P1128 & P1130 Limp Mode

[blue62]

Those two codes indicate that you have a lean condition that the DME can not correct.
So think to much air or not enough fuel.

I always go with simplest things first then work my way up step by step to the more complex.

So lets take the possibility of to much air first.
Look for things that could cause this.

1. Wrong signal from the MAF.
But you replaced it.
Was it the correct one for the car????

2.Vacuum leak.
You can use a vacuum gauge and do a vacuum test.
Your looking for a reading 18-19 on the gauge at sea level.
There is an adjustment to that reading as you go up in elevation.
Google vacuum tests.

3.Vacuum leak at the AOS but you replaced it.
Double check your work.

4. Bad seal at the crankcase filler cap.
The rubber seal on the filler cap can go bad.

5. The crankcase oil filler tube is known to get brittle and crack.
check for cracks.
Mine had a hole rubbed in it where it passes under the edge of the engine bay opening.

6. a smoke test may be a better way to go then a vacuum test.
But I always do my own work and a vacuum gauge is $20.00.

7. An exhaust leak ahead of the O2 sensor can cause these codes.
This is unlikely in your case because both banks are affected and this is a duel exhaust system.

If I didn't find anything on the to much air possibility I would then look at the possibility of not enough fuel.

1. You can do a fuel pressure test at the fuel rail or have it done.
That will tell you if fuel delivery pressure is within spec.
It will tell you if the fuel pump, fuel lines, fuel filter, are all good or possibly part of the problem.

2. plugged or dirty fuel injectors.

3. It is rare but you could have a faulty fuel injector relay.
Sometimes the little points inside get carbon on them and they act up.
I think they are around $10.00 at any auto parts store.

I WOULD NOT CHANGE OUT THE O2 SENSORS.

Think of any sensor as a witness to an event.
They (sensors) then tell the ECU what they see.
The ECU makes adjustments based on that (and other) witnesses reports.

It is unlikely that both of your O2 sensors are bad (giving false witness).
Because you have the same issue.(codes) for both banks. and each banks exhaust is separate from the other.

So the problem is upstream from the witness (O2 sensor). They are just reporting what they see.
Hope this makes sense.

[rexcramer]

1126-1128 codes on a 97 Tip. Lots of places for vac leaks. Lots of hard to inspect plastic tubes that have been heat cycled for 17 years. I finally took mine to an indy and they used a smoke generator and found it. They charged me an hour +/-$125 and problem solved. I forget where the leak was.

I suggest you get some diagnostic help before you X/O 4 O2 sensors on a guess. O2 sensors aren't cheap. Let us know how you make out.