Skip the auto shop - Our mechanics make house calls

Q: im fuel injected. acts like no gas is coming through system. once i pump pedal it starts up alright

asked by on

So I am seeing this is a common thing with Jeeps. I have a 1999 Jeep Cherokee sport 4.0L V6 straight 6, and a little over 182k miles. I have already changed the plugs, replaced the ignition coil (coil pack), wires, tps, air change sensor, radiator, oil pressure sensor, brake flush and I am still having the same problem. When I first start it up it runs fine. After the engine warms up periodically it will run rough and then die/ stall at times. If I am parking it dies losing all rpms to 0 I have to turn the key off and sometimes it will start back up immediately and sometimes it takes up to a minute. I have noticed that if I sit with my foot on the gas and break and keep my engine at at lease 1,000 rpm it will not die. but if I don't do that it will usually die on me. However, if I am on the interstate, I can get on it and it runs perfectly. It has a lot of power and runs great. It's just when it dies it's like I am out of gas. The fuel pressure is normal and the pump is fine i believe.

My car has 183000 miles.
My car has an automatic transmission.

It’s either a fuel or ignition issue, however you do have to check the air induction system, such as any idle air control valve, mass air flow sensor, and so forth. With regard to the fuel possibility, it’s relevant that you note that it runs well cold. When a car engine is cold, the PCM is programmed to enrich the mixture. That may explain why when cold, it runs OK as there is adequate (extra) fuel. Once the engine warms up though, and it goes into closed loop operation, the PCM uses the oxygen sensors to adjust fuel supply. I would use am automotive scope (oscilloscope) to verify the operation of the oxygen sensors, however if the sensors have never been replaced you might consider just replacing them outright as they would be pretty old. Of course, it is always good to test with a scope as that gives you more diagnostic data to understand what is going on with the engine. Often, what will happen in case like yours is you there is a combination of problems, so I would check the fuel injectors as well. Ideally, if you are really trying to "restore" the engine, the injectors should just simply be removed from the fuel rail and sent out to one of the many labs that test, refurbish, clean, and install new internal filter baskets. Mr. Injector is an example of these labs. If you service the injectors, obviously put a new fuel filter in. If the oxygen sensors and injectors are OK and yet you still have a problem, check engine compression and scope the cylinder secondary firing patterns which diagnostic will let you know if you have a fuel or ignition system problem. If you desire that a certified mechanic walk you through all of this and identify (and repair) the faulty components, simply request a rough running engine diagnostic and the mechanic will get this resolved for you promptly.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. im fuel injected. acts like no gas is coming through system. once i pump pedal it starts up alright

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Vehicle shakes

You should have all the tires checked for a bent rim. You can check this by having someone follow you while driving on the road. The other person can let you know if a problem is visually noticeable. Another alternative...

Q: stalling engine

Hello there. Usually this type of issue is caused simply by clogged or dirty fuel injectors or the throttle body being dirty. When an engine gets warm it is more dependent upon the efficient flow of vaporized gasoline. When the...

Q: Hi Patrick, I was told by my machanic when my engine light sparked in that I need a oxegen sensor, and said that it has to be fixe

Oxygen sensors are tested using an automotive scope or oscilloscope. In your circumstance, if there are more than 100,000 miles on the sensor, the sensor output should be verified on a scope. The mechanic should show you the output waveform...

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.