br1anstorm
NAXJA Forum User
- Location
- United Kingdom
I have a 1993 XJ with 4.0 H.O. engine (ie non-Renix). Owned since new, no engine modifications, has had new ignition coil but few other replacement engine-parts aside from routine filters etc. Mileage now 178,000, but it has not been heavily used off-road.
Until recently the engine has run reliably and flawlessly, starting first time every time (it has a good Optima battery).
Recently two slight problems have appeared. I don't know if they are related. Only sometimes, the engine is reluctant to start... churns a few times and then usually fires if the throttle pedal is pushed to the floor. Feels slightly as if it's either not getting enough fuel, or not enough spark.
Also, once running the idle speed seems to be higher than normal - at least until the engine is warm. As I recall it has always idled solidly and reliably at about 700 rpm ever since it was new. Now, sometimes but not always, it is 1000-1100 rpm. Blipping the throttle pedal doesn't necessarily bring it down.
I don't have OBD scanners or similar diagnostic tools. So far, I have only done some simple basics:
The symptoms remain - but are intermittent. I have browsed the forum and there are hundreds of 'high idle' posts and hundreds of possible explanations! This post from Yellaheep at https://www.naxja.org/forum/showthread.php?t=965655 seems to be close to my situation, but I'm still not clear about how to troubleshoot. I can't throw replacement parts in randomly (I'm in UK, no junkyard options and spares are like gold dust). What other checks can I do and - importantly - in what order, in order to narrow down the cause(s) of the problem(s)?
Until recently the engine has run reliably and flawlessly, starting first time every time (it has a good Optima battery).
Recently two slight problems have appeared. I don't know if they are related. Only sometimes, the engine is reluctant to start... churns a few times and then usually fires if the throttle pedal is pushed to the floor. Feels slightly as if it's either not getting enough fuel, or not enough spark.
Also, once running the idle speed seems to be higher than normal - at least until the engine is warm. As I recall it has always idled solidly and reliably at about 700 rpm ever since it was new. Now, sometimes but not always, it is 1000-1100 rpm. Blipping the throttle pedal doesn't necessarily bring it down.
I don't have OBD scanners or similar diagnostic tools. So far, I have only done some simple basics:
- put in some clean quality fuel, in case I had a bad tankful;
- cleaned the inside of the distributor cap (whose contacts were a bit dirty/corroded);
- checked and cleaned all the spark plug leads;
- checked that the throttle pedal or cable isn't catching or sticking in the footwell carpet.
The symptoms remain - but are intermittent. I have browsed the forum and there are hundreds of 'high idle' posts and hundreds of possible explanations! This post from Yellaheep at https://www.naxja.org/forum/showthread.php?t=965655 seems to be close to my situation, but I'm still not clear about how to troubleshoot. I can't throw replacement parts in randomly (I'm in UK, no junkyard options and spares are like gold dust). What other checks can I do and - importantly - in what order, in order to narrow down the cause(s) of the problem(s)?