P030x, P0174 Can I use my electrical diagnostic tools better?
 

My vehicle is an 1997 5.4L F150 with 112,000 miles on the odometer. It
recently began stumbling (misfiring) @ 1500 rpm and @ idle (600 rpm)

So far a sampling of the diagnostics codes is;
- P0305 - cylinder 5 misfire
- p0308 - cylinder 8 misfire
- p0174 - system too lean bank 2

following the diagnostic protocol @
http://troubleshootmyvehicle.com/for...shooting-p0171
-and-p0174-page-1, I found that the Long Term Fuel Trim 2 was 10.2%
and the Short Term Fuel Trim 2 (SHRTFT2(%)) swung between -3.1% and
2.3% (indicating normal operation?) while the Long Term Fuel Trim 1
was 8.6% and the Short Term Fuel Trim 1 (SHRTFT1(%)) swung between -
2.3% and 1.6% (indicating normal operation?) but the Short Term Fuel
Trim 1 (SHRTFTB1S1(%)) swung between -3.9% and 10.2% (also normal
operation?). (What is the difference between SHRTFT1(%) and
SHRTFTB1S1(%)? - Autel AutoLink AL439 OBDII scanner)

I then induced a rich condition with a little ether starter fluid in
the intake through a recirc? tube and the pre Catalytic Converter
Oxygen Sensors, O2S11 and O2S21, moved up to .895V and .890V
(indicating normal conditions?)

That the misfires are all on one side seems to rule out problems with
the fuel filter/pump (correct?) The indicated problems seem to be;
- COP on cyclinders 5 and 8
- Timing chain components (unlikely because problem occurs with only two cylinders.

Two other observations/procedures;
- I cleaned around the throttle plate with carb cleaner which didn't
seem to make a difference
- I cleaned the MAF sensor by spraying sensor cleaner which didn't
make a difference but I noted that one wire is metallic but the other
is black (is this normal?)
- The scanner is also showing an Initial Tank Vacuum Vacuum Reading (MOD $10) fault with test pressure of -15692 Pa outside the limits of -2490 Pa to -1494 Pa and Vapor Generation Max Pressure Rise fault with test pressure of -15692 Pa outside the limits of 249 Pa to "unlimited" Pa. (Is this related to a leaky gas cap? or?)
- we also have an engine tic on startup

Are my conclusions correct so far?
What should I check next?
Are there other tests that I can perform with the scan tool (or scope) that might help in this case?
Would pictures of live data be useful? what parameters?

Thanks

Going about it backwards.

Make believe the 174 doesn't exist. 9 times out of 10, it will disappear after handling the other bank 2 DTC's.

Fuel delivery, Misfires are always first. Some might think, - Misfires on bank 2 should cause Rich DTC's vs Lean. Sounds logical , but it isn't how it works. That's another explanation lol.

Is it missing @ idle, -warm idle rpms are?

ANY other DTC's present or pending, - your monitors clear ?

Yea, these trucks aren't programmed to idle @ 600 rpms. So, answer what I got so far, try not to leave anything out.

It is missing @ low(warm) idle - which is 690 rpm. The recent DTCs after a suburban test drive are again P0305 and P0303 (pending). (Whats the difference between pending and set?) I am going to dump all variables to the PC - are there any graphs of one variable vs/overlaid on another that can help a diagnosis? Thanks

The story continues
 

I replaced the fuel filter - brown gas came out one end and the filter was hard to blow through - so it's time had come. Where does the brown color come from?

I tested the fuel pressure at the rail - it idles @ 29 psi and it shoots up to 36 psi when revving the engine to 2000 rpm and when the ignition key is first turned on.

The pending code is still P0305 - no other codes set. The model year is 1998. The vehicle misfires and is sluggish @ 1200 - 1600 rpm when driving, surges @ 1500 rpm, but seems to have power if I can accelerate past 2000 rpm.

Could the fuel pump cause all these symptoms? Why are no other cylinders misfiring? What do you suggest I test next with the scope, code reader, or stethoscope preferably?

Thanks

I would say that you have a problem with either the plug or the COP. I would remove the plugs, clean out the plug socket with WD40, a round plumbers wire brush, and rags. These plug sockets accumulate a lot of dirt and debis over the years and your plug may not be getting a good seat. Either put in a new plug or clean up and re-install the old plug and torque it back down. Use di electric grease at the connection between the plug and the COP. Clean the COP connection before adding the grease and re-install the COP. If it does not fix the problem, try switching the COP's with the COP's on other cyclinders and see if the misfire travels with the COP's. If they do, change the COP's

Since it went all of a sudden, I think you have a problem other than the COP's both going bad at the same time.

You should also run a bottle of injector cleaner through your next tank of gas. the miss could be from clogged fuel injectors.

I do not know your truck but if your engine is real dirty, no new plugs for a while, no changing the fuel filter for a while, this will give you a hint on where the problem is coming from. If you fix the misfires you will most likely clear the P0174 code.

Nice to See If My Advice Solved The Problem So Im Doing the Same For All
 

Caveat: The remedy below worked, however, it may not be the root problem - Ill keep checking.

Remedy: I replaced two COPs and plugs on #5 and #8 that were showing P0305, p0308. The plugs had some "dry sooty carbon deposits" - Haines indicating "a rich mixture and weak ignition" - Haines. The gap on the plugs was ~.07 vs ~.062 on the new ones - may be my measurement. After 20 minutes city driving no codes were set and idle and firing under acceleration, now seem smooth.

JBrew, you were right; code p0174 was not a prominent symptom - it went away by itself in the end. If anything, misfires on bank 2 caused a lean DTC to be set.

Frank_Ford, you said, "Since it went all of a sudden, I think you have a problem other than the COP's both going bad at the same time" - #8 was not as frequently identified with a code as #5. Your comments make me think that it might have been the plugs and not the COPs. You are right, by not changing, more than one thing at a time, I could have identified the probable cause i.e. plug or COP. After changing out the plug on #8, way at the back, I was in the mood to replace both COP and plug. From what information I have, should I anticipate plug problems on the other cylinders.

Thank-you to you both

Re graphical indications of this problem, I still haven't graphed the data, and the question is still open in my mind - "are there any graphs of one variable vs/overlaid on another that can help diagnose these kind of problems"? I found the report @ http://workshop.search-autoparts.com...76047&d=151503 very eyeopening in this regard - someone else that would rather analyse until just before paralysis set in before picking up a wrench.

Thanks