I’m going nuts here with this thing. I think I’m overlooking something stupid but hopefully someone might remind me what I’m missing here. Long story short, I blew headgaskets last fall, ( engine is basically a stock shortblock, ported GT40 heads/ intake, acufab 70mm throttle body, 3” Pro M blow through tube, and On3 turbo kit and tuning with PMS series 4). I pulled the engine to fix head gaskets and replace an oil pan gasket. When i put the vehicle back together it runs but sort of rough. It will basicallly fall flat on its face when I try to accelerate under a load. I can watch the wide band go from super lean to pig rich, and that’s when it will run and cut out. With the spout out it will not idle when it’s warm.
I have so far:
- verified fuel pressure ( 40psi with vacuum line disconnected, 35 at idle, connected)
- smoke tested for vacuum leaks
- verified O2 sensors are plugged in lol
-maf is plugged in and reading
-Cleaned salt and pepper connectors
-Replaced cap and rotor
-I put new plugs in with the engine ( Autolite Iridium)
-set tps voltage to .97
-Set base timing at 10 degrees
- removed and cleaned Maf
- verify engine grounds
I do not have any codes because my check engine light bulb doesn’t work and I don’t have a obd1 scan tool. I am going to probably clean the maf again and triple double check. What else am I missing here? Thanks in advance
It ran real good before the head gaskets, ( too good lol). I swapped:
-camshaft, went from an E cam to stocker with 1.7. Rockers
-Throttle body ,75mm acufab to 70mm
- upper intake, cobra to tubular gt40
Pretty sure that’s it. I’m just wondering if there is some trash blowing around and contaminating my Maf? I don’t know. I’m running out of ideas.
That’s a great idea about checking temps on the headers. I will do that tomorrow. I will check again for a vacuum leak. I might pull the plugs also. This thing is weird. Almost like it’s low on fuel, then almost clears up but the data it’s showing me on the PMS screen all looks good. Either way it’s running. That’s when I figured it had to be fuel related. Put the gauge on and that looks good also. I could have sworn it was a low fuel pressure issue but the gauge proved me wrong I guess.
Ist ideas...
Long time ago I had an issue where the fitting on the tubular bottom was hitting the drivers valve cover and I had to grind the vacuum fitting down to clear. That is without a spacer. Tubular can also be tight on the injectors without a spacer.
I have found so many issues with my infrared thermometer. Much more accurate than my fingers.
If you've still got the oem wiring harness & obd1 port in place,you don't need a scanner or the cel to run the code tests.Just use a jumper wire & 12v test light.
1) Connect one end of the jumper wire to the STI terminal and connect the other end of the jumper wire to the SIGNAL RETURN terminal (@ the diagnostic port)
2) Now connect the test light clip to the (+) battery post/terminal and insert the test light probe into the STO terminal (@ the diagnostic port)
3) Turn the koeo & the code test will begin.
If you've still got the oem wiring harness & obd1 port in place,you don't need a scanner or the cel to run the code tests.Just use a jumper wire & 12v test light.
1) Connect one end of the jumper wire to the STI terminal and connect the other end of the jumper wire to the SIGNAL RETURN terminal (@ the diagnostic port)
2) Now connect the test light clip to the (+) battery post/terminal and insert the test light probe into the STO terminal (@ the diagnostic port)
Make sure youve got the hego ground wire attached to a rear intake bolt,rear cylinder head
bolt (i.e. - crossover pipe bolt) etc.It'll trigger the o2 sensors to read lean if its not connected.Its the orange wire with a ring terminal on the injector harness.Im not familiar with how the pms works compared to the factory ecu,but if it doesn't have a screen you can look at to view live data,I would ohm out the ect sensor,with the engine cold & hot.If the ect is bad,it will tell the ecu that coolant temp is much warmer than what it truly is and that will trigger the ecu to lean the fuel mixture.Were you ever able to pinpoint the true cause of the blown gaskets?? Could it have been caused by a bad adjustment in the tuning?? I always thought it was usually just one gasket that would bite the dust when an engine suffered from a detonation episode,but you got had a double whammy.I would definitely check the old plugs for lean signs.Make sure youve got your pcv system set up correctly too,so that it wont pressurize the crankcase.If there is enough unmetered air allowed into the engine,it will also trigger a lean condition.Just like a breathered oil filler cap does if the pcv system is setup in stock form.
Make sure youve got the hego ground wire attached to a rear intake bolt,rear cylinder head
bolt (i.e. - crossover pipe bolt) etc.It'll trigger the o2 sensors to read lean if its not connected.Its the orange wire with a ring terminal on the injector harness.Im not familiar with how the pms works compared to the factory ecu,but if it doesn't have a screen you can look at to view live data,I would ohm out the ect sensor,with the engine cold & hot.If the ect is bad,it will tell the ecu that coolant temp is much warmer than what it truly is and that will trigger the ecu to lean the fuel mixture.Were you ever able to pinpoint the true cause of the blown gaskets?? Could it have been caused by a bad adjustment in the tuning?? I always thought it was usually just one gasket that would bite the dust when an engine suffered from a detonation episode,but you got had a double whammy.I would definitely check the old plugs for lean signs.Make sure youve got your pcv system set up correctly too,so that it wont pressurize the crankcase.If there is enough unmetered air allowed into the engine,it will also trigger a lean condition.Just like a breathered oil filler cap does if the pcv system is setup in stock form.
Yea I did actually only have one side leak, cylinders 3,4. I can monitor the O2s live on the PMS. I took a couple of snap shots with my phone of it today. I had a small window of time between work and work lol. I removed he Maf again and cleaned it again just to be 100% sure that wasn’t it. Car ran a little bit better then it started to act up again once I tried to give it throttle. I checked header temps when it was warm and all were within 30 degrees of each other. Around 380-400 degrees right after the header flange. I really didn’t find anything else new today. More dead ends with the small amount of time I had.
I still want to check codes, and I want to pull the plugs and see what they look like. It acts like it a fuel delivery problem.... I might check the fuel lines and rails to make sure there isn’t a restriction. I would figure I’d have fluctuated fuel pressures but who knows at this point.
This picture is of when this thing was running rough. I was tipping the throttle in at 5% and it wouldn’t rev up. Maybe this would help someone? I do t know
I would reset the stock ECU, disconnect the 02s than tune the PMS to give you 14.7 a/f in each rpm/load cell (not wot cells). Once you do that plug the 02s back in.
I’m sorry but the O2 readings are not actual voltage but a “load” reading given by the PMS. I might actually have to dig out my fluke meter and do some testing. They do appear to be low compared to other videos of cars running. I don’t want to assume but, they could be relatively close to actual voltage. I will verify tomorrow hopefully.
Yea you should have. I was up. I had a class in the city after work. It was a late night but this car is driving me nuts. I still think I’m overlooking something stupid. I’m going to unhook the O2 sensors tonight and reset the pcm. Triple check my engine grounds again to make sure I didn’t leave any off
Update: unplugged O2 sensors. Still runs like crap. Reset PCM. Crap. I have come to determine that it’s running rich at idle 10.0 and leaning right out - - - , after throttle is given. It acts like kit starving for fuel. Should I unhook the fuel lines from the rails and check for volume? Maybe it has the right pressure but not enough volume? Could the fuel pressure regulator be giving me this issue? I have two other fuel rails with regulators in them, I could switch them out.
With 02s unplugged start tuning with the PMS. It will show you what load/rpm cell to a adjust. For idle adjust the idle cell to get as close to 14.7 as possible. Bring the tps to 1% than adjust the first rpm and load cell. Probably the first load-1. Keep adding fuel to get it to 14.7. Don't worry for now how much fuel you have to add. If it's 20%, 30% whatever, give it to the engine, it's just a number. Do that for all the rpm/ load cells
It's really not hard.
With 02s unplugged start tuning with the PMS. It will show you what load/rpm cell to a adjust. For idle adjust the idle cell to get as close to 14.7 as possible. Bring the tps to 1% than adjust the first rpm and load cell. Probably the first load-1. Keep adding fuel to get it to 14.7. Don't worry for now how much fuel you have to add. If it's 20%, 30% whatever, give it to the engine, it's just a number. Do that for all the rpm/ load cells
I understand what your saying but I really don’t want to change the tune because it was running good prior to the gasket change. Do you think the tune would change that much and I don’t have another issue or a root cause of this behavior? I agree with what your saying and I understand what to do to change the tune but, the vehicle still feels like something is wrong ( besides the tune). I’m going to give a call to a friend of mine who tuned the car for me. Last time I talked to him he seemed to think something was wrong and it wasn’t in the tune itself. He said the tune is probably off but not enough to make it run like that
So I noticed tonight my pcv valve had come out of the lower intake. ( probably from me poking around back there) I then placed that back in but still lean. So I decided to bust out the service manual and do some reading. Lots of reading. I’ve got some pinpoint tests to do tomorrow on my fuel system. I checked my fuel pressure but I think it might be on the low side. It was 39psi with engine running/ vacuum disconnected and 34ish with the vacuum line connected vehicle running. It also took two ignition cycles to reach 39 psi with KOEO.
So I figure this; tomorrow is Friday, I will stop and get some drinks on my way home from work and I’m going to stay out there until I have answers. I have two other fuel rails and regulators I can try. I also have a bad feeling my lines going from the frame to the rails could be bent? Who knows. I do know #### is getting torn apart and answers will be had lol.
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