1996 Geo Tracker hesitation upon quick acceleration

[gorkyb]

I've been getting this severe hesitation, or loss of power if you will when accelerating rapidly only, when accelerating gradually there is no problems, the car does the same whether is cold or already warmed up, it does the same thing whether I'm driving or just idling in the driveway in neutral. Basic outpin test on the MAF passes, egr main stall test passes also. Scanner reads tps working. Any ideas?

[fixkick]

TPS?
the ECU can not warn of bad TPS only those totally shorted or open full time.

but all other odd things, it thinks the human is doing that and ignores most TPS glitches.

eg: fast foot fails. ECU thinks you did it slow; it dont know that until too late. (maf proves , reality late) (enrich mode failure)

eg2: Slow foot works. sure, that always works as that is the MAF'S job. enrich mode , is not active here.

the fast foot, adds fuel to the AFR, we before the MAF can react.
the TPS does that,
many bad TPS, 100kmiles. will drop out with a fast foot. (the carbon in side is worn) and are always intermittent at the time failed.

for sure this is spark drop out
or fuel starvation,
finding out which is hard.

since it wakes up, at WOT, then id say, its not spark. but

the top magazine guy on this is, a guy named WARREN (last name) at motormag
he uses 2 ways.
1: add propane at bog, (hose thru fire wall)
2: or use a fake TPS,

the first way proves its lean ,as you crack the propane valve. bang power back.
the second way
is a 5k ohm resistor in a box wire to the TP pin..

driver one drives, passenger 2, plays with pot.
driver 2 watches driver 1 and sees his foot move down, and he mimics this with his POT.
bang, fixed. bad TPS.
I have all his published articles. love that guy. they are on line too.

he does the same with bad MAF or bad MAP. same trick. (the trick if substitution, and not a new $200 TPS) or $1000 MAF.

[gorkyb]

Seems like spark to me also, you can smell the fuel coming out of the tail pipe. I will check out Warren.

[fixkick]

odd how P030x are not stored?, or in pending, watch the pendings carefully on 4wd cars, as the misfire monitor is , detuned for offroad.

there should not be a fuel smell. unless...
that smacks of RICH misfire, flooding... (not TPS glitching to zero and lean)
this sounds like rich misfire or spark dropout , the latter does throw fuel the tail pipe. (rich misfire,is lost spark or out of control injection rates, pure rich) ECT at 180F,
the misfire cold and hot, tells me, its rich misfire. should be worse cold. rich+illegal rich, cold nets, huge rich.

A scan tool run live , when running car and moving will help here. you can see all the sensor data. and pendings popping in then off?

loss of power, is it bogging or misfiring, misfiring can always be felt. bogging is fuel starvation and is like towing a 2000 brick , linear, loss of power, not violent.
misfire is like running a chain saw with a bad spark plug.... heard and felt.

gradually there are no problems.
does this mean you have full power up a hill WOT> that puts max load on the injectors, and fuel pump and MAF; and acid test. for can I get full injections rates.
was ECU in closed loop before , you tipped in the throttle fast?
was LTFT looking good , at cruise, -4% not -40 or +40%
I have a scope and can find a bad TPS in a heart beat. that is why I mention Mr.Warrens tricks, Scopes see the error, but you can force the TPS signal to good and see the ECU wake up.
All sensors can be simulated, (no 02) but all the important ones. ECT,IAT,FAM,mAP, TPS.
watch for pending CKP or CMP errors. DTC 355 and 340? OTTOMH. any pendings at all, are worrysome.

pendings means , a failure I'M ignoring, (ecu is the IM)

the other trick is easy, per ASE or motormag doctrine.
if lean add fuel.
if rich?, add air.
at idle we add propane , if moving we can do that trick too. its not hard,just a hose added to a propane tortch, nozzle removed, hose on, crack the valve at the right moment.
add air. this is always easy, make a leak,
there are 4 or more vacuum lines, pull one and you have a leak.
can be done on the fly too. (helpers. make this oh so easy)

spark is first. if spark fails all other things are useless. fuel, air, good engine. all just windows dressing.
the spark must happen or the fuel can not burn. (otto cycle)

i have driven cars , many with a timing light duct taped to the hood or window of said car.
i drive, with the trigger duct tapped, on ...... flashing full time. (duct tape rules my life...???)
i drive, it misfires, , light looks happy.
i move the mag pickup to spark wire #2, and repeat, 4 times.
this is not an acid test , the spark can be weak and the light will flash, happy as a clam..... the test does add value..... if it fails. its a god send. to any diagnosis.

You had many distributor failures.
are you sure they are all corrected 100%
the rotor must not be firing between posts, no illegal , China rotors that do that nasty trick, the rotor must go on one way or all bets of.
1 way works perfect.
1 other way, the spark is dead.
1 other way, it misfires.
the side connector must be good and pins fit perfectly.

lest me explain the rotor tip the cmp reluctor star, device relation ship.
if you time the engine , this puts the cmp at the firing point, but if the rotor is wrong, it fires to the wrong cap point. (in one wrong case, spark must jump a huge distance..in the cap.. )
I played with one , doing it all wrong to see what would happen, it's a real bad deal.

the cMP star, is hard machined to the rotor mount, this is 100% fixed. and can not be changed. getting the rotor right, is a top deal here.
i keep mentioning this because there are 1000 of posts. from those that buy fleabay $2 rotors, and are not buying BOSCH. or better..

sorry if all that is sorted. but i think spark is bad. still. new stock spark plugs gapped at 0.028" or near) and no funny type plugs. real J plugs.factory type.

[gorkyb]

Hello! Well, I finally had a little bit of time to work on the Tracker, unfortunately the symptoms have been going from bad to worse. Originally the issues was what I stated at the beginning of this thread, however the issues are piling up now. To begin with, the car will not start unless I depress the gas pedal, I tried different settings on the pedal and either one works randomly to make the car start. Meaning I depress the pedal 100% and also around 20% and either one can fail or succeed in helping the car start, either way the car only starts if the pedal is depressed at some degree.

Then the car has an erratic idle, without me touching anything it will try to shut of on its own and then it will try correcting itself to remain running. It kept running but at some point it just shut off.

There is a code stored and one pending, both P0300, but the CEL is not activated on the dash board. I know the bulb is good because it comes on when I open the ignition.

I am attaching a screen shot of the freeze frame and screen shots of the obd2 scan while I had the car running at idle only, on these screenshots the car never left neutral and at some points I accelerated up to 4100 rpms (it cannot be seen on the screen shot of the RPM graph but that was the max value)

What I noticed on the scan is that the load is at around 20% when I think it should be less right? specially at idle. Let me know your thoughts.

---

continuation of screenshots

[fixkick]

hello and good morning Gorky.

most of all that looks ok. maf at .25lb/min is normal. and near 2 lbs, as you gun it , in neutral. all normal.

that right foot action is a bad sign, it say, engine is starving for air.
As you know the ECU set (and ISC) set up all air flow, to start, this is not happening.
This tells me:
the IAC is stuck closed or ISC is dead, and may be the idle switch not closed at idle (TPS) (if the switch dont close, the ECU will fail to operated the ISC correctly (dead ISC for start and idle)

if not a lack of air?, then the EGR is stuck wide open, (adding lots of air helps when this happens{EGR leaks}) with an index finger, exercise the egr main diaphragm
and see that it closes, (thunk closed) if not its bad.clean that.

if fuel pressure is good?, then you have plenty of fuel flow.

p300 freeze frame is just the last failure. recorded the last DTC. that failed stores a freeze frame.
What counts live DTC and pendings.

is car starting hot ok.? fails only cold?
are the spark plug fouling?
do you have full power, either hot or cold coolant.

Theory:
failed starts, can be flooding due to injector leaks.
and holding throttle WOT, ECU cuts all fuel , cranking, clearing said flood and a huge black cloud at tail, got black cloud?
if not, then it was not flooded ,
if WOT crank ups , start the car, it's means lack of air. why?

when you crank the engine, I believe the MAF is ignored and the ECU has rules for startup air, it has control of the isc and knows the behaviour
of the (thermal air rates) IAC, and adds an exact fuel rate based on some simple rules (a table) cranking. colder richer.
for a given coolant temperature, the fuel rate is fixed cranking , so if adding air helps that means lack of air,cranking (or EGR stuck wide open)

THE MAF IS pretty much useless at low cranking RPM/s 100 to 300 rpm , due to its non linear nature at that low speed, inaccuracy and just heating up.
This fact explains why the cranking rules are the way they are ( ISC, IAC, and temperature tables)
this knowledge help to understand , poor cranking performance.
Is is a 3 liter FORD MAF (ecu TABLE PLOTS, fooling the ECU. (this is very accurate, plot) shows the nonlinear nature of the beast.


good luck to you .

[gorkyb]

Thanks for the detailed explanation, I tried starting the car this morning and nothing, strong crank hit it doesn't start, tries test fuel and nothing, gauge shows required fuel pressure. Going back to my prior distributor problems maybe te fact that is raining all day today has something to do that I'm loosing spark? I will check into air starvation tomorrow. I think the only thing I haven't replaced on this car now is the ISC.

I clearly understand your last post so I will write down a plan to start testing tomorrow and report back my findings. Thanks again for taking the time.

[fixkick]

no spark , this is a flash back to no spark.
if compression above 150psi, It is.
and spark is good, it must run on test fuel (not flooding.)
did you not say the hood top rear gasket is no good, and that is not optional, the distributor is not water proof.

sorry no water allowed here, id get some shower seals or such in a pinch, see if i can seal the hood.

[gorkyb]

Did timing test with strobe light, spark and compression test just now.

Timing test results: strobe light with inductive clip on wire to spark plug on cylinder 1 showed 5 degrees retarded when cranking.

Spark plug test: First, all 4 spark plugs were wet with gasoline. While doing test I could not see a spark, maybe I did not ground the test spark plug properly, but I assume there is current going because otherwise strobe light would not light up?

Compression test: FI fuse and all spark plugs off, distributor unplugged. Results were as follows: 70, 165, 140, 150. Battery was getting kind of low by then due to all the cranking. Still cylinder one seems way out of spec. I did this test twice just to make sure, same results both times.

I hooked up the battery tender overnight. Next step, check timing belt? Also spark plug on cylinder 1 had a little bit of oil.

[fixkick]

hello:
some ,(most) strobes can be very sensitive, and can even fire off injector coils...
the test spark plug is the acid test. just a normal spark plug, not the modern huge gap test plug, for HEI.
your compression done , WOT, ?

the 150 is marginal cold, the 160 is ok 170 is min hot, but yours is cold the rings hate to seal cold.
70 must be not WOT? (hope) or lash set wrong. its not the timing belt cuz they'd all be very low, like all at 90 psi is very common, with belt /cam retarded as it loves to do.

the spark plug not fully shell grounded, will spark at the gap and the shell to nearest metal. or if held make you glow like lightning Bug.zap.

stock weak spark, not HEI , .028 gap.here.
http://www.fixkick.com/videos/neat/neat.mp4

HEI, no can do... this works on very new cars.
http://www.fixkick.com/videos/msd/test.mp4

all the best to you, and good luck !