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'01 Escape - shuddering in overdrive going uphill

Hi all! I have an 2001 Ford Escape V6 3.0, about 130,000 miles. When the engine gets under high load and low RPM, before downshifting, it will shudder (misfire?). Local shop couldn’t reproduce it, but they thought it might have to do with slightly cracked vaccume hose, which they gouged me to replace. No improvement. Next they wanted $700 to replace Valve Cover Gaskets. I decided to become a mechanic and learn how to do that one myself. Sure enough, there was a little oil dripping onto one plug. I replaced the gaskets and all 6 spark plugs successfully. Still didn’t fix the problem though.

Symptoms will occur reliably when driving at 45-50 MPH with the transmission in overdrive (1500 RPM), and I begin a slight incline. The vehicle will kind of chug forward (feels like sporatic misfires) in overdrive, getting down to 1200 RPM before deciding to downshift. Generally, I can just give a little more gas to force downshift and avoid the nasty-feeling misfires. Some days, however, it is much worse, and will misfire at idle, and make me feel like I have to treat the gas as an on/off switch to keep the engine from dying. (It has never actually died.)

During a really bad day, I got a flashing check engine light. I did not check codes in time - they’ve all cleared.

I now have an ODB2 reader logging real-time data. All I can do is prove the conditions that cause the symptom: high engine load at low RPM is the recipe. Nothing seems to show a cause… I may just not know what I’m looking at :-/ . I haven’t monitored long enough to record a ‘bad’ day.

I’ve read about ignition coil issues on this engine, and weather might explain why this is worse some times than others. However, I wouldn’t expect that to be load dependant.

Most of the time it feels like the transmission just isn’t shifting when it’s supposed to, but on the bad days it seems more than transmission related. When stopped at a light in Drive, this can still occur.

Any ideas my friends?

Thanks for reading,

You might want to read your owners manual. Some vehicles do not advise operating the cruise control in hilly terrain. In addition, check to see what your Escape considers cruising speed. 45-50 mph sounds a little on the low side for cruising. I would also replace your fuel filter and have a fuel pump pressure test run. A clogged fuel filter or low fuel pump pressure can cause the symptoms you are having as well.

Thank you - I will look into the fuel pressure. Sorry for the confusion - when I said cruising, I did not mean using Cruise Control. I meant simply neither accelerating nor braking.

I think you are lugging the transmission and the clunking is either the converter locking and unlocking or hunting for the right gear. You should not be in overdrive at 1500 rpm, more like 1800-2000. I fear you are ruining your transmission and putting extra strain on your engine.

I am inclined to agree with Bing. One thought, unless I missed it in the reading. How long have you had the vehicle, and is this a new phenomenon ? If it is a recent issue on a car you have had for a while, when was the transmission last serviced ?

I think the above posters are correct. Lugging maybe. Perhaps the fuel delivery system or a problem with the air/fuel mixture. But the symptoms you are reporting could also happen (or be made worse) if you have spark plugs with too large of a gap, or a problematic EGR valve. Since you replaced the plugs (and gapped them to the spec, right?), my first guess would be you have some kind of EGR valve problem. Do you notice any pinging when this happens? That would consistent both with the spark plug gap and the EGR problem. If this were my car, I’d check the vaccuum system too, for any leaks in the hoses or fittings or in the vacuum controlled devices. You need a hand held vacuuum pump for that. And I’d check the PCV valve while I was at it.

There’s a number of different things that could cause this. You really need to scan it for codes again because the CEL does not have to be flashing for a code to be present.

If no codes are present then the cause of this problem becomes much stickier to locate. This could very well be caused by an ignition miss at a coil or something of that nature so do not rule it out.
Did you inspect the plug terminals in the coils for corrosion, etc when changing the plugs?

From your description the engine is stumbling at times and this could go back to the ignition miss theory.
An air leak anywhere in the intake manifold system or the intake air tract can also cause problems so make sure beyond all doubt there are no leaks at all; and it doesn’t take much of a leak to create a problem.

Recently my Lincoln picked up a subtle buck that would come and go. I tracked this down to a breather hose on the valve cover which had hardened with age and was gripping the plasick nipple tightly. The hose was rotating freely on the nipple and depending on vibration it was causing fresh air to be pulled into the intake tract which then throws off the MAF sensor.
(On another Lincoln I had a similar problem with the same hose but in that case the old hose had split with a razor like cut in it that was not readily visible. At times under acceleration, manifold vacuum would flatten the hose and spread the cut open which would then create a buck for the same reason a the current Lincoln.)

Thank you each for your comments! What a helpful forum!

I’m definitely going to start with a transmission flush (Monday). It’s overdue. I agree that it feels I’m lugging the engine - the transmission just WANTS to be there.

The thing I’m unclear about with the transmission theory is if lugging should cause misfires under normal circumstances. I drove a manual Civic for a lot of years, lugged it more than I should… it would slow to a crawl, but never misfire or shudder. My driver gut is saying, “while the transmission may not be shifting right, that doesn’t mean the engine should crap out under the load”.

@Bing: I found some ODB2 data confirming an increasing misfire count. I think that rules out converter locking/unlocking/hunting for right gear.

@GeorgeSanJose: Plugs were properly gapped. I hear no abnormal noises when this happens.

@ok4450: I’ve desperately been scanning for codes and freeze frames. While I could probalby cause a code again, I sure feel safer forcing the downshift. I don’t want to make things any worse than I have to. I have managed to figure out a few extended ODB2 PIDs and continue to log anything I can think of. Im afraid it will take a lot of fiddling before I learn how to really use this data though.

Could anyone provide some guidance what sensors/values to look for to identify Vaccume leaks? ok4450 mentioned leaks could throw off the MAF sensor - MAF data I’ve logged has followed the throttle curve pretty closely.

I imagine I should be able to check fuel pressure via ODB as well… I’ll have to research to find what normal looks like…

Can you tell I prefer hacking ODB PIDs over opening the hood? Kinda pathetic, eh?

Next steps:

  • Transmission Flush (overdue anyway)
  • Compression Test (I have the tool, might as well)
  • Vaccume leaks (Will need to buy a hand pump)
  • Fuel Pump Pressure (Not sure how to check this)
  • EGR Valve

i had similar issues with my 04 ford escape. misfiring, slowing on hills, flashing cel. i replaced 2 of the 3 catalytic converters, the spark plugs, the coil packs, the intake manifold gasket because there was some oil going into the plug hole. have you noticed if the misfiring is worse when it has been raining or is foggy or otherwise moist or humid out? the problem with mine was that there was water on the pcm pins. idk if the water follows the bolts from the firewall or what, but i took the blue rubber part off and used compressed air to dry it out and then i used a bunch of dielectric grease on it in the bolt holes, on the pins even on the wires coming out. never had a misfire again. some people have commented on the youtube vid i made saying it was their issue as well.

lol, didnt notice this post was 7 years old.