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P0301 and p0303 on start up


Redranger45

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Rough idol on start up!

Got my truck back from the engine rebuilder. New engine. Driving home from a long drive it started misfiring badly. Took in and they check fuel injectors, said they did some rewiring on harness, sent computer off to be fixed, new plugs, new wires, put in all new gaskets. After 10 trips there I installed a new cat., downstream o2 sensors, new vacuum tubes, new IAC, new throttle body control sensor, new coil. Still misfires and rough idol for about one minute until warm then seems to run well. Today however it was misfiring badly on hwy. I have used the starter fluid test and found no vacuumed leaks that way. Plugs are new but should I check the gap? Motor craft. Brand new motor craft fuel injectors. Engine rebuilder says they checked compression and it was good. If it was an internal problem would it not be all the time? I put a fuel pressure gauge on fuel rail. Mine is a 1999 ford ranger xlt extended cab flex fuel, v6 3.0. I have listened to injectors with scope and all sound good but I probably need to listen to them when I fist start up and its running rough. Fuel pressure is 35 at key on then 57 with engine on and parked it is steady. When I cut engine off it drops to 53 holds fuel pressure for 15 minutes or longer. The regulator is in the fuel pump and there is a dampner on the fuel rail. I can change fuel filter, not sure what else to do. Hoping for some help with this. When it starts it does rev up a bit then gets rough then the idol drops.
 
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RonD

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Welcome to TRS :)

All fuel injected engines should REV when started, that's just the IAC(idle air control) Valve being open all the way for starting, then computer closing it to set "target" idle RPMs, about 1,100rpm cold, 750rpm warm
REV up means IAC Valve is working

So 3.0l Vulcan engine was fully rebuilt?

No new/used heads, they just rebuilt existing heads, reason is 2004-2006 3.0l heads had an issue with recessed exhaust valve seats causing intermittent loss of compression, intermittent being key word there.
I would expect rebuilt 3.0l to have 170psi average compression across all 6 cylinders
3.0l Vulcan runs 9.3:1 ratio

Spark plug gap can be 0.044, +/- 0.005
Wider gap is better for lower RPM power and cold starts
Narrower gap is better for higher speed/RPM driving

Simpler and better test for vacuum leak is to unplug the 2 wire connector on IAC Valve while WARMED UP engine is idling.
With IAC Valve unplugged it will close all the way and RPMs should drop to 500 or so, engine may even stall, either is GOOD, it means no vacuum leak
If RPMs do not drop then there IS a vacuum leak

Specific cylinder misfires could only be lower intake manifold vacuum leak, not that that's the problem, upper intake vacuum leak would effect all cylinders so P0300, random misfires.

Not sure the 1999 3.0l will startup and run without the Cam Position Sensor(CPS) but I would try unplugging this sensor, 2 wire connector, top rear of engine.
And then seeing if it will startup.
The CPS operates the Sequential Fuel Injection, without a CPS signal the Computer will switch over to Batch Fire Fuel Injection.
Sequential EFI opens each injector only when its cylinders intake valve opens.

Batch Fire EFI opens 3 injectors(V6 engine) at one time and alternates which 3 every 1 RPM.
This keeps the lower intake full of the correct air:fuel mix so Lean or Rich condition is less likely to occur in a specific cylinder
Batch Fire was used on most EFI engines until mid-1990's, it is less fuel efficient than Sequential EFI

So just a test to see if #1 or #3 fuel injector might be the problem.
 
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Redranger45

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Yes they had done a valve job on the previous rebuild so we had to get new heads for this rebuild. I do not know which year they were but they told me they bought new heads and put them on. I took off the IAC and the engine rpms dropped, almost cut off. So I assume no vacuume leak.

The shop initially tested all fuel injectors and said they were fine, then had me buy new ones which I dropped off and they put in. Then they suggest I get motorcraft injectors which I did and they put in.

It seems to only do it from a cold start up. If the truck has been running and you go out to start it starts up fine. Very smooth.

So the other day the engine light was off. I started truck and it was. Running rough at idol and I was watching it warm up. While parked and warming up the check engine light came on. This time a p0303 code. Goes back and forth between p0301 and p0303. I clear the code and drove about 400 miles after warm up. No code. I drove another hundred miles today. No code. Whatever is happening seems to only be happening during warm up.

If it has been sitting for a few hours and cold the engine shakes pretty bad. If I rev up the engine it does not help but I am not sure if the sound is flooding or lack of fuel. Then after a minute or two it smooths right out. Runs like a new engine unless I leave it parked a few hours and then we do again.

I can unplug the cam but did not really understand how that would tell me if there was a problem with a particular injector? Also if a valve was sticking intermidently would it not stick while driving as well?

I had recently tried filling up with e85 as the truck is flex fuel and it ran really rough. So I am just through my second tank of premium and the truck never has a problem after the warm up period. I think the problem I experienced at hwy speeds was the system trying to recalibrate for e85.
 
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RonD

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Batch Fire fills lower intake with air:fuel mix so would lessen chance of misfires if a single injector was acting up.
But not sure computer would change to Batch Fire with CPS unplugged, Sequential can be run by Crank Sensor only

There are two temp sensing devices on the engine
Temp SENDER is use only for the temp gauge in the dash
AND
ECT(engine coolant temp) SENSOR is used only by the computer, this sensor sets CHOKE mode, so computer runs engine Rich with high idle(1,100rpms) when started cold
Do you get the higher idle?
That means ECT sensor is working

If it isn't working or is reporting warmed up engine when its cold, then computer won't set CHOKE mode and engine will stumble until it does warm up.
 

Redranger45

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Got a new ECT and will put in tomorrow and let you know. Thanks!
 

Redranger45

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Throttle body position sensor

Ok. I was about to put new air control temp sensor in when I noticed this bare wire to the tbps. This is the sensor the engine rebuilder said was the problem and replaced. Would bare wire cause the problem I have described? Anyway rewiring now. Sorry don’t seem to be able to insert pic. There are three wires going into the tbps. Red, grey, Black with white stripe. At base of plug that connects to sensor the black wire is cracked and bare wire is exposed.
 

Redranger45

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Ok I rewired and that seemed to solve for a few days. Ran with no codes and started up smooth. Today it ran a little rough at start up and threw the p0300 check engine light. Going to put the coolant temp sensor on tomorrow and see. I have noticed that every time the check engine comes on is when it’s parked at idol. Never when I’m driving. It was coming on everyday before then after the retwiring did not come on for a few days until today.

I’m wondering if the fuel pump could be causing this. The only times I have checked the fuel pressure it seems to stay at 57 but I have not been able to drive around with the gague. If the fuel pump or regulator is intermident I wonder if it could cause these issues?
 

Redranger45

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IAC leaking

So with engine off I blew cigar smoke into vacuumed hose. Smoke leaking out of cap of IAC. Is this normal or a vacuumed leak? Brand new IAC.
 

Redranger45

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I installed a new engine coolant tempt sensor. The check engine light has not come back on. It seems to run better but will just wait and see if light comes back on. Thanks!
 

Redranger45

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Ok since I put in the coolant temp sensor there is no more check engine light. That and rewiring the plug to the throttle body position sensor seems to have taken care of the codes. It still seems like it is starting up rough though. And there is this strange sound like something is unmuffled. Like an o2 sensor is lose. But I can’t feel any leaks.

Today I took off all vacuum lines and pressure tested. Seems there was leaking near the vacuum resivoir. I bought new tubbing and used new grommets and sealed that off.

What next with no codes but rough idol for a minute or two? Do I change camshaft position sensor ehich has never been changed or just take to a different mechanic?
 

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Gonna sound weird, but was having similar problems. Replaced injectors, replaced fuel pump (long story) pressure fine. Still problems. Begin thinking heads were a problem from late night reading. Pressure tested and fine. Then started replacing little things plugs, wires, etc. Ieoukd replace Rey and wait, code came up. Then the last thing replaced was PCV. Can’t explain it, but problem gone. Knock on wood!


Sent from my iPhone using Tapatalk
 

Redranger45

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Yes. Thanks.?it has definitely been a process. I think it was a series of issues.
I replace one thing and then have to wait for computer to reset to be sure if results. Last night I warrentied out the dpfe sensor just to be sure and realized when I put in the engine coolant temp sensor I had left the tube from the oil pan to the air intake unplugged. Put that back in and seems much better. Unplugged the battery for five minutes and no roughness. I’ll give it another day of of driving and see if it sticks.
 

Redranger45

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Well the check engine light came back on again. I went ahead and took to a new mechanic so we will see what they say. Hopefully will have an answer today. I am betting there is a leak in the intake manifold that I could not detect.
 

Redranger45

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Solved

Well it’s a head gasket leak. They did a leak down test. I trust this new guy. Actually when I first bought the truck he did all the work for 10 years. But then I started working on car. Anyway I don’t think I should go back to the origional shop. The warranty ended in May and even if they would do it I don’t trust them to do it right. I know this guy will do it right. I am guessing it will be between $500-$1200 to replace the head gasket.

If he will do just one head should I ask for that or have him do both?
How hard is it to replace a head gasket? Do I have to mess with timing or anything like that? Or just take off heads and put back together?
 

Redranger45

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Not solved yet

So when I spoke to the mechanic he said there was coolant in the number three cylinder. He said they used some kind of scope that allowed them to see the cylinder and that it was very smooth and clean. Said that is how it is when coolant has been leaking into it. He said they have taken the valve cover off and are doing some kind of a pressure test that will make coolant come up through the rocker arm. He said depending on where the coolant comes out they can tell if it is a head gasket, intake or exhaust leak. He said if it’s not that he does not know what else to do. So if it’s not a leak I have a now constant misfire in cylinder 3 with two shops unable to diagnose.

So here is one more question. At this point I have paid the engine rebuilder 4 k for a rebuilt engine with new heads. They have said they will cover any leak and replace. Is it acceptable to charge me that kind of money and then say well we can’t figure out what is causing it, sorry. To put another way is it ok for me to say I’ve paid you for a rebuilt engine. You need to fix it.
 

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