First of all , a lot of compliments for your forum , where i found many useful info
I am a recent italian owner of a wrangler YJ 2.5 TBI . The car has 185000 miles and run pretty fine , except for a irregular ride at low stable throttle opening : i.e. mantaining the engine stationary at 1500 or 2000 rpm (in 1st or 2th gear ) the car jerks and hiccups ; if accelerating and in wide open condition the engine response and power became ok.
This happens in both cold or warm engine .
The jeep is equipped with an alternative fueling system by Liquefied Petroleum Gas ( rather common in italy for saving reasons) , switching to LPG fuel the car run perfectly on all throttle conditions , and considering that LPG require a perfect ignition system , i exclude any spark system issue.
The jeep is without O2 sensor and catalystic converter ( as far as i know this is a standard for '90 export in italy )
A list of checks done:
- vacuum hoses \ PVC \ air intake sys \ EGR & canister solenoid \ wide open throttle switch
- at idle or full open throttle all is ok , so i exclude fuel line , pump or filter issues .
- injector spray patters seems good
- no leakage or unrestrictions appears at exhaust or intake manifolds
Can You kindly suggest where focus troubleshooting and address additional tests ? ( may be fuel pressure or TPS sensor ??? )
thanks in advance