Question about 1985 Mercedes-Benz 190

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1990 geo prizm.sat for 2 years. black smoke, no idle at normal op temp. changed spark plugs, air filter, added fuel system cleaner, still same problem. it used to idle with ac on, but no more. any ideas

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Sounds like the fuel distributor is stuck ,you may need to open the air filter and check the big round plate and see if there is dirt on it, clean it and see if there is improvement ,also the air valve may be stuck shut right next to the air filter

Posted on Jan 21, 2009


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I have a 90 geo prizm I have changed the plugs ignition control module fuel pump and fuel filter the car runs for a few minutes till at normal temp then shuts down when put it in gear any suggestions

wow , year, body name Prizm stated, Prizm is a TOY corolla.
but not the engine, or trans.
my wild guess this is the TOY 4aFE engine. 1990
i have 50 guesses for you, would you like me to toss dice and spit one out? or would you like to try real diagnosis.?
your call.
using real tools, lacking tools, its impossible to do this.

sorry. EFI systems and ENGINES are complex with huge numbers of failures, possible.

sounds like an auto trans there, shifting from Park to drive..
Best is to say DRIVE,
and when you do that a huge load is put on the engine.
and if its stalls its cause by 1 of 2 reasons.
idle controls dead;
or engine is weak.
so if you use the fast right foot trick you lean which it is.
is engine rpm at spec, hot ?
is engine rpm at 800 or more in park.
when you shift to drive, the rpm most hold at 800.
if not the engine is weak for sure if the fast right foot cant make car move.
if the trick above works, i can drive using the fast foot trick, then we do idle speed controls tests.
if not (its misfire, caused weak engine)
the engine is weak, top reason misfire or under injected.
under injected is lean and bogging engine, and stalls.
the 50 other causes. starts now. or up to 10 more tests.

starts ok.
idle cold ok, no misfiring? or engine shaking
can you drive it dead cold???????????????
then are you saying only the hot engine , shifted to drive
causes a stall but not driving a cold engine>?

if all that is true, then use the hot right foot, happy foot.
you foot can in fact bypass the idle controls of all EFI engines made (gas).
This trick adds air and the ECU adds fuel matching your added air.
see how this magic works.?
so does it work. this trick.? i can drive now it a happy right toe?
THE key answer, to diagnosis.

and if you hear /feel or see misfire, that too is key and no blind net bunny can see this.
it must be seen and reported.
spark plugs gaped to spec>/? not guessing?
new spark plug wires, on a car this old the original are all DOA.
compression at 150PSI or more , at sea-level to 1000'feet.
if not , say so, and the readings as WOT. (open the throttle to do compression tests are its all just a wasted effort)
cap and rotor new, (26year old parts here are junk)

also battery voltage need to be 13.3v to 15vdc running.
if not ?and the alternator is dead, the voltage drops and EFI stalls the engine, so we always check system main voltage on all cars the run bad, and fuses.

we also check fuel pressure ! on all engine that flood or bog.
and the flash codes, (magic 1990 jumper clip flash codes)

Apr 25, 2016 | Geo Cars & Trucks

1 Answer

I have a 96 geo prizm and it cuts out and jerks at acceleration and wont pull a hill and stalls at lights

I would start with a tune up-fuel filter,spark plugs,fuel injector cleaner,air cleaner-then if your still doing the hurky jerky you may try replacing the fuel pump-Denny

Nov 04, 2013 | Geo Cars & Trucks

1 Answer

1990 Jeep Wrangler 2.5l idles rough/ black smoke/ fuel odor

You could pay a garage to diagnose the problem cheaper than throwing more parts at it.
The problems may be connected or they may be different issues.
Yes I would change the oil and filter, but first I would make sure the fuel system is not dumping too much fuel into the cylinders.
The O2 sensor helps the computer decide on how much fuel the engine needs, along with the other sensors. And you said you have already replaced the O2 sensor.
A mechanic would take a scanner and "read" the sensors and look for something out of normal range.
The fuel pump and fuel filter are off the list as far as causing a rich mixture goes.
I would start with the rich mixture and then see if fixing that issue takes care of the no start when hot issue.
Change the oil and filter first, and see if the injector is on too much.
You can watch the spray and tell - at idle it should be very light.
Also look at the engine temp - is it warming up to normal 195 degrees? Can you tell if the fuel pressure regulator is blown and pouring fuel into the throttle body ?
Without a scanner its going to be more difficult, but not impossible to diagnose.
Let me know what you find out.

Jul 23, 2012 | 1990 Jeep Wrangler

2 Answers

1990 Jeep Wrangler 2.5L Idles Rough/Black Smoke / Rich Fuel Odor

thrown parts never fixes cars. 50 causes, can be 49 time guesing wrong or worse added a new defective part to the mix.
yes finish the tune up, why did you do it last>? odd no?
vacuum leaks cause, high idle on all jeeps!!
and then the ECU sees bad idle and tries over and over to reach
700rpm (spec) and cant so hunts it (that hunting today is deemed ******* , ask toyota why , fines)
all vacuum leaks do that , if it sucks AIR , illegally it will do that.
illegalll means air not from the ISC stepper drive device.
bad hoses, bad gaskets what ever.

does engine reach and hold 180f coolant temperatures???
this is first. it must, does it?
ill not guess, I propose doing a thing called TESTING.
lots of thoughts, really .... here are mine, plus RENIX facts.
I owed 2 , 1988s, with dang REnix french EFI? a horrid system.
TBI is yours TBI not MPI? (count the injectors there) mpi is 4.
no sold scan tools work on it and no CEL lamp. on RENIX.
nor does the key on 3 times trick. work before 91, dang!
1991 it changed to far better and the 3 key trick works then...

black smoke is: (rich)
high fuel pressure. (id be all over this)
injector leaks, (do a leak down test )
ECT bad, e (old name CTS)
on a hot engine, it reads (ohmmeter tests)
25,000 ohms is wrong, for 0degr. F.
317 ohms is about par for 180f normal temp , is yours 300 hot unplugged??????. a simple 5 min test.
if not the thermostat is bad or CTS bad. (IR gun it to learn this)

i see that rough idle , its MISFIRING and its really flooding .
and black smoke is always results of that, and most CATcons this old are now dead, (cat converter on all mine broke-up to bits and gone inside, and stinks any time it's rich or misfiring) par for 90s./:

the 1990 wangler books are rare, but can be found on ebay
buy one is my best advice,

its and old jeep
and its best to check compression on all old cars.
did you? x5 warm or hot, and WOT tested, (throttle open)

the 2.5L most 1990(not 91)
have TBI and ****** RENIX EFI (French junk)
only jeep dealer scan tools work here, not you.

the injector must not leak. just 1 injector here,
(key off running does it dribble now? must not) looking with eyes./
(the SM is in my hands) service manual..
2.5L (NOT 4.2L)
conducted a tune-up last
cap,rotor, wires, sparks and filters is a full tuneup on any neglected 90s jeep.
good engine first
good spark
then fueling last.
order matters, on old cars,
new cps.
yes all injectors tick but yours has only 1.
and takes a stethoscope to hear. (or my mag sensor tool)

this AMC spark system uses and ICM 2.5L only
and 50 tooth CMP sensors in the Distributor. (CPS you called it?)

my guess you replaced the TDC sensor
TDC sensor (mounted at the rear of the engine on the flywheel housing) CKP its called today. (yes names all changed long ago)

in a real shop we sCOPE the spark to see if its ok.
then check
Fuel pressure, the EFI in this car can not correct bad fuel pressure
its blind to it.
this engine has a very odd TBI
it has a pressure test port
and a FPR pressure adjustment screw.

here are the SM words on this, and I quote.
Fuel pump operating pressure is 14.5 psi (100 kPa). The fuel pressure regulator is adjustable by means of a Torx® head screw on the bottom of the pressure regulator.
  1. Remove the air cleaner assembly. Remove the screw test port plug on the throttle body, then install a fuel pressure test fitting. Pressure test fittings are available at many auto parts stores.
  2. Connect an accurate pressure test gauge to the test fitting.
  3. Connect a tachometer to diagnostic connector terminals D1-1 and D1-3, then start the engine and accelerate it to 2000 rpm.
  4. Read the fuel pressure on the gauge. If necessary, turn the adjustment screw on the bottom of the fuel pressure regulator to obtain 14.5 psi (100 kPa) of fuel pressure. Turning the screw inward increases the pressure and turning the screw outward decreases the pressure.
  5. Once all adjustments are complete, install a lead seal ball to cover the regulator adjusting screw. Turn the ignition OFF, then disconnect the tachometer and remove the fuel pressure gauge. Install the original plug screw into the throttle body, then install the air cleaner assembly.

top is test port
bottom is adj screw. (this is like 1st test on rich fuel)

1: cyl compression at spec, WOT.
2: a real tuneup completed ,not just spark plugs. (ICM bad?)
3: ECT reads 300 ohms hot (CTS)
4: fuel pressure at spec. 14.5psi.
5: injector not leaking. (had bad fuel in the last year, or now?)
6: there are no sold scan tools work here, so id have to scope
all ecu pins to find cause. sorry but its sticking RENIX.

has the car sat unused for a year, ? no history
when was car a good daily driver, ? last decade? last week?

Mar 14, 2017 | 1990 Jeep Wrangler

1 Answer

Black smoke while pickup from low rpm.

black smoke generally indicates the engine is running rich (too much fuel) this could be caused by a number of things, I would start by changing the air filter and running some quality fuel system cleaner.

if that doesn't help then you might have a faulty injector(s) or it could be in need of spark plugs and plug wires. there are quite a few problems that could cause this, even something as simple as a coolant temp sensor being faulty.

hope this helps

May 24, 2011 | Toyota Land Cruiser Cars & Trucks

1 Answer

1997 Geo Prizm - does not start

sounds liike a fuel problem, turn key on without starting listen for fuel pump kicking on if it does now check the connections at the pump/fuse if it is kicking on the you can check the fuel pressure by checking the little valve on the fuel rail next to the intake looks just like the air valve on your tires if there is no pressure then check fuel filter.

Jul 15, 2010 | 1997 Geo Prizm

4 Answers

My girls 1990 Geo Prizm keeps stalling. After it sits for 10 minutes or so, it start back up, but sometimes will only make it a block or two before dying again..It is an intermittant problem, but it...

next time it stalls pull the plug wire from the spark plug. have an extra spark plug with you and stick it in the boot. lay it across a known ground and turn the car over. its probably not firing.. sounds like its an ignition module faulty that acts up when it gets hot

Jun 05, 2009 | 1990 Geo Prizm

1 Answer

1994 Metro Geo rough idling and lagging up hills

dunno if it'll fix it- but check your pcv valve - 5$ for a new one - also check your egr valve- should be able to move depress it with your finger- if not, carb cleaner is safe to use to clean it up- remove it and clean it. this should help the idle

Apr 17, 2009 | 1994 Geo Metro

1 Answer

Car won't start without adding gas to air intake then won't idle

Check the fuel filter, you may have clogged it when you filled the tank.

Mar 15, 2009 | 1989 Audi 90

3 Answers

1990 celica 2.2 5s-fe wont idle, wont erach 1400rpm

your problem is in your throttle sensor that controls the idle it is located right behind your intake and it has two screws that mounts it i am almost positive that this is where your problem is comig from

Dec 31, 2008 | 1990 Toyota Celica

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