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?