Lurchy shift

#1
Hey gang,

So I’m waiting for AAA right now after experiencing some new and strange symptoms. After my ‘02 Montero Limited warmed up this morning, I was sitting at a stop sign. When I accelerated, there was a split second where it seemed like power cut out between 1st and 2nd gear. It was so brief I wasn’t sure if I had imagined it.

Anyway, the symptom started repeating at every stop light, then every gear change. The gaps where power was dying became longer and longer. And now my truck is dead on the side of the road. Transmission fluid looks great. Oil is about a quart low (leaks).

Has anyone ever had this issue? My gut is telling me that the ECU is losing its mind. Oh, an the truck has 215,000 on it.
 

REDONE

[s]hard[/s]MEDIUM Core!
#2
Hopefully the AAA guy will have a code scanner in his truck. I betting on a sensor, like MAP, MAF or TPS. ECUs are pretty robust (especially by 2002) and usually it's an input that fails, and the input isn't identified until the ECU is already replaced.
Sucks to be stuck on the side of the road! I hate that! Hope your day gets better from here!
 

jeep-N-montero

Expedition Leader
#3
Have you recently had the transmission flushed? If yes then there is a chance it loosened some gunk that made its way to the filter and may be clogging it up a bit.
 
#6
Is replacing the ECU a job that can be done at home? I recall a post on this forum once where someone mentioned replacing it, but had to replace all the locks and ignition as well because of the chip in the keys.
 
#7
Update:

I got home and decided to disconnect the battery to see if resetting the computer would change the symptoms.

When I reconnected the battery and tried to start it the battery was dead! It’s a really old battery.

I replaced the alternator last January with a cheap O’Reilly’s unit.

I’m starting to think the strange lurch was a coincidence and I’m actually having an alternator/battery issue.

I’m hoping some more experienced folks might chime in.

Cheers,

Jason
 

jeep-N-montero

Expedition Leader
#8
Update:

I got home and decided to disconnect the battery to see if resetting the computer would change the symptoms.

When I reconnected the battery and tried to start it the battery was dead! It's a really old battery.

I replaced the alternator last January with a cheap O'Reilly's unit.

I'm starting to think the strange lurch was a coincidence and I'm actually having an alternator/battery issue.

I'm hoping some more experienced folks might chime in.

Cheers,

Jason
A dead or weak battery will certainly affect a lot of things, if the sensors are not able to send and receive the proper voltage it can send the ecu into limp mode to save the engine/trans. Install a new battery and report back.
 
#10
Bad news...I replaced the battery and it fired right up but died after it went off of high idle. And would not start after that.

I have no idea what the problem is.
 

REDONE

[s]hard[/s]MEDIUM Core!
#11
Well, I wish you would've read the codes before you replaced the battery. Unhooking it reset it, so now the computer doesn't know what the problem is either. I'm still betting it's a sensor: Crank Position, cam angle, Throttle position most likely. Could be the MAP or MAF, since it's quitting right between high/low idle (closed/open loop), but it should still run without either of those, it'd just run really bad.
 
#12
Well I picked up a code reader and decided to give reading it a shot anyway. That didn’t work, I don’t want to start buying parts if I don’t have an accurate diagnostic. I think I’ve put myself in a position where I need to have a mechanic look at it.
 

Salonika

Monterror Pilot
#13
Get an in-line spark checker and see if you are getting spark. Not many things will cause a total no-start condition. Is it acting like it is trying to start at all? Crank and cam sensor failure will cut the ignition so you wouldn’t have spark if one of those sensors failed.
 
#14
Thanks for jumping in Salonika,

It will start just fine, but it will die when it goes off of high idle. After researching MAF symptoms, I'm starting to think that's what it is. I'm going to clean the MAF tonight to see if that improves anything and go from there. If it is the MAF, it seems like an easy fix, plug and play. I will report back.

Cheers,

Jason
 

Salonika

Monterror Pilot
#15
Check the condition of all the vacuum lines on your intake plenum......the surge you could have experienced may have been from a loose vac line, or one cracking, etc. You'd be amazed what even a small vac leak will do to the engine balance. At idle, I popped off the EVAP line once and stuck my thumb over it. I rolled my thumb around and played with allowing different amounts of air in there and it was surprising how sensitive it is. Fully open, that opening made the engine shake horribly. Good luck.