Hello.

I have a 2000 (4.6) Expedition that is hesitating under light acceleration. It's most noticeable when lightly accelerating from a stop. It's also noticeable when cruising at speed then giving it some gas to slightly gain speed. Under medium and heavy acceleration there is no hesitation. It was running fine up til a month or two ago.

I bought it last year (July), and this is what I did to it:

New plugs
Flush coolant
New Gas filter
New air filter
Clean EGR buildup
New plugs
Oil changes (engine, tranny)

Today, after some googleing, I figured my problem was with the IAC valve. I took it off, cleaned it up following some instruction I found on a forum, and although it seems like the problem got a little better, it's still present.

So I was wondering if there was a way I could tell if the part was bad or not. I know some parts you can hook up an ohm meter or something like that and test the resistance of the part. Is this a part you can do that to?

Or maybe the problem lies elsewhere? Another forum pointed to a possible vacuum leak, how do I test for that? I don't really hear any hissing anywhere.

I really don't want to bring this to the shop. No offense to any mechanics out there, but I have yet to bring a car to a shop and not gotten lied to. I mean, if it comes down to it I will, but I'd like to know what, for sure, it isn't so I can try to keep them honest.

Thanks!

Edit:

I almost forgot - there is no check engine light on or codes.

 

This could also be caused by dirty injectors, or a dead spot in the TPS.

 

I'm pretty good at running Sea Foam through my system. How do I check the TPS?

Thank you

 

Remove the intake boot at the throttle body intake and disconnect the negative battery cable. Remove and clean the IAC again. Give it a soak with throttle body spray cleaner and give it a good tooth brush cleaning. Spray/saturate the throttle body till it's clean and spray the TPS (Throttle Positioning Sensor) clean too.

Dont feel like you're offending anyone, you're in the right place seeking answers to get your vehicle running right.

 

Will do. Will report back tomorrow.

 

OK, took everything apart, cleaned it up real good, and the problem seems to actually be worse.

Riding on the expressway at 65 today, I could feel the constant miss or stutter, and when I gave it a little gas it got way worse. It actually rattled the whole vehicle a bit.

Still no codes.

So what should I do? Take it to the shop? What are they going to do? If there are no codes, aren't they in the same boat as me? Will they just start stabbing in the dark and changing things?

Should I drop the money on new COP's and just replace them all? Ugh. This Expy is perfect in every other way. Runs (besides this) and shifts better than all of my friends newer vehicles, so I want to get this fixed before it farks anything up.

 

you could have an cop going bad or you could also have a bad plug or injector, the dealership has computer that can do a power balance to see if you have a weak cylinder can also check the misfires that haven't gotten bad enough to set a code

 

So I should just have them diagnose it and fix it myself? OK. I'll give it a try.

 

A decent scan tool that can read Mode 6 data will suffice.

I use a laptop-based scanning system that can be bought online for under $125...

 

I would be very interested in your results as I have had the same issues and haven't found a solution even though I have:

- new fuel filter
- new plugs
- new injectors
- cleaned CPS

Haven't checked the TPS (going to do that after I post)

The oddest part is that I have had the same as you - no codes, I have a reader from a buddy of mine (Innova 3100c) and it isn't showing any codes (nor codes pending)

 

Our 2001 Expy started doing this recently, so I'm tgging this thread for outcome...

 

Update: just removed and inspected CKP - still have issue.

 

Well, rest assured, I'll get to the bottom of it. I'm OCD and hate this sort of thing.

 

Hi Manuel

I am having a similar problem to you. I just posted my own question because I'm not sure we have the same cause for our problems.

The first thing I suggest you do is check the fuel pressure. You can rent the tool from Autozone for free and its such a quick and easy test. If the pressure is fine, then I suspect you have a missfire.

When I bought my 2nd Expedition it had a missfire which I spent ages trying to diagnose. The engine management is supposed to throw an error code if the engine missfires, but mine never did and the fuel pressure checked out fine.

In the end I replaced all the COP's (coil on plug) and fuel injectors and the problem went away. Replacing the COP's and injectors is a fiddly job, but it need not be expensive. You can get 8 COP's from eBay for abuot $100 and a set of reconditioned injectors for about the same. Send your old injectors back and they'll give you $30.

On my wife's Expedition the IAC became blocked and the truck had a very rough idle. Eventually it stopped idling at all. Your symptoms don't sound like the IAC to me. The IAC give the motor air at idle and also keeps it running when you step off the accelerator. During acceleration it is shut. If it was stuck open yuor truck would lurch forward when accelerating, not heistate.

 

Do these look like a decent score?

NEW IGNITION COILS 97-05 FORD EXPEDITION V8 DG508 (8: eBay Motors (item 170490527122 end time May-31-10 08:45:40 PDT)