car has rough idle, gas smell in exhaust, CEL codes

My girls 95 Jimmy SLE 4.6L Vortec was having a CEL for insufficient EGR flow a while back. I figured I would try cleaning the EGR and if the CEL came back we would then replace it. Well the CEL came back on so I figured it was probably the EGR again but we had the codes scanned and it came back with three different codes.

P0300 - Random/Multiple Cylinder Misfire Detected
P0141 -O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
P0172 - System Too Rich (Bank 1)

Does the P0141 indicate a bad O2 sensor? If so, which side is this and which O2 sensor? I don't even know how many she has or where they are located. I would have taken a look but it's bitter cold and the garage is being occupied by my SVT Contour at the moment (head gaskets).

Would the bad O2 sensor in Bank 1 be causing the P0172 code? If the bad O2 sensor is fixed would that correct this code?

And for the P0300 code. What should I be checking first? Spark plugs? Distributor cap?

I'm not sure where to start really and everything above is just pure speculation and I may be way off, thats why I am asking for help.

DTC's are always checked out starting with the first one, as others can be generated as a result of it. P0300 is usually the result of secondary ignition which includes distributor cap and rotor, spark plug wires, spark plugs, and ignition coil. Another possibility, (due to the fuel smell in the exhaust), could be a problem with fuel delivery, ie leaking fuel lines or fuel pressue regulator. If there is a fuel leak, it could set all of the DTC's you are seeing. Check fuel pressure first. Should be 60 to 66psi key on, engine off, pump running, and must remain above 55psi for 3 to 5 minutes after the pump shuts off.

Given the history of the CPI engines, I'd lean toward fuel leakage in the plenum either from the regulator and/or the fuel lines aka "Nut Kit". The plugs, wires, cap and rotor are still possibilities though. A fuel pressure leak down test is a good place to start. If you don't have a fuel pressure tester you can do a visual inspection by removing the vortec cover and IMTV (easiest, less invasive) , or pulling the upper plenum (much better view) and looking for washing. Washing is recognized as golden spots that are very clean as a result of the leaking fuel washing away carbon deposits from the plenum which should otherwise be black.

Fuel leakage in the plenum can cause a strong fuel smell, misfires, plug the EGR with carbon chunks, hard starts, stalling, and even engine damage due to the excess fuel leaking into the engine oil.

old_master, thanks for that article you sent via PM.

I will have to get a fuel pressure tester and check that first and go from there.

A lot of the symptoms you both are describing are happening to her car. rough idle, fuel smell, dirty exhaust, hard starting, hesitation under acceleration, etc.

Now, I know this isn't good for the car and she got horrible gas mileage but it is bitter cold out some days and I have my SVT in the middle of the garage as I am replacing all the upper seals, brakes, etc. So I don't have the ability to pull her car in yet and work on it. If she continues to drive it to work and home, 2 mile round trip, is it going to cause major damage to anything? I would like nothing more than to pull it into the garage now and work on it but I just don't have that option right now. But if it's going to cause more damage then I'll have to figure something out.

And the "nut kit", I recall reading about that before. Is there a write up on this? I'll search now but if you have a good link I would appreciate it. Just looking for an idea of what I may be in for is all, not jumping to conclusions.

And the "nut kit", I recall reading about that before. Is there a write up on this? I'll search now but if you have a good link I would appreciate it. Just looking for an idea of what I may be in for is all, not jumping to conclusions.

There's some info and pictures in these threads:

http://www.automotiveforums.com/vbulletin/showthread.php?t=462726

http://www.automotiveforums.com/vbulletin/showthread.php?t=473110

http://www.automotiveforums.com/vbulletin/showthread.php?t=503238

nice, thanks! those helped a lot.

I will get a pressure tester and start there first.

I quickly looked on AutoZone just for some quick price references and saw a price for the regulator but didn't see anything for a "nut kit" or fuel lines or anything. Is that part a dealer only item or can it be purchased elsewhere? If so, is it referred to as a nut kit or some other name?

Now say this is the problem and this is what cause all the codes to pop up. Would this have killed the O2 sensor or could that still be ok? I would assume the spark plugs would probably be fouled from something like this.

Also, if it is that, is it a for sure thing that fuel did get into the oil? Just wondering because then I would make sure to replace the oil and filter as well.

The fuel line ("Nut kit") is made by Dorman and their part # is 55163 and runs about $60 at most auto parts stores. If it leaks the engine will run rich and can allow raw fuel into the crankcase, so the oil and filter should be changed. As far as the oxygen sensor, driving the vehicle should clean it off, and it should be fine.

alright thanks. I called AutoZone and they said they didn't carry it but I'll call some other parts stores and check. I did call a dealership and they have one but it's 92.90 plus tax, so ~$60 sound much better.

I went to harbor freight to get that tester you linked me in the PM but got there 7min late! didn't realize their hours changed in the winter, oh well. So I will get that tonight and hopefully get that checked and see how the pressure checks.

well, picked up the pressure tester yesterday and checked it. With the fuel pump running and priming the system, the pressure was at ~63 PSI. But as soon as the fuel pump stopped running the pressure dropped immediately to 55 PSI and looked like the second hand of a clock after that, the pressure dropped pretty fast.

So we pulled the plenum off and saw the passenger side of the intake manifold was clean and a puddle of fuel that had collected around one of the bolts. Pretty obvious the pressure regulator was the culprit (looked very similar to one of those links, just not that "washed"). The driver side with the nut kit was nice and dirty so I didn't touch that.

I also noticed the small vacuum hose that plugged into the back of the plenum had rubbed a hole through itself so I cut that when re-installing everything to cut out the bad part of the hose.

I pulled and checked the distributor cap and that looked fine so I didn't replace it. I had replaced that, the rotor, wires and plugs about 2 years ago I think anyway.

Went to AutoZone and bought a pressure regulator, gasket for the plenum, spark plugs, oil, oil filter and an air filter (was going to do that on the next oil change anyway).

When we pulled the spark plugs the ones on the passenger side smelled of gas pretty strong.

Got everything replaced and primed the fuel pump a few times. Connected the pressure tester again and checked it again. With the pump running the fuel pressure was at ~63 PSI and after it stopped running the needle SLOWLY crept down. After about 3-4 minutes it was at ~56 PSI. So we pulled the tester and started cleaning up. Figured that was good enough, besides we were getting pretty cold by this point doing this outside since my SVT was taking up the garage. But it was a decent evening/night so we decided to do it, finished cleaning up about midnight (didn't start until 8 including time to go to autozone and wait for them to find the regulator) so it was a bit cold.

Took it out for a test drive through the neighborhood, onto the freeway and back home. No SES light, the exhaust smells much better (if thats possible :tongue: ), idles much smoother, just feels and sound much better in general. She just filled up the other day and had ~42 miles on this tank so we will see when she fills up the next time if her gas mileage gets better.

Thanks for your guys help, we really appreciate it and my girl is very happy her car is running better. Thanks again.

Other than a little cold, you made it through the job. Pressure and leakdown specs look great now. Your fuel mileage will increase substantially now that the leak is repaired. Check the fuel pressure and leakdown regularly as the lines, (nut kit) won't last forever and will give pretty much the same symptoms when they start leaking. Thanks for posting back.

yeah, I figured now that I have the pressure tester I will do it on a regular basis, maybe at the oil changes, to keep an eye on it. Not like it takes long or anything.

Thanks again for the tips and help.

I'm glad to hear you got it fixed. Thanks for posting the outcome. :thumbsup:

I Have A 1996 Jimmy 4.3 4x4 Have A Code 304 1880 What To Do And How To Fix

I Have A 1996 Jimmy 4.3 4x4 Have A Code 304 1880 What To Do And How To Fix

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Thanks

ok, I'm bringing this back up because her car has started doing this again, hope no one minds.

The idle has started surging a bit and her gas mileage has dropped a little, then her CEL came on with a P0300. The CEL came on one day after work, then the next day it was out. I checked the fuel pressure and it started at ~63psi but at 3min it had dropped to 38psi and at 5min is had dropped to 36psi.

I pulled the upper intake manifold and it was hard to tell if the clean area was from the previous time or recent so we decided to replace the fuel pressure regulator but that didn't help at all. Luckily they didn't have a problem with returning it.

So the question is, where do I go from here? What should I check next?

The person at the store had mentioned I could connect a vacuum pump to the fuel pressure regulator and verify it is working correctly. Should I do this and if so how do I go about doing that and what should the specs be?

The side of the manifold that has the "nut kit" is nice a dirty so those aren't leaking. I'm guessing it's either a bad check valve in the fuel pump or a leaky injector? Those are the only other places I can think of, correct? How should I check those? Pull spark plugs and see if any of them are fouled and smell of gas?

thoughts?

Leakdown is excessive. 1995 CMFI pressure should be 58psi to 64psi key on, engine off, fuel pump running, and must remain above 53psi for 3 to 5 minutes after the pump shuts off. You will need to isolate the fuel pump somewhere between the pump and the test port immediately after the pump pressurizes the system. If pressure drops below 53psi, the problem is in the plenum. If the pressure remains above 53psi, the problem is in the tank.