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Discussion Starter · #1 ·
I have a 98GT that has 49,000miles on it. I blew the stock motor 1month ago spraying. I just put a brand new 03GT motor in it with coldair,massair,TB,intake spacer,coil packs, Msd, plug wires, Steeda pulleys, longtubes, offroad hpipe, catback, king cobra clutch, tremec trany, aluminum driveshaft, pro5.0shifter, walbro 255 fuel pump, 4.10's,etc. Anyways, about every 4 to 5 days the check engine light pops up. The car seems to run fine and the obd2 says that the car runs lean on banks 1&2, but i just put it on the dyno and the car has plenty of fuel? And it takes so long for light to come on, every 4-5days? I checked vacum hoses and put water treatment in tank and checked everything and has new fuel filter. What do you think is causeing the problem and how do i fix it? I am up for any advice and i would appreciate it greatly as i am tired of working on the car.?

Thanks Josh
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187import:

Oxygen sensor or connecting wire might be at fault.

Some RTV/silicones are not O2 sensor friendly. Was any fresh RTV used during the swap? Maybe some anti-seize got onto the sensor?

I'll check the shop manual when I get home and post a few more "look ats" for you.
 

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Just a thought do you have MIL Eliminators for your O/R H-pipe??? because a friend of mine has a o/r h-pipe with no mils and every once and a while the check engine light comes on because of that.
 

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Discussion Starter · #4 ·
chris

yeah i have the mil's. what do ou mean by rtv? I put the o2's back in the new headers and hpipe accordingly. People are tell me possible slow vacum leak, or my 98pcm isn't compatible with 03 motor? Anyways, it takes 4 days to come on and doesn't seem to effect the way the car runs. The code is p0171/p0174, lean on banks 1 and 2... Let me know...

thanks
josh
 

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187import:

RTV is silicone sealant ('gasket maker').

I don't know about year-to-year PCM compatability. Luckily, there are a few souls on this board who have swapped in new motors and used their original PCM. The MAF and the coolant sensor are wired differently on the new engines. The MAF has an internal temperature sensor now and there is only one coolant temperature sensor. I am not sure if either of these items would contribute to the check engine problem.

I agree that a slow vacuum leak could cause the trouble, too. (I had to run some errands last night so I didn't get a chance to crack open the shop manual or even get near the computer. Hopefully, tonight will be under better control). I will see what I can find about the codes.

Chris
 

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what exactly are the trouble codes that are in memory.

also how healthy is the fuel pump. Didn't the 98's have lots of issues because they were the first year for the returnless and got a smaller fuel pump?
 

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Discussion Starter · #7 ·
Chris
Thanks for trying and just let me know what you find out. About the coolant sensors, i was able to use both from 98 on new motor. I just made a T fitting and put it were the 03motor has 1spot and bam, i was able to use both sensors.

The 98's still have return style but with 99up fuel pump assembly. What you have to do is custom fit the fuel pump for a 96-97 into the 98assembly. I've done that with a 255walbro..

Codes are p0171/p0174, reads lean on banks 1&2
 

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import187:

No luck in the shop manual, the info required is in the PCM manual (I don't have one). The little that is written does say the code is associated with the "heated oxygen sensors" but does not give any troubleshooting steps. I think the links in the earlier post have much better diagnostic steps.

Anyway, let us know what you find, please.

Chris
 
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