I have a 97 1500 4x4 with the 5.9, auto trans, it has 190,000

I bought the truck in june and since then ive replaced the tps, iac, map, lower plenum, both 02 sensors, complete tune up, fuel injector o rings.
I removed the cat and installed the 02 sensor spacer on the post cat 02.

When I first bought the truck it ran fine but you could tell it had 190,000 on it. so i did a tune up, cold air and removed the cat and installed a flowmaster. After that it was a little better. I drove it for 2 months with no issues, then cel came on i had it checked and it was a post 02 issue.

I installed 2 new 02 sensors and cleared the code and it was fine for a week then light came on and it was same code. Well i figured it was a old motor and all sensors were original equiptment from 97 so i changed them all and did the lower plenum fix and spaced 02 at same time. I drove it like that for about 3 weeks with no problem ran fine it was alot stronger with better throttle response.

Well the cel came on again, same code but now when the cel comes on the truck runs like im pulling a loaded trailer. if i stomp on the gas it feels like it clears its self around 3300 rpm almost like its flooding out but clears out at the higher rpm. but from idle to 3300 its a dog. It takes forever for the rpm to come up. If i disconnect the neg and wait a few and take it out for a drive it runs great, as soon as the cel comes on it runs like crap. it usually takes a couple days for light to come on but everytime it does it runs crappy. i disco the batt and its fine. this has been going on for like 2 weeks now ive talked to several shops and they tell me to check the things ive already changed. so after hearing that i pulled all the new sensors and exchanged them for new ones but still having the same problem..

Any Ideas????

Thanks

 

what CEL code number do you have?

 

What do your spark plug wires look like? How about your plugs? Dizzy cap and rotor? Have you tested your coil?

I would check and replace all the above items, should be around $100.

Also your cat might be clogged again.

 

He removed the cat so I don't think it's clogged. What brand o2 sensors did you buy?

 

i belive the code was 0420. i stoped having it scanned when it kept coming on. I did do complete a tune up, cap, rotor, coil, wires ,plugs and all new sensors. Ill have to look at the reciept to see what brand 02 . I bought them from a napa store, I know that there not ngk or bosch. I dont get why it will run perfect until the cel comes on then runs like crap until i clear the cel by disconnecting the batt. Could it be a problem with my computer? if so how would i check something like that?

Thanks
tom

 

P0420 is indeed a recognition by the pcm that the cat is not functioning properly (since you don't have one).
http://www.p0420.com/

the question is, what else (if anything) does the pcm do in response to that condition. some people report that it does nothing other than set the light, others report that it makes their truck run like crap (like yours). maybe its a year specific thing.

try this - remove your rear o2 sensor and zip tie it to the frame so it just hangs in fresh air. see what happens.

 

ok i'll give it a try tomorrow thanks

 

Don't these trucks operate in open loop at or near wide open throttle? I'm wondering if the truck is going into open loop at or near the 3300 rpm's, ignoring the 02 sensors, and letting the motor run ok. Also, I'd think it would take a couple of days after disconnecting the battery for the computer to fully relearn/set fuel trim. I could be wrong, but I'm thinking either one of the 02 sensors is bad or the rear 02 sensor is screwing with the fuel trim data (richening or leaning the fuel mix) because of the readings its getting because of the cat being gone. I talked to several mechanics and exhaust shops. Some said post cat sensor didn't affect fuel trim at all, but most said that my truck (1998 ram) would not run right without the cat. I got a lot of "sometimes they run ok without the cat, sometimes they don't" answers.
Is there an easy way the op can force the truck to stay in open loop and see if it runs ok?

 

ok, so i pulled the rear 02 and drove it 50 miles. I left the cel on and it was still doing the same thing, actually seemed a little worse. what brand 02 sensor is the best to run on these trucks?

 

NTK (cheaper) and Denso (pricier). DO NOT get Bosch.