85 xj6 4.2lt. fuel injected, (Problem will not start cold), Condishions.. Good fuel pressure, Good spark, Timing set at 10deg btdc, New injectors, and injector plugs ends have been tested "good" with diods, Oil fill cap tight, Crank case vent boot good, No vacume leaks, Alt air valve working withen specks, No exhoast leaks. I'm at whits end with this one, any sujestion.

model car not told. guess pickup truck , a USA car?
cam timing wrong?
32 years old when did it last run perfectly last month, year ,decade?
2.4L engine.

back fires to tail pipe end or inside muffler.
and backfire to air cleaner too?????? that is not a good sign ever if true. (bad valves or timing to them wrong)

FPR bad, can cause huge fuel injector pressure and flood the engine. fast.

no car this old do I touch and not do a compression test first
done WOT, sparks out.wide open throttle
all over 150PSI and near equal
and make sure cam chain is not a train wreck, and guides etc there.
filters and spark plugs and wire sets new.HV wire sets..
fuel pressure at spec,(FPR this old is NO GOOD)
check for bad fuel or evidence it was bad.
where is this air mix thing? air bleed on throttle body>?
got 4 injectors or 2, 4 = MPI and 1 or 2 is TBI (injectors on throttle body)
1991 is a bad year huge changes in fuel injection types. 1 year.
I can not see under your hood and go MPI/or TBI or SFI


FPR is the fuel pressure regulator , but not the same on all injection types this year.

what timing are youtalking
ignition or valve ?
10 degrees btdc is about right so check for other problems like crank /cam sensor position sensors , immobilizer ,or ignition control module

Check fuel pressure regulator. The actual pressure with a gauge the clean injectors. I'd double check the timing. It also can be the throttle body. Only so many fuel problems the take a good look at the distributor. Small crack or bad wire gives off spark but might not be enough small 4 cylinder for their pecission motors need to be precise check fuses and main busses those are easy and cheap fixes

I think I would be looking at the crank angle sensor and/or the cam sensors on this vehicle.It seems to me the engine isn't getting the signal to fire up.What happens when you squirt some fuel into the combustion chamber ? If it fires up I would be looking at cleaning the injectors.If it doesn't fire up What's the pressure on the fuel rail. does it have a buy pass pressure valve on the rail.Some suggestions good luck

100 psi per cylinder is way too low--should be in the vicinity of 150-165 per cylinder
back firing indicates wrong firing order and as you have replaced the plugs etc check that you have the leads on the correct plugs in the correct order
the timing for the engine should be around the 10 degree btdc and not tdc

out? off?
the tool is called, a timing light, and is about a $20 tool.
slowly start pulling up to speed.
that includes, going up hill at wide open throttle at full power?
BTW1 , it s toyota engine. (not rare or odd at all)
engine power loss (no bad fuel) can be only 3 things
1: engine bad, lost compression (valve lash never SET:????)
2: bad spark and includes, bad timing. old spark plug wires cap .,rotor.
3: bad fueling. (under or over, weak fuel pump pressure)
a mech discovers that first.

this engine, has DIS, no distributor
and the book says, no spark timing. that means its fixed by the cam/crank sensors.
ever tune it up , using the op. guide in the glove box> (free on line)
every 60k miles a full tune up, ? if not, why do that now?
there are 2 toy engines, used, 1.6L and 1.8l and there are
unique service data for each, working with out a book (FSM)
or using alldata.com for facts, hear, means failure.
the VIN shows the 2 engines, vin 6 code or vin 8.
so does the RPO tag in glove box.
this is an EFI car, and we first look to see what type.
this car is MPI, multipoint injection,not TBI
the key fact that makes diagnosis much more easy.
the timing spec, (USA are you) is printed under the hood
open hood look up, see that? BTDC timing? 10deg BTDC?
step 9 in the FSM
"Using a fused jumper wire, connect terminals E1 and TE1 together at the DLC." (i use a paper clip)
this is the timing freeze jumper allowing you to adjust the distributor to hood spec timing.
ok , compresion is above 150psi WOT.
ok ,tuned up, 60k mile list, (filters and spark parts ,dont skip fuel)
ok , we made it to step 3 bad fueling
the classic:
1: too much fuel
2: too little. fuel.
we check that the coolant thermostat hits and holds 180F or more. HOLDS ! if not , all else is useless.
of temps are low it will flood with fuel... bingo.
too lean?
1: low fuel pressure.
2: bad O2
3: clogged injectors, bad fuel?
too rich
1: too high fuel pressure. (bad reg)
2: bad 02
3: leaking injectors. (2 causes)

that is the flow, the logical flow.

for sure if the ECU is getting bad inputs, the injection rates
will be wrong. and some ECU go to limphome.
ever lean to read the ECU flash codes?

this engine DOHC the 2 cams are gear driven side by side
but has belt from crank to cam.
it lasts for 60k miles, and slips. bad.
its on the service schedule. to replace it.
if it slips power is lost about 80% or more. bad cam,is result.
my online source is weak on GEO.;s
so can not tell if this engine uses a MAF sensor
it too ,dead or weak can cause huge power loss.
Toy says 4A is map system
toy shows 7A as,stroked out 4A, and has MAP too
MAPs never fail (well, hose leaks?) MAFs do.(easy)

they used 2 engines all years. second gen car.

1.6 L 4A-FE I4, 105 hp (78 kW)

1.8 L 7A-FE I4, 105-115 hpconclusions:
can be easy as a tuneup? duh factor, 1.
or bad fuel pump. or reg. bad.?
bad wiring to pump. low voltage to pump.
bad injectors.
to find it , we have lots of tests.
doing them in order saves time
in a real shop we have 5 gas, and start at the tail pipe
end and work forward.

eg; all this puppy is real rich and expells oxygen. (misfire)
see>?
DIY is a unique way to fix cars
DIY with no tools is a comic show.

and worse?
no way to use alldata.com (use it)

You need 3 things.
Compression
Good hot blue spark to all plugs.
Good gasoline and proper fuel pressure. 63-64 lbs.
If you have all 3 then move on to injector pulse to all injectors.
I think each injector is on a separate driver on that one.
Check for pulse to all of them.

You may be weak on fuel pressure . even a couple of lbs low on a cold start will cause a no start.
Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems.
one test is to give it a squirt of carb cleaner not starting fluid. If it starts then you have a fuel pressure problem.
Run the full fuel pressure test and post back pressures.
Here is the guide lines on testing.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel. Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.

The 75-85 is only a check on the capable full pressure of fuel pump.
If you can not find the rubber return line check full pressure by plugging return line or just or the true full pressure can be taken direct at the end fuel filter.
What are the pressure readings that you have when done.
What are your cold start pressure readings?
Post back what you have. Good luck

1 Inspect Battery Damaged or faulty battery and/or connections. here is a list of things u can check hope this helps Shaun 2 Inspect Coil - Ignition Damaged or faulty ignition coil or ignition coil circuit. 3 Inspect Fuel Filter Clogged or dirty fuel filter 4 Inspect Fuel Injector Pressure Regulator Faulty fuel injector pressure regulator or circuit. 5 Inspect Fuel Pump Improperly functioning fuel pump or circuits. 6 Inspect Wireset Damaged, worn, or deteriorating spark plug or coil wire(s). 7 Inspect Control Module-Ignition Faulty ignition control module or circuit. 8 Inspect Solenoid Switch Damaged or faulty solenoid switch or solenoid switch circuit. 9 Inspect Starter Damaged, worn, defective, or faulty starter or starter related circuit. 10 Inspect Neutral Safety Switch Damaged or faulty neutral safety swittch or circuit. 11 Inspect Fuse Corroded, burned, or shorted fuse may be interupting power source. 12 Inspect Fusible Link Corroded, burned, or shorted fusible link may be interupting power source. 13 Inspect Battery Cable Corroded, broken or poorly connected battery cable. 14 Inspect Spark Plug Wire Loom - Performance Improperly adjusted or worn/malfunctioning carburetor. 15 Inspect Distributor Cap Loose or cracked distributor cap 16 Inspect Distributor Cap And Rotor Kit Loose, cracked, or worn distributor cap and ignition rotor. 17 Inspect Fuel System Pressure Incorrect fuel pressure being delivered to carburetor or fuel injection system. 18 Inspect Fuel Injector Plugged, dirty or poorly connected fuel injector. 19 Inspect Ignition Switch Worn, damaged or faulty ignition switch or circuit. 20 Inspect Spark Plug Fouled, damaged or broken spark plug(s). 21 Inspect Belt Incorrectly routed, adjusted(tensioned), missing or worn drive belt(s). 22 Inspect Timing Belt Slipped or broken timing belt. 23 Inspect Timing Set Slipped timing chain or worn timing gear(s). 24 Inspect Fuel Tank Contaminated fuel from rusted or deteriorated fuel tank. 25 Inspect Ignition Timing Incorrectly adjusted engine timing.

Check for voltage to fuel injectors..A set of noid lights will help with this...Good Luck