still having bad starts

so i have a 95 xj, i was getting really rough starts so i did the research and replaced the cps. didnt fix it so i replaced the distributor pickup. didnt work either.cleaned the iac valve. after resetting the computer it would run ok for a day or two. i replaced the starter the same time. it was on its way out anyway. i was thinking either the map sensor or the pcm itself or maybe the distributor itself. also around the same time this started the oil pressure sender started reading red lined and beyond, so i replaced the sender seems ok now. im tired of throwing money at this and just need some better ideas. sometimes it bucks so hard it stalls. seems to do it more often if the engine is hot, i read the threads on the newer xj and the fuel pressure problem but i dont think that pertains to the older ones.

Verifying fuel pressure would be a good idea no matter what year your XJ is.

Assuming you haven't seen a check engine light? If you have, you must pull stored codes for guidance.

Gotta do it with a fuel pressure gauge installed on the schrader valve on the fuel rail. Compare your numbers to factory spec.

What is the condition of tuneup hardware? Plugs, wires, cap, rotor, fuel filter.....don't want to be chasing your tail because of a sub-par tuneup item.

Besides freshening that stuff, don't throw any more parts at it. As you're finding, it becomes expensive quickly and isn't particularly efficient. Test your way to a solution.

Map sensor can be tested. This does not sound like a PCM issue.

i dont have a pressure guage but i could get one. all the basics have ben done about 6 months ago,(cap,rotor,etc..) i pulled the codes but they were just the normal crap about battery disconnected. i dont think the cel ever comes on, unless it blows the motor up....

seth15210 said:

so i have a 95 xj, i was getting really rough starts so i did the research and replaced the cps. didnt fix it so i replaced the distributor pickup. didnt work either.cleaned the iac valve. after resetting the computer it would run ok for a day or two. i replaced the starter the same time. it was on its way out anyway. i was thinking either the map sensor or the pcm itself or maybe the distributor itself. also around the same time this started the oil pressure sender started reading red lined and beyond, so i replaced the sender seems ok now. im tired of throwing money at this and just need some better ideas. sometimes it bucks so hard it stalls. seems to do it more often if the engine is hot, i read the threads on the newer xj and the fuel pressure problem but i dont think that pertains to the older ones.

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CPS wasn't it for sure, that'd be no-start. Distributor pickup was a decent guess. Cleaning the IAC was a good guess too, and a cheap one. Resetting the computer: good idea. Starter: well, you didn't lose anything I guess... Oil pressure sender is unrelated and it needed doing anyways, no loss there. So far I think you're doing pretty OK for someone who's throwing parts!

It's probably not the PCM or distributor, might be the MAP (do some diagnosis before replacing though.) I'd definitely borrow a fuel pressure gauge like birchlake said - autozone rents em out. You have a 95 so it's not heat soak, probably not fuel pressure regulator but it's cheap to try it - try turning the key to RUN for a few seconds, back to off, back to RUN for a few seconds, back to off, back to RUN for a few seconds then START ("poor man's prime".) If it starts nicely, it's your fuel pressure regulator / check valve going out, otherwise I'd bet on something else.

Well, if the battery is disconnected the PCM loses its mind and things will be a little rough until it relearns--so, why are you getting the battery disconnect codes? That is what I would start checking.

Also, "really rough starts" isn't very descriptive. Can you provide a bit more detail?

Well I'm atempting to get my hands on a fuel guage. As per the map sensor I'm probally gonna replace it anyway. It's 15 years old, it's about time. The starter was done because from the oil leaking onto it from filter changes it finally started screwing up. It was the original so it's time, just picked a he'll of a time to start screwing up. I'm getting the "battery has been disconnected within last 50 starts" which is pretty obvious what that means. But the problems still persist, when it starts it'll run like it's missing a cylinder and jump around so much that it ripped up my mounts pretty good. It's stalled a few times if I can't imediality start moving. If I can get moving and wind the engine up over2500 rpm it seems to quit. This only happens when the engine is still hot, it takes about 45 min to cool down then it doesent do it. I pulled the plugs today and did notice that they've Bern foulded with carbon pretty good, and they're only a few weeks old. Just for reference I use ngk v-powers. Which I've used for years and never had a problem.

All the plugs carbon fouled--black, fluffy?

What injectors?

Definitely check your fuel pressure, and post up the numbers.

When was the last o2 sensor change? What thermostat are you running? What temperature is indicated on the gauge after 20 minutes of operation?

I'd check the fuel pressure as has been suggested, but for the opposite reason most would think. The black plugs probably result from too rich a fuel mixture. This can be caused by a bad fuel pressure regulator (fuel pressure too high). I believe that your year still has the fuel return system and the vacuum operated fuel pressure relief valve. I had the same things happen to me on a '93 Ford pickup.

the plugs are fouled black, i put a new o2 sensor in last summer because it was running rich. which it still is so thats why im thinking map sensor or to high fuel pressure regulator. as per my injectors theyre the stock ones, i have a new set of mustang ones sitting but haven switched them yet. i still gotta get the pressure tester, when i find someone who rents it.

What does your temperature gauge indicate after 20+ minutes of running?

What is the condition of the battery and alternator. Weak electrical supply can cause these symptoms. If this is only when HOT, you may be getting some heat soak at the injectors, try adding some heat shielding.

well my temp. after 20 min is normal running temp. my battery is in good shape, the alternator is ok, for the most part. the heat shielding is a good idea but i dont know how to make one for the injectors.