i have tried turning the key on as many as 5 times before starting and this did not help, one thing that i did notice is that when checking the plugs for the sensors i had a ground, voltage on the wire to the sensor(purple white) but on the sensor going back to computer i also had voltage, i checked all the sensors i could and it seems that only the ones on the tb are doing this, maybe that will help someone figure this ****ing problem out for me

 

The fuel pressure regulator output should be at least tested to see if your pressure sucks initially and then after a few minutes comes up to within proper operating range. That was why I had suggested to just click it one time and check the pressure. That test will tell you immediately if you have a problem with the regulator at the pump. This is not uncommon by the way.

So, now you think it's a wiring issue at the TB now? I can't understand what you think the problem is. I see your concerned with all the sensors at the TB and how there's voltage on the PCM side and the battery side. Which sensor going back to the computer are we talking about? Don't assume that it's not normal so quickly. The only way to tell would be to get the schematic of that circuit and look at it. It will show where voltage is present and where ground is for that circuit. Then you will know if it's right or not vs. guessing.

If it was a sensor-or bad wiring, it would do this more often than just the first start of the day.

What is the time frame for when it will not start properly? Have you timed that out? There has to be some amount of time before it craps out. It sits overnight, and every morning it craps out so, there's a time factor involved here that would tell us something. Whether it's related to temp or fuel or, perhaps moisture / electrical related.

It may also be a problem with your cold start / warmup mode. This is a time period that lasts from 2-3 minutes and involves the O2 sensors, exhaust temp, coolant temp sensor, and the PCM preset delay time. The timer must first be met and after that is met, the coolant temp sensor must be reached, in order for the PCM to go into closed loop mode. However, this is based on the fact that the fuel pressure is correct.

However, this would happen every time when the truck was COLD- this relates to temp vs. fuel pressure. Again, if we had the time frame for WHEN this started to occur along with some real numbers for the fuel pressure at startup vs. turning it five times and no numbers, it would make it much easier to narrow down vs. how we are going about it now.

We are grasping at straws vs. obtaining any useful information. Let's measure the time period in between running good and crapping out and run that simple 101 test on the fuel pressure in the am while COLD. Turn the key ONCE- look at the guage- note pressure. Start the vehicle- note the pressure.

If the pressure is low at any time during any of those tests- your fuel pump is bad and needs to be replaced and, if it's fine, we know it's not your fuel pump and can start looking into open loop mode. Again, sometimes, the pressure regulator can operate intermittent at first start and after a period of time, it gradually increases to the proper range. But, without testing anything and getting any numbers, your flying blind.

How about just bringing it in and having someone run a scan on it during cold startup on a scanner?

 

I did try the key one just once but i did go more other times made no difference. normally it takes about 10 hours for the truck to get like this but if its cold outside it can happen faster. I have checked the fuel pressure before starting in the morning and it is consistent with the other results that i posted. as for the wiring I figured out that this could be a problem from looking at the diagram, however because the truck isn't running I don't know if that has something to do with the "closed or open loop" modes. as far as which sensors thats the iac, map and tps. Again the time changes with the temp but about 10 hrs is my best guess with normal fall weather. I also checked the vacuum earlier and its at 18" which is normal.

 

Ok, did you measure the pressure though this time / recently? Not in the past but, recently? In your case, the truck runs bad and, if the pump is bad, the key test is not going to tell you anything. It will still run like **** regardless of the key <ON> test because the output is still the same. That's only good for a hard start condition which you don't have. All your doing is pressurizing the lines with the key <ON> method.

A good pump shows no change and, a bad pump with a faulty regulator running at low pressure at cold will also show no difference regardless of the number of key <ON>s. The best thing is to rule it out by measuring the pressure as was described. I know you said you had done this but, I am not sure if this was done recently or in the past.

So, now we have a 10 hour window. So, we look at what goes on in ten hours time. And, it's worse / shorter window the COLDER it gets. That is looking like something is not controlling or, operating correctly in open loop mode. The O2 sensor temp drops as does the engine temp sensor.

How long of a time period before it settles in? If it's about 3 minutes- it may be related to warm up mode. In warm up mode, we can rule out your O2 sensor as the exhaust is cold and the sensor is also cold so, it will not output squat until either the exhaust heats it up or, the internal heater does. Once the timer has passed the 3 minutes, and, the O2 sensor heats up, it then puts out the voltage to help the PCM adjust your fuel mixture. Now, if your A/F mixture is way out of whack, there's no way to control this at startup and, if your running lean, it will run rough and then straighten out once the O2 sensors and the coolant temp comes up. Those sensors now help to aid the PCM to control the A/F mix. A rich running condition at startup yields super easy starts and very smooth idles. However, as things warm up, the idle goes south.

If your fuel pressure is low, you will be running lean as there's less flow through the injectors. The PCM doesn't monitor that pressure so, it doesn't know if it's low or high for that matter as it's just running static parameters based on everything working at proper specs. This includes your IAC motor as well. It's supposed to be gapped a set amount at startup to allow proper air flow.

If it's not, the truck runs like total junk at startup until it goes into closed loop mode where, the A/F mix can now be adjusted by the PCM.

This is why I was hoping to really get some numbers vs. the useless key <ON> test.

Also, you have to check those sensors with the truck running. You have to backprobe those as described and check for output voltage of each sensor. Checking the input voltage is always going to show +12VDC as your finding out and is not going to tell you if they are good or not only if they are seeing + voltage on the input side.

All the + voltage comes from the battery side. All the switching is done at the PCM side. However, there's common feeds on both sides and, if you probe them, you will find continuity. So, it's not uncommon to find voltage all the way across the harness at the PCM.

The battery side / power dist center also feeds the PCM. All those sensors that your referring to have an input and output voltage. All have a common feed as does the injection circuit. So, you will have common feeds that apply power to the sensors and, some may even trace through to the PCM to be switched on / off depending on the senor and / or circuit. Most common is the switching of the - side vs. the + side.

But, again, it depends on the circuit design and what is being switched. Some components can't run with what is called a floating ground. In that case, the + side is switched on / off while being grounded at all times.

I don't have schematics for your truck. If I did, I would go through those sensors to see what we have tied into those.

The Haynes manual is very limited. The dealers have some really detailed ones that even include the pinouts. You may want to ask them if they can order them for you.

 

when i checked the vaccum yesterday I rechecked the fuel pressure and it's still the same as it's always been. I would say that sometime around 3 minutes is right on a hot day it seems to be shorter but as its not warm out anymore that could just be my imagination. I know that the truck runs rich but I think that is the thermostat, I will change that tomorrow and hopefully once the truck is warmed up it won't run rich anymore. I'll do the backprobe as well tomorrow and hopefully get some better readings that can help you. If theres any other test you think would be helpful in diagnosing let me know as the truck will be sitting until am tomorrow.

 

When it runs rich, the idle is usually smooth (in warm up mode). At startup / warmup mode, the PCM is set to run it real rich anyway as that is the method of starting in the cold. Then, as it heats up, it leans out the mix over temp. Hotter it gets, the leaner the mix. Colder it is, richer it runs.

Check / replace your coolant temp sensor by the way. I think I covered all the things to look at and, now that I have the manual for your truck, (big thank you to Sheriff for sending me one) I will have a go at it later today.

The things that you need to check are the fuel pressure and, since you have done that and it's at 45 psi, (both with one key <ON> and while running cold) we can rule that out and move on to the warm up mode and see what may be causing the issue.

The static parameters are based on air flow- this is your intake. Do you have your OEM intake to put back on by any chance? Reason I ask is that my truck would NOT idle right with that intake or a 14 x 3 air hat. Change that back to OEM and then test.

Check the engine temp sensor / coolant sensor. I would even replace it as it's dirt cheap. Also, replace the sending unit as well. Might as well do those at the same time you change out the 180 T-stat.

Speaking of that...I forgot that you have a newer truck than I do and, on some of those PCMs, those are programmed differently as far as the lower temp limit is concerned. I have an email from Hypertech engineering that just came in yesterday in fact in response to my questions about these 180 T-stats.

Those can be problematic in some models he noted. I don't have time now to explain is as I am rewiring all my fuel injector connectors but, later on, we will talk more.

Change out the T-stat for one, change out the temp sensor and sending unit as well as see about putting the OEM intake on. Let's get back to a OEM baseline and then put the intake back on and note if there's an improvement or not.

Chris

 

okay I will change out at least the t-stat and the temp sensor and ill see about the sending unit $. I may be able to get an oem intake but ill try again with these new parts and hopefully it will at least run right once its warmed up(not rich)

 

have you ever replaced your cat? or the o2 sensors? i was having terrible problems and thats what it was. just a guess but you never know could be it. but with you not throwing any codes its hard to tell.

 

I don't run a cat but still use both o2 sensors and it hasn't thrown any codes so I'm going on the assumption that they're working.

 

sorry with all the rain i haven't been able to work on my truck will try again tomorrow