My 96 Cherokee LTD 4.0 has been randomly (usually when warmed up) lurching whilst stopped in traffic and then stumbling during acceleration.
I have it narrowed it down to the fuel pump or injectors. I have eliminated everything else because I also have a single point injection LPG system
and I have not yet experienced this whilst using it so I am pretty sure it is not the ignition system.
I have just replaced the tps and battery. Cleaned the ICV and throttle body. Eliminated vacuum leaks.
I know I can test the pump and the injectors but unless they happen to misbehave while I am testing them I do not expect that the test will prove anything.
Is there a way to discover which is causing the problem?

Any suggestions appreciated.

 

and is the assumption correct that you have an auto trans? Are you sure there's no issue that direction?

 

Checking the fuel pump psi is crazy easy and free. Check it cold and warm. Mine did the same thing. Only happened sometimes. Psi was at 20. There are a lot of videos and the tester is rentable at any parts store.

 

sorry yes it is auto. if it were a transmission problem would it not also pay up on lpg?
rail pressure seems fine but i assume if it were measured during one of its tantrums it may not be fine.

 

I should also mention that so far the check engine light has not come on.
This is almost a daily occurrence. Usually on the way home when there is more traffic and air temp is higher and less airflow on the radiator.
Heat is definitely playing a role here. It almost never happens cold. not that the car is overheating, would rarely get above 90 deg C.
In the mornings runs at 75 deg C. On LPG its runs at a lower temp I guess because of the LPG converter taking heat from the coolant.
Maybe this is a factor as to why it does not play up on LPG. But it sometimes does it at 75 deg but MUCH more likely in the higher ranges.
I am thinking something electrical failing intermittently. Bad earth on a sensor connector?

 

BillyBoy, I should also mention that I live in Australia (it's summer here) and there are no parts shops around here interested in renting me a gauge. $150 AUD to buy one.
I have however measured the fuel pressure at 46psi give or take at a cold idle.
This I did with a tyre pressure gauge on the schrader valve Gauge is now inoperative so fuel did not do it any good but measurement is good enough to know that I have enough fuel in the rail.

 

update...It was definitely not the fuel pump. on the bright side i now have a spare pump.
driving on lpg durung a 40deg C day i think confirms that i cannot replicate this problem on lpg.
it is becoming more and more prevalent on petrol though so i guess sooner or later whatever is causing it will fail completely and then i will get to the bottom of it.
Guess i am towing on lpg this Christmas.

 

I admit to knowing very little about the lpg system but I assume when I switch from petrol to lpg the switch also cuts all power to the injectors.
It has just occurred to me that this switch may be the faulty culprit. In which case I have posted this thread in the wrong section.
Please feel free to move it. Please feel free to weigh in if you happen to know anything about this that may help me. But I now think
it is the LPG system that is causing this issue and being such an old system finding anyone who knows about them is going to be difficult.
I have a few leads to work on for the moment. I will start with replacing the switch on the dash (if I can find one).
Sorry for wasting your time

 

I think the expression is - "No worries mate!"

I wouldn't call it a waste of time - it's a learning process.