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I no longer think that the brakes are the number one clue.
1) When you get your Amazon meter, we need those voltage numbers
2) We still need your fuel trims but just at idle, out of gear. There are 4 numbers with sign. I will explain them after you get the readings. Example:
STFTB1 -1.5 LTFTB1 +3.5 STFTB2 -1.1 LTFTB2 +5.0
3) You need to get rid of that misfire.
4) You should do the fuel pressure test in the sticky
5) You should check the strength and cadence of the spark (when its running crappy if possible). Look for 1" of strong blue spark at the plug end of the wires.
6) Make sure that your new TPS is working properly. KOnEOff, move slowly through full range on the gas pedal and watch the TPS live data to see if the voltage is nice and smooth.
7) Does it run better with the MAF unplugged?
8) If you still have not found it at this point then you should look at all of the other sensor values in live data to make sure that they make sense. Example: with a cold engine does ECT read like the outdoor air temp? Does the MAP read like the atmospheric pressure at rest? What does the system voltage look like, are the O2 sensors looking OK, waht are the MAF values ...
9) Still no joy, then you should borrow that vacuum gauge.
Your fuel trims are different in your description vs what I see on the gauges. Let’s go with the gauges. On a given bank you add the short term and long term trims together to understand how much the fuel delivery is varying from the theoretical for that set of sensor conditions. Long term is a time based average and short term is the instantaneous departure from the average. Added together that’s your fuel trim right now. Positive numbers mean the pcm is adding fuel to compensate for a lean condition and visa versa. When the total is less than +/- 10 then your in pretty good shape. The closer to zero the better. You are at -1.6 and -3.9 which is very good. Try to capture it when the truck is running like crap to see what you get otherwise nothing to see here and it’s time to move on to the other stuff on the list.
Update,
Still waiting on the mail for the gauges and the volt meter as the one a person had up here was broken.
The negative cable was installed wrong, as I found a diagram i replaced it with a new unit, in the course of that I found the Mega-Fuse actually rusted and the positive cables full of corrosion. I have a Positive cable here I am going to try to swap today and I have the to fuse block cable coming in the mail. I did some testing with the lights on an found a correlation between the lights being on and sudden shutdowns and hard to start behaviour. As on two occasions this week shaking the positive cable was enough to get the truck right for up to 30 min it seems like the major power wiring is a good place to continue.
2002 S-15 Sonoma with the V6, truck stumbles and stalls on brake application, much worse at night when the headlamps are on. Have replaced tge TPS, AIC, Fuel Filter, Plugs and wires, ignition coil MAP sensor and the fuel pump. On nice days she runs great as long as I set the idle high, now when warm runs fine till throttle application in gear and truck moves and engine dies like shut off. Any assistance or ideas appreciated.
Sounds like electrical problem to me. Try installing some extra grounds between body and engine and between engine and battery.
Well I got the Positive cable out and I found that they had ripped the end off and jumpered in a new end using a folded washer some zip ties and a lot of tape. All of it hidden up under the block out of sight.
It is still not perfect, but it is running better.
So for whatever reason the new MEGA Fuse and the Fuse block wire showed up today (A week early!) So I swapped them in, I also replaced the battery tray with a new one as the old was rusted to hell and gone and put it all together. In normal operation everything seems fine, but when running with the lights on I had a stall. The previous drops in RPM when applying the brakes etc appear to have been solved, although I will find out more with tomorrows cold start. Still waiting on the Voltmeter and Vac gauge.
Since your truck stalls when the headlights are turned on then you most likely have an electrical system problem. Either the headlight circuit is defective or the load of the headlights is overwhelming a marginal battery/alternator/wiring/connectors/grounds/fuses. I await your system voltage readings.
06-18-2020, 05:18 PM
