mark15200

Hey guys...I don't post a lot but here's one...

1991 XJ 4.0L Manual Transmission. Teaching my son how to drive a Manual, the few times he choked it out it was hard to start. It would only start up with the gas pedal to the floor. This only happens after its choked out. It starts normal every other time, cold or hot. My first thought was ICV.

Any thoughts?

agreen

I have experienced this a couple of times. It usually boils down to a rich condition made worse by low rpm. The ecu tries to compensate for the low rpm by opening the IAC all the way and adding a little more fuel to the injector pulse. That part is programmed. Sometimes if you're already running rich because of an old O2 sensor or some other condition, the extra fuel can wash the compression out of the cylinders and make it hard to start. By flooring the gas pedal, the ecu does a "clear flood" mode and cuts the injectors.

There was once where it was due to a worn out engine, though. Low compression ony compounds the issue, especially if it was already running rich AND the kids keeps dumping it.

Good luck with the patience.

mark15200

Good information....Thanks. It has 200,000 miles on it....could be a tired engine. I may go after the O2 sensors and see what happens. He actually does really well with the manual. When my Patience is tested I just smile and laugh!

agreen

Changing the O2 can't hurt if you don't know how old it is. If you do an O2, do the front. I don't even know if a 91 has a downstream sensor. If it does, it's just a catalyst efficiency monitor.

Get an NGK brand too. It won't let you down.

mark15200

Will do thanks!

donalexinder24

hi

This is useful information....

Thanks. It has 200,000 miles on it, so it's possible that the engine is worn out. I'm thinking of going after the O2 sensors to see what happens. He does a fantastic job with the handbook. When my patience is put to the test, all I can do is grin and chuckle!

mark15200

Changed the O2 Sensor, Removed the throttle body and cleaned it. Changed TPC and ICV. Still after stalling it is hard to start. Otherwise it starts and runs like a top. I even stopped at a stop sign and turned the key off then started right back up no problem. I don't mind changing those parts because they are relatively cheap and probably original. Am I just dealing with a tired engine? Couple of more questions. It being a manual is it programmed to idle a little higher when in neutral and coasting to a stop. This seems normal. For example: If we coast to a stop from say 15 mph down to stop it idles a little higher until completely stopped. And then idles normal. Is the computer programmed to keep the idle up a bit when it sees speed in between shifting gears?

agreen

Mine does that, but I run an automatic ECU. I wondered if that would be the same for a manual ECU.

You can do a compression test, but I doubt it's bad if it barks off easily otherwise. How do your spark plugs, cap, and rotor look?

Brynjaminjones

What condition are the ignition components in? I've had a 4.0 that had a weak spark. It ran great most of the time but if it was running a little rich, the spark was weak enough that it would "flood" and stop running. After that point I couldn't get it running again.

mark15200

The Distributor cap and Rotor are new. Plug wires look relatively new. Probably replaced within the past year. We just bought it a few weeks ago. I have not replaced them yet nor the spark plugs. That is the next step for sure. I do think it's flooded after it chokes out. Luckily I've been driving a manual for years so it's rare it happens. My son is learning and getting better and rarely chokes it out but when he does it would be nice for it to fire right back up.