The dreaded flashing Check Engine Light

[Motojoe86]

I do.View attachment 190987 View attachment 190988

Are these weld on or clamp/bolt in?

 

[Motojoe86]

Update guys, I put on new alternator, belt, and did qn9thrr clean of maf and tb. I havent been on highway yet but ive held it near 3k rpms for about 30 seconds and no cel. So far its l9oking like the alternator was the culprit but i will follow up upon highway travel. Thanks again everyone!

 

[Tonyrodz]

Are these weld on or clamp/bolt in?

I bought them to be welded in, but I guess they could be clamped if you expanded the ends, or used those type of clamps to do it.

 

[iamdub]

What might it read for a restricted cat?

Vacuum would drop the higher you rev it

 

[Scottydoggs]

Update guys, I put on new alternator, belt, and did qn9thrr clean of maf and tb. I havent been on highway yet but ive held it near 3k rpms for about 30 seconds and no cel. So far its l9oking like the alternator was the culprit but i will follow up upon highway travel. Thanks again everyone!

sounds like you found it, no power can make it run like crap real easy.

 

[rockola1971]

sounds like you found it, no power can make it run like crap real easy.

The battery/ignition system loaded down causes the reference voltages to be all out of wack and with the PCM even getting low supply voltage all kinds of funky symptoms will appear.

PCM, MAF, Injectors, Idle speed sensor, Transmission control solenoids, fuel pump, relays that supply power to various things such as A/C Compressor, Fuel Pump, ignition coils, Crank and cam sensors and much much more all need a certain window of voltage feed to be able to operate or even give a feedback (signal) voltage back to the PCM for correct output voltage of the PCM to various items that it controls.

There arent alot of things to go wrong within an alternator (electrically) except for the rotor, brushes, regulator and diode pack. An alternator is essentially a 3 phase generator that outputs ac voltage which is fed to the diode pack (full wave bridge) which in turn converts ac to dc. A diode pack can short to ground which causes the battery system and everything attached to it (electrically) to be loaded down. It can short across itself which means your battery and everything attached to it is being fed ac current instead of dc. That is not good for the battery nor any of the auto components that are strictly designed to be operated on dc.

Excluding mechanical failure (bearings fail) the most common failures of and alternator (electrical) are bad voltage regulator, shorted diode pack (to ground) and worn brushes that get slid sideways partially out of the brush holder. The rotor and its commutator could get worn but that is more common on pre mid 80s and older than the newer series of alternators.

Hurry up and get that thing on the highway and mash the throttle to see if its all good now! And keep an eye on that battery! It could have been damaged if it was fed alot of ac. Check the water/acid level if its not sealed.

 

[rockola1971]

A quick and dirty way to tell if a cat is clogged is to hit its inlet and outlet side with a IR thermometer (Infra red gun). The outlet should be real close if not equal to the inlet temp reading. If the outlet is substantially lower its because the cat is clogged.

 

[01subCT]

I'm wondering about this post an how the alt worked.ive been chasing this problem with my 01 suburban for years.ive replaced mutiple new pumps I hollowed out my cats done several tuneups.ive scanned it replaced air flow sensors.on my truck it doesn't happen all the time but when it does flash it starts to run like crap.idles like it's git a nice cam lol an also gets very rich.then just like that stops flashing and runs fine.im leading towards an o2 problem.ive replaced those also but I'm wondering if they were just garbage ones.im gonna thtie sone Bosch ibes in and see how I make out

 

[Sgtduckyboy]

Update guys, I put on new alternator, belt, and did qn9thrr clean of maf and tb. I havent been on highway yet but ive held it near 3k rpms for about 30 seconds and no cel. So far its l9oking like the alternator was the culprit but i will follow up upon highway travel. Thanks again everyone!

well, how did it do? we are all wondering! I have some similar symptoms as well as bad alternator symptoms,, I got a lifetime warranty alternator, thinking of taking it in now, test it, demand replacment, see if that clears up both sets of issues... great job getting this post some attention and thanks to all the experienced ** owners to reply!

 

[CamReynolds]

typically only two things make the cel flash is, needing a tune up real bad, but you got that covered, the other is clogged cats. clogged cats cause? yup you got it, random misfires.

it likely also feels down on power too when wot.

One time I was doing donuts in the mud and I got a flashing cel. It went off and has never come back on. Do you think this was a clogged cat?

 

[Scottydoggs]

if it was only the one time i think you just made it angry lol

maybe you were bouncing off the rev limiter? or over revving it?

 

[Motojoe86]

well, how did it do? we are all wondering! I have some similar symptoms as well as bad alternator symptoms,, I got a lifetime warranty alternator, thinking of taking it in now, test it, demand replacment, see if that clears up both sets of issues... great job getting this post some attention and thanks to all the experienced ** owners to reply!

Hey guys, im sorry I hadnt been back on with crazy 16 hour days last week. Unfortunately it was not the alternator. I forgot to mention that i installed a new 875 amp battery as well. I changed fuel filter and alternator friday. I just was on the highway for firat time yesterday amd for about 2 minutes at 85 mph all was fine and then the cel started blinking again. At this point im thinking its one of 9r a combination of cats, o2 sensors or fuel pump :-(

 

[Sgtduckyboy]

Hey guys, im sorry I hadnt been back on with crazy 16 hour days last week. Unfortunately it was not the alternator. I forgot to mention that i installed a new 875 amp battery as well. I changed fuel filter and alternator friday. I just was on the highway for firat time yesterday amd for about 2 minutes at 85 mph all was fine and then the cel started blinking again. At this point im thinking its one of 9r a combination of cats, o2 sensors or fuel pump :-(

I just replaced my MAF and my trims went from 22% to 10-12%. So now I'm ready to get this tweaked by Lewis over at diablewtune. Anyone here heard of him? So far he's been great and caught my lean condition and said it needs to be fixed before moving on.

 

[Motojoe86]

Thanks again everybody for all the insight. So far, still havent figured it out. Im gonna try to get it hooked up to run live diagnostics. Ill list current work done vs my next thoughts and continue listening to feedback lol. Thanks a lot guys!!!

Work done:
-new battery
-new alternator
-new belt
-new plugs
-new coils
-new wires
-cleaned maf
-cleaned throttle body
-oil change
-trans fluid and filter
-fuel filter
-air filter
-pcv valve
-fuel pressure regulator
-diffs and t-case fluid replacement
-fuel pressure test (idle and neutral acceleration)
-crankshaft position sensor
-im sure theres a few that im missing

Thoughts of work still to do:
-catalytic converter
-oxygen sensors
-fuel pump
-vacuum test (intake manifold?)
-timing?

I dunno. A lot of the stuff done, I dont mind too much as it clearly wasnt maintained by last owner and needed a lot of it. Starting to get quite expensive and frustrating now. Truck is supposed to become my daily driver but I have been driving my tundra til I can trust this. Appreciate all tye suggestions and help you guys are giving. Sorry, some 9f this stuff is taking a little while and I cant check or update until i have the funds and time to do certain parts. Im fixing as my finances allow lol

 

[Motojoe86]

I just replaced my MAF and my trims went from 22% to 10-12%. So now I'm ready to get this tweaked by Lewis over at diablewtune. Anyone here heard of him? So far he's been great and caught my lean condition and said it needs to be fixed before moving on.

What do you mean your trims? Was that causing blinking cel?

 

[Motojoe86]

Also, someone tild me it could be sticking lifters... Does that seem inline with the symptom does anyone know? And if so, I presume theres no easyish fix for that without tear down? Thanks!

 

[Sgtduckyboy]

What do you mean your trims? Was that causing blinking cel?

I didnt get blinking CEL, i got solid on, but I had many of the same symptoms you have mentioned, thats why I was watching this thread. Do you have code reader, preferably one that can read data? I have the Autel AL619 https://www.ebay.com/sch/i.html?_fr...autel+scanne.TRS0&_nkw=autel+scanner&_sacat=0

Reading the 'trims' is where you monitor/observe your short term and long term fuel trims, STFT and LTFT. these are what the adjustments your PCM is making in order to keep A/F ratio at optimal 14.x to 1. so, if any sensor is reading badly, malfunctioning or sending a reading that is a result of another faulity part (gap in intake gasket for example) this will cause the PCM to adjust Air fuel mix to compensate. you monitor it warmed up in closed loop, at idle , 1500 rpm and 2400rpm to see where the activity occurs. in your case, it seems to be under higher load, low vacuum, high air flow, situation for example. You also could just be having misfires(but many things cause that i am finding out), thats what i see by a basic check. I had those too along with bad reading from MAF, our cases are similar possibly but may have different causes. you have done a lot, but cleaning your MAF can cause damage if you do it incorrectly or if its already damaged, it wont show as anything changed after cleaning if damaged/ or operating badly prior to cleaning. if you have a buddy with a working Tahoe, no CEL, try to trade parts, the MAF for starters. this thing, I am finding out can be a ***** to figure out and simply needs replacing. mine was $80 on amazon, opened box returned. i heard dont use aftermarket MAF's, only AC Delco/Delphi are recommended.
If anyone finds anything i said wrong, please correct. this is the first time I have tried to put this into words and may have missed something or be confused myself!
Thanks

 

[Sgtduckyboy]

Also, someone tild me it could be sticking lifters... Does that seem inline with the symptom does anyone know? And if so, I presume theres no easyish fix for that without tear down? Thanks!

Hmm, sticking lifters, can be fixed, if lucky, by trying different methods to 'clean' them.
back to the AL619, it will tell you which cylinder(s) is misfiring. this is a big key. if its one or two vs all, can you tell you if its isolated to cylinder(s) or global to the engine, thus helping to find the cause. MY AL619 told me it was cylinder 6 when mine went bad in November, which started my whole project to rebuild the top end. i couldnt tell where the god awful sound was coming from but i had misfire in 6. tore top end apart, there it was,, lifter to exhaust in 6 , stuck in the bore!

I would try the cheap/easy ways to fix the lifters. does it sound like they are clicking/clacking/ticking/tacking , at idle, cold, warm or at high load? does your oil pressure guage work? what is it reading(its not real accurate i hear)? does it move up when under accelaration or higher rpms? these would be signs its working and you have some oil pressure. thats going to be a key, i feel, to try to 'clean' the lifters using one of the various ways mentioned. One i would like to try if i ever need it, is using transmission fluid. its high in detergents and some have had success quieting their lifters down with it. its a flush, not a replacement! you can find that info if you search.

 

[iamdub]

As far as we know, the only code he's gotten is P0300 which is a random misfire. If it was a particular cylinder misfiring, the code would be P0301 for cylinder #1, P0302 for cylinder #2, etc. I'm sure he would've mentioned ticking if it was doing that.

Weak fuel supply and clogged exhaust present very similar characteristics, but I'm leaning towards a weak fuel supply or ignition failures. Again, a trained and experienced eye watching a live data stream should be able to find something fairly quickly. An odd signal from the crankshaft or camshaft position sensor, MAF sensor, MAP sensor, etc. right about the time it throws the misfire code should stand out.

 

[Sgtduckyboy]

More flashing CEL info:
http://www.tahoeyukonforum.com/threads/2001-tahoe-blinking-check-engine-light.28786/

As far as we know, the only code he's gotten is P0300 which is a random misfire. If it was a particular cylinder misfiring, the code would be P0301 for cylinder #1, P0302 for cylinder #2, etc. I'm sure he would've mentioned ticking if it was doing that.

Weak fuel supply and clogged exhaust present very similar characteristics, but I'm leaning towards a weak fuel supply or ignition failures. Again, a trained and experienced eye watching a live data stream should be able to find something fairly quickly. An odd signal from the crankshaft or camshaft position sensor, MAF sensor, MAP sensor, etc. right about the time it throws the misfire code should stand out.

That is not fully correct. My one code reader only saw p0300 but my other one read p0306. So, based on what I have seen, it's dependent on the code reader.