Hesitation on acceleration

[jim_jiminy]

Hi,

So I'm getting some hesitation on acceleration in 1st.

Put my foot down and revs drop then go.

The pedal some times is stiff initially.... but after a bit seems normal.

The other day the car kept stalling... just when startled. When I drove it for a bit was fine.

I had a recent engine swap but it was doing it before with the last engine.

I swapped the maf for a no name one from eBay but engine then started dropping and gaining revs in pulses so put the old one back in (sensor).

What you guys think? Only happens in 1st gear pull away, did it with last engine too.

Throttle cable?

Any help appreciated!

Many thanks.

[Carolyn]

Did the replacement engine come with it's own throttle body?

If so, one has to ask, 'What wasn't changed?'.

The exhaust manifold with its O2 sensors comes to mind.

If you have the same throttle body, then it probably needs a damn good clean.

[jonbill]

I'd second the throttle body as suspect. Maybe while your cleaning, check the resistance across the tps terminals - between the signal and either of the other two you should get a smoothly varying resistance with throttle opening.

[jim_jiminy]

I'm gonna give it a proper look this weekend. Just waiting for an answer on if the throttle body was replaced or not.

One thing I did notice is when I put the aircon on, the idle speed was fine. Off and it struggles.

The accelerator pedal is very stiff first time use it, after that it's fine.. until the next time it goes stiff...

[Carolyn]

That's because the ECU turns the idle up a little when the AC is on.

All points to sticky Idle Air Control valve and/or a stiff butterfly.

I'd do the throttle body regardless of what has already been done. 

[jim_jiminy]

Did a bit of investigation and found the tube pre filter box had come away and disconnected.

Put it back together, idle speed seems sorted now!! but it seems the filter box is too close to the engine by 1cm for the retaining plug to hold it all, so could slip off again as the box is loose.

Also I tried to get the hose off the throttle body to give it a good clean, but ended up giving up as just couldn't get it off. What's the procedure for this? Hesitation is still there so I want to give it a good clean.

Cheers.

[shnazzle]

That pipe clip definitely fits onto that retaining plug, you just need to loosen it a bit. It looks fine to me.
In any case that pipe will make little to no difference to anything other than noise. It should be a lot quieter now when you floor it, when the pipe is properly connected to the one that is covered in the clear plastic.

It definitely sounds like sticking.
One less invasive approach would be to buy two cans of EGR cleaner spray and run that through the intake.

You run the engine at about 2.5k rpm and spray this in in bursts. It has worked very well for me in the past.
The engine will likely stall a few times but that's fine, just restart and rev a bit higher.

Take the intake box off and spray it straight into the pipe. That way it'll hit your maf as well and give that a bit clean.

If that doesn't work, take the big pipe off the throttle body (it might need a bit prying), hold the throttle body open and wipe with a lint-free rag.
It's hard but might just wipe enough grime off the butterfly to resolve sticking.

If that fails I'm afraid it's a throttle body off clean. Which is fun.