Introduction and a question on poor starting.

[fixkick]

ok, 2nd one this week posted this forum, a trend , ? im so glad its that, no not something serious like bad injectors or flaky.

[renaissanceman]

I replaced the FPR this evening after work, it did not totally solve the issue, just changed it a bit. My long term fuel trim was 0.0 before the new regulator, and now it sits at 15 or so at idle. This indicates I have a fairly sizable vacuum leak?

I pulled a vacuum line while the engine was running to see what it did to the long term trim (it increased it as expected), and it made a distinctive hissing sound. When I put it back, I realized that the sound decreased in volume, but did not stop entirely. The idle is low across the board, with the A/C engaged it only can get it up to 900 or so now. Sigh.

[fixkick]

+15 or - 15,?

+ is adding fuel, if the 02 is old , the trim numbers will be wrong. the ECU assumes the 02 never lies or gets old.
im confused now, 2 trackers,
ok its the 96,
the G16b MPI engine the FPRreg is a very dynamic device, it increases fuel pressure 6PSI at wide open throttle.

yes, pulling vacuum line cause lean, big time, best is not to do that unless you wanted lean. LTFT will go PLUS side to match leak.

is o2 new? not 18 years old. (hopeless that)
is #4 exhaust tube cracked, like most are (from port 6 inches down hidden under shield"?)



idle is low across the board (how low, 800 or 500 ? or?)
ok the ecu can not control idle,
scan tool shows no DTCs, so its not in limphome, so idle controls are active hot, and must be 750 to 850 steady.

the perfect running engine runs -5 LTFT. (MINUS)
this this means the naturally rich MAF< (by design) by +5% is sucked back to STOICH by using -5% TRIM. (o2 good, or all readings are useless)
when you accelerate, or go WOT, the MAF rules AFR. and is +%5 rich or AFR 12:1 or near. closed loop is canceled now.
if the maf is lean you burn exh. valves fast. (flogged )
in closed loop the maf errors (by design) is compensated to STOICH. (at hot idle and light cruise steady right foot on flat ground)


I test (im sure yours is good now) at key on, leakdown test done then ,idling, the 1/2 throttle and gunned to WOT for 1second to see if fuel pressure are good for MPI.
this MPI does not like air leaks, all air leaks must be corrected by O2, if it can correct then it will go lean and bog or in some cases go rich and make more power.

---

is engine still starting slow?

i forgot to say in first post

is CLosed loop ok hot idle (CL = true) on scan tool?
and idle is bad.
hard starts still>


if CL is failing, i fix that first, find out why ECU sees sensors wrong, or are wrong.

that bad idle is for air leaks or CL is dead.
if CL is dead, that means AFR is out of control. that is why i fix that first. IDLE IS ALWAYS last, to fix and work right.

things that can make CL fail. (all G16b not just yours)
biased 02. (18 years old, sure)
air leaks from MAF to intake valves, every inch (air density system it is)
MAF weak. (or just dirty)
dirty injectors.
leaking injectors.
#4 exhaust port tube cracked, or any air leaks hear 02, upstream from exhaust ports to CAT brick.
(ill not list fuel pressure, im sure you checked it at 4 states at least)
ECT fibbing , no .
IAT fibbling ,no, in fact missing on 92s so only makes minuscule corrections.
isc sticking,


keep in mind EFI stuck rich may run beautifully, the engine makes max power at 12:1, so if stuck there, it does make more power, STOICH is max Mpg , in smog.

to get hot idle to 800 rpm? try turning the bleed screw, CCW, id count turns first. key off from closed (CW)
this is idle duty cycle set screw. but is air bleed.
get idle to 800 , so is it closed loop now? hot idle, if not we need to fix that.

as you turn screw, expect ECU to suddenly gain control of idle, the ECU is hard coded to 800 and the CKP sensors tells it RPM and with those 2 facts
it works full time servo mode to hold idle at 800. if it cant hold this speed it is because, of
1: egr leaking. (main)
2: or isc cant close. (common)
3: lean AFR , and CL false. (dead CL)

how is that.?

[renaissanceman]

+15 or - 15,?

+15

+ is adding fuel, if the 02 is old , the trim numbers will be wrong. the ECU assumes the 02 never lies or gets old.
im confused now, 2 trackers,
ok its the 96,
the G16b MPI engine the FPRreg is a very dynamic device, it increases fuel pressure 6PSI at wide open throttle.

yes, pulling vacuum line cause lean, big time, best is not to do that unless you wanted lean. LTFT will go PLUS side to match leak.

is o2 new? not 18 years old. (hopeless that)

Brand new Bosch O2

is #4 exhaust tube cracked, like most are (from port 6 inches down hidden under shield"?)

Actually, the exhaust is cracked on that runner. O2 sensor reads properly, though.

idle is low across the board (how low, 800 or 500 ? or?)
ok the ecu can not control idle,
scan tool shows no DTCs, so its not in limphome, so idle controls are active hot, and must be 750 to 850 steady.

low by about 100 across the board now -- 700 in park, 900 with the A/C on. (it used to be 800/1000 before the new regulator...) [/color]

the perfect running engine runs -5 LTFT. (MINUS)
this this means the naturally rich MAF< (by design) by +5% is sucked back to STOICH by using -5% TRIM. (o2 good, or all readings are useless)
when you accelerate, or go WOT, the MAF rules AFR. and is +%5 rich or AFR 12:1 or near. closed loop is canceled now.
if the maf is lean you burn exh. valves fast. (flogged )
in closed loop the maf errors (by design) is compensated to STOICH. (at hot idle and light cruise steady right foot on flat ground)


I test (im sure yours is good now) at key on, leakdown test done then ,idling, the 1/2 throttle and gunned to WOT for 1second to see if fuel pressure are good for MPI.
this MPI does not like air leaks, all air leaks must be corrected by O2, if it can correct then it will go lean and bog or in some cases go rich and make more power.

---

is engine still starting slow?

The engine starts easier, and the hunting/bouncing idle is gone. It still doesn't rev up past 1200 when stone cold.

i forgot to say in first post

is CLosed loop ok hot idle (CL = true) on scan tool?
and idle is bad.
hard starts still>

The car holds closed loop just fine.

if CL is failing, i fix that first, find out why ECU sees sensors wrong, or are wrong.

that bad idle is for air leaks or CL is dead.
if CL is dead, that means AFR is out of control. that is why i fix that first. IDLE IS ALWAYS last, to fix and work right.

things that can make CL fail. (all G16b not just yours)
biased 02. (18 years old, sure)
air leaks from MAF to intake valves, every inch (air density system it is)
MAF weak. (or just dirty)

Cleaned the MAF -- it reads about .4 lb/min at idle

dirty injectors.
leaking injectors.
#4 exhaust port tube cracked, or any air leaks hear 02, upstream from exhaust ports to CAT brick.
(ill not list fuel pressure, im sure you checked it at 4 states at least)
ECT fibbing , no .
IAT fibbling ,no, in fact missing on 92s so only makes minuscule corrections.
isc sticking,

I'll test the duty cycle of the ISC and then pull for cleaning. PO may have screwed with the bleed screw to compensate for FPR leaking a ton of raw fuel into the intake...?

keep in mind EFI stuck rich may run beautifully, the engine makes max power at 12:1, so if stuck there, it does make more power, STOICH is max Mpg , in smog.

to get hot idle to 800 rpm? try turning the bleed screw, CCW, id count turns first. key off from closed (CW)
this is idle duty cycle set screw. but is air bleed.
get idle to 800 , so is it closed loop now? hot idle, if not we need to fix that.

as you turn screw, expect ECU to suddenly gain control of idle, the ECU is hard coded to 800 and the CKP sensors tells it RPM and with those 2 facts
it works full time servo mode to hold idle at 800. if it cant hold this speed it is because, of
1: egr leaking. (main)

EGR was pulled, cleaned and seems to be ok -- it stalls the engine hard when pressed open by hand.

2: or isc cant close. (common)
3: lean AFR , and CL false. (dead CL)

how is that.?

Thanks for being so helpful!

[fixkick]

It still doesn't rev up past 1200 when stone cold.
that is odd.
very odd. even with new FPR.

is fuel pressure rising?, with right foot action.? from say 30 psi idle to near or near 36 psi gunned, (in park) for 1sec. slammed wot? not over revved.

+15 trim hot. why is it adding so much fuel. odd that too. seems the o2 sensor is crying way lean and adding fuel to correct that. -5% is best.(about)

so unplug the 02, drive, dead cold , go over 1200 rpm, .? if yes, now you know why, 02 is fibbing lean or is lean.

on the old 95s, the 02 can cause horrid rich running. with exhaust leaks.
on 96+ its limited, and if to far off the LTFT over limits hit and you get the DTC to match./

the o2 sensor comes on line in say 10 seconds from cold start, ive no idle how that effectt cold running mode. at all.
i thought not until 150F is crossed, but not sure.
but id unplug it. and test.

i bet PO fiddled the bleed to hide, FPR issues, too.. 700 rpm is not super low, and will run there, fix later.

[renaissanceman]

So I makeshifted a smoke machine using a peanut butter jar and a pack of cancer sticks and found nothing.

I then jumped terminal 2&4 on the diagnostic terminal intending to check duty cycle of the ISC, and it immediately killed the engine. I found that strange, so I backed the bleed screw out two turns, and the engine was able to run with the jumper in place.

When I checked the voltage across 6&4, it showed a duty cycle of ~80% even with two turns of the screw (!!!!). Turns out that some PO turned the bleed screw all the way closed! Another turn or two out and I was getting 50% duty cycle and very nicely regulated 800 rpm idle.

With the jumper removed, it regulates very well and runs MUCH better. When started hot the rpm jumps to 1200 momentary and then settles at 800 without any hunting! We'll see how it starts cold, but I think this one may be solved.

[fixkick]

oh gawd, I love these ideas. home made anything.
so you were right, they used bleed to hide other problems, great, 800 is happy feet.
the isc was doing all the air work. on hot starts, overloading, it. my guess causing rich cranking. (the 16 has no dash pot to add air cranking)

[renaissanceman]

oh gawd, I love these ideas. home made anything.
so you were right, they used bleed to hide other problems, great, 800 is happy feet.
the isc was doing all the air work. on hot starts, overloading, it. my guess causing rich cranking. (the 16 has no dash pot to add air cranking)

Yep, I made it today using 5 feet of 5/16 ID vacuum line, a peanut butter jar, some wet paper towel, JB weld and a pack of cheap smokes.

Bursts of air were provided to the left line by a small 12v air compressor, which pressurized the jar, forcing air through the burning cigarette and into the PCV barb through the hose on the right. Took about 15 minutes to build, another 15 for the glue to cure.





Took about 15 minutes to build, another 15 for the glue to cure. Cheap, easy and it worked pretty well for a one time use kind of deal.

[renaissanceman]

Cold start is 1500 RPM. All is well!

Thanks a million, as usual.

[fixkick]

a smoke machine , for near free. can save huge labor. finding leaks.

now engine , needs Nicotine Patch , LOL !@