Question about 1990 Jeep Wagoneer Limited

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1990 4.o will start and run but when engine warm up,emisinos light comes on and then fuel pump loses pressure,

Its had map,sensor. crank idle sensor. cold start injecter, and a fuel regulater,put on.

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I think the problem is this joseph, its an inbread p.o.s of a should burn it and buy a 350 chevy ha ha ha!

Posted on Jan 09, 2013


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SOURCE: Jeep GCL Backfires Stalls

Aaron, I had the same problem. It is the most expensive part of course the computer. I replaced everything as well till I replaced it. They are remanufactured and have had problems with them as well. I am on my third one now at 200k miles. Oh and by the way it does not show up on the diagnostic check. Good luck


Posted on Dec 01, 2008

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SOURCE: no injector pulse, no current to the injector

Check the pickup in the distributor as this is the cam sensor. The injectors run of the pulses created while the rotor is turning around. It should be a plastic disk located under the rotor button.

Posted on Mar 13, 2009

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SOURCE: I have a 93 Jeep Wrangler 4.0 that cranks and mentioned that there is no spark coming from the coil when it's in no start...Is there power from the alternator going to the coil?
One other item...If the timing chain is worn and stretched, it is possible that the cam sensor and crank sensor are out of phase with each other, just enough where a temperature difference will change starting ability.
One question...while in no start, have you tried changing the throttle position while cranking to see if it lights at part or 3/4 throttle?

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SOURCE: 1996 jeep grand Cherokee 4.0L no power at coil got


Posted on Oct 28, 2009

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SOURCE: 1995 Jeep Wrangler 2.5L Fuel Pump/Check engine light

Could be one of several items...I'd check the fuel pump relay, auto shutdown relay and the ignition switch itself. I'd bet on it being one of those relays but, we all have been fooled at least once!!! I'd also make sure that body and engine grounding is good and clean. Relays can't work properly without a good ground.

Posted on Nov 03, 2009

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I have a 1990 jeep wrangler 4 banger 2.5l manual tranny She runs and starts fine but I can only drive about 1 mile before it starts losing power. It gets to the point where I'll be in first gear trying to...

do a 60k tune up first, all below assumes you did, spark parts, filters. dah?
first off the engine EFI runs a map sensor, (called speed density system)
so that means if the engine can pump air (compression tests PASS)

the MAP see that, air flow (calcs) and matches air with proper fuel.
1990 is a vary bad year, it has the horrid, Renix french pos EFI system. (owned 2, can taLK days on this ecu FROM H3LL)

but there is no CEL lamp, nor any scan tool , that will work here.
(unless you can find a working DRB tool, ) NO FLASH CODES !!!
above poster never seen RENIX, so.. .answers wrong. ITS OK.
1993 this changed (Chrysler) and started OBD1 ECU which we can scan easy. (innova 3140)

all this means is you must be smarter than the average bear.
are you>? got tools, meters. and all that? you will need it.
and a FSM book or login to like we do.

if compression test pass, and vacuum at 19" idle and gunned throttle drops low fast and if you release throttle it goes why high fast 25inches>? and goes to 19inchs again, the engine is ok and cat not melted, all that in 5min work (vacuum tests) and vacuum not bouncing? 1 glance, no its steady vavcuum.
so I wave my magic wand, go, gee engine is ok.
i then check fuel pressure use a REAL gage.
it idle and throttle gunned. for spec pressures.

if all that pans out> whats next? well EFI is next,.
i check the MAP sensor voltage at 3 points.
key on, idle and gunned. for spec, readings. if not map is bad. or just clogged.
check all the other sensor by hand is next. and ill not attempt do post what ever mech ,knows here, "basics"
a volt meter , you can check them, ECT, IAT, etc.

my wild guess low fuel pressure. (BASE ON OK 1 MILE)
or FPR stuck wide open' (bad fuel pump reg)
or a bad wire to fuel pump, such that pump does not receive full 12vdc power.

here is map readings, ill post this because many books fail to show it.

if input to map is good, but output wrong, the map is DOA.

Mar 09, 2015 | 1990 Jeep Wrangler

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Engine dies

if it shuts off while driving down the road. and restarts after 10 minutes, its usually a bad crank sensor that does this. it messes up timing and shuts off fuel supply.

Apr 05, 2014 | 1994 Chevrolet Suburban

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My engine misses and loses fuel pressure, and engine surges when switching between brights and dims. Can this happen because of a bad battery?

Check altenator to see if charging.
Check fuel pump, replace if needed.Check Throttle positioning sensor, replace if needed.

Jan 21, 2013 | Cars & Trucks

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1990 Buick Silouete loses power when accelerating, as engine warms it gets worse. Changed filter and had gas tank cleaned out recently did not solve the problem. It drives ok at normal speeds, it spudders...

You are a 1990 Oldsmobile sihouette with a 3.1 these vehicle are speed density in other word you are equipt with a MAP (manifold air pressure) when this sensor fails you loose the ability to accelerate or hesitate as you accelerate make sure the vacuum hose is connected to it and it is no leaking vacuum if the hose is okay and it is electrically connected correctly your fix is to replace the MAP sensor

Aug 05, 2011 | 1990 Oldsmobile Silhouette

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We replaced the feul pump on our 2001 tahoe July 2010. It has been giving me trouble starting again. We can hear the fuel pump and know it's not that, but aren't sure where else to look. Was researching...

could be map sensor, could be fuel filter,if it was a sensor your check engine light should be on. i have a 2002 chevy avalanche and it was hard to start and the fuel pump was working but it has a valve in it that will not allow the fuel to run back into the tank and empty the lines, and the valve was bad which the only way to fix the problem was a new fuel pump unfortantually just cause it is a new fuel pump does not mean the check valve in it did not go bad

Mar 04, 2011 | 2001 Chevrolet Tahoe

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upper 02 sensor run on a loop till the engine gets warm then it reads the sensor get you back on the road fast it will work better if the engine is warm when you take out the o2 sensor

May 04, 2010 | 2001 Dodge Durango

1 Answer

Our 1999 Chevy Truck looses power after the engine warms up. We have changed the knock sensors, o2 sensors, catalitic converters, and the fuel pump relay? What are we missing?

Have you had the s10 scanned for the DTC codes. Auto Zone scan free of charge and this should help figure out why your loosing power when the engine warms up. You could have a faulty MAP sensor or a weak fuel pump, dirty fuel filter.

Not knowing what has been done, here is a few things you can do and check.

You may be weak on fuel pressure, even a couple of lbs low on fuel pressure can cause low performance.
Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems. Run the full fuel pressure test and post back pressures.
Here is the guide lines on testing.
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.
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.
Post back fuel pressure readings.

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 done.
What are your cold start pressure readings?

You need 3 things.
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.

The next thing you can look at is the Cap and Rotor, inspect for any damages and corrosion which is common to accumulate in the distributor due the a clogged vent screen at the bottom of the distributor. That is where is ICM is located also and my be on it's way out and needs to be replace.

Best thing to do is check for any DTC codes at Auto Zone and that should help determine what is causing your loose or power. A bad fuel pump and dirty fuel filter will not trip any DTC codes.

Start with the simple and check all the fuses, the wire leads to the MAP sensor, it's located on the passenger side on the intake manifold by the throttle body. Check then check the distributor Cap and Rotor and replace, check the fuel pressure reading, and almost forgot to check the MAF sensor.

Try this in the mean time, turn you ignition to the run position "engine not running" and pull the fuse to your ECM for 1 min and place back in. Turn your ignition off for 5 sec and turn on again for 10 sec and then start the engine. It may stall out, let it. just start it again and let idle for 2 min and go for a test drive. This will reset your ECM to default and relearn all the sensors on the engine and transmission. Any DTC codes will have been erased and any DTC codes will be new to the issues your engine is having. Good luck and keep me posted, be glad to help you get your S10 running 100% again soon.

Jan 26, 2010 | 1999 Chevrolet S-10 Pickup

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Long Crank Time When Hot

Timing belt/chain may have been put it slightly off time, when motor rebuild

Jan 13, 2010 | 1993 Dodge Spirit

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