Hard start when cold, seems rich, but throws lean codes

[Cyfun]

I've got a '93 Expo that I'm fixing up. When the engine is cold, it will crank and crank but not want to fire. It reeks of gas, and if I give it full throttle while cranking it, it will backfire a bit into the exhaust. After a few minutes of this, it will fire up but run really rough and I have to keep giving it gas, but after maybe 20 or 30 seconds it will smooth out and run fine. But the whole while it will bellow out white smoke. I can't tell if it's smoke or steam from a coolant leak, but it doesn't smell like coolant. Even after it starts running fine, it will keep puking this white smoke for a couple more minutes, but once warmed up will have a minimal exhaust cloud. I should also note that it's been between +20 and -20 degrees here lately, and yes, when it's colder, the problem is definitely worse.

I never had a CEL until I replaced the upper and lower intake manifold gaskets the other day and disconnected the battery. But after I got it back together, it still was very hard to start. Once I got it started and warmed up, I took it around the block, but when I hit about 20mph the CEL came on. The codes it gave were 172 and 176: "Oxygen sensor not switching – system is or was lean" both right and left. I cleared the codes and ran a KOEO test, and it gave those codes along with 136.

So far, I've replaced the upper and lower intake gaskets, cleaned the IAC, replaced the vacuum lines to the FPR and checkvalve, even tried capping off all vacuum lines including that going to the brake booster. I tried testing the coolant temp sensor but wasn't sure how to interpret the readings. I checked the vacuum line going to the FPR to see if the diaphragm might be leaking fuel, but it didn't seem to be. Replaced the plugs and wires with Autolite coppers and BWDs respectively. The MAF appeared to be clean, but I shot it with some cleaner anyway. Ran a bottle of injector cleaner through the tank as well. Ran a compression test, the #6 cylinder was 150, four cylinders were 115-130, and the #1 cylinder was 90... but I did this on a cold engine with a harbor freight comp check tool so these numbers are probably low. 90 isn't great, but if I had a bad coolant leak or something, wouldn't it be much lower?

I've also replaced the rad, water pump, thermostat, and heater core due to massive coolant leaks, but after having done so, haven't noticed any more loss of coolant.

My best guess right now is the engine coolant temp sensor, some other massive intake leak somewhere that seems to go away once the engine warms up, or somehow both of my o2 sensors are indeed bad.

I've searched and searched and found several forums posts about similar issues, but not many of those threads mentioned what they finally found the culprit to be.

 

[Ramblinwilly]

You've got quite a bit of information here but I'll give it a go. My advice is to tackle one issue at a time but I'd tackle the compression/exhaust issue first then go from there. This doesn't sound like a simple sensor replacement will fix your issue.

Considering the relatively low compression and the exhaust smoke, I'm thinking head gasket(s) to start with. A poor head gasket can cause a loss of compression, a loss of coolant or both. You've got a 20% difference in compression between #1 and #6 that's why I'm leaning towards the gaskets. These COULD BE the culprits. A mix of gas and coolant doesn't ignite very well

Could be other things like sticky valves or lifters and manifold gaskets (vacuum leaks). Could be a combination of all of the above. I'd take a shot first on the head gaskets. Not to difficult to do and at the same time:
1. Clean the intake manifold and replace gaskets; common problem that causes vacuum leaks resulting in hard starting and other performance issues.
2. Check the condition of the valve train assembly and valves, and get a good idea of cylinder health. You may get lucky and see evidence of a coolant leak around #1 cylinder.
3. Check the condition of the heads for warps and cracks.

If I got this vehicle without knowing any history or anything about the vehicle this is what I'd do.

Hope this helps
Willy

 

[Cyfun]

Thanks for the ideas, Willy. I just did all my upper and lower intake manifold gaskets, hoping that'd be the problem, but it doesn't seem to have helped. Also replaced the coolant temp sensor yesterday as it was easy and only $12, but that didn't help at all.

But do you think having a slight coolant leak in just one cylinder would cause the whole thing to not want to start? As I mentioned, I have to crank on it for a good few minutes, and it's worse when colder. When I do get it started, it spews white smoke out the exhaust. It's below freezing here so can't tell if it's coolant or running rich, but when I stick my face in the exhaust, it doesn't smell sweet like coolant at all, but does smell of gas.

I just checked my fuel pressure, hoping my FPR was over pressurizing my injectors, but it was 30-40psi. And as I said, I immediately get codes from both injectors indicating a LEAN condition. Since it appears to be running rich, why would they be saying it's lean?

I need to go back and do a compression test when the engine's warmed up. I'll try and do that today.

 

[Cyfun]

Ran a bottle of Seafoam through the intake as I'm anticipating having to change the injectors anyway. Seems to run a bit smoother, but does still have problems starting. Even does it when warm now; it'll take about 5 seconds to fire up and then run rather ****ty until you rev it a few times. Definitely acting like it's flooded.

Also, tonight I had it in for the oil change, and while it was draining, I pulled my fuel pump relay and spark plug #1 and ran another compression test. It peaked at about 120psi, so do you still think it could be a leaky HG? A buck twenty seems pretty good for being the lowest of all cylinders on a poorly maintained engine with 190k miles.

 

[Cyfun]

Good news, everyone! Changed the oil today, replaced the cardboard-based Fram filter with a shiny new Motorcraft. And fed it a gallon of Delvac 15w40 with half a quart of ATF. It fired right up, no smoke, so I went for a little drive, seemed to run well. But on the way back home, got another CEL when I was coasting down a hill.

Another thing I forgot to mention is that the transmission kickdown happens REALLY early, and also when I floor it and go thorough a few gears, when I let off it doesn't shift back up into high gear immediately. I always figured it was the crappy Ford auto trans.

So when I got home, I ran my codes. I had a lean left oxygen sensor code, but also a code saying that my TPS voltage was too high... wat? So I tested my TPS, and sure enough, it puts out 5v no matter where my throttle's at! So I'm about to run to the parts store and grab a new one, only 36 darra!

Let's cross our fingers that this fixes it!

 

[Cyfun]

Okay, so I'm a tard. I measure across the top and bottom wires of the TPS. Supposed to measure the top and MIDDLE wires. My old TPS was still crappy, but this was definitely not the problem. After replacing it, topping off the oil and coolant, I went for a little drive. It seems to run fine once warm, and if I floor it and go through a few gears, it hauls ass. But when I was cruising down a hill doin about 40mph, the check engine light kicked on, and it threw a code 176 again. No 172 code though.

So it's probably safe to say that my left o2 sensor is bad? Either that or I have a big vacuum leak somewhere. But would bad o2 sensors make it flood out when cold starting?

 

[Ramblinwilly]

Ok now. We're running better than when we started right? And the better running condition started after changing the oil and adding tranny fluid to oil right? My only "guess" here is that you had a sticky valve or lifter.

 

[Cyfun]

It's been hard to tell if it's better or worse as the temperature was as low as -20, but has been up to 40. Definitely better on warm days.

I was starting to lean toward leaky injectors, so I pulled off my upper intake manifold... only to discover coolant in my back two ports! Soooooo I pulled off the lower intake again, and the rear coolant ports were definitely leaking. Looking at the lower intake, it seems so silly that the ports just dead-end. I was half tempted to shove a bunch of JB Weld coolant-friendly putty in the rear coolant ports of the heads, but decided against it. So I cleaned off my lower intake gasket, put on a lot more black RTV around the coolant ports, and started putting it back together.

It was then that I realized my crappy Harbor Freight torque wrench is apparently broken, as it wasn't giving accurate torque readings. Probably wasn't tight enough the first time around! So I replaced it and retorqued the lower intake. Definitely much tighter than it was. Also cleaned out the injectors as best I could, and replaced the rail seals. The seals at the end of the injector were a ***** to get to cause of that stupid plastic cap on the end, so I just let them be. And I also made sure to lubricate the seals when I put them in this time to help prevent leaks and make it slide on easier.

So I got it all back together again, careful to torque everything down properly, went to fire it up, and... same ****! Doesn't want to start, but reeks of gas and backfires a lot.

At that point I was pretty damn frustrated. But as it acted this way with the MAF unplugged and engine cold, figured it's likely not the MAF or oxygen sensors. Which leaves the coil or the crank position sensor.

Forty dollars on a new crank pos sensor later, and it fired right up! However, it was about 20 degrees warmer out today, so that could be part of it, but it definitely seems to run better. Drove it around town, no more codes got thrown. And I'd left the battery unplugged overnight so previous codes would clear and the computer would relearn it's trims.

The temp today has dropped to single digits, so I'm about to go try it again. Wish me luck!

 

[Cyfun]

Ok now. We're running better than when we started right? And the better running condition started after changing the oil and adding tranny fluid to oil right? My only "guess" here is that you had a sticky valve or lifter.

Actually, I'd had no noticeable lifter noise before my oil change. But AFTER, I was getting all kinds of clatter! It went away after 10 minutes of warming up, but still seems odd that newer, heavier oil would cause MORE lifter noise.

Ah well, who knows, maybe it just needs to circulate more.

Oh, and while I had the lower intake off, I noticed this little plastic funnel-shaped thing that was loose on one of the pushrods. The rest of the lifters look like they have the cones clipped to their top, but this one was only half as tall and had no way to clip on to the lifter. So I broke it and took it off with some pliers. I'm guessing these are little safety measures designed to keep the pushrods from popping off the lifters?

 

[Cyfun]

Success! Sort of. It definitely starts easier and runs better, but I still have to floor it when it starts or it misfires. But after a few seconds it runs just fine. No more smoke/steam out the back, either. So maybe I still have a vacuum leak somewhere. Oh well.