ok so ive done a lot of work to this vehicle all of it really necessary but through all of it I still have a rough running engine from time to time. usually starts cold and idles perfect, but after hot and sitting at light its is a little rough like a cylinder is not properly firing but not actually throwing any misfire codes. just not running smooth like new and I would think after all the work it should be as it only has 100k miles on it. also at higher speeds when torque is needed I can feel it not exactly right, im not in a situation where its bad like it stalls etc, but I had a 78 thunderbird and after redoing a lot on it, the motor ran like it was brand new! heres a list of whats been done engine wise intake manifold gasket (it was leaving trace elements of greyish sandy crap on the top of the antifreeze but I could tell no water in oil, however when I pulled it off, it was bad, you could tell, one of the water jackets had a little tear in the rubber and other parts of the rubber were starting to kind of tear away like it had been way over torqued and smashed, and it was the newer felpro metal gasket so it has been changed before. the lim had a crack by the temp sender from someone cross threading it, when I tried to replace it, a part chipped off so I got another manifold all together. I replaced the distro plug o ring, injector o rings and cam sensor while in there, the injectors looked clean) crank sensor (it was leaking a little) complete tuneup, double platinum delco plugs and new wires new air filter o2 sensor before cat new airflow sensor and map sensor, new throttle sensor also seafoam engine treatment through induction replaced all worn rubber grommets, including the one on the vapor line by fuel pump in tank, canister grommets good, pcv valve checks out from what I can tell, no vacuum leaks. heres some of my conclusions coil packs / module? (not misfiring bad enough for me to think they are bad) head gasket blowing out (no overheating at all, no oil antifreeze mix, no antifreeze loss, a little oil loss but maybe needs a quart after 3000k miles, and I see it leaking from front and rear mains, engine is oily on the bottom after 1000k miles since complete clean, no its not leaking from distro plug its on both sides right under where crank seals would be and it doesn't leave a drop of oil in garage) low compression (starts like brand new car even when hot, doesn't always do it sometimes runs better, I cannot see the typical signs of head gasket failure, and no engine codes at all) I don't have a tester fuel pressure, I don't have a tester but all injectors appear to be working, and they were very clean like new when I did the LIM job. no gas coming out of regulator vacuum port. fuel canister? I don't know if this could even cause this, but for a 100 miles or so I drove it forgetting to hook the vac line into the valve on back of motor and the canister started to smell like gas and then I found it. (all vacuum lines in proper place) EGR, ive changed the gaskets when lim was done, I cleaned the path in the uim when apart, the egr valve looks good, no codes. just a ****ty gm engine that will never run like new again? my main concerns would be going on a long trip and having fuel pump or all out head gasket failure, however I would like to make this engine run like it came off the showroom floor if possible. idle cold is always good, idle warm is a little off but not real bad, engine power is ok from what I can tell, its a 3100 pulling a wagon, but I can get on her and pass someone. motor has bouts of running rough at high speeds but not always, when it does I can tell its not the front end, its the motor running poorly but yet again no misfire codes. plus the whole front end I redid, I mean everything down to ball joint tie rods struts, brakes, tires, all 4 new, alignment done. but I know the difference between body shake and motor shimmy at highway speeds. hmm im kind of perplexed, ive been driving her and nothing has gotten worse, all my fluids are clean and new. anybodies thoughts?
It's sad to say I had similar problems with my Hemi Dodge quadcab with less than 80,000 miles. Actually 73,000 when fan clutch, water pump and head gaskets were replaced. I spent over $2000 including things my son replaced and eight months with out the truck. Still got CHECK ENGINE and DRIVE BY WIRE codes. Idle was around 1100 instead of 600. It actually ran fine. Son went on line and found many problems with the 2004 hemi engine. After all major changes were made in 2005. Perhaps we shouldn't have checked other reports. I wanted to pull a 19' flat bed trailer with a car and the topper covered bed 1000 miles and return empty several times. Got scared and traded it off while it was running fine. The dealership fixed the problems and has the truck listed for $12,000. I love that truck and still don't trust it. Sometimes we gotta throw in the towel and get rid of our headaches.. I love that truck! That truck may run another 100,000 miles or not made it half way to Illinois.
Can you afford to have a shop hook up a scantool, then take one of their techs on a fair-distance drive (10 or more miles on the highway)? I've had a few customer's cars over the years that I've had to do that to find the problem.
You are the epitome of a shade tree mechanic just throwing good money on guesses. Do you actually think these problems can be solved by the suggestions of a committee? There is a distinct diagnostic tree to follow when trying to solve running problems. They almost always start with checking the fuel delivery system. 1. Do you have the correct gas cap on the car? 2. Have you removed the fuel filter and checked or replaced it. 3. Fuel pressure needs to be checked, both key on and running. There are specs for both and they operate within a very narrow range. 4. Injectors don't appear to be working. You have to check them with an ohmmeter and make sure they are within specs. This is just beginning stuff and it goes on several pages from there. You can't skip steps or you might miss the problem. Plugging a scan tool into a car seldom will give you an answer if it doesn't set hard codes and intermittents need to be caught while driving the car. We had a new Buick with a 3100 and it was nothing but problems. Had to have new pistons after a year. Sounded like they were swapping holes. Luckily all our problems were under warranty. However, we got rear ended sitting at a stop light and the car was totaled, perhaps for the best.
