How to use EFIlive to debug a flashing 'service engine soon' light.

[bubba68ss]

I am trying to diagnose a flashing SES light which i get while cruising at about 2600 RPM's on the freeway. Can anyone recommend the best way to do this? From what I have read it has something to do with a misfire (but I am not getting any stored codes). How do I monitor for this condition? Is there a cylinder misfire count I can watch for? Unburnt fuel number?

[joecar]

Flashing SES = misfires detected

With your EFILive scantool, connect and click the OBD tab, and see what DTC's are read.

Some PCM's support a per cylinder misfire count, on the PIDs tab look for the pids MFCYL1C, MFCYL2C, ...

[Gregs]

I am trying to diagnose a flashing SES light which i get while cruising at about 2600 RPM's on the freeway. Can anyone recommend the best way to do this? From what I have read it has something to do with a misfire (but I am not getting any stored codes). How do I monitor for this condition? Is there a cylinder misfire count I can watch for? Unburnt fuel number?

Flashing check engine light will be a random misfire. I've found it best to diagnose misfires the old fashioned way, the misfire counts can't be exactly trusted. I would check your intake gaskets, fpr, maf/map, etc...

[joecar]

Gregs has a good point.


If you can't find the cause, you'll have to also do compression/leak down tests, check your coolant level.

[bubba68ss]

I have about 4k miles on this engine. i did the swap in August, I'm hoping gaskets are holding up... It's weird, I am not getting any p0300's or anything... I do not feel any misfires either. I even looked at the LTFT's on my scangauge II (I have mounted to my dash) while the SES was flashing and and they were within specs.

Besides a cylinder not getting spark or fuel, what else could cause a misfire? You mentioned a compression test? The only thing I have noticed that is odd is my oil was getting real dirty real quick but I did have a bad leak and it was also a fresh rebuild... As for wiring, I added two additional injector wires but I soldered and heat shrinked them.

[ScarabEpic22]

So this isnt in a stock vehicle? Do you have headers?

[bubba68ss]

So this isnt in a stock vehicle? Do you have headers?

It's a 99 s10 with 0411 PCM and a 5.7 with a 2002 Chevy express tune.

[joecar]

oil getting dirty quick = compression/blowby leak

[bubba68ss]

oil getting dirty quick = compression/blowby leak

Exhaust gas getting past the rings? Damn. Engine has new rings, valve seals, everything.

[bubba68ss]

Just did a dry compression test and the cylinders ranged from 165-180. Can I rule out any 'blow-by' or leaky valves? Does that rule out the engine internals?

[joecar]

That's only an 8% spread, so compression is ok... what about leakdown...?


Are you losing coolant...?

What is fuel rail pressure...?

Do plug wires and coils pass the dark test (external arcing when viewed in darkness)...?

Does MAP follow vacuum hand pump (while viewing on scantool)...?

Does TP follow throttle movement (while viewing on scantool)...?


What are LTFT''s and wideband AFR when problem occurs...?
Do you have a log file...?

[bubba68ss]

I will check those next. I did find one spark plug resistance at 7.3K Ohms. The rest were at or a little below 5K Ohms.

[bubba68ss]

Leakdown test produced between 4-7% and one 9%. I read that under 10% is acceptable. Did I do it right? I set compressor to 110psi, went through a regulator set to 100psi on the gauge after it and hooked to cylinder at TDC and recorded the psi drop. most dropped to 94. unplugged it from cylinder at it rose back to 100. The harbor freight leak down tester was very flaky so I had to do it this way.

Fuel pump primes up to 60 then drops to 55 with key on. While running, it reads 49-50 psi.

Not losing coolant.

I see no arcing, but when I had the coil wire disconnected and moved away I was cranking the engine and coil was arcing to the heater hose (arcing to rubber?) which was pushed right up against the coil. I re-routed it.

TPS follows the scantool.

MAP hasn't been checked.

LTFT's are around 4 and 8 when the light starts flashing.

No wideband reading yet. Will get the wideband and the MAP checked this weekend.


That said, do my tests indicate any problems? I am about to drive the same stretch of freeway tonight and I will check for problem again.

[joecar]

Leakdown is acceptable.

Running rail pressure should be 58+/-1 psi... 49-50 psi seems to low (about 20% too low)... what pressure is spec'd in your service manual...?

Ok, retains coolant, does not burn it.

Be careful don't let coils not have a path to ground (disconnect the primary, either at the coil or at the common subharness connector);

These coils are able to produce sufficiently high voltage to make rubber heater hose conduct (50kV+)...

if the coil does not have a secondary path to ground, it can arc internally (causes internal damage).

[hog]

Agreed, Vortec 350's should read around 58-62 psi at idle and should read at about 62-66 psi at WOT or KOEO(key on engine off-or with pump running, engine not running). Pressure should rise quickly when throttle is quickly snapped open when engine is running.

+1 on these coils being very high on the voltage, its the same coil as used on the GEN 2 LT4 engines.

peace
Hog

[tokymon]

you can log misfires in the scanner its not hte most accurate

[joecar]

Agreed, Vortec 350's should read around 58-62 psi at idle and should read at about 62-66 psi at WOT or KOEO(key on engine off-or with pump running, engine not running). Pressure should rise quickly when throttle is quickly snapped open when engine is running.

+1 on these coils being very high on the voltage, its the same coil as used on the GEN 2 LT4 engines.

peace
HogSo your FPR is manifold referenced...?

If so, temporarily remove the reference hose and measure rail pressure (base pressure), it should be a steady value...

and as you rev the engine (with hose removed) rail pressure should remain steady.


With the reference hose connected, rail pressure should equal base pressure minus MAP.

[THEFERMANATOR]

Agreed, Vortec 350's should read around 58-62 psi at idle and should read at about 62-66 psi at WOT or KOEO(key on engine off-or with pump running, engine not running). Pressure should rise quickly when throttle is quickly snapped open when engine is running.

+1 on these coils being very high on the voltage, its the same coil as used on the GEN 2 LT4 engines.

peace
Hog

I've checked quite a few 5.0 and 5.7 vortecs with the injectors in the intake, and every single one has idled around 49-52 PSI, and jump to about 58-60 when you snap it WOT. Also you may want to try another distributor cap. The stock crab cap with the corrected firing order is notorious for random misfires.

[hog]

So your FPR is manifold referenced...?

If so, temporarily remove the reference hose and measure rail pressure (base pressure), it should be a steady value...

and as you rev the engine (with hose removed) rail pressure should remain steady.


With the reference hose connected, rail pressure should equal base pressure minus MAP.
The stock Vortec 4.3/5.0/5.7 has its vacuum referenced FPR actually inside the plenum, there is no hose that can be attached or detached.
So with these engines, base pressure is achieved by testing fuel pressure with the engine off and with the fuel pump running.

You can see it here on the left side of the fuel distribution block.
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/injectordebris.jpg

Here is the Vortec 305/350 L30/31 intake on the right side with its upper plenum installed enclosing the FPR/poppet spider. The intake on the left is a marine 305/350/383 built by GM for Mercruiser. It has a vacuum referenced FPR with the hose that you mentioned, on a stainless steel conventional MPFI fuel rail with injectors that can be upsized. The stock marine injectors are 24 lb/hr(28.4 at 4BAR). The marine FPR runs at 58psi(4BAR)(base pressure) and at idle runs at around 51-52 psi with the vacuum reference attached. I have 1 of these intakes on my 97 rcsb. It doesnt have the intake spider inside the plenum. It breathes better than the stock truck intake making better low rpm torque and marked upper rpm power. The stock intake causes over 5000rpm performance loss. The stock intake limits injector choice. The stock poppets flow 22.? lb/hr roughly.
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/marineL31endtoend.jpg

Here is a pic of the marine intake lower, it is much cleaner than the stock truck intake without all the injection "debris" impeding airflow..
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/insidemarineintake.jpg

peace
Hog

[hog]

I've checked quite a few 5.0 and 5.7 vortecs with the injectors in the intake, and every single one has idled around 49-52 PSI, and jump to about 58-60 when you snap it WOT. Also you may want to try another distributor cap. The stock crab cap with the corrected firing order is notorious for random misfires.
I have 3-1997(3 L31 350's) and 2-1998(1 L31 and 1 L30-305) within eyesight, they all idle around 58-60psi and when revved quickly, they spike up to around 65-66psi. With the engine off, fuel pump running(KOEO-or Key On Engine Off-taking the reading while the pump is priming, it only primes for 2 seconds if you bump the starter or turn the key to the run position). KOEO is akin to removing the vacuum reference hose on other vacuum referenced FPR setups.\
The FSM's and Chiltons give a fuel pressure spec of 62-66 psi.
49-50 psi is too low IMO. These poppets are not opened electronically like conventional injectors with pintles, tehre are poppet valves at the end of the spiders legs that are opend via fuel pressure. They start to not open as fuel pressures fall under 45 psi.
I wonder why our numbers are so different?

There is/was a campaign for the California registered vehicles that run the CSFI(Central-port Sequential Fuel Injection) from 1996-2002. The MTBE Cali gas would clog the CSFI spiders, so GM developed an MPFI conversion spider that replaces the CSFI poppet spider with an MPFI spider. Because this was an emission issue, GM replaced the CSFI units with MPFI under warranty up 100,000miles IIRC. The MPFI spider replaces the poppets at the end of the spider legs with miniature versions of conventional pintle fuel injectors. These MPFI spiders flow the exact same as the poppet spider and have the same 62-66 psi fuel presssure spec as the CSFI spiders.
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/spidercomparo.jpg
Stock CSFI spider on top, MPFI conversion spider on the bottom.

I just did a quick search and found this article. It has cross sections of the actual poppet.
http://www.off-roadweb.com/tech/1012or_csfi_to_mpfi_vortec_engine_fueling_fix/

peace
Hog

[joecar]

Hmmm, interesting.

[bubba68ss]

I found my problem... I'm surprised this wire passed the OHM test a week ago. This was hidden by the heat sock. It started arcing out through the sock onto the header pipe. This was #2.

14461

[hog]

Great, congrats.

peace
Hog

[joecar]

Glad you found it :cheers: thanks for posting what it was.

[Mikz86ta]

That'll do it. I have had my share of 4.3 headers and plug wires doing battle in the heat of the moment...pun intended :)

[joecar]

lol at the pun :)