Extremely rich and rough idle
- Thread starter AfricanSnowOwl
- Start date
The ECU was a DA1, but a faulty DVOM led me to believe it was outputting incorrect vref voltage, so I replaced it with a refurbished one from Autozone. I double checked the part numbers from the company that refurbishes, and it checks as a speed density 87-88 5.0 mustang. There was absolutely no change to the idle when I swapped the computers out. I also opened it up to check the capacitors.
While it's running, if I pull any plug wire there is no change in idle. The vacuum stays the same, the idle rpm stays the same, and the rough idle doesn't change at all. All plug wires have a strong spark though. It actually didn't even change if I pulled 2 plug wires...
The fuel in the tank is only a few weeks old. I ran it til it died before that, and then filled it with 93.
The code 67 I think was coming from the A/C WOT relay. It had multiple wires coming out of it that were bare, one of those wires was the red 12v wire, which was touching the other bare wire.
If I pull the IAC, it will sputter and almost die. I tried pulling the MAP connector, and the idle changed. Not significantly worse, but it definitely changed. My understanding is without the sensor it gets 5v to the signal wire?
I've pulled the #1 plug and checked the TDC on the balancer a few times. Every time it always lines up to what looks like the TDC mark, and the rotor points at 12 o'clock. I also tried purposely stabbing the distributor "one tooth off" in each direction, and then 180 degrees off just to check. It hold the 14 degrees I have set with the spout removed, and if I plug it in you can see the computer take over timing and move it.
I bought this car from a co-worker earlier in the year. He was the only owner, but this car spent the last 8 years sitting in a parking lot on base. He would move it from spot to spot once every month or so. I did a basic tune-up before I drove it home(plugs, wires, cap, rotor, fuel filter), but I honestly can't remember if the idle was this jacked up before I started messing with it. I do remember the idle hanging high every time I came to a stop.
I pretty much did everything all at once. I immediately did a 5 lug conversion and then changed all fluids, replaced all vacuum lines, new battery, full exhaust, EGR/smog delete, replaced every single sensor, upper intake gasket, 70mm TB, 3G alt, fuel pump. I then started trying to single out this idle issue.
While it's running, if I pull any plug wire there is no change in idle. The vacuum stays the same, the idle rpm stays the same, and the rough idle doesn't change at all. All plug wires have a strong spark though. It actually didn't even change if I pulled 2 plug wires...
The fuel in the tank is only a few weeks old. I ran it til it died before that, and then filled it with 93.
The code 67 I think was coming from the A/C WOT relay. It had multiple wires coming out of it that were bare, one of those wires was the red 12v wire, which was touching the other bare wire.
If I pull the IAC, it will sputter and almost die. I tried pulling the MAP connector, and the idle changed. Not significantly worse, but it definitely changed. My understanding is without the sensor it gets 5v to the signal wire?
I've pulled the #1 plug and checked the TDC on the balancer a few times. Every time it always lines up to what looks like the TDC mark, and the rotor points at 12 o'clock. I also tried purposely stabbing the distributor "one tooth off" in each direction, and then 180 degrees off just to check. It hold the 14 degrees I have set with the spout removed, and if I plug it in you can see the computer take over timing and move it.
I bought this car from a co-worker earlier in the year. He was the only owner, but this car spent the last 8 years sitting in a parking lot on base. He would move it from spot to spot once every month or so. I did a basic tune-up before I drove it home(plugs, wires, cap, rotor, fuel filter), but I honestly can't remember if the idle was this jacked up before I started messing with it. I do remember the idle hanging high every time I came to a stop.
I pretty much did everything all at once. I immediately did a 5 lug conversion and then changed all fluids, replaced all vacuum lines, new battery, full exhaust, EGR/smog delete, replaced every single sensor, upper intake gasket, 70mm TB, 3G alt, fuel pump. I then started trying to single out this idle issue.
Might not be a bad idea to do a smoke test.
Hmmm... after reading that I think it might be worth pulling the lower intake to replace the gaskets.
I didn’t do a smoke test, but I did spray everywhere with carb cleaner, and when that didn’t produce any results I tried spraying propane. Also no results. I’m thinking I’ll try the lower intake gaskets since it’s cheap and I have no idea what else to try.
I didn’t do a smoke test, but I did spray everywhere with carb cleaner, and when that didn’t produce any results I tried spraying propane. Also no results. I’m thinking I’ll try the lower intake gaskets since it’s cheap and I have no idea what else to try.
Propane and carb cleaner are good ways to check. Smoke test is probably the best way. I guess if it was me I would invest in tuning and datalogging. Getting a datalog gives you good info to at least point you in the right direction if not pinpoint the problem exactly.
Have you went back to 65mm tb?
Didn’t see much on plug gap.
But maybe the extra air in is blowing out your spark.
Like adding more boost would for me
Mine is also 52-54 gap
Guys running more boost are gapped 28-32 because of spark blow out
70mm may be cause of 42/92.
But maybe the extra air in is blowing out your spark.
Like adding more boost would for me
Mine is also 52-54 gap
Guys running more boost are gapped 28-32 because of spark blow out
70mm may be cause of 42/92.
Yeah, that was going to be my next question. I had a slight suspicion the TB could be to blame. The only reason I put the 70mm TB on in the first place was because the spring was rusted and sticky on the stock one. I ended up throwing the stock one away, but lowering the gap is worth a shot. I'll give that a try tomorrow.
Put the new MAP sensor in, no difference whatsoever. I don't think it's going to be the plug gap either, but I'll still try bring it down maybe to like .048-050. I would think spark blowout would get worse with higher rpm or engine load, but mine seems to be better in those situations.
I would also think if the lower intake gaskets were creating an internal vacuum leak that it causes the car to run lean? My car does behave like it has a vacuum leak, just running rich instead. I still bought the gasket set and plan to tear into it sometime in the next few days. It wouldn't surprise me if the gaskets are bad. Pretty much every other gasket I've encounter on this car was bad.
I would also think if the lower intake gaskets were creating an internal vacuum leak that it causes the car to run lean? My car does behave like it has a vacuum leak, just running rich instead. I still bought the gasket set and plan to tear into it sometime in the next few days. It wouldn't surprise me if the gaskets are bad. Pretty much every other gasket I've encounter on this car was bad.
The slipped lower intake gasket is a good theory. It would't show up when spraying with carb cleaner due to being an internal vac leak, but it may appear if you run a smoke test. I'd probably invest the time to build a setup and give it a shot, unless you just want to dig in and change them out to be safe
I got the lower intake off today, no real surprises there. The gaskets were definitely blown on the rear coolant passages. The intake port areas of the gaskets seemed to be fine, but hard to tell. It was the original 34 year old ford gaskets. If there had been a vacuum leak, would it be something easily visible? Also, the lower intake just lifted right off. Shouldn't the gaskets have been pulling it to the heads making it require at least some sort of force to remove it?
I'll reassemble tomorrow. The lower had about a half inch of sludge coating all of it, so I decided to soak it in purple power and then scrub it.
I'll reassemble tomorrow. The lower had about a half inch of sludge coating all of it, so I decided to soak it in purple power and then scrub it.
You about replaced or touched every thing else
hope this is it.
I to would assume some effort to pull apart or break seal
I got the lower installed today. Used "the right stuff" gasket maker for the front and back(skipped the rubber gaskets), and also put a ring around the coolant ports. Followed the torque sequence, and now I'm just giving it 24hrs to dry before I try starting it up.
I did notice that the rubber PCV grommet on the back of the lower intake was significantly loose. Loose to the point it would just fall out if you turned the intake upside down. That could have potentially been something causing my problem, so I put a ring of rtv around the base of the grommet to give it a good seal.
I also apparently stripped out the threads on the heater tube connector, so I'll have to figure out a way to make that work. Seems like I can rig some hoses and a 90 degree connection up pretty easy. Don't feel like spending $100 on a new one from LMR.
When I initially removed the lower intake manifold, all of the bolts were pretty loose. Loose to the point that I could've used a nut driver to remove everything. That plus the fact that it was free to move around with no give whatsoever after the bolts were out leads me to believe that there wasn't a good seal between the lower manifold to the heads. I'm really hoping this fixes the issue. Honestly if this doesn't fix the issue, a drastic change in the engine/tranny swap is in the very near future.
I did notice that the rubber PCV grommet on the back of the lower intake was significantly loose. Loose to the point it would just fall out if you turned the intake upside down. That could have potentially been something causing my problem, so I put a ring of rtv around the base of the grommet to give it a good seal.
I also apparently stripped out the threads on the heater tube connector, so I'll have to figure out a way to make that work. Seems like I can rig some hoses and a 90 degree connection up pretty easy. Don't feel like spending $100 on a new one from LMR.
When I initially removed the lower intake manifold, all of the bolts were pretty loose. Loose to the point that I could've used a nut driver to remove everything. That plus the fact that it was free to move around with no give whatsoever after the bolts were out leads me to believe that there wasn't a good seal between the lower manifold to the heads. I'm really hoping this fixes the issue. Honestly if this doesn't fix the issue, a drastic change in the engine/tranny swap is in the very near future.
I think you might be on the right path with gaskets being bad.
But chasing down problems like this are a pain in the ass.
I’ve been playing with foxbodys since “91” and had my last one for almost 11 years now and it still surprises me with strange problems time to time.
I have read this thread more than once trying to think what it could be besides gaskets and the one thing that keeps coming to my mind but you said it is a one owner car, it almost sounds like someone put a cam in it not knowing any better.
But gaskets leaking would do the same too.
Hope this works for you.
But chasing down problems like this are a pain in the ass.
I’ve been playing with foxbodys since “91” and had my last one for almost 11 years now and it still surprises me with strange problems time to time.
I have read this thread more than once trying to think what it could be besides gaskets and the one thing that keeps coming to my mind but you said it is a one owner car, it almost sounds like someone put a cam in it not knowing any better.
But gaskets leaking would do the same too.
Hope this works for you.
Got it all back together today and fired it up. Let it warm up and checked for leaks, then set timing. No leaks! but it is still the same rough and rich idle. The vacuum gauge was low, 14", with a rapid vibration that steadies out at higher rpm. According to a bunch of different sites, that indicates worn valve guides? Is a bad idle a symptom of that? Can you still have messed up valves or valve guides and pass a compression test on all cylinders? There is only a little bit of grayish smoke at idle sometimes which I assumed was due to the rich condition. It doesn't appear to consume oil, but I wouldn't really know either. I've driven this car maybe 5 miles total since I brought it home.
Messed with the car again this morning. I noticed the idle was wildly uncontrollable. It wasn't the typical surge, it was just all over the place. The car then developed a rattle type noise that appeared to be coming from somewhere in the center of the engine. Shortly after that, tapping noises from the driver side valve cover. Peeked at the oil pressure gauge, and it was reading somewhere between 0-10psi. It's an Autometer gauge, but the lowest reading is 10psi which is what it was at.
Now I'm faced with 3 options:
Option A, tear into this engine, rebuild it and throw an HCI combo and stand alone EFI at it(I don't trust the 34yr old harness, plus it's SD). This is the most budget friendly, but my T5 is on it's last leg, so I'd pretty much need to replace that too.
Option B, try to find a modular 4.6 / 5spd. FB marketplace is surprisingly empty of Ford engines around here, so I'd have to use eBay. Plus I'd need the harness, k-member, and either hydro boost or manual brakes.
Option C, which everyone will hate me for, is a 5.3 LS swap. FB marketplace has about a million of these for very cheap. The main reason I don't like the LS swap is that fact that I'd be pretty much be limited to using an auto since a T56 is way out of the budget.
No matter the option, there's no rush.
Now I'm faced with 3 options:
Option A, tear into this engine, rebuild it and throw an HCI combo and stand alone EFI at it(I don't trust the 34yr old harness, plus it's SD). This is the most budget friendly, but my T5 is on it's last leg, so I'd pretty much need to replace that too.
Option B, try to find a modular 4.6 / 5spd. FB marketplace is surprisingly empty of Ford engines around here, so I'd have to use eBay. Plus I'd need the harness, k-member, and either hydro boost or manual brakes.
Option C, which everyone will hate me for, is a 5.3 LS swap. FB marketplace has about a million of these for very cheap. The main reason I don't like the LS swap is that fact that I'd be pretty much be limited to using an auto since a T56 is way out of the budget.
No matter the option, there's no rush.
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