Rough Idle, Hesitation, possible fix.

I recently bought my first Ex about 2 months ago. When I first got it there was a little lag time, or hesitation sometimes taking off from a stop. It also idled a little low for my taste and shuttered from time to time. It is a 2004, 4.6, with the "drive by wire" throttle. It was doing this when I test drove it, but I got this vehicle far below bluebook so I felt I could spend a little money on it if needed to get it up to par.

About 2 weeks ago I started to notice it taking a turn for the worse. It would die often in the mornings, and some times during the day, It was idleing around 3-400 RPM's ( just barely even running). The lag/hesitation between the time I pressed the accelerator and when it actually started to take off was brutal. A good 3 seconds some times. Then when it did finaly WAKE UP it was like I had it half way to the floor. A real pain to drive this way. When I would shift from park into gear it would clunk really hard. Harder in Reverse than in Drive. It was even shifting throughout the gears a little funny.

I started doing tons of research online and trying to narrow down what could be causing it. The only code the computer threw out was the Low Idle Code, but that was it. Once I reset the computer it never threw the code again even though it was still running like crap.

I decided the truck needed a tune up anyway and that should help. So I changed, Air filter, Fuel Filter, Oil change and filter, Cleaned the injectors, changed plugs, tested all the coil packs, Replaced PCV valve, TP Sensor, and checked for vacume leaks. After all that it had way more pep, but still wouldnt Idle right and had the hesitation.

I finaly decided to pull the entire throttle body and just LOOK at it. Once I got it off I noticed all the gunk and crap that was completly cutting off air supply when the throttle plate was in idle position.( assume this is because when I changed the Air Filter I noticed they had a K&N Filter and used WAY too much oil in the filter, I just use a dry filter with a little oil around the seal and change it with every oil change.) I gently cleaned every bit of the buildup out of the entire throttle body with WD-40 and some rags. This took about an hr in itself. Carb cleaner would have taking about 10 mins but was told not to use it on this throttle body.(not sure why?) Put it all back together and it runs like a new truck!

Idles around 750RPM's and no hesitation. No more clunking into gear going from park. Every bad symtom I had is gone. The only reason I posted this long thread was because I have been seeing many complaints with the same issues I was having, and everybody was just buying new parts and nothing was getting fixed. So I think a good cleaning would do the trick in many cases.

Sorry for such a long post!

Ike

Good fix!

hmm interesting find. glad that fixed your issues

Thanks for the post same problem with my truck i'll try it out see what happens

There is a TB cleaner available.

tonedeafaudio said:

Carb cleaner would have taking about 10 mins but was told not to use it on this throttle body.(not sure why?) Ike

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Ike, welcome aboard.

Thanks for sharing with us. Glad you got your issues resolved.

There is a throttle body cleaner on the market. It is the only thing that should be used to clean the throttle body. Other chemicals can destroy the factory coating.

Thanks again. :biggthump

Thanks for the post. I have an 04 4.0 V6 that is doing a similar thing. I purchased it at 85K miles, now has 93K. My wife has an identical 04 XLT that sounds great when it cranks, runs, shifts, etc. Mine has, in the last few months, started running very weak. When it shifts from Park to 1st gear, the shift feels very soft, and the truck is very slow to leave a stand still. Side by side with hers, it feels like it has half the hp. Maybe I should try checking the air filter and TB?

Thanks

I have a 03 explorer and mine currently is having those same problems, when idle at the light or on park it tends to shutter and sometimes it turns off on me, and I have a K&N intake system on my car. Maybe I have been putting too much oil on the cone filter. I will try cleaning my TB and let yall know if this works for me. Thanks for the tip.

I have an 03 4.0 V6 the truck is very slow to leave a stand still afer truck gets up to temperature. it feels like it has half the hp. there are no vaccuum leaks. I removed the passenger side headlight to allow fresh air in the air cleaner box and seems to fix problem, the headlight is a few inches from the hole where air goes into the air box, is there susposed to be a air pick up tube that collects fresh cool air and not the hot engine air under the hood?

new engine,harmonic balancer,plugs & wires,coil pack,mass air flow sensor,throttle position sensor,fuel filter,air filter, injectors and o-rings, pcv valve,egr sensor, cam shaft sensor, coolant sensor, intake gaskets, degreased whole intake inside and out, ran truck with out catalytic converters.

I am stumped

Possible cat converters going bad.

the trucks runs really well for the first 2 minutes smooth throttle and full power, then starts to mis and studder,

if the catalytic converters were bad wouldn't it run bad all the time?
I am thinking it might be the injectors running lean, the truck sat for 1 1/2 years with out running,

is there a way to test the injectors? or rebuild them?
what other cars or trucks have the same flex fuel injectors that I could use for the explorer, I will look in the junk yard or ebay?

I've got an 05 limited 4.6 and it has the exact issue you had. I will now be pulling off the TB and cleaning it.

swetrid said:

Possible cat converters going bad.

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I took the catalytic converters off and drove around with just the manifolds on the engine, still no difference. weird no check engine light either.

I ordered new fuel injectors will see if that fixes the problem.

I pulled the throttle body and intake system. Cleaned everything. Did it last night, so far so good. i'm back to running like normal.. Now all I need to do is a tune-up. great right up, Thanks.

new injectors did not fix the problem, runs great full power for two blocks, and then it seems like the truck fouls out, not a smooth throttle responce and loss of hp.

I am stumped

I am using the superseded harmonic balancer, tested and works fine.





and why no check engine light when i drove truck around without exhust and O2 sensors?
when I put the key in acc I can see that the CEL light works. can it be a bad computer?

The plot thickens!!

FYI things that I replaced
new engine (2000 miles on engine), harmonic balancer, crank sensor, plugs & wires, coil pack, mass air flow sensor, throttle position sensor, fuel filter, air filter, injectors and o-rings, pcv valve, cam shaft sensor, coolant sensor, EGR Valve Pressure Sensor, EGR Valve Pressure Switch, intake gaskets, degreased whole intake inside and out, ran truck with out catalytic converters. tested fuel pressure 67 lbs

I unpluged the tps, and the cel did come on, so the light works.

I bought the truck second hand with a blown engine. do you think the ecu was reprogramed to try and make the truck run better because of the bad timing chains, and now that it is a new engine the timing is messed up?

the trucks runs great for 3 blocks full power, and then it goes down hill slowly loosing power. after 3200 rpms it kicks back in and full power again, after about 15 minutes of driving it will barley take off from a red light,

any body have Idea's because I am out of them.

Do you have a way to monitor the fuel pressure while you are driving? I'm thinking maybe a fuel pressure regulator? I'm too new to Explorers to know their system yet, but that's where I'd look.

ford tech said that when i changed harmonic balancer that i threw out the timing, he said that the crank shaft chain gear is not keyed. so when i loosened the crank shaft bolt, and didn't lock down the cam shaft in place it all could spin and loose timing.

( update I have a 4.0 engine on a engine stand in my garage, I looked at the timing gear that drives the chains in the front cover behind the harmonic ballancer, the gear is keyed and cant loose timing if you take off the pully, the ford tech gave me mis-informed information!)

I also found that the 8 intake bolts have a rubber grommet that was shrinking when the truck got hot, causing a intake leak.

I put a timing light on the crank and the mark was about 1/2 to 5/8 of an inch before the timing mark when warmed up (running really bad). when I start truck and it is cold for the first minute it is right on the timing mark. running great

Is this normal, where should the timing mark be?