engine hesitation on low throttle

[gregk9 0]

Hi Guys [n gals].

94 spec vr6, engien seems to hesitate on low engine revs or throttle. if you gun it, its fine and runs well.but at low speeds it seems to hesitate, almost a misfire or fuel starvation prob.

did think it was a fuelling/ starve problem, but have filled the tank and it seemed to run better, but then it came back again

does anyone have any clues where i can look, without visiting the dreaded v dub dealer for a costly diagnostic?

[vr6madmike 0]

Dirty throttle body

[ip 0]

I just spent a month working through this exact same behavior in my car (could have written your post myself). I figured fuel starvation myslef but it can't be that since it would manifest more often at high revs (where fuel flow is at a maximum) than low revs.

I replaced the following before finding the actual cause:

1. Plugs

2. Coil Pack

3. MAF

Turns out it was..... HT Leads! Really surpised me that it could be that simple but there you go. They looked fine and there was no sparking visible (even when sprayed with water) but replacing them solved the problem straight off.

There is a guy selling sets of HT leads for the VR6 on eBay for £27.99 plus postage. I bought these and was surprised at how good they were. Really nice connectors and decent cable (nice and flexible so fits in cable guides properly).

I'd start there, then the plugs, then a coil pack and lastly the MAF. I've now got a spare MAF I can sell you but I doubt you will need it (apparently the early MAFs were quite relaible).

Hope that helps.

ip

[gregk9 0]

thanks for replies, but i am not convinced its an "ht" thing, someone else has already replaced the plugs and leads, the leads being a genuine V dub set! if it were ht, surely it would misfire moreso at high rpm/speed, this thing is fine at such, its only lower "town speed" it spooks and hesitates.

[ip 0]

As I say, mine only ever missfired (or partially fired really) at low revs. High revs were fine. It's all to do with 'easiest path to earth'. Normally, the easiest route to earth for the spark is over the spark plug tip (as you would hope). Under specific conditions, the mixture of fuel/air/compression within the cylinder means that the resistanc across the spark plug electrodes becomes greater than that of the path through the HT lead insulation and out onto the chasis/engine/whatever. Under these conditions, you'll get a partial missfire on the affected cyclinder.

For my car, it was only ever between 1200 and 1500rpm . I too had plugs with less than 2000 miles on them and a set of VW HT leads that (according to the service log) were only 4 years old with less than 10,000 miles on them. My suspision is that they had been yanked out without using the correct lead removal tool at some point and so had become damaged in the process.

You're right, it could be something else (coilpack or MAF) but these cost a lot to try out (unless you have a mate with a donor vehicle) while the HT leads (which should be replaced every 4 years or so anyway) will only cost you £34.

Naturally, it's also worth getting vag-com onto it too but this showed up no fault codes on mine at all.

Cheers,

ip

[petervr6 0]

had the same prob with mine only missed at low revs and it was the HT leads...

[gregk9 0]

fault found!

turned out to be the fuel pump relay clicking in and out intermittantly.

Thanks guys for your suggestions, but glad i didnt go all out for another coil pack and leads first!

[ip 0]

Good catch. I forgot that I had tried that out on my car. It is a common failure and I should have suggested it in the first place.

[petervr6 0]

cool happy for you nice and cheap..

[harvey05 0]

how do you cheak the relay?

[gregk9 0]

the quickest way is via diagnostics, but if like me you dont like spending money, then but looking at the faults and symptoms you have.

the engien seemed to hesitate, rather than misfire, so have to think fuel, knowing how fairly reliable vw fuel pumps are, didnt want to replce fuel pump straight away, so went for next thing, check voltage supply to the pump to eliminate the relay or car alarm circuits.

so found that the pump relay was clicking "in and out", thus loosing power supply to the fuel pump, causing the fuel pressure to drop, causing the hesitation.

hope that helps anyone else with similar problem.

you dont need bags of money and have to keep running down to the nearest garage with diagnostics, just step back and write down all the faults and problems.

then see what suggestions arise after that, before opening wallet! [ha ha].