2000 dodge neon, surges in gear

[Mark1968]

Working on a 2000 neon with about 88k miles. When in gear with the brake applied it wants to rev the motor and lunge forward.
Has new upper and lower motor mounts set at the right distance. New tps sensor. Only code shown is for upstream o2 sensor.
Also noticed the scanner shows timing jumps around from 6-9 degrees, which I'm assuming means the timing belt is due. I think those get changed about every 90k.

Got a couple of those molded rubber 90's which are dry rotted, gonna replace those too.

Any ideas?

 

[paratrooper307]

Working on a 2000 neon with about 88k miles. When in gear with the brake applied it wants to rev the motor and lunge forward.
Has new upper and lower motor mounts set at the right distance. New tps sensor. Only code shown is for upstream o2 sensor.
Also noticed the scanner shows timing jumps around from 6-9 degrees, which I'm assuming means the timing belt is due. I think those get changed about every 90k.

Got a couple of those molded rubber 90's which are dry rotted, gonna replace those too.

Any ideas?

The timing belt is probably due, but timing jumping around is not necessarily indicative of a belt problem. On a fuel injected car, with a distributorless ignition system, it will vary the timing considerably because it is not limited by the advance curve of a distributor. My Corvette would run anywhere from 8-20 degrees at idle depending on what it felt like, weather conditions, etc.

That O2 sensor may be a source of the problem. If it is not providing accurate information to the computer about the mixture, that could very well result in surging, as an FI car will do everything it can to stay running, while a carbed vehicle will do everything it can to quit running.

If that thing hasn't blown the headgasket yet, be on the lookout, it's probably coming.

 

[4xcrazy]

From what I learned with dealing with multiple O2 sensors, the first "upstream" one is the one that actually informs the computer as to what it needs, the second one after the cat simply tells if the cat s working.

Went through this crap with my dads car a few years ago, it kept giving a CEL for that secondary O2 sensor, turns out the cat was burnt out due to the fact he drove it too long with a misfiring cylinder, which was due to a malfunctioning coil pack, made it run rich.

I bought a new $125 coil pack and the thing fired right up and ran great, but wouldn't pass emissions in Phoenix due to the fact the CEL was lit.

I "sourced" catalytic converter, replaced it and been running great ever since.

 

[Mark1968]

The timing belt is probably due, but timing jumping around is not necessarily indicative of a belt problem. On a fuel injected car, with a distributorless ignition system, it will vary the timing considerably because it is not limited by the advance curve of a distributor. My Corvette would run anywhere from 8-20 degrees at idle depending on what it felt like, weather conditions, etc.

That O2 sensor may be a source of the problem. If it is not providing accurate information to the computer about the mixture, that could very well result in surging, as an FI car will do everything it can to stay running, while a carbed vehicle will do everything it can to quit running.

If that thing hasn't blown the headgasket yet, be on the lookout, it's probably coming.

I had wondered about the headgasket, but I don't think that would cause what I am seeing.
I'll do the o2 sensor today and see what happens.

 

[Mark1968]

Unplugged the tcc and now it's alright.

 

[paratrooper307]

I had wondered about the headgasket, but I don't think that would cause what I am seeing.
I'll do the o2 sensor today and see what happens.

Good deal. I just meant that that particular generation of Neons was notorious for blowing the headgasket by 80k miles.