2000 5.3 Hesitation, back fire, miss

[AZ-Z71]

Hello all,

 

I'm having an issue with my 5.3. I don't remember exactly when it started but I have noticed it getting worse over the last two weeks now. As for mods I have a K&N cold air intake (which has been on for like 10 years) and Black Bear tune (1 year old) and I have deleted the mechanical fan for an electric fan (1 year ago) since the truck has a 6" lift and a 3" body lift my mechanical fan would never work correctly in temps over 95 F.

 

The problem:

I first started to notice the truck would back fire when standing on the gas pedal and it winds out then shifts to the next gear you can here a pop or two. The Black Bear tune has been in for a year now and I don't recall it doing it when it was first done.

 

This progressed to hesitation and sputtering at stop lights when you go to pull away from the light, and while sitting at the light you can feel a miss in the engine. The tach does not move one way or the other. I later played with the AC switch and it seemed like it did it more with the AC on than off.

 

Yesterday while driving the truck between 60 and 70 while lightly on the gas, you can feel the miss through the engine, kind of like a rumbling feeling in the seat. It would do this off and on. If coasting, I did not feel the miss.

 

I have no SES light on in the truck to indicate a misfire on a cylinder. Prior to all this I ran a can of sea foam through the fuel tank and this maybe happend two weeks later and two tanks of fuel from different stations. Yesterday I fill up from a third station and it stills happens. On other thing I noticed yesterday was when the fuel gauge was at 1/4 tank it would bounce up and down a few marks. Once filled, it no longer did this and the truck is at 3/4 and the gauge didn't move.

 

About 4 years ago I replaced the fuel pump, as it was totally dead one day when I went to start it.

 

Things I have done recently:

I had a light for a bad o2 sensor, drivers side after cat, replaced that. Also had an exhaust leak on the drivers side last cylinder, removed manifold, replaced gasket. I also changed the factory cats to flow master cats because there is a rattle in the truck which I was told could be the cats, replaced, but that didn't take care of the rattling. I'll save that problem for another thread. Had a large leak in the emissions system and replaced the hose and solenoid located under the bed of the truck and that fixed that issue.

 

I'm at a total loss with out it spitting out an SES light to at least point me in the right direction.

 

Any help would be appreciated. Thanks.

[Jsdirt]

Backfiring of any kind would point me towards an ignition problem.

 

Plugs, wires, & cap / rotor (if it has a distributor), ignition coil, or coil packs, or wiring. Probably some electronic do-dads in between too, which are always suspect.

 

Need to troubleshoot all of it so you're not just throwing parts at it, & wasting money.

[Swimmer8366]

Check out your injectors and fuel rails that's what mine was when mine was acting up

 

Sent from my Z981 using Tapatalk

[AZ-Z71]

The last time I had a fuel injector problem it gave me a misfire code on x cylinder and I could listen to the injectors and find the dead one for sure. I'll try to listen to them and check out the fuel rail. A guy at work said it could be coils/wires and plugs too.

 

In the mean time, I put the scanner on it to see what it was doing. At first I could feel a miss but it didn't last long and I even flipped on the ac (the lights and door was open as it was night out) and nothing happened. So here is my data in case it does any good.

 

ABSLT TPS = 0.4%

RPM = 600 (596 to 605)

Calc Load = 2.0%

MAF 0.76 LB/M

MAP 9.4 "HG (sometimes up to 9.7)

Coolant 196F

IAT 95F

IGN ADV 20.5 degrees but would go between 19.5-22.5 degrees at idle.

ST FTRM1 = -1.6 (-2.3 to 0)

ST FTRM2 = 0 to 2.3

LT FTRM1 = -1.6%

LT FTRM2 = -4.7%

Speed 0

Fuel Sys 1 and 2 Closed

O2S11 (V) moving above 0 below 1

ST FTRM11 = -2.3 to 0 (would flick to -3.1)

O2S12 (V) = 0.790 (steady)

O2S21 (V) = moving above 0 below 1

ST FTRM21 = 0.00 to 2.3

O2S22 (V) = .790 (steady)

 

All above values with truck in idle and the ac on.

 

I also took temp readings at each cylinder at the manifold and they all seemed to climb in temp evenly, I was looking to see if one cylinder was colder than the others.

A visual inspection in the dark, I didn't see any arcing on the plug wires. truck has 160K on it, so the coils and wires are original. I do believe I changed the plugs before though.

 

I'm going to get a test plug and test the coils and the coil wires next. I can see the valve covers have a leak to them, both sides on the back side towards the fire wall. I have gaskets for them and will be changing those maybe this weekend.

 

Other things to look at, the Fuel Pressure Regulator to see if there is fuel in the vacuum line. I can buy a gauge and test the fuel pump pressures.

[Jsdirt]

From what you posted, your o2 sensors look lazy, but your fuel trims don't look too bad, which is strange.

 

The UPSTREAM o2's should rapidly change between 100 - 900 mV, or .1 - .9 V.

 

Downstream (after cat) should remain steady, which they look to be (those don't matter as far as how the engine runs - 100% emission-only sensors).

[AZ-Z71]

My part should be here by this weekend so I can test the coils and the plug wires.

 

Figures I would have something weird going on as it seems to be the coarse lately.

 

I'll probably take it out on Friday or Saturday on a 50 - 60 mile trip. I'll plug the scanner in and see if I have a problem and then see what type of reading I get on live data.

[AZ-Z71]

They sent the wrong part it needs to be an HEI tester and they sent me a Stens which is for small engines like lawn mowers......

 

Anyway I just ordered new plugs and wires and those will be here next week, I just pulled a plug and it is an AC Delco 41-952 which was their double platinum I must have put in there some time back. However when I checked the gap on the plug it was 0.065. I think normally these should have been 0.060 or 0.040 cant remember because I read so much about plugs lately now I'm confused. Anyway I got a set of 41-962 which in my research is the correct plug for this truck 99-2006. Over those years they went to the iridium 41-985 or 41-110 but I think they reversed from 41-110 back to 41-985.

 

Also drove the truck twice no with and without ac on and I have not had an issue of missing. Still backfires if pedal is down to the floor and transmission shifts up but I do notice that only happens once the motor is warmed up.

[barry G]

that vacuum is very low.

idle would be 18 or so.

 

I also found amps draining to the wrong places can steal the coil(s).

how does it do with high beams on, all the lights?

 

I cleaned up an old 96, it skips past the next generation as if to be a race truck..

 

all ampere related.

[Jsdirt]

What type of "coil tester" exactly are you buying? These new systems are completely different than the old tried & true HEI systems.

 

No fancy equipment needed, really. If the coils aren't working, you'll have a check engine light on (blinking if real bad misfire), which alot of the time points you to the exact cylinder with the issue. It's probably not lit since it only happens at high load or full throttle runs. That makes things a little more tricky.

 

As far as testing goes, if you have an inductive amp clamp, you can test the current draw of the coils through the fuse panel - you'll need to know the normal amp draw of each, as this will be all 8 if I'm not mistaken. Or you can just do each primary wire to each coil separately for a more accurate reading. One or 2 out of whack should point to the bad coils.

 

I threw a set of NGK iridiums in my '07 5.3 . They're identical to the AC Delcos it came from the factory with in every way but the labeling. Iridiums are the way to go if you want to run them for 100k or more. Make sure you put anti-seize compound on the threads first - they'll be in there for a LONG time.

[txab]

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