Help with engine issues/emissions

Artyom

New Member
Apr 11, 2024
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Hello, I’m new to mustangs and just bought a 5.0 1995 v8 Mustang (manual) a few days ago.
The car has some unknowns, but from what I know and see it has a Trickflow intake, looks like ignition was upgraded as the coil wires are ford performance, and egr delete. This is everything that is known to be done in the engine bay.
The car runs great, shifts well, feels like all the power is there. However, I was told by the seller it will not pass emissions (Colorado), and the emissions came back high. I asked if he had the results so I can see what was high on the emissions but he did not have the results. The car also has a rich smell, and sometimes the idle will be random and surge.
I’ve been looking around everywhere online just to get an idea on what’s the cause and how I can look into fixing the engine up, but it’s becoming very overwhelming especially after pulling codes.
I still have tests to do, like compression test, test for vacuum leaks, and just do a deeper inspection on the car but haven’t had much time yet.
Ok, so any advice on these issues would be much appreciated as I’m new to mustangs and never worked on anything bigger than a 4 cylinder.

EGR system:
From what I know the EGR delete has been somewhat done properly? It has the block off plate, and the sensor is unplugged and fitted with the eliminator. From what I’ve read, to do this properly you have to basically remove the EGR from the ECU so it doesn’t interfere with the fuel tables. I would like to get the system back up and running for emissions testing here. But I’m missing the pipe that goes from the header up into the EGR. Which is no where to be found online so I’ll have to make my own or find at a junk yard. Would this possibly be the main issue to the car running rich? It’s thrown a few codes too which I will list.

Codes:
I hope I read them correctly but heres what I got.
KOEO
113: ACT sensor is greater than max of 4.6V
173: HEGO sensor circuit indicates system rich (right)
176: HEGO sensor circuit indicates system lean (left)
334: DPFE or EVP circuit above the closed limit of 0.67 volts
121: TP sensor was inconsistent with the MAF/MAP value in last 80 drive cycles

KOER:
116: ECT out of self test range of 0.3 to 3.7 Volts
121 again?
314: Thermactor air system inoperative (left)
311: Thermactor air system inoperative (right)

Any insight to these codes and what could cause them would be greatly appreciated! From what I’ve read 314 and 311 can be from the EGR delete. Possibly 334 as well?
I plan on cleaning the MAF, clearing the codes and running it a little to see what codes pop back up. Then doing a leak test once I build the little homemade leak tester. Feel free to let me know if I got anything wrong or miss understood something as I’m always open to learning!
 
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I have that pipe from what I know. I’ll look tomorrow to make sure! The pipe I’m missing for sure though is coming off of the exhaust manifold on the passenger side and goes directly into the EGR?
 

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it’s sold. But thank you! I did manage to find the part on oem ford parts somehow. Expensive but it will fix some codes hopefully and help me pass emissions. Anyone know why one bank ran lean and the other bank ran rich? It’s making me nervous.
 
Would need more data to begin to even speculate that. How are you concluding that the banks are rich/lean?

Could be vacuum leaks, could be o2 sensors, could be exhaust leaks. Part of the troubleshooting process
 
I think you should finish the diagnostics you were on track doing. That complete picture will aid in resolving the questions. I had a lien O2 sensor reading a few years back; I replaced that sensor and it resolved the issue. I’m not saying that’s it, just info.
 
I got my lean and rich code through reading the codes.
I do plan on continuing with going through diagnosing things. I’m just very new to this engine and car, so I’ll gladly take any advice.
 
If the entire smog system was deleted then you are needing more than just that header to EGR pipe. You need to clear the codes that do not have anything to do with the smog related items and then see how it performs.

Does the car have cats on it still? If you roll under the car and there are cats is could be that they gutted them so pulling the h-pipe off and verifying the they are still intact is really the only way to be sure.
 
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I got my lean and rich code through reading the codes.
I do plan on continuing with going through diagnosing things. I’m just very new to this engine and car, so I’ll gladly take any advice.
I suspect an intake leak... Between either, the upper and lower plenum or the lower intake and block.
 
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Here are the engine bay pictures.
From the looks of it the original exhaust has been cut and some things have been welded on. I will have to verify the cats are not gutted.
I can verify the smug pump still has the belt around it. From what I know the EGR stuff is still there.
 

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Ok, so good news. Cleared the codes, then scanned them with a code reader this time and in the proper procedure. I think a lot of the codes I got originally were false due to the engine not being at operating temps while doing the KOER test.
The only codes I got back were 121 (KOEO and KOER) then I got codes 137 and 173 (KOER).
so with that narrowed down a lot more, my plan is to get the EGR system back up and running so it will throw a code and the computer will properly adjust the fuel and timing and not use the EGR system. Just for the time being until I can get that tube.
The car has some weird stumbling or surging at idle but its rare. My guess is the EGR or the ICV needs to be cleaned.