Lt1 idle problem
#4
Join Date: Nov 2007
Location: Eastern PA,
Posts: 10,351
What code do you have in the computer?
Do you still have an EGR valve? If that is not sealing it could cause those exact symptoms.
A dripping injector could be flooding out a single cylinder. ( plug check should show that) Should also have a "random miss fire" code
Other things that could effect this, Air temp sensor, map sensor and of course MAF sensor or any wire leading to them.
No load idle issues can be the tuffest thing to find because very minor things can cause a lot of variation. Micro cracks in the intake gaskets, carbon build up on the valves. Carbon build up in the intake (normal from the EGR valve) even a failing optical sensor like the one in your Opti can cause idle issues before it effects real driving. Heck it can be the PCM quad driver not reacting fast enough (very rare, normally they just fail)
Do you still have an EGR valve? If that is not sealing it could cause those exact symptoms.
A dripping injector could be flooding out a single cylinder. ( plug check should show that) Should also have a "random miss fire" code
Other things that could effect this, Air temp sensor, map sensor and of course MAF sensor or any wire leading to them.
No load idle issues can be the tuffest thing to find because very minor things can cause a lot of variation. Micro cracks in the intake gaskets, carbon build up on the valves. Carbon build up in the intake (normal from the EGR valve) even a failing optical sensor like the one in your Opti can cause idle issues before it effects real driving. Heck it can be the PCM quad driver not reacting fast enough (very rare, normally they just fail)
#5
My codes are all transmission related after my t56 swap. I deleted the EGR a while ago and its got a new MAF and MAP sensers. i dont think its valve just cause i had the heads off a coulpe of years ago and they looked really good. But it could be a lecking injector cause its really rich when its idleing almost burns your eyes lol i have new plugs for the car which i might put in this weekend
#6
Join Date: Nov 2007
Location: Eastern PA,
Posts: 10,351
Completely discounting something because it is newer can be a mistake. I did warranty work on GM cars for 7 years and I have worked on cars right off the carrier that did not run right and everything on the car had less then 100 miles on it. I will agree that if you have a problem like this and then you replaced a part and it stayed the same then most likely that is not the cause.
I did have one car that had two bad injectors. The garage that was working on it took one new injectors and replaced each injector one at a time. They then assumed the injectors where good since they could not fine a bad one. 2 days later they gave up and brought the car to me. I hooked up to our Scope and it showed two cylinders messed up. Customer said replace all of injectors. Next morning the rough idle was back. One of the 6 new injectors was leaking. Wow was he pissed, figured we had no idea what we where doing. Funny thing was it was one of the injectors that was working according to the scope. He wanted all new injectors. In some cases you just can't win.
I used to keep known good MAP, Air temp and Maf sensors next to my tool box. New does not = known good.
You could find someone with HP tuners in your area to program out the trans error for a reasonable fee. I found a guy in my area to program out my air pump codes when I do headers and fix my speedo for $50. It would be nice to know if the SES light would flash/flicker when the idle drops real low.
I did have one car that had two bad injectors. The garage that was working on it took one new injectors and replaced each injector one at a time. They then assumed the injectors where good since they could not fine a bad one. 2 days later they gave up and brought the car to me. I hooked up to our Scope and it showed two cylinders messed up. Customer said replace all of injectors. Next morning the rough idle was back. One of the 6 new injectors was leaking. Wow was he pissed, figured we had no idea what we where doing. Funny thing was it was one of the injectors that was working according to the scope. He wanted all new injectors. In some cases you just can't win.
I used to keep known good MAP, Air temp and Maf sensors next to my tool box. New does not = known good.
You could find someone with HP tuners in your area to program out the trans error for a reasonable fee. I found a guy in my area to program out my air pump codes when I do headers and fix my speedo for $50. It would be nice to know if the SES light would flash/flicker when the idle drops real low.
Last edited by Gorn; 04-30-2016 at 08:33 AM.
#7
got to admit I don't know anything about fuel injection other then tpi or single throttle bodys ,but trying to catch on with gorns experience ,when they run right there great when not they can be pain to work on
#8
Knowing my computer is tuned for 30# injectors what would happen if I put the stock 26# injectors in? I assume it would lean it out but not sure. I have the stock ones in a box put away for one of those just in case moments