Backfires/Sputters in closed loop only!!!!!!!

T

toddbroussardco

New Member
Joined
May 7, 2007
Once the car goes into closed loop at 160 degrees,she bucks,pops,etc.:mad: ...She runs super in open loop:D ..We have ruled out cam sensor (used Caspers tool to verify)..Any suggestions....Thanks,Todd
 
Hi,
Wow, that's a pretty impressive list of modifications! In this case, unfortunatly, it also opens a lot of cans of worms, so to speak.
As always, there are two main avenues to look down when addressing your problem. First and foremost is ignition. Then comes fuel, which in your case, may very well be the culprit.It seems like you are experiencing lean misfire. Why? I would start looking at simple stuff like fuel pressure, and progress from there. Programming may be also an issue.High boost levels just aggravate the issue. Frankly, I just don't know. You are going to have to work this one out alone. Keep in touch, fill us with info, and we all will figure it out. Good luck with your problem!
 
Appreciate the reply 83ttype...87NAT and I worked on a few items earlier today..We r also stumped..Im am thinking it to be a sensor related problem...As I said,you can watch the scanmaster...when temp. hits 160..she runs like crap...I am trying to get some help before I start throwing parts at her..I have an electronic temp. guage and it matches the scanmaster temp. within a few degrees...
 
Ok I doubt you got egr on that block
Does it feel like a fuel miss or ignition miss?
Tested injectors one by one? Ohms
Plug wires?
ya got coolent sensor or the O2 to check
low fuel pressure.

Ignition module getting too heating up and breaking down?
Could have cracked insulator on spark plug?

could be anything
 
I am leaning towards his 02 sensor being bad. I told him to check his cross counts tomorrow. His cam sensor was was 180 degrees out for a long time. I set the cam sensor correctly today but the long term effects could have fouled out that sensor.

I am pretty sure it is a fuel related problem. It feels like it is just getting overfueled when the rpm's come up. I dont think it is heat related with the coil/ign because after I set the cam sensor the car ran great and spooled fast and pulled hard. It is like clockwork: as soon as the scanmaster stops blinking and the ECM hits closed loop it sputters/ bucks under part throttle low boost. This is happening with no alky being injected also, so I ruled out the alky. A wire or spark plug problem would show up under open or closed loop so I ruled that out also. It is surley sensor related. Any further input from you guys would be appreciated.
 
Installed a used O2 sensor that I had.The problem is still there..but it now happens at a bit higher rpm/boost.. I will buy a new O2 sensor tomorrow,and try it...
 
Mine bucked/backfired from a bad TPS sensor. Others have had problems due to bad crank sensors. I think I even had bad spark plugs cause problems. Is the coil pack ok?
 
Todd- You will need some kind of a scan tool to test the TPS when it sputters. Mine tested fine at idle but the problem showed its ugly face when under load. The TPS volts dropped to 0 and then picked up. A new TPS cured it. Good luck!
 
Well guys..I think I fixed the problem..Decided to knock the dust off of the new crank sensor,that I have had in my tool box...The old sensor appeared to have oil/road grime residue between the sensor ports.I guess that had something to do with the failure.Thanks for all the suggestions..Todd
 
Todd, hope you got it fixed, but I don't see the connection between closed loop and the crank sensor signal...
 
Hey Chuck...I have put about twenty miles on the car since changing the crank sensor...No problems yet...Now that I think about it,the crank sensor is functional 100% of the time...Correct??? Todd
 
Yep!

toddbroussardco said:
Hey Chuck...I have put about twenty miles on the car since changing the crank sensor...No problems yet...Now that I think about it,the crank sensor is functional 100% of the time...Correct??? Todd
Click to expand...

Don't try to leave home without it!!:D :D
 
Hey Chuck....The problem is back.....I have brain stormed and recreated events....The last part I touched was the maf,before closing the hood...87NAT has a known good used stock maf...The problem took a lot longer to appear.I will post the results on the swap....Todd
 
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