View Full Version : Runing Rich, WAY rich
01-23-2008, 09:22 PM
Ok, so, I've been having an issue with my new engine runing VEARY rich during cold start/warm up on cold days(-10c and below) After some diagnoses it came to my attention that I neded to replace the ECT sensor and repair the conector, so thats done. Problem improves but still rears its ugly head when its cold. Ran a ECM self test and getting code 11 for all tests. When I drive the truck right after start up it will spit and studder if i press the throttle more then about 1/4 of the way down. Did a fuel pressure test and thats within spec also. Im suspecting it could be the ACT sensor sendinf a slewed signal to the ECM, anyone have any opinions about this problem? Its so bad that the mpg has gone way down.
01-24-2008, 04:25 PM
replace the iac.its well worn and cleaning may not do.also make sure its on the right way
01-24-2008, 05:45 PM
um, the engine is new, along with the TB EGR spacer TPS sensor and IAB. It idles fine holds a steady 650rpm, it just runs stupidly rich and has tearable drivability untill it starts to warm up. Once the throttle is opened the IAC isnt realy doing much. If i start it up and just drive away it mis fires and studders for a few min untill it warms up.
01-24-2008, 08:59 PM
the iac is the choke it operates @ 25 % greater duty cycle when cold start.you never want to believe.i have told you several times before.it does very little after warm up, just during stop in gear with auto or upon clutch engagement on stick.
01-24-2008, 09:56 PM
i believe lol....you dont believe that its NEW lol it cant be worn out. Im not arguing, maybe im juss not getting it. How does it effect things once the throttle plate is opening. I can kinda see how it causes issues when just idling, but why would it affect anything at 1/2 throttle?
01-25-2008, 07:19 AM
like a choke it adds air when cold.your efi car acts like a carb with no choke.either its on backwards or its not functioning.the only other sensors that might effect cold start ,iat ect.or an o2 heater circuit.
01-25-2008, 05:32 PM
a choke adds air when cold? I thought it restricted the amount of air being taken in to change the intake charge. When an EFI engine is cold, the ECM dumps more fuel in to start and during warm up. Thats how i understood things in school and thats what it says on the ford fuel injection site. the IAC is functioning, if it was "dead" then it wouldnt idle at all. the ECT is new, and functioning as it should. I was having a problem with the ECT circuit, there was a huge voltage drop. After properly repairing the conector everything was fine acording to the DMM and like i said befor, there are no codes. theres the link for the info i was getting, do you think im misreading somthing?
01-25-2008, 08:51 PM
1/2 right it adds fuel and air.only your not getting air which is why its rich.if idle is not increasing to 900 rpm when cold you got a bad or non funcining iac .why do you fight that fact.i'm thru,live with it if you must.but you don't have too.lol ,sorry for the rant
01-25-2008, 09:28 PM
Have you checked for a bad fuel preasure regulator ?
Check for fuel in the vac line .
01-26-2008, 03:08 PM
haha, stranger, that was far from a rant budy. and you have yet to give me SOLID useful information. YOu give some info, without asking anything. I already said it idles fine. It starts, jumps to 1900 goes down to 1000 and goes down to 650 in a normal amount of time. If it wasnt getting enough air, it would die. explain that to me? Man you gotta realize that im not a backyard wrench spinner, I do it for a living and have done the school thing. Learned a lot from experience and from thouse i work with and friends. WE are ALL stumped. Why do you refuse to consider an issue with fuel control and juss keep going on and on about the IAC? Its had three different IAC's on it, with no change, and no, i didnt manage to get three bad ones, they were pulled off of other vehicles. if you gave me somthing new to work with, then it would be usefull. you juss seam to be stuck on the IAC and when your told that its not the problem, you get pissy.
What's the bio on your electronics?
Your engine is new, OK. But what about your computer and sensors?
Do you have a chip or tuner?
Ultimately that stuff has control of your entire fuel management system and it could be on the fritz no matter how old or new it is. If you can source a second ECM for a reasonable price maybe that would add some insight.
You may have to ignore what your computer and code reader tell you and start changing out components even if there's nothing apparently wrong with them. Get another ACT if possible. If your system is Mass Air you could also suspect the mass air meter. Is it dirty?
Has any part of your harness been damaged? Exposed and damaged wires can cause any number of hidden problems.
01-30-2008, 09:07 AM
Thanks for the second opinion man. Um, the ECM was a donation so im not exactly sure what its from other then it was an HO engine. I gave up on the code reader long ago, more or less just use it as a referince. The ECT was replaced when the engine went in. I also checked it with a DMM and its working. I also checked the ECT conector and wireing for any out of spec voltage drops. When i replaced the engine I took a few hrs to inspect the engine harness and its in good shape. I didnt look at the half that stayedi n the truck tho, and i just read that the two ten pin conectors can some times cause problems so I plan to clean them next. Im also going to take a look at the ACT today during luch
Chic N Stew
01-30-2008, 09:21 AM
My s10 does that, its just the carb that needs to be adjusted, don't know if yours is FI or carb
01-31-2008, 01:00 PM
High Desert Ranger
01-31-2008, 01:10 PM
I wish you could find out why this is doing it. I have a 84 TurboCoupe that I parked because it was runninf so rich that it was pegging the neddle of the smog machines. I had replaced everything from the computer to Vane Air Flow Meter to ECT, ACT, checked fuel pressure and flow. Long after I parked I thought about a sensor getting mixed signals and making the computer throw the extra fuel at it, but i didn't have a o-scope to look at the signals to the injectors to see if they were being kept open for a long period. I did have the wire harness out of the car and repaired some wires, but maybe when I put it back in the vehicle I laid it over or crossed some signal wires over each other and it was picking up the signal from something else and causing the problem.
Maybe also check your ground connections, i was once told that.
02-01-2008, 09:48 AM
when i swaped engines i replaced the ground straps and checked the harness grounds to be sure everything was in good shape. Me and the guys in the shop have been brainstorming over this for a while now, I will let ya know when we come up with a solid therory.
02-05-2008, 09:49 AM
During start up & for 120-180 seconds afterwards (at that cold start up temp), the engine only looks at the incoming air temp, coolant temp, throttle position and maf signal.
If the ECT fails, it typically fails to the max cold reading it can give, -40*F (roughly -40C). I have seen this more than once.
For the engine to reach closed loop operation (general cruising, and pretty much everywhere except WOT), the coolant has to reach ~170*F (varies a bit between ECUs/models), so that would have explained your crappy gas mileage.
The IAC only controls your idle speed, it has absolutely nothing to do with the fuel.
The air charge temp isn't capable (iirc) of richening it up enough to sputter, it mainly pulls/adds timing.
A code 11 = system pass for key on/engine off, key on/engine on, continuous memory.
Have you changed anything non OEM from the donor? MAF/TB/injectors?
02-06-2008, 12:29 PM
thanks for the info, but you mostly told me things im already aware of. Its speed density btw. I havent run a scan for a while now, but like two weeks ago it was passing everything even th oit ran like shat. Thats why im stil tryin to figure it out. Im tempted to replace the IAT.
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