voltage interference. I also remeber reading at least two posts on LT1 Engine Tech in the past 6 months where people posted the solutions to long running low speed stumble problems. But if you are going to get skeptical about suggestions, I'll back off and let you work it out.

 

I have a gutted cat so that is out of the question, anyhow, my manifolds do not turn red hot...

how would I disconnect the egr, would I just take off the vacuum line that connects to it..and how close is too close to the knock sensor wire where it could cause a problem...and I am sorry if you took my statement about a previous thread of my situation offensive, but I was serious, I am not trying to start an argument with you or anyone else, I'm just trying to fix my car as fast and easily as possible, I have done searches and read for hours at a time, however no one seemed to have the same symptoms as me, unless I didn't understand some of the problems others had as being related to mine, and believe me I would much rather read a thread which discusses the same type of problem I have rather than waiting for someone to help me out.

thankyou

and also this problem does not only happen at low speeds in happens in high speeds to

 

my temp. gauge also goes al the way up and then back down and sets a code, would this be caused by the sensor in the water pump housing, because when I changed my opti, I cleaned out the housing with brake cleaner, I probably got some on the sensor, would this cause it to get messed up you think

thankyou

 

Really need to know what the engine exactly is doing...IE if it is for sure lean like the code says, or if its rich, unluckily its not OBD2 so you wont get any misfire info.

EGR sticking would cause a rich condition not lean, but it could be the problem if it is infact rich when this happens.

Did you check for spark at each cylinder, are you absolutely positively sure all the plug wires are in perfect shape, youd be surprised what a pinhole in the insulation of a wire will do to driveablity.

Pull the fuel rail off with pressure in the system make sure theres no dripping fuel from any of them, then disconnect all the injector wiring with pressure in the system and pulse very short amounts of 12v to each injector if you dont have any proper equipment to do it and make sure they turn on and off properly.

If you have a DVOM go crazy with voltage drop tests on everything, injectors, coil primary, coil secondary, all the harness wires going to the opti. If you have access to an Alldata/Mitchell type program find out the manufacturers specs on resistance/amp values for everything.

Valvetrain shouldnt be a problem if its intermittent.

Coolant temp sensor in the WP could be a problem, do a resistance test on that as well if you can and compare it with factory values. Dont have to worry about the one in the head since its dedicated to the guage.

Sounds like youve spent a ****load of money you probably didnt have to by not "Diagnosing" the problem. No offense by that, I did that all the time before I learnt how to diagnose stuff too, but parts changing can get real expensive, especially if you replace $1000 worth of stuff over a bad plug or wire or something.

That reminds me too, check the plugs, you can even replace those cheaply and it wont hurt to do anyway.

 

well I just finished replacing the ect sensor, and it felt like it may have been better, didn't really get to test it to much but when I got on the throttle in 2 when it was at like 10mph it sounded like a little sputter but then it cleared right up, that may be normal cause it's so low of a rpm in second and just going to wot, but I will definately test it tomorrow (put it to the real test) and hopefully all wil be well
It may be a new begining a a celebration that my car might be running good finally

btw thankyou for the info jonadis
and I'm still learning on diagnosing, guess I'm not really to good at finding problems yet

thanks

 

well I test drove it to day, in the process raced a friend with a vw gti 1.8t running 20 pounds of boost and smoked him 4 times to pleasure his excuses (damn imports)..so it seems to be running much better, however it still feels like sometimes there is a little loss of power, and at times it will just get better, prob. gonna scan it tomorrow again to see if I can find anything...cause theres def. still sumthing wrong, not sure but I think I may have a litle exhaust leak, you think that could cause something like this on and off

thanks