Ok, now the background. I moved the Jeep to Minnesota from Hawaii. No problems in Hawaii. Before shipping, I did a basic tuneup (oil, filters, spark plugs). When I did this, I replaced the stock filter for a K&N. I also replaced a small section of vacuum hose that had a big crack along the bottom of it. This hose came down from the throttle body and T'd into a line coming from the purge solenoid (80% sure that's what the thing mounted off the relay box is that clicks sometimes.)
For the first several weeks, there were no engine codes. I hooked it up to an OBDII reader and verified there were no codes. There were 4 lights flashing on the reader: O2, CAT, EVA, HTR. Now, I get an engine light when I start the Jeep, until it does it's first stall, then the light check engine light goes away.
When my wife picked the Jeep up from the shipper, they drove it up to the pickup area, turned it off, and it wouldn't start again. All the stall symptoms started about a week after this. The shipper had a couple guys look at the Jeep and mess with it until they could get it started. Ever since, the alarm system hasn't worked the same. Not sure if the pickup from the shipper is important, but you never know.
Lasts week, I changed out the K&N for a paper filter to see if there was any change. It went a whole day of driving without stalling, but then went back to stalling again. I disconnected the battery, cycled the key, and let it sit overnight to reset the computer. I started it up the next day and started getting incredible gas mileage, though it was still stalling. Gas mileage in Hawaii was 13.4 avg over 4 years. Gas mileage went up after fixing vacuum leak, to about 16 mpg. Ever since resetting the computer, it's been averaging over 18.5 mpg.
After resetting the computer and driving it for a couple days, I took the airbox off and visually inspected the throttlebody. I started the Jeep and watched and noticed the throttle plate wasn't moving to adjust the throttle plate and the idle. So, I think the engine is starving of air because the IAC isn't working and the throttle plate stays closed for some reason. With the vacuum leak, it could have been drawing air in through the vacuum line via the suction drawn behind the throttle plate. With the vacuum leak fixed, there's no source of air. That means the problem could have existed in Hawaii and been part of the gas mileage problem.
But, I'm not ready to change out the IAC. It makes sense that some signal may not be telling it to open.
So, I took the Jeep to hook up an OBDII reader again with the check engine light in, and it returned a code 0601 checksum code, again with the same 4 flashing indicators (O2, EVA, HTR, CAT.)
When I had the airbox off and was watching it idle, about halfway between the time I would restart it and the time it would stall, there was a clicking that would start. I traced it to a thing that has 2 vacuum lines and an electrical connection to/from it. I believe it's a purge solenoid related to the emissions system. So, once it starts clicking audibly (about 2 clicks per second), the Jeep soon stalls.
I've been to the forums, but most help there is "Replace your PCM and see what happens." I don't like the "replace some expensive part and see what happens" style of troubleshooting that happens all to often - even at dealerships. So, I'm hoping for some insight into this complicated picture of electronics, emissions, vacuum lines, sensors, etc. That can relate these symptoms to a common component.
Thanks for your time. Jason
have the same problem?
Saturday, July 25th, 2009 AT 1:10 PM