Miss when steady-state

[TankII]

As I'm on my way into work, the SHO will miss after running steady-state for 10 to 15 minutes. Ambient temperature makes NO difference.
Full throttle before-hand, stop-and-go, on-off - no problem.
Run steady-state for a while, and it starts to miss. Get off highway and nurse it through a couple of stop-lights, and it will be fine until I get on and start cruising. Rarely dies completely, but it comes close
Replaced (since 2004/20,000 miles ago):
Engine (2004) - Complete makeover w/ CPS, water pump, sensors, etc. Ran fine at Lime-Rock in 95+ degree heat.
Fuel pump (2006) - Now has a higher volume pump than before. Have autocrossed with no issues since.
Catalystic Converters in 2008
DIS was replaced in 2000, at around 160,000 miles.

Only issues other than this:
P/S leak I can't pin down.
Oil leak on Crank Sensor seal (only one I didn't replace)

I've put very few miles on it since 2004, as you can see, as it was rusting badly. I've replaced a bunch of panels these last two months, and drove it to work today. Started to miss at it's usual spot, but once I got into stop and go traffic, it was fine.

Maf?

TankII

 

[TankII]

I've also cleaned the plug wells out and sealed them.

 

[Huntervf]

I suspect MAF or a throttle position sensor.

Take the MAF off, spray the heck out of the sensor with some electronics cleaner and give it another shot.

I've seen many a MAF issue that never set a CE light or code either. My ATX had a similar issue a couple years ago that I traced to the MAF.

 

[rubydist]

I am convinced that the last crank sensor I had to change was due to the front main seal leaking oil all over the cps. If your front seal leaks like you say, I'd start planning to spend a few hours getting to know the front end of your engine....

 

[TankII]

I am convinced that the last crank sensor I had to change was due to the front main seal leaking oil all over the cps. If your front seal leaks like you say, I'd start planning to spend a few hours getting to know the front end of your engine....

CPS, Front MAIN seal, water pump, other CAM seals, rear main, bearings, other misc sensors - all replaced. The only one I didn't do was the Cam seal behind the Cam Position Sensor. Of course, that's the only one leaking, but it is leaking onto the exhaust, subframe, and firewall, not Crank area.

I'll try cleaning/replacing the MAF and see how it goes. This MAF has been used behind a K&N exclusively.

TankII

 

[Huntervf]

This MAF has been used behind a K&N exclusively.

Ding ding ding! It's quite likely then that the MAF sensor could have a build up of air filter oil.

I'm now taking wagers on a MAF issue

 

[TankII]

I cleaned the MAF last night. It didn't look dirty at all, but the throttle response this morning is much better. Granted, that tank-full of Premium is probably starting to kick in too...


I didn't have it out on the Highway long enough to see if it would miss, but so far, it hasn't.

TankII

 

[St Louis SHO]

Keep us posted. The oil leak into the cam sensor can cause this exact issue.

 

[TankII]

Yesterday's commute went without incident. I'll keep you posted.

 

[Huntervf]

Oily K&N filter FTL.

Clean MAF FTW

Just a warning too, could be that MAF is getting weak. I had a similar prob with my 93 ATX, cleaned the MAF twice over the course of a year after getting stuttering and general lack of performance from the engine. I'm not running a K&N either, so it wasn't sucking oil. When I started getting the symptoms a third time, I just replaced the MAF with a new stocker, and I've been fine ever since.

 

[TankII]

Last night I drove it for several miles with no problems, mostly stop and go, but some sub 50MPH back roads.
This morning as I was driving in to work at 12:15 AM (Engine still warm since I got home last night at around 10:30 or so), it started to miss again. I dropped it to fourth and ran it up a few RPM's. I went into downtown, stopped at two stoplights, then ran steady at 35MPH through the next three green lights (about 1.5 miles). As I approached the next light, which was blinking red, the car started to miss again. As I stopped and pressed the clutch it died (first time in 11 years!). I was able to immediately start it, but the RPM's stayed zero until I hit 4K in first. It stuttered a bit a couple of times as I drove the remaining mile to work, but it didn't stall, even though I didn't hit any red lights the rest of the way.
I realized this morning I didn't swap the Cam Position Sensor when I did the work as I broke the one that was on the motor and swapped a used one on.

Hmmm.

TankII

 

[encryptshun]

Mine is similar situation but it only does it from 35-60 mph

 

[TankII]

Drove home fine last night. Today, short trip, and after I restarted to head home, it was missing at idle. I had to rev it up hard a couple of times to clear it.

I'll swap MAF's and let ya'll know.

TankII

 

[TankII]

Swapped the MAF. Throttle response is better.
I'll keep you posted.

 

[Ishodu]

You say you cleaned out the plug wells? Were they full of oil? If they were the wires are likely no more good. The oil was actually insulating them until you removed it.

 

[TankII]

Oil in wells with new wires. Engine sat for a while (Waiting on rebuilt tranny, which was dropped by Shipper, and took three months to resolve!) before I switched the sensors, bearings, pump, etc. Wells were clear when I first put the plugs in, but I found them full of oil shortly thereafter. Ends were properly cleaned, along with the Plug wells and plugs. Di-electric grease was applied.

Problem was happening prior to any engine work being done.

Morning update:
Drove in @3:30 AM. Made it to work, no problems. Parked the car, dropped off my lunch-box, went back to car to move to parking lot. Car bucked under load until I reved it up a couple times in neutral. Ambient Temp 71, RH - 85%
Mid-monring update:
Drove home @9:30 to meet the delivery guy dropping off a new Boiler (Old one is leaking) - No problems. Ambient Temp 77, RH 75% (Estimated). Car sat for about 15 minutes, then I hopped in and drove it back to work. Back at work (Ambient Temp 84, RH 75% estimated), the temp guage hit the 'N' when idling at lights before the fan kicked on, but it ran fine the whole way.

Note, I didn't go over 4,000 RPM more than once each way, kept it below 75 MPH, and used the Cruise Control as much as possible.
Oh, and DIS was replaced 9 years/65,000 miles ago, but swapping for another known good one (Before I changed the MAF) made no difference.

 

[TankII]

Drove home from work yesterday. 89 degrees, about 70% RH (Estimated). Made it 1/2 way home, and started to miss when steady@72 MPH (Cruise NOT on). Badly. Going down a hill, then level road. Got ****** off and dropped it to fourth and nailed it. It stuttered, then ran solid to 100. Backed off down to 72 again (Cruise on). Went the rest of the way home fine.
Bought a new TPS (One of the few used items from before the work) after testign it and hearing a squeek. This morning, drive in was fine, and i was NOT light on the car. I'll try another steady-state drive home to see if the problem surfaces.

 

[Huntervf]

Just wondering, did you ever pull codes?

 

[tompumped]

Fix the oil leak and replace the cam sensor. Then go from there.
Check the codes before replacing the sensor.
Which plugs and wires are you running? I had a problem once with wire going bad in probably 10k.

 

[TankII]

Motorcraft Wires and plugs. No codes, so far, which is why it is driving me nuts. If the wires go bad, it will backfire through the intake. It flat dies with the miss, and I can smell unburnt fuel.
No problems driving home with the new TPS...