Eli Lilly

My 2nd XJ died of old age 6 months ago and I got another one immediately and it's been nothing but problems. The thing it just started doing last week is it won't start unless the gas pedal is pressed to the floor. You can crank it all you want but it won't start. Press the pedal to the floor, crank, and it starts right up. Runs fine, no idle problems. A weird jerk, when moving, when you let off the gas all the way that started about the same time as the starting problem.

My thought is TPS but I can't think of why the TPS would impact starting. I was wondering if anyone else had ever heard of any similar no-start scenario, I searched and couldn't find one.

-E

MAN00XJ

I dont remember the long, technical diagnosis, but I immediately thought of the TPS before even opening your post. The TPS detects where the throttle is, of course, but in doing that, it detects how far open the butterfly is on your TB. If the TPS is bad, it is not getting a correct measure of how open the TB is, therefore doesn't want the ignition sequence to work. When you push the pedal to the floor (or sometimes its at a different position) it tricks the TPS into believing the butterfly is at the position it wants it to be, and allows it to start... replace, or adjust the TPS. Probably need to replace it. You can get a voltage meter and test the voltage to see what it is reading, which is how it knows where the butterfly is sitting. I dont know what exactly it is supposed to read, because i dont know the specs of your rig, but a simple search can find it. Good luck.

BLUE1

I've just had the same problem for a few weeks now, it finally refused to start the other day and threw the fault P0320 ignition /distributer engine speed sensor. Changed the crankshaft position sensor which has cured the problem.

Eli Lilly

Thanks, I'm going to swap out the TPS next week and I'll post back to this thread. I'll keep an eye on the CPS, too, if replacing the TPS doesn't do the trick.

-E

Eli Lilly

Replaced the following from donor vehicle with no change:
- TPS
- IAT sensor
- MAP sensor

Swapping camshaft position sensor (the one under the dist) tonight, will swap and clean IAC this weekend.

More details of symptom:

- Starts fine when engine cold
- When engine is warm, will crank but not start unless gas pedal is pressed
- When first cranking without pedal pressed, tries to half-arsed start for a second but stumbles
- If pedal pressed to floor, starts right up, idles fine, runs fine
- If pedal slowly pressed while cranking will eventually catch and stumble itself from a very low RPM up to the proper RPM, in a few seconds


I'm fairly stumped at this point.

-E

COSXJFAN

X2!! CPS and done...

Eli Lilly

The one mounted to the bellhousing, right?

Thanks,
-E

COSXJFAN

Yes...

Quazzimoto

Coolant temp sensor.. Sounds strange but mine cracked and I had the same issue its like 10 buks and it dosent get any easier to fix.

Eli Lilly

Ended up being the IAC. Without changing anything else, I verified that the engine wouldn't start without flooring it. Then I cleaned the TB with B-12, paying special attention to the idle ports. Afterwards it starts easily.

I also checked the coolant sensor, which is new, during an earlier troubleshooting attempt. The connector was corroded, so Quazzimoto saved me some future drama there.

I'm keeping my eye on the CPS, though, already had a crank-no-start there due to corrosion on that connector.

Thanks all,
-E

Eli Lilly

Update: Worked fine for about a week, then problem suddenly reappeared and got worse. Became more difficult to start, started stalling when accelerating from a dead stop, and oscillating when gas pedal released. Nearly every sensor has been swapped (IAT, IAC, TPS, now CPS) with one from my other XJ or replaced outright. Today I had the shop do the CPS, since I wasn't sure about doing that myself, and it didn't make a difference either. No codes, either.

The shop unplugged the coolant sensor and the symptoms seem to go away. That would mean that a brand-new sensor is bad. But I also know that the PCM runs in open-loop mode with the sensor disconnected, so it's ignoring input from a number of sensors.

Anyways, we'll see what happens when I swap the sensors later tonight. But it's been a real XJ nightmare so far.

-E

Eli Lilly

OK, was Quazzimoto for the win! The new temp sensor, from Advance, that I put in a month or two ago has failed and returns 600K ohms.

-E