Intermittant limpmode

[Azplinker]

Last couple of trips car will enter limpmode. I can reset it by shutting of the engine and restarting it, but it will return. To make it occur again, I have to drive it around. No CEL code that I noticed. Was thinking of leaving the diagnostic jumper in and driving around to see if a code gets set and I just missed it in the confusion of the traffic problems of getting off the road. Is that a good way to troubleshoot this or is there a better way?

[fixkick]

yes, drive with the lamp flashing 12, see if it changes,
keep in mind the early ECU can get lost.
it can also go to backup mode (CEL DEAD)

lost is , like the fuel pressure is real low or too high and it can't inject correctly and gets lost but keeps trying hard.

tell me how you know it';s in limhome?
http://www.fixkick.com/ECU/LimpHome/failsafe.html

one trick if 02 sensor is funky is to unplug it see if car runs better, or worse.

[Azplinker]

yes, drive with the lamp flashing 12, see if it changes,
keep in mind the early ECU can get lost.
it can also go to backup mode (CEL DEAD)

lost is , like the fuel pressure is real low or too high and it can't inject correctly and gets lost but keeps trying hard.

tell me how you know it';s in limhome?
http://www.fixkick.com/ECU/LimpHome/failsafe.html

one trick if 02 sensor is funky is to unplug it see if car runs better, or worse.

Car drops idle to 500 to 600 rpm. Won't accelerate past 2-2.5k rpm or shift up. Barely drivable. Was on on ramp so continued for two or three miles at maybe 15-20 mph. Got off freeway and shut off engine. Restarted and it drove fine for about two miles. Stopped out of traffic with foot on brake but didn't shift out of drive. Tried to leave but it was back in limp mode. Didn't think to check CEL light but shut off engine and then restarted.
Was able to drive normally again.

What do you mean runs better without O2 sensor plugged in? Just idling or actually driving around?

[Azplinker]

yes, drive with the lamp flashing 12, see if it changes,
keep in mind the early ECU can get lost.
it can also go to backup mode (CEL DEAD)

lost is , like the fuel pressure is real low or too high and it can't inject correctly and gets lost but keeps trying hard.

tell me how you know it';s in limhome?
http://www.fixkick.com/ECU/LimpHome/failsafe.html

one trick if 02 sensor is funky is to unplug it see if car runs better, or worse.

Car drops idle to 500 to 600 rpm. Won't accelerate past 2-2.5k rpm or shift up. Barely drivable. Was on on ramp so continued for two or three miles at maybe 15-20 mph. Got off freeway and shut off engine. Restarted and it drove fine for about two miles. Stopped out of traffic with foot on brake but didn't shift out of drive. Tried to leave but it was back in limp mode. Didn't think to check CEL light but shut off engine and then restarted.
Was able to drive normally again.

What do you mean runs better without O2 sensor plugged in? Just idling or actually driving around?

No codes when it goes to limp mode. Tried running without O2 plugged in. Ran terrible and smelled really bad.

[fixkick]

bad caps in ecu, like all do 1 time, 89-95
if you drive with that jumper planted, DLC conn. and the 12 cadence stops or skips mid-stride that is, CAPs bad (ecu crashing)
it must do 12s full time running, this is not hard to do and is first on the list, as is EGR sticking open.

there are lots of fail modes for stalling, over 50 most are inside engine, so if it runs ok , mostly, then it's not low compression. and is EFI related.
one other fail mode, is exhuast leaks. (#4 exhuast man tube cracked wide open sucking in air, causing 02 sensor lean and engine very very rich. misfiring, and wanting to flood out.
but the 12s is first.

the other reasons, front crank bolt loose and cam jump timing? some even jump back. most just go retarded cam and stay here. but not always.
bouncing cam belts are like drunk monkey.(unpredictable)
day one,? check it? that bolt at 94ft/lbs, 17mm head.

pull the PCM yet, and look for green death, (day 2 check)
see the hell page.

ok, the o2 out , was rich, very rich. implies it may be ok. the 02. but should not go way rich, (SEEMS exhaust is not cracked)

the FPR likes to jam this old and can jam either way, open or closed, (closed floods engine, but stuck open causes weak power dueo to low fuel pressure)
pull the PFR hose off, is the vacuum line leaking fuel, bingo.





http://www.fixkick.com/ECU/hell/html/index.html

ever do a full tune up,? with filters. air and fuel. all spark parts, and wire sets?

this ecu does not store DTC for long, like new cars.
and they can clear fast. hiding the cause, so drive with the jumper let it flash 12s. (or it goes dead, or?)
500 rpm mostly is EGR stuck open. i clean it and defeat it the prove is not cause, then put it back after i fix true cause.
500 can be flooding (spark tips soaked in fuel)
500 can be lost fuel pressure.
or stuck closed ISC, if the idle can be returned to 800 -1000 easy with your right foot, this is a sign that the isc may be stuck closed.

id be sure the crank bolt is tight, and 12 work running, first.

[Azplinker]

bad caps in ecu, like all do 1 time, 89-95
if you drive with that jumper planted, DLC conn. and the 12 cadence stops or skips mid-stride that is, CAPs bad (ecu crashing)
it must do 12s full time running, this is not hard to do and is first on the list, as is EGR sticking open.

there are lots of fail modes for stalling, over 50 most are inside engine, so if it runs ok , mostly, then it's not low compression. and is EFI related.
one other fail mode, is exhuast leaks. (#4 exhuast man tube cracked wide open sucking in air, causing 02 sensor lean and engine very very rich. misfiring, and wanting to flood out.
but the 12s is first.

the other reasons, front crank bolt loose and cam jump timing? some even jump back. most just go retarded cam and stay here. but not always.
bouncing cam belts are like drunk monkey.(unpredictable)
day one,? check it? that bolt at 94ft/lbs, 17mm head.

pull the PCM yet, and look for green death, (day 2 check)
see the hell page.

ok, the o2 out , was rich, very rich. implies it may be ok. the 02. but should not go way rich, (SEEMS exhaust is not cracked)

the FPR likes to jam this old and can jam either way, open or closed, (closed floods engine, but stuck open causes weak power dueo to low fuel pressure)
pull the PFR hose off, is the vacuum line leaking fuel, bingo.





http://www.fixkick.com/ECU/hell/html/index.html

ever do a full tune up,? with filters. air and fuel. all spark parts, and wire sets?

this ecu does not store DTC for long, like new cars.
and they can clear fast. hiding the cause, so drive with the jumper let it flash 12s. (or it goes dead, or?)
500 rpm mostly is EGR stuck open. i clean it and defeat it the prove is not cause, then put it back after i fix true cause.
500 can be flooding (spark tips soaked in fuel)
500 can be lost fuel pressure.
or stuck closed ISC, if the idle can be returned to 800 -1000 easy with your right foot, this is a sign that the isc may be stuck closed.

id be sure the crank bolt is tight, and 12 work running, first.

---

Changed bad caps last year per your recommendations. Pulled FPR hose and felt vacuum and idle speed raised to 2k. No fuel leaking. Have changed filters, fluids, wires and dizzy cap last year. Last issue was blowing out coolant so replaced 195* thermostat with 185* O'reilly one.

[fixkick]

Great the ECU wont crash, a key step, thanks.
the FPR, at idle, the pull vac hose (19"HG) drops vacuum to 0 and the fuel pressure will rise about 8psi. causing engine to go rich.
if engine was lean before(why is it?) (as the pulled hose will suck air causing leaner) the will raise RPM.
best is to pinch the hose then pull it. (preventing air leaks)

I think engine is lean: (the scan tool, if we had one, would tell us that fact)
but i bet it is lean. (low idle due to gross lean-ness.?)
top of list:
1 MAF reads wrong (low or only dirty) the tests are easy with a voltmeter. (Clean it from a distance do not spray"CRC maf clearer" close, stay 8"+ inches away. )

2 air leaks anywhere from MAF out, to head intake valves. but air leaks will not cause WOT powerloss, will not ! unless such leak is massive and bypasses MAF.

3 low fuel pressure. (it is dynamic pressure on all MPI engines(maf based) low pressure at idle and rises as vacuum "HG" drops.

4: DEAD INjectors, clogged, (do they all click)? leaking injector? (noid test passes, ohms of coil passes, 10ohms?)

MAF:
the maf key on is. key on only 1.0

[Azplinker]

Pre-warm idle is around 1200 rpm. Actually cleaned MAF with CRC mass air flow cleaner last week per your directions. Due to hesitation at WOT. Seemed to respond better after cleaning. Even put techron in tank a couple of times in the last month to try to improve performance. Have summit adapter and pressure sender on fuel rail but sender failed a few weeks after installing. Guess I need to replace that. Too difficult to get any response from Deft Racing supplier for replacement. Never answer email and no customer service. Considering the Rhino adapter. You think it will work ok?

[fixkick]

so check the output of maf, make sure it as the right voltage at 3 data points, keyon,idle and gunned.
yes that deft is daft. its just cheap china importer, and no real knowledge of part.
just use any pressure gauge, a pipe fitting from any gauge, even an oil pressure guage to 60 or 80 will work ,or the harbor frieght guage.
that summit racing fitting fits NPT threads, and all american pipe fits that.
never seen a Rhino adaptor but is in england, why buy from so far?

here is always to do it, i hope.

http://www.fixkick.com/INJECTORS/Schrader-vales.html

the summit fitting is Cream-de-la-cream, why need other part, very confused i am, why?

A 1/8" NPT pipe thread it is.


connect that to any guage, (real) by real i mean any bourdon tube guage.
air gauge.
oil gauge
hydraulic gauge.

first google hit
http://www.northerntool.com/shop/tools/p...aQodwjAAoA

at random,

nice gauge too.
all brass too. no junk plastic,

---

just to test
when done close off with 1/8" pipe cap plug. in the hole.
for next time.....
it is the best of best.

---

the best gauge for live data pressure driving is Stewart WARNER BUT ARE $$$$ , LIKE 10X THE DAFT GAGE.

---

I DO WISH YOU , GREAT SUCCESS !!!!

[Azplinker]

OK, here goes.
fuel press. @ key on= 41 psi
after 5 min key off = 40 psi
@800rpm= 40psi
@5000rpm no load= 38psi

MAF @ key on= 1.37 - 1.40V.
@ 1500 (cold idle)=2.30V.
@ 800 rpm = 2.12V.
@ 4500RPM (No load) 2.90V.