95 yukon back fire

[youngjs1974]

95 yukon, having problem with back firing through TB, Stalling, sputtering & will not accelarate. Does not do it all the time seams to be spuratic.Have check timing, fireing order. Have changed o2 sensor, cap, rotor, coil, plugs, wires, EGR valve, fuel filter. No engine light coming on. Any ideas?

 

[SunlitComet]

Have you fuel pressure checked. Should be at around 13psi. And make sure the spray patterns from injectors looks good too.

 

[retorq]

Fuel pressure won't make it back fire thru the intake.

Double check your timing and make sure you don't have a valve hanging open. Are you 100% sure it's backfiring thru the TBI and not popping thru the exhaust?? Check the ignition module while you are there, mine went out and was popping thru the exhasut but matched the rest of your description.

 

[youngjs1974]

95 yukon backfire

Ok here is a update. Work on it thiss weekend. Rebuilt TB. changed broke worn vacuume lines, pcv valve. Checked timing with light got it within 4 degrees of 0. Had dash apart checking to see if service engine light was out. There is not one. Got it up and running sunday. drove around no back fire not suttering felt a little under powered. Let set over noght. Was on the way to work monday. and was putting dash panel (overlay) back on at stoplight. Plugged wire harness in for head lamps and engin started to die. Volt meter was a 0, oil pressure gauge begged out and the ABS light that is always on was out. Pulled over enfing would not get above 1500 rpms and was stuttering worse than ever. 40 min drive back 3 mile to repair shop and left it for them to trry and figure out.

 

[SunlitComet]

you were missing the bulb for the engine light? If so it was likely pulled because someone was annoyed at the light being on which means there was a code trying to alert user of a problem. Let us know what happens next.

 

[kcb37]

Did you unplug the est wire when you set the timing?

 

[youngjs1974]

95 yulon back fire

The bulb was not missing, there was no spot for one. Been in the mech shop for 3 days and they are at a lost also.

 

[SunlitComet]

That is not right. If it has any kind of fuel injection it has the engine light. That needs to be investigated further.

 

[youngjs1974]

I pulled the inst cluster out and there is three holes with no bulbs, but they are for the disel vertion. One was up shift, one glow plugs and I cant remember the other but it was not a service light. All the rest of the holes had bulbs in them and were fine. Checked the discription on the rest and none said service light. The only lights were a APS, Brake, Bat, seat belt and check gauges.

 

[SunlitComet]

It has got to be there maybe that unknown one.

Remove the warning lights and hold the panel up to the sun or something every warning indicator should shine thru. Service Engine Soon one should be in the far upper left of panel.