No throttle and lots of smoke

[1949gmc]

I was hoping someone here could help me solve the problem I'm having with my LLY. My truck is a 04.5 with 34,000 miles, never had a lick of problem with anything under the hood. Last week as I pulled away from home, it didn't have any throttle... nothing, just idle. Temp was above 30. When I stepped on the pedal, it would rev up a little (up to about 850rpm) and blow a lot of smoke. Acted like it was loaded up if it were carburated. No lights on the dash. When I got to the end of the block, I stopped, put it in park and revved it up to the governor. Coughed and sputtered at first, but then cleared out, just like it was loaded up.... lots of smoke. I changed the fuel filter at work thinking that would solve it. It didn't. It's happened two more times since the filter change. Last time was today after I'd been driving around for 45 minutes.... sitting at a light waiting for the green and when it changed.... nothing. Just idle. Pulled into a parking lot, revved her up to clear her out and she was good as new.

Now, I've read about the injector harness problems and initially thought that might be it, but then I read somewhere that an electrical problem would trigger the SES light. Again, I've had no SES light. I'm guessing that either it's A) the fuel itself (I'm running a blend, not bio) or B) possibly a mechanical failure of an injector??

Any help would be greatly appreciated.

[DmaxMaverick]

Welcome aboard!

Have you checked/replaced the air filter? Fuel filler cap? Other than that, it sounds like fuel quality. What do you mean by "blend"? Even at 30°F, fuel can begin to have issues, and bio, if it's in your "blend", can make it worse. With no DTC's, it difficult to say.

[1949gmc]

Here's something that was brought to my attention.... my SES light does not come on when I first turn the key on. Should it? I guess I've just really never paid attention to it. I had the whole speedo head replaced last year under warranty. You'd think it should work.

Air filter is okay.... doing some research on the fuel to see exactly what we've got. Gas cap appears to be okay.. not on crooked or anything.

Also, did I read somewhere that the DMAX has an 8 year/100K mile warranty? Injectors would be covered by this...... yes??

[DmaxMaverick]

LB7 injectors are covered for 7 years or 200K. Your LLY isn't included. The OEM warranty you have is 5 years or 100K on the engine and fuel system.

The filler cap needs to vent properly. It may look good, and still be bad. Either test or replace it. Any smog shop can test the cap. If you have to pay for a test, just replace it. Cheaper that way. Unlike gassers, the cap is less likely to be the cause of running issues if it is lose or removed. If it is not venting properly, it can cause excessive vacuum on the supply side of the fuel system, starving the pump. The cap should maintain a fairly neutral range of pressure/vacuum at approximately 2 PSI to 2". This time of year sees the most of this issue, with wild temp swings (cold/freezing to warm fuel while running).

The SES lamp should come on when the key is in the "run" position with engine off (like before cranking, or if the engine stalls or fails to start). If you never see the lamp, something is wrong. If you've had your IP cluster messed with, it could be as simple as a poor connection. If the SES is not responding, you need to check the PCM with a scan tool. If hard codes are present and the SES is not showing, the lamp or IP cluster may be bad or poorly connected. Either way, you need to check for DTC's to get an idea of what the PCM is seeing/reporting. Seeing the desired/actual fuel pressures and sensor readings would also be very helpful. The conditions you describe should generate some DTC's and trigger the SES, at least temporarily. Check for codes before trying anything else! You may get Autozone to do it for free. If not, get your hands on a scanner or code reader.

Do you have any engine related modifications installed? What you are seeing could also be EGR related. Have you modified it at all? I know your sig says "bone stock", but I've heard it time and again, "I did this, but it shouldn't have anything to do with that". Be sure to check that air filter. If it's due for replacement, damaged, or has ever been wet, it could be as simple as that.

There are other possibilities, like turbo vane servo, etc, but we really need to see any codes present before taking WAG's.