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P0303 Code +

2711 Views 4 Replies 4 Participants Last post by  ImperialCrown
I have a 97 TnC 3.8 AWD. Picked up 2 - O2 sensor codes (P0134 and P0135) and 2 TPS codes (P0122 and P0120) and then a P0303 code on a misfire on #3.
Changed upstrem O2 sensor.
Changed TPS.
Put in new plugs , wires and coil pack.

Car in park runs fine, rev up and still seems smooth. Put it on road and a little load makes it start to pop.

Also originally had a P0700 code for the TCS, but I figured I would take car of that after I took care of these other codes.

The van has about 170k on it.

Can anyone help? Car has run fine till this started.

Thanks +
1 - 5 of 5 Posts

· Virginia Gentleman
8,737 Posts
Are you losing a significant amount of power as you try to accelerate? I'd check the catalytic converter for blockage - may need to replace it.

The P0700 code is just a generic fault code telling you the TCM has other fault codes stored. You'll need a more specialized scanner (DRBIII) to retrieve those codes - the typical engine scanner cannot get the TCM fault codes.

· Registered
1,147 Posts
Make sure the battery and charging system is in good shape. Sometimes false codes can be set when there is a voltage dip. I had it happen on my 96 Minivan and it was an alternator that would charge fine at idle, but slowly died off as load was added. Replacing the brushes in the alternator resolved the problem. The weak alternator also killed the battery in my case, so I ultimately had to replace both.

· Registered
5 Posts
Discussion Starter · #4 ·
Catalytic is interesting idea. Did not think of that.
Easing in to accelerator I'm not getting any problem, however, trying to go up an incline, even a minor one, it begins to pop and sputter, thus a loss in power. It seemed like it happened when it tried to downshift and the RPM went upward of 2500+. What was strange, I was able to, under smooth gradual acceleration go beyond 2500+ (on a flat run). When it shifted it was a little off (strange RPM stutter) but it did not pop.
What concerns me is that if it was the catalytic, wouldn't I get codes for other cylinders misfiring?

· Super Moderator
1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
17,323 Posts
I would also recommend the correct replacement OEM parts. I have had aftermarket O2 sensors and spark plugs cause running problems on these. Use the Champion platinum plug listed on the underhood label or in the owners manual. The O2 sensor should be NTK/NGK or Mopar.
How does the #3 plug look? If it is carbon fouled or the gap has closed up, that can cause misfire. Intake manifold pop-back can be from a lean mixture. It takes a long time to set a P0420 cat code.
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