Engine Missing - results of all tests - Please Any Ideas!

[gottadiesel]

My issues began with a Lexus AFM question but have graduated to a whole different level, so thought it best to begin a new thread with a compilation of the process I have followed. Once again in-case anyone did not see the original thread, here is the link ( "http://www.supramania.com/forums/showthread.php?125196-Lexus-AFM-Clarifications-Please" ) and below are the list of mods and results of testing done in the last 48 hours:

1988 5spd 7mgte
Motor & tranny top to bottom complete re-build - Stock internals
Greddy 2.0mm MHG
ARP Head, Main & Rod Bolts
Upgraded oil pump (BP'd for higher flow)
Arizona Performance HF Oil pump hardpipe.
DM 57 Trim bolt-on upgrade
Synapse Engineering BOV recirculated with custom 1.5" nipple on intake
Alum 2.5" hardpipe & intercooler
AEM TruBoost
Apexi Neo
AEM Wide Band
Lexus AFM
Siemens 550cc injectors
AFPR
Denso MarkIV TT FP
Stage 3 Action clutch
Full 3" exhaust

Primary symptoms:

Missing during throttle run-up (not driving) and when driving. does ok under about 5% throttle then begins to start missing, more to do with manifold pressure or something not actual position of throttle.

The #1 spark plug was the only one turning black and would after a few minutes begin to foul, but with very little running time, i had a hard time telling if it was oil or gas issue. I could see an oily substance on the top of the #1 piston, all others looks clean. All other plugs were always clean, so my testing so far has been focused on #1

I did the following tests, not in this order, but based on following a path as I ruled out possible issues:

Compression Test at Operating Temp
#1 - 165
#2 - 165
#3 - 165
#4 - 167
#5 - 165
#6 - 170

Leak Down - I only did #1 and #2 so I have a comparison to one that did not appear to have any issues -

#1 - 10%
#2 - 12%

Pulled injectors, went to a specialty injector shop - had them do a flow test -
All flowed @ 559cc variance less than 2%

Fuel Pressure set @ 34lbs with vacuum
- CPS. rebuilt one from Halsupramk3, also replaced wiring back about 12" to rid harness of any corroded wiring that was found, no change when manipulating the wires going into CPS.
- TPS - re-calibrated last week , had a different issue with a serious stumble and it went away after resetting, also tested via code 51 when I just barely touch throttle pedal.
- Ingnitor - tested per TRSM - passed (including the 3vdc testing process)
- Coil Pack - tested per TRSM - passed
- Resistor Pack - tested per TRSM passed
- O2 sensor - tested using the mVA ratings per TRSM, seemed normal after EGTs got passed 600
- Changed all spark plugs - they are gap'd at .28
- Checked resistance of ignition wires - MSD8.5, also tried changing back to stock ones
- Switch far left coil pack for far right coil pack - issue did not follow
- Checked for any arcing by turning all lights off in shop so that is was pitch black - rev'd up motor, two of us watching from either side of car, no visible arcing
- Checked all grounds - I also adding additional grounding with a termination wheel at the battery (6awg wire), I added them to valve cover, alternator, plenum, another location on block.
- Was suspicious of vacuum leak, so took plenum and intake off, bought new gaskets, checked all surfaces, carefully put all back together, but no change on start-up. but the lower gasket was moist around #1 chase all the way the the atmosphere, the others were a little moist around chase opening, but only like 1/4". But this lower one was part of the kit, was a little cheesy so was glad to get better gaskets anyway for those pieces.
- Last test, not sure how accurate, but used a timing light while revving engine, to see if the missing was coming from the ignition side or the fuel side... seemed obvious to me that the light would be following when it would miss. #1 and #6 seemed to be the worse (which makes some sense since they are on the same coil pack, yet I switched them and problem did not follow pack) yet I was getting some misses in light on all of the wires I tested... No missing then coming down to idle (let off throttle) Not sure if a timing light can really keep up with that though??

I am also wondering if the missing is happening on all of the cylinders randomly, but there was some oil in #1 and #6 after initial runs to get everything seated in, so 1st set of plugs, #1 and #6 were black, others clean, next set of plugs #6 was clean now, but #1 black, but also now #6 piston had no visible residue, where the #1 still did, so wondering if that just made it worse for that one, as when it missed, it would also have oil or something thrown at it, so it would foul faster between the combination of the two issues at once.

Still no codes at this time, have had zero codes thrown since start-up.

I know that was a lot, but I want it to be clear that I have checked everything I could think of to check (so asking for help, not asking to be spoon fed lol)... Any and all ideas would be appreciated, even if they are far fetched (CajunKenny, that does not include you, as my flux-capacitor is working just fine :icon_bigg)

Thanks!

 

[gottadiesel]

I did want to add one point of interest, not sure it matters - This particular issue was not here before I tore car down and it was not here for the 1st 122 miles of break-in. Nothing significant took place when it this issue started. I was troubleshooting a lean condition issue, seemed to resolve that with added restriction on the un-metered air-path on the Lexus AFM and think perhaps I had a coupler that had wiggled a little loose on the IC piping etc... but one of the test starts, I noticed the missing started and has not changed or gone away since...

 

[gennro]

Find another AFM electronics and Ignitor and swap them out if you can ans see if the problem goes away.

Also what air filter are you using?

Also I really like your post actually made me want to help you out since you took the time to put together all that information to help troubleshooting.

 

[gottadiesel]

Find another AFM electronics and Ignitor and swap them out if you can ans see if the problem goes away.

Also what air filter are you using?

Also I really like your post actually made me want to help you out since you took the time to put together all that information to help troubleshooting.

Thank you, appreciate it.

Filter - AEM DryFlow

I was already working on getting the AFM electronics from earlier issue of Vf signals seeming to not be steady.

I was become suspicious of the ignitor, as I am sure you saw I did test it, but bench testing only can tests so much and when inconsistent could be issue of after it heats up from current running through it...

I was getting to the point of starting to throw some parts at it... but yeah it is nice having confirmation as to which parts... so I appreciate your suggestion.

 

[gennro]

Yeah 20 year old parts such as an ignitor or afm can do it.
Now what you can do is start the car and unplug the AFM and see if your miss goes away.

Then for your ignitor use a heat gun and a ice pack and add heat or cool it and see if that changes anything.

 

[gottadiesel]

Aw yeah good idea... so if you unplug afm, ecu just goes back to guess and runs down the middle for fuel (or is that just O2 sensor)? What input will it use to determine to add fuel?

I can use tech air on ignitor...

 

[gennro]

Aw yeah good idea... so if you unplug afm, ecu just goes back to guess and runs down the middle for fuel (or is that just O2 sensor)? What input will it use to determine to add fuel?

I can use tech air on ignitor...

Yeah the engine will run with the AFM unplugged after it is started.

 

[polobai]

ground your ignitor try some ngk 3330(old part #) plugs.

 

[gottadiesel]

ground your ignitor try some ngk 3330(old part #) plugs.

On Treo Device today, so hope it works ok to post...

Isn't the ignitor grounded through mounting? maybe there is an insulator, not with car, will check tonight.

I am using standard NGK coppers, new part # IIRC is 6282... at this time gapped at .28 was going to go down to .26 once broke in and boosting higher...

Thanks for suggestion

---------- Post added at 02:30 PM ---------- Previous post was at 02:25 PM ----------

Yeah the engine will run with the AFM unplugged after it is started.

Ok, I will try that tonight. Thanks

 

[polobai]

The ignitor is grounded through the mount but it's a weak ground...an electrical system is only as good as it's weakest ground

 

[Pokey2301]

i would say start with fuel pressure, my wife's car was doing something similar and it turned out to be her fuel pressure regulator

 

[gottadiesel]

The ignitor is grounded through the mount but it's a weak ground...an electrical system is only as good as it's weakest ground

Yeah good point, as you may have read, I added like 5 more grounds to my motor and accessories... so I will create a solid ground to the ignitor and see if that helps...

Quick turn around job came in, so looks like it will be tomorrow evening before I can touch the car again... I appreciate all of the suggestions so far, will come back with results when I have them...

Thanks

 

[gottadiesel]

i would say start with fuel pressure, my wife's car was doing something similar and it turned out to be her fuel pressure regulator

Thank you for the thought, I have somewhat ruled that out as it is a new Aeromotive Fuel Pressure Regulator with a gauge and it does hold steady during all operations.

 

[jdub]

Vf is used for O2 sensor feedback control - that is not your problem. Vs is intake air volume input - that is what you want to look at. I would start by simply unplugging the AFM connector and re-insert to insure a good connection.

The ignitor is indeed grounded through it's case - there's a write-up in the articles section on how to wire a proper ground. Not to sure if it will help, but it is a good idea regardless.

It is possible for your fuel pressure to be too high - 34 psi is a lot with the Lex/550 combo - yes, I remember your lean situation. I run 27 psi with that set-up.

 

[Pokey2301]

it sounded like a similar problem to my wifes car, but after reading more of the posts, i think youre on the right track

 

[gottadiesel]

Thanks Jdub for your time - see below

Vf is used for O2 sensor feedback control - that is not your problem. Vs is intake air volume input - that is what you want to look at. I would start by simply unplugging the AFM connector and re-insert to insure a good connection.

Yeah, I guess I was making sure that I was not peaking out the ECU trying to add fuel, as I assumed that it is best to be running at the 2.2vdc which is baseline fuel for the ECU... But yes my next game plan that I had not tested yet was to check the frequency of the karman signal to make sure the AFM is sending consistent signals and is not floating or fluctuating... make sense? I guess the big picture I was not sure if the AFM could trigger an ignition miss? perhaps I am missing a relationship dependency on the info that the AFM is sending versus what the ECU is telling the ignitor to do? But also big picture I wanted to test because of the other little issues I was having with mixture and holding a steady idle etc...

The ignitor is indeed grounded through it's case - there's a write-up in the articles section on how to wire a proper ground. Not to sure if it will help, but it is a good idea regardless.

Thanks - I will find the article and ground accordingly

It is possible for your fuel pressure to be too high - 34 psi is a lot with the Lex/550 combo - yes, I remember your lean situation. I run 27 psi with that set-up.

Hhmm I know it is set a little higher than ideal, but at this time if I lower it, it will barely idle and will start to falter if you rev it up for lack of fuel... but that may be coming back to an issue with the AFM and I am making up for it in pressure which in the long run I agree is a no no, so my hope is to find the cause of my other issues and when is starts running too rich then great can back it back off... not sure if that is logical or not... but was my game plan.

Also something a little puzzling, there is an adjustment screw on the throttle body that I have looked again and again in the TRSM and it does not even look like the picture in the manual has it. It is opposing the PCV vacuum connection and when you back it out, vacuum seems to increase along with idle and the opposite when you turn it in... So where would I find out how to properly set that, so it is not a variable in the equation?

 

[jetjock]

Since idle speed is ecu controlled the idle air bypass found on earlier throttle bodies should be fully seated (closed).

 

[gottadiesel]

Since idle speed is ecu controlled the idle air bypass found on earlier throttle bodies should be fully seated (closed).

Good to know - Thanks! I think the TRSM online is actually an 89 if IIRC, so perhaps why it does not show it... either way it is not fully seated so I will do so and reset EFI in case it altered it's learning process...

By tomorrow I should have 2nd ignitor and 2 additional AFM electronics so can rule those out or even better one of them fixes the issue...

Thank You!

 

[gottadiesel]

THANK YOU to all you helped out on this thread!

I drove it 40 miles today and no missing, no hesitations up to 5psi and 5k rpm anyway... :icon_bigg

So here is the situation, I know I will chastise myself 1st, I replaced two things at once before driving... Well yesterday I grounded the ingintor with JetJock's article, saw slight improvement, but no fix. Today I replaced the ignitor with a known good one, started it, seemed better but not perfect, then replaced AFM with a unknown one, but a stock supra one, versus a stock lexus one. I know it is said they are the same, although the last digit in part # is different... so either mine was no good or there is something different about them...

Anyway so after replacing both the ignitor and the AFM resetting EFI, NO MORE MISSING yipee

I still have some fine tuning, idles a little low and vacuum still shows a little low and a little lean at idle (but rich once I put the throttle into it, runs all the way down to 10 at 60%... but I will continue to do some fine tuning while I am getting it broke in... I am still waiting for my Neo to return from Apexi also...

Thanks again to all!!!