Acceleration hesitation ?

[Paul]

Got myself a second hand Ford Focus 2007 1.8 Hatchback, and its great bar something I’ve noticed, mostly when first starting a car and pulling off.

It seems like there’s a delay from when I press the pedal, and the revs rising up, and sometimes the revs just shoot up very quickly even with a very light press on the pedal.

I had this confirmed today when my brother tried using it, and he immediately noticed a delay too without me even mentioning it.

From what I know of the car, it had been put in storage for a few months until the owner wanted to finally sell it. The battery died so had to be charged up. When I got the car, I pulled some codes from it, many seemed to be regarding the battery dying, but a couple had faults regarding the Throttle Position Sensor. The codes are –

Fault log report generated by Torque for Android
=================================================

Vehicle VIN:
Vehicle Manufacturer:
Vehicle Calibration ID:

Current Fault Log
——————
U1039: null

Pending Fault Log
——————
ECU reports no pending faults

Historic Fault Log
——————
ECU reports no historic faults
Other discovered fault codes
(possibly pending, current or manufacturer specific)
—————————————————-
B2103: null
U1900: null
B1318: null
U2200: null
P2122: Throttle/Pedal Position Sensor/Switch D Circuit Low Input

End of report.

Anyone able to give me a few simple ideas to start off with before I start digging into it deeper ? I have a few ideas, such as the TPS (which is attached to the pedal AFAIK, and are only available in together) being faulty, maybe a sticky butterfly valve, vacuum leak, or spark plug related (I checked the ones currently sitting in the car, they look absolutely fine from what I can see).

Any ideas where to start with this ? I’m starting to look like an idiot stalling the damn car as I haven’t given the acceleration enough time to catch up with me

Topic

[Paul]

1 quick additional thing I have noticed, the issue is lessened when the engine is cold, but quickly comes back shortly after driving. Might explain why it seemed OK after the service. Throttle cleaning this weekend coming up, may also remove the potentiometer and inspect it for anything obvious 🙂

[Austin]

I’m assuming you’re talking about the same clamp that we were discussing on the intake snorkale. just take it off and replace with a screw clamp.

[Paul]

Finally got around to cleaning the throttle body. On the front I could see some slight carbon build up, and when I had my dad press on the pedal (ignition on, engine off), the back of it was absolutely caked in the stuff. Lightly sprayed some throttle cleaner on it and gently tried cleaning with the tooth brush, you could feel just how sticky the stuff was, tooth brush was completely black by the end of it, and I don’t think I managed to get much off it, and I didn’t want to put too much force on the butterfly either.

Wiped up, put it all back together, and started the engine, fired up pretty fast, revs flew up and sharply dropped to the point where it almost stalled, but I hit the pedal and it managed to stabilize, however it appears I have stupidly created a new problem, with the revs not dropping immediately, instead sitting at where I had it for about a second or 2, before plummeting down to normal idle speed. Doesn’t seem to have made an affect on the response either.

I should have taken pictures really, but should the back of the butterfly valve (and chamber) really have that much carbon crap covering it ?

Another thing I noticed, which while I had the air tube off took the opportunity to get a better look into where the air filter sits, is the little sponge that I believe is PCV air, I noticed when I removed this quite a bit of oil deposits sitting in the bottom (the sponge itself didn’t seem too bad). Should this be there ?

Almost at my wits end, might be time to just take it to a dealer and hope they don’t rip me off or say they’ve fixed it when they haven’t.

I may take a look at the MAP sensor when I get the time too.

[Austin]

1. Don’t be scared of that throttle blade. get in there and clean it. Yes it’s normal for alot of carbon build up to be sitting in there.

[Paul]

I gave it another good clean today to see if it would make a change, sadly not, however I did notice the weird electrical noise I could hear was actually coming from the potentiometer on the throttle body (and as I was cleaning the butterfly valve, it slightly changed the noise). It sounds exactly like this – https://www.youtube.com/watch?v=zvwJBM4jzSU

I did try to use my dads car to see if he had the same, but his throttle doesn’t seem to engage until the engine is running, so I cant really hear it over the engine. When switched off, I do catch what sounds like the same noise from the throttle until it turns off.

Do we know if this is normal noise ?

[EricTheCarGuy]

I don’t think your methods are very conclusive. It would be better to measure the voltages and compare them to spec to get any real answers. Otherwise you’re just guessing and that can lead to parts being replaced that don’t need to be, and possibly damage to other systems.

[Paul]

I agree Eric, I’m really bad with the electrical/voltage side of things …. which this seems to be, so I’ve booked it in with a dealer next Thursday to get their diagnostics done plus opinions. I will update you all next week 🙂 Hopefully with the cause !

[EricTheCarGuy]

Sometimes that’s the best option. Keep us updated on what they find and good luck.

[Paul]

And the Ford Dealer verdict is …..

Nothing wrong with it, they couldn’t find anything. No codes, nothing stood out, diagnostics were all good, took it on 2 separate test drives, nothing. Thankfully they didn’t charge me for it (+1 respect for the dealer), so I’m left questioning myself, wether its just a new car that I need to get used to (although my dads does stand out as being more responsive), or its just the very early stages of a problem (the dealer suggested to just keep using the car, until it becomes an even bigger, more obvious problem).

Feel like I’ve wasted everyone’s time on this, so I apologise 🙁 I think I will just have to get running with it and get used to it.

Thanks for the help everyone, I really appreciated it 🙂

[James]

Can you bring me up to speed with the complaint and all the things you have done so far? I see you have torque, and that will be helpful in the diagnosis. What are you’re LTFT’s and STFT’s like at idle, and under load?

[Austin]

Just watch it, can’t fix anything if it’s not broken. The hardest thing for techs to diagnose is an intermittent problem, and one that really shows up. If you don’t have an idea of where to look you’ll pull your hair out looking at everything. Drive it till it brakes then fix it. Keep doing preventative maint.

P.S. I can’t speak for everyone, but most people are on this forum to help others. If I thought I was wasting time I wouldn’t dedicated it to this forum. banana:

[Author]

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