Car pops and bangs in overun

[Gavin Waddell 18]

As per title my car pops and bangs on over run sounds like a modern gti.

 

I had the emissions set up for the mot and everything is good apart from the PPM which was a bit high but co2 was ok.

 

the car does smell very rich so I’m s

guessing the unburnt fuel makes it pop and bang in the exhaust?

 

would adjusting the dizzy help? More advance?  If it pops and bangs the timing is to retarded?  I can  never remember and also if I’m looking at the dizzy from the front of th car turning towards me retards the timing ?

 

Thanks Gavin 

[welshpug 1,621]

I'd leave it alone!

[calvinhorse 870]

Hole in exhaust? 

[PhilNW 40]

1 hour ago, Gavin Waddell said:

 I can  never remember and also if I’m looking at the dizzy from the front of th car turning towards me retards the timing ?

Dont guess - Get a timing light to check properly , 

 

Once you have eliminated any timing issue , you can look for other causes 

[Gavin Waddell 18]

Welshpug: you say leave it alone, any reason why?

 

Calvinhorse: no holes in the exhaust, the mot is very strict over here, I will check the manifold isn’t leaking.

 

Phil: I thought  commen practice with these engins was to time the timing  was set by rotating the distributor taking it for a run and listening for pinkin? I have read in other posts that getting a timing light on the flywheel through the access hole was a pain.?

 

popping and banging can’t be a sign of healthy running, plus I’m not 19 anymore.

[PhilNW 40]

11 minutes ago, Gavin Waddell said:

I have read in other posts that getting a timing light on the flywheel through the access hole was a pain.?

It is a bit of a pain but not impossible just a bit of patience - I take off air intake then push back cables and pipes back with 1 or 2 length of wooden broom handle to open up a gap to shine a decent timing light through.

Edited June 30, 2021 by PhilNW

[DamirGTI 323]

Popping exhaust is usually lean mixture ... idle mixture is different/separate than what it is while actually driving it .

 

D

[Thijs_Rallye 86 4 Cars]

Does it keep popping and banging on overrun or just a few times? In the first case check if your idle contact in the tps is working as it should.

[Richard309Sri XU5JA 205GTi 7]

I think that's a good suggestion. 

 

Gavin - 

First reference I found to help to do the dynamic timing, is the Haynes manual chapter 4 ignition linked to chapter 3 Fuel and exhaust systems. Sections in those chapters tell you how to do it/dynamic timing referenced back to idle settings. 

 

That tells you the rotation direction of the dist. to, advance/retard in there.Also shows pic. of where to get into exactly to see and line up the timing mark and the marking plate. 

 

  

 

[Gavin Waddell 18]

It will pop and bang constantly, if I’m going down a hill and leave it if fourth gear it will do it non stop. I initially thought the TPS could be wrongly set up, so I looked at Haynes a set it up as as per. 

When I let off the throttle a low speed/rpm I can also feel a jolt, like a harsh cut off. I know the TPS and idle control on a Peugeot is a bit s**t. 

[camgti 56]

This sounds just like the issue I had. Changed absolutely everything and still no joy. But I did fix it! 
 

Was tight valve clearance on the exhaust valves causing it to pop and bang on the overrun and cut out like a hard limiter once warm at 4000rpm. Wouldnt do it cold. Smelt rich just like you said. 
 

Get a set of feelers and measure the clearance cold and report back what you get. Mine needed 4 thou taking off. Once done it was sweet as. 
 

 

[PhilNW 40]

When did it start happening? Has it always done it or something recent?

[Gavin Waddell 18]

It’s always done it, I’ve had the car for 20years now.

One thing it has started doing is it’s developed misfire also between  2-4K rpm it hesitates cuts out then cuts back in above 4K it’s alright. Which it neve did before.

i changed the img amp for Bosch BLACK!! And not blue I know they can bit a bit hit and miss. 

 

These cars never ever a dull moment.

[DamirGTI 323]

Might be AFM going bad ... worn/whipped out potentiometer carbon track .. if you have a spare AFM try replacing it and see what happens .

 

Is this by any chance specifically engine temp. related , or is it the same no matter the cold or engine running fully warmed up .

 

 

D

[Gavin Waddell 18]

I will replace the AFM with a spare, whilst try to find my non start issue I had last year I did the old bend the wiper arm trick maybe not a good idea.

 It does it less in the morning when cold, but when I leave work in the afternoon it does it straight away pretty much. If it only did it warm it would point to a dodgy CTS (i replaced it last year).

[PhilNW 40]

Seem to recall that one of the original problems was  a replacement fuel pump which was no good. Putting the original pump back on sorted it.

 

Did you ever check the actual fuel pressures for the original and replacement pumps? 

[Gavin Waddell 18]

That’s right phil, I put a new OEM pump I’m but I never checked the actual fuel pressure it was giving. 

 

I know that the TPS is a simple switch of no fuel when closed and extra fuel at WOT what happens in between though?

 

im going to try another AFM and see what happens. One thing at a time.

[PhilNW 40]

New OEM pump (Bosch) should be OK, thought you had put on the original old pump  (memory fade!)

 

As you say TPS is a simple switch gives open closed and WOT positions as I understand, it see 

 

 

Edited July 4, 2021 by PhilNW

[PhilNW 40]

On 7/2/2021 at 8:36 PM, Gavin Waddell said:

One thing it has started doing is it’s developed misfire also between  2-4K rpm it hesitates cuts out then cuts back in above 4K it’s alright.

Is the misfire specific to one cylinder or a general misfire. try and see what happens by removing a plug lead on each cylinder in turn and see if the misfire is worse or no different

While the emissions' have been set , the misfire is (as you suggest) probably unburnt fuel causing the rich smell.

[Gavin Waddell 18]

I haven’t checked, I’m away in Monaco at the monso will have a look when I get back.

[camgti 56]

CHECK YOUR CLEARANCES!! Cant stress this enough. Your car has exactly the issue mine has. I swapped everything over from another car I was lucky to have and nothing worked or helped until  I checked the clearances and the exhaust valves were too tight. Pops and bang on overrun and massive hesitation from 3-4k. Wont rev past 4k. 
 

It takes 30 minutes to check. Check them cold. If they are fine then you have another issue. 
 

Dont waste your money buying new parts when you can check this first. 

[Richard309Sri XU5JA 205GTi 7]

I need to check mine also  

 

got these values from H's if helps for 205 (1.6)

 

 

Edited August 12, 2021 by Richard309Sri XU5JA 205GTi
wrong photo

[Gavin Waddell 18]

So  i was able to have a play with the car and i switched the AFM for a spare one and it seems to have cured the problem drove to work with no worries so will see tonight on the way home, pretty cheap and easy fix finally.

 

Will look into valve clearance this winter when the car is offthe road.

 

Gavin 

[PhilNW 40]

 

happy days again

[Gavin Waddell 18]

So not really happy days, took the car to work today and it felt it hesitate a few times only for a millisecond. 

 

Then tonight on the way home it did it a few times it only seems to have between 2-3k rpm then stops.

 

It wasnt really running on three this time more jerky hesitation on off on off. Then clears after 3k rpm.