Hello. My 2000 monte carlo 3.4 is reading a zero on my diag tool. Was wondering why this would be. Also I just bought this car and it has different motor. It came with a 3.4 but has different 3.4 in it. Question being egr had to have new pigtail and still cant get work right but now runs pretty good after re-wiring the whole car basically but still bogs at wot? Runs perfect otherwise, small miss to it but someone said computer maybe? Any help greatly appreciated

 

In the life of the 3400 v6, I believe there have been a couple different EGR's used. Who ever swapped it more than likely needed to just switch over the upper intake to say with the EGR your car was using. Or the pig tail was a result of someone cutting or damaging the original connector.

What tool are you using to read fuel pressure? If it is a tool that scans the PCM, I admit, I don't know that the PCM reads fuel pressure. Best way to check fuel pressure is with a gauge at the fuel rail. If you have zero fuel pressure the car would not run.

As for the bogging down and the small miss, those might be related. And it might be the car needs a little maintenance. Below is a thread full of general maintenance these cars need around 100k miles. If that car is on factory (or BOSCH) spark plugs, I would change them with new AC Delco/NGK brand plugs and ensure the gap is correct. Also, is it throwing any check engine codes?

https://montecarloforum.com/forum/fw...0-miles-46078/

 

Its likely just not a supported field for this car/pcm. Use a mechanical gage to verify if you have concerns.

Could use some context on this - what do you mean a different 3.4? Like you swapped in a different 3400 from a different year?

I'd normally suggest swapping the EGR from the previous engine to avoid doing electrical changes, but it sounds like you're past that point now.

Curious what you mean by "rewiring the whole car"? I know there were some year to year changes in the 3400s, but I wouldnt think you'd have had to literally start from scratch.


For bogging at WOT, you should use the scan gauge you've got to read the sensors when it happens. What are the fuel trims doing as you start to get into the throttle? What are the misfire counts showing? Etc etc

I'd also be curious about what the EGR is doing since it sounds like there are some issues there. Perhaps its getting stuck open (or closed) due to not being wired up 100%?

As it sounds like you've got a scan tool, you need to use that to get you on the diagnostic path. I wouldnt just start replacing random parts at peoples suggestion. There are a ton of things that can cause a miss, so you need to see what the data is telling you so you know which system to dive into with other diagnostic tools.

 

so thank you so much for responding. As the scan tool is a bluetooth device ran through my phone called Garage Pro with sub to all the good stuff. However will not turn off service light even though says it will or abs light. Also wont read the vin. The motor is out of a 03 model with around 80-85000 on it . I have changed plugs (ac delco) wires, tps, iac,oxygen sensor, egr was new when i got it just wired wrong but may still be. I followed the wiring diagrams but to no avail. The codes its giving are P1404, 0443, 0134.
Also new coolant temp sensor and says its running hot on scan tool but its not. also does not have a cat or second oxygen sensor Smells like using alot of gas if let idle for 15-20 min. Thanks so much for the help hope i gave info needed.

 

Live data at idle with a little gas.

 

No cat or rear O2 sensor??? What has been done to the car to avoid getting at least a P0420 code? Has the PCM been adjusted?

As for your other codes, in brief, doing a little Googling, looks like they relate to the EGR, EVAP Purge Solenoid and the upstream O2 Sensor. To Bumpin's point, these can be all potential causes to problems. I would start with finding the diag charts for each one and stepping through it to figure out the issues.

And was this car like this when you bought it??

 

TBH turning off the engine light isn't really helpful anyways. Pulling the battery for a few minutes will do the same thing, but its not really useful unless you know you've fixed an issue and want to make sure it doesn't return. At a time like this (where you're diagnosing issues), turning it off doesn't really benefit anything.


I'm kinda ignorant to the 3400s, but just a couple years difference required a full rewire? The reason I'm getting so hung up on the rewire thing is engine electronics can be so picky. All it takes is one forgotten ground or a single wire not making a good connection to create all sorts of issues. Not saying you did anything wrong, but if its never run right after this engine swap / full rewire, it would certainly be up there on my suspects list.

Can you elaborate more on this so we can help you fix it? What wire colors + plug did you start with and what wire colors are you converting to? I'm no expert in this, but perhaps someone with an 03 on here can tell you which color goes to which pin on the plug. Theres only a handful of wires, so this should be pretty easy to get you back up and running again. As EGR is used at low + part throttle, it would also be up there on my suspects list.

How are you measuring that the temp sensor is wrong? Is this part of the rewire issues or a bad sensor? Regardless, I'd get it fixed before you get too deep into diagnostics because the pcm uses ECT in several ways, so it needs accurate data.

I'll second Maniac, what did you do to the pcm to compensate for no rear O2? I know several years of the 3800 have a cat test mode and can sit way rich trying to get some kind of response out of the rear. If your pcm is stock, perhaps its doing something similar which is why you smell gas?

Is this where its misfiring? Can you add some kind of misfire counter so its more obvious exactly where its stumbling? Is it constant or does it come and go? Is it cylinder specific or jump all around?

I don't see anything particularly alarming here- adding the fuel trims, timing value, and front o2 reading would help also. The one thing I am curious about - why does rpm drop to 0 twice? Did you shut it off / turn it back on at those points?

 

ok so the egr wires on the pigtail are white which is fine i guess. the others are
A) yellow/black
B) black
C) Grey
D) - not sure but have 2 yellow and white ones but if one is hooked up its worse than other then it starts stalling at red lights and acceleration from stop. Either way i have extra one
E) red
Misfire is constant at idle when giving slight gas you can hear it in exhaust.
The diagnostics report I print says its overheating but is clearly not. no rewire there.
When I first bought the car it had new exhaust front to back no cat no mufflers so i put a resinator in middle and two mufflers in back myself to quite it down.
It was lets say horrible but i thought was fixable but here i am 57 days later on here. The oxygen sensor on it was new but i bought another and if i plug it in it makes car die at lights around corners, basically anytime you let off gas and push back down it wants to die then catches and real high rpm for 30 or so seconds then back to same. I seen something earlier about tps put in wrong but i think at this point if it was that i would know. However when it acts up a little i reset everything through the diagm. , the throttle position relearn trans relearn,. seems to help a little but still have horrible gas milemage and some smell of gas every so often.
The rpm drop is what i was saying i didnt turn off it just literally dies but doesnt. The oxygen sensor reads 0.455 plugged in or not no rewire there that i know of.the wire thing was just alot of random wires not hooked up so i went through it all . its way better than was but still have a purple and blue i think over by fuse box under hood that are cut and i have no clue

 

also i cant seem to find an accurate vaccum line diagram. sounds like maybe a whistle or something under intake.