This is a Drive-By-Wire 2007 LQ4 in an old Jeep with the stock computer running a stock LQ4 manual transmission tune with VATS/torque mgt/EGR disabled. It ran perfectly this morning. Voltage is fine. It just happened...I'm at work and haven't had a chance to check codes/fuel pressure yet.

Here's how it happened:

I was leaving work on my way to racquetball and really getting on it pulling out onto the highway (bumped the rev limiter) and it just *died.* It felt like the computer just told it to shut down. After rolling to a stop by the side of the road, I cranked it over a few times and it would kinda fire very sporadically (like maybe once every ten cranks) while cranking, but not start. The fuel pump seemed to be working as it was supposed to (I could hear it).

I got out and looked under the hood for a couple of minutes and then got back in and tried it and it just fired right up and idled perfectly.

I went to take off again and it started out okay, but when I hit the gas to accelerate a little, it died again and wouldn't restart.

after a couple of minutes I tried it again and it fired right up again. I was able to limp back home at low speed/not giving it much gas.

Back at the shop here at work, I experimented with it and it seemed to be able to rev as high as you want as long as you move the gas pedal VERY slowly.

Any quick movement of the pedal caused it to instantly die and not restart for a couple of minutes.

Any ideas about what the problem might be?


THANKS,
Jake Harsha

 

it MAY be fuel pump getting weak and cant keep the fuel pressure up during a quick change like that since it will suck it up faster

 

Hmmm...bu that doesn't explain why it seems to rev fine as long as you go slowly (all the way up 4500 anyway). Or why it won't re-start for a couple minutes.

I'm going to try disconnecting the battery and see if the re-setting computer helps anything.

 

Post a copy of your tune - does it say "reduced engine power" when this occurs? Mine did this as well after my swap until I went under ENGINE DIAG- and maxeout the airflow tables.

 

Figured it out. It sucked so much air it had ingested the cone-shaped top portion of the air filter I was using. When you hit the gas hard it would seal itself against the intake side of the air box and you had to wait until the vacuum dissipated and it would start and run fine until you got on it again and it re-sealed the top of the air filter cone to the airbox.

Easy fix!


Thanks for reading and thanks for the replies,
Jake

 

LoL - Otay panky