I've been reading a lot of threads about code 35 (IAC malfunction) that a lot of other people with the 3.1L v6's have been having along with myself that never leads to any conclusion. I've noticed that whatever the problem may be, seems to be exacerbated by heat in the summer. I seem to remember that I was told at one point by a local shop that there was a short in the fuel injection wiring harness. I've been noticing the problem since about late 2011/early 2012 on my car (stalling at a stop light, high idle at park). In the last month or so, I haven't had a lot of time to do many tests on my car cause of my job but tunerpro rt told me that I had a lean condition yet when I pulled open the throttle plate on the TB there was a puddle of gas in the bottom and when I pulled the spark plugs they were coated in gas and were pretty much shot. Mine seems to be a more advanced case and is sitting without being driven until I can find the problem. The ecm says it has a lean condition yet it seems to be dumping gas. I hope anyone else with this problem finds some answer or conclusion because even I'm beginning to feel like I'm looking for a needle in a haystack here. If I find the problem I will let everyone know. Also, does anyone know where I might find a replacement fuel injection wiring harness for our 3.1's? I found this one on oreillys website but it says its for the v8s but it also says for the 7730 ecms which I believe our v6's use?

http://www.oreillyauto.com/site/c/se...991&vi=1251762

 

If the ECM is reporting lean, but there is excessive fuel being added, I would replace the O2 sensor, it's likely defective. I would also thoroughly check for an exhaust leak, especially at the manifold to Y-pipe connections. I have seen some cases where you could not hear a leak at this point because it was actually sucking in outside air and not pushing exhaust out. Became a venturi effect, much like how some crankcase evac systems work on race cars. This causes a lean condition to be reported, even though that is not really the case.

If you're seeing fuel in the plenum (just behind the throttle) body you have some serious issues here. The injectors are no where near the plenum. I would in this case suspect that the fuel pressure regulator diaphragm has torn and is allowing fuel to be pulled into the plenum through the vacuum hose. Check for fuel in the vacuum hose. You can also disconnect the vacuum hose and power the fuel pump, if you see fuel come out of the vacuum hose the fuel regulator definitely needs to be serviced then. Just be careful if you do it this way, fuel can cause a lot of pain and serious injury if you get it on you or in the wrong orifices. Getting some fuel in my ear trying to diagnose a fuel issue on a friend's Civic a number of year ago gave the worst pain I have ever felt in my life, it literally dropped me to my knees, and I have, or at least had a pretty high tolerance for pain.

About the IAC issue, it could be related to the fuel issue, but if not, be sure to clean the IAC passages, and maybe even replace the IAC with a new or known good IAC. They do wear over time and get "lazy". I have one in my Datsun right now (GM EFI, and GM throttle body), that every now and then will get out of sync with what the ECM thinks the IAC position is and the engine will sit at about 2000 or 3000 RPM depending on how out of sync it gets.

Yes, the 3.1 in the third gens also uses a '7730, but I'm not sure how close that harness would be. I'm sure it could be used to replace a V6 harness, but would likely require some modifications to do so.

Also I have rarely found any issues with a harness, especially ones that would require replacing the entire harness.

 

Thank you for the response Six, after driving it about five or ten minutes it literally smells like firecrackers. I have been told elsewhere on this forum that if I continue driving it like this it will destroy the catcon. I actually have a new FPR on hand, I pulled the vacuum hose off the port to it and no gas came out but I think I am just going to go ahead and replace it regardless to rule it out. I hosed off the IAC with brak lean and put it back in, I only bought it three or four years ago but I think I will just replace it too. At this point I'm just shotgunning for parts hoping I hit the problem. Can you think of anything else I might need? I already plan on picking up a new EGR valve, PCV valve, o2 sensor, new TBI and IAC gaskets.

 

Well that's just wonderful... I tried to go outside to start the car and the starter will engage but won't turn over or even crank. I have power though, cleaned off the battery terminals to get a good connection so I'm wondering if it's the starter...

 

Thought I'd give a little update since it's been awhile on my code 35 journey. I changed out all 6 injectors with new SMP fj105 injectors and a new fuel pressure regulator. After that I couldn't get the car to start because I had my brother hose out the throttle body and plenum with carb cleaner and the excess fluid had ran down into the cylinder and hydrolocked it so the car wouldn't turn over until I pulled the spark plug and cleaned it out. Afterwards, the car seemed to have a hard time starting and would misfire a lot when taking off. I took it to the local shop and they said that they couldn't find any trouble codes and the car started up every time without any issues. I did some research on older posts with this issue (code 35 iac malfunction) and the only conclusion that I found was that they eventually said in the final post that it was because of a damaged/destroyed throttle body gasket. Mine was literally cracked in half and had to piece it back together to get it to the shop. I bought accel spark plug wires and I'm going to get the ac delco iac/tbi gasket kit as well as a new o2 sensor and pcv valve and see if that doesnt help with the misfire issue and come back with a new update. I just originally posted this because I saw this was a recurring issue in the summer with our 3.1's. Also autozone found nothing wrong with my starter.

 

Well the car doesn't seem to be smelling like rotten eggs anymore and I don't seem at the moment to be burning through nearly as much gas I was. I don't seem to have as much power though, when at a complete stop the car wants to sputter and take it's time getting up to speed. When I was trying to get it up the hill I could feel it misfire and the exhaust sounds kinda bad. I don't know if anyone is even reading this but does anyone maybe have any ideas as to what's going on?

 

Sounds kind of like a timing issue to me. Whens the last time you have checked the timing/replaced the timing set?

 

I don't think I have ever changed out the timing set, I just changed out the spark plug wires though. The car seems lately to have had a hard time starting, takes a few cranks to get it to start. I took the starter to autozone and they said it was fine so not sure what could be causing that.

 

Check your timing with a timing gun and report back. Stock timing is 10° BTDC. You need to unplug the EST connector to check and set timing. IIRC the EST connector should be in front of your blower motor. Single tan wire with black stripe and a connector on it.

If its not the problem than it would be good to scratch it off the list.

 

Well, the new spark plugs helped a little but I can still feel it misfire and sputter. Still has a hard time starting when it's hot outside. Since it's a cheap fix I'll try changing out the fuel filter and see if that helps.

 

You need to check the timing just in case. If you go throwing things at it you may wind up spending more money than you need to to find out it was something completely different.

Though if it is the original fuel filter, safe bet to swap that out anyway. Definitely get that timing checked out though, cause it sounds like either the timing or the ignition control module. Could be a combination of both but until the timing is ruled out its really just guessing...

 

Okay thank you Willie, I'll likely get the timing checked out this weekend. I just figured since the fuel filter was a cheap fix I'd go ahead and do it anyway since it's never been done on my car since I've owned it. So this connector is in the engine compartment I would assume?

 

Yes its in the engine compartment. Its a single wire, tan with a black stripe and a single black connector. Located by the blower fan. It should be one of the only wires coming out of the loom.

Unplug it before you start the car, then start the car and check the timing. This will give you the base timing. If you dont unplug it, the ECM will be controlling timing, so you wont be reading base timing.

 

Sorry for the slow response, I'll check it out in the next couple of days when the rain slacks off. Thank you willie.

 

No problem, let us know how it goes