New spark plugs - loss of power

[ACJJ619 1]

Hey, I'm fairly new to 205 ownership and I've recently bought a 1988 1.6.

 

I always do a full service on a car whenever I buy one, and this is no exception. However since changing the spark plugs today the car seems to perform slightly worse, particularly at lower revs or on partial throttle. It does start quicker though - it used to turn over for a couple of seconds before starting but now it's probably half that.

 

The plugs I removed were a set of Champion C7YCX and I've installed a set of NGK BCP6E after doing some research on the recommended plugs for a non-cat 1.6. I can barely actually find any information on the Champion C7YCX so I don't know what the deal is with those.

 

Any ideas?

 

Thanks

 

 

[DamirGTI 342]

Anything you've done before the spark plugs ? like timing belt replacement maybe ?

 

Those Champion plugs are equivalent to NGK BCP7ES ... anyhow , won't be the plugs but rather something else "out or on the way out" .

Check for spark in dark garage or at night , should be nice thick blue/white colour , if orange/yellow that'll be weak ie. no good .

 

 

D

[ACJJ619 1]

I removed and cleaned the AFM with carb cleaner but that's all. I suspect there's an issue with the AFM as the car came with a spare when I bought it. It ran worse when I fitted it though so I'm unsure whether the spare was bought by a PO to install or whether they'd already replaced it and that was the old broken one.

 

The two little wire sensor bits in the AFM are a bit bent and it's missing the small black protective cover that's meant to surround them.

 

I'd replace it for a new one if they weren't a million quid.

[Richard309Sri XU5JA 205GTi 8]

39 minutes ago, ACJJ619 said:

The two little wire sensor bits in the AFM are a bit bent and it's missing the small black protective cover that's meant to surround them

the air temp. sensor in the air way "tunnel" within the AFM? just before the air flap/air vane 

 

 

[ACJJ619 1]

I'm not sure, I guess so? It's the two bits of wire that stick out right next to the flap.

 

Something else I've noticed is that when I push the flap all the way open, it looks like it sits slightly wonky in there. Like the end of the flap isn't vertical with the walls of the tunnel, it's on the wonk...

[Richard309Sri XU5JA 205GTi 8]

57 minutes ago, ACJJ619 said:

I'm not sure, I guess so? It's the two bits of wire that stick out right next to the flap.

in this location this as photo below? can you upload of photo of it also 

 

57 minutes ago, ACJJ619 said:

Something else I've noticed is that when I push the flap all the way open, it looks like it sits slightly wonky in there. Like the end of the flap isn't vertical with the walls of the tunnel, it's on the wonk...

 ah that could be a problem Ill just triple check with this one if this one does that also not sure never watched it before too closely 

 

on your AFM you got bosch part number ending in 056? on the plastic cover over the potentiometer part of it - big black plastic mostly flat 

 

with your plugs

what torque did you use i) to get the old ones out ii) put the new ones in

what gap is set i)old one ii) new ones? 

 

Edited September 6, 2021 by Richard309Sri XU5JA 205GTi

[DamirGTI 342]

There's small bearings on the flap shaft , possibly one is worn out .. but then the flap will usually scrape on the AFM body and also bind at certain flap opening angle .

 

IAT sensor , can check measure with multimeter .. on Jetronic , wont really make any difference if it's good or bad really you'll hardly notice .

 

Sounds like an old tired/abused AFM , have another one to try out ?

 

D

 

 

 

[ACJJ619 1]

Thanks for the replies guys.

 

It does feel a little rough when opening/closing the flap. If I'm very gentle I can sometimes get it to bind at certain angles but I do have to be quite gentle for it to happen.

 

I've uploaded two pics of the AFM open and closed. It does look quite tired, particularly when compared to the spare I've got. It ran worse on the spare though weirdly.  Maybe it just needs adjusting?

 

Sparkies I torqued to 20nm or about 18 ft/lbs. Not sure on gap, whatever the BCP6E is as standard. Looks the same as the previous ones.

[ACJJ619 1]

Update:

 

I tried the other AFM and couldn't get it to work smoothly with any kind of adjustment. I tried following this guide but to no avail.

 

I switched back to the previous AFM and tried following the guide again but it says to turn the throttle air screw fully in, and my car wouldn't start with it like that. The best mix of throttle air screw and AFM adjustment for my car seems to be 5.5 turns out on the throttle screw and 12 turns out on the AFM, which is quite different from the guide. At these settings it idles at around 1200. Any lower and it's just super lumpy.

 

I'm tempted to start pulling HT leads off while it's running to see if anything happens. Wouldn't surprise me if it's running on 3 cylinders, although it does feel smoother at higher revs/throttle.

[DamirGTI 342]

I'm doing them like so :

 

- TB stop screw , undo so it's off the throttle leaver , then back in till it barely touches/makes contact with the leaver (use thin feeler gauge to spot the "contact)  .. then do 4 full turns on the screw in and stop , and re-set the TPS switch .

 

- TB air/bypass brass screw , set about 2 turns from fully closed for now ... fine tune after the engine reaches operating temp. with some load on (lights or cabin heater)

 

- AFM mixture screw , turn fully down till it bottoms out , then back up counting 7-8 turns and stop .

 

- Check/adjust the ignition timing as/if needed , and further re-correct the idle via TB air/bypass brass screw afterwards .

(* check timing belt , if the engine is timed up properly *)

 

- Check the tension of the throttle cable , must not be to loose nor too tight , and the TB must fully open and close of course according to the pedal movement .

 

That'll get you closest stable running engine , might need to fine tune some of the above but in small increments .

 

However that's if the car you're working on is in overall good nick , if there's any vacuum leaks , worn ignition parts , mechanically tired engine , and especially badly adjusted AFM or bad AFM potentiometer track , can "screw play" for days/months you'll just be running in circles frustrated to the bone .

 

Check the AFM insides , open up the black plastic cover and take a few pics of the potentiometer/carbon track ..

Unfortunately AFM's are impossible to adjust properly on a DIY basis without either WB sensor and gauge or ex. gas analyzer  ... as you need to see what the mixture is doing on idle and across the entire rev range and adjust/correct accordingly .

 

D

Edited September 7, 2021 by DamirGTI

[ACJJ619 1]

Thanks, I'll give it a go.

 

I'm a little sceptical already though just from the TB bypass screw - mine seems to require unscrewing quite a lot for the car to idle properly. 2 turns...I expect it'll barely stay running and be so lumpy it rips the engine mounts off  We'll see though...

[Richard309Sri XU5JA 205GTi 8]

13 hours ago, ACJJ619 said:

I'm tempted to start pulling HT leads off while it's running to see if anything happens. Wouldn't surprise me if it's running on 3 cylinders, although it does feel smoother at higher revs/throttle

I have also in the past carefully removed the injector connectors one at a time for diagnosis, - so in that way you are not putting unburnt fuel through the system. I realise it wouldn't be for long but some of the unburnt fuel will be going into the oil past the rings I think - I had that alot when I was running on three cylinders after rebuild. the oil will be diluted by and mixed with petrol. I had a sump full about 5 litres of itLoL that was chronic over fueling though I must say as the CTS connector was broken also.                                                                                                          

Edited September 7, 2021 by Richard309Sri XU5JA 205GTi

[ACJJ619 1]

1 hour ago, Richard309Sri XU5JA 205GTi said:

I have also in the past carefully removed the injector connectors one at a time for diagnosis, - so in that way you are not putting unburnt fuel through the system. I realise it wouldn't be for long but some of the unburnt fuel will be going into the oil past the rings I think - I had that alot when I was running on three cylinders after rebuild. the oil will be diluted by and mixed with petrol. I had a sump full about 5 litres of itLoL that was chronic over fueling though I must say as the CTS connector was broken also.                                                                                                          

Ah yeah that's a better idea, I'll try that. Thanks!

[Richard309Sri XU5JA 205GTi 8]

no worries glad to help

 

18 hours ago, DamirGTI said:

There's small bearings on the flap shaft , possibly one is worn out .. but then the flap will usually scrape on the AFM body and also bind at certain flap opening angle .

@DamirGTII have also got an old one that also sticks/vane sticks. I thought it was just dirt through the gateway/tunnel section cleaned it out but not I realise it does still stick again now and again when moving back and forwards. I presume that it is not easy if at all to replace the bearings? must have to take it all apart - that could be tricky! LoL 

[DamirGTI 342]

I had one too back i the days picked up at the scrapyard from an crash damaged 205 ... Internals (potentiometer/carbon track) where in mint condition , but sadly the flap door was also off center catching/scrubbing on the base of the AFM .

 

That AFM was obviously no good while driving , as the top of the flap door shaft is the potentiometer wiper which needs to be 100% centered in relation to the potentiometer plate , and must move/swipe smoothly on the carbon track from fully closed flap to fully open .. any catching/scrubbing/binding of the flap door will make the erratic signal/reading made by the AFM and sent to the ECU and thus poor engine response/performance at certain rpm. range . 

 

Bearings are on top of the flap door shaft under the potentiometer plate and cog wheel/spring , two small bearings , bottom part of the flap door just pivots against the bottom AFM cover . If decide to disassemble , need to be careful , wiper arm needs to be removed and most important cog wheel/spring secured/locked in current position with zip ties or similar otherwise you'll be at lost with the spring preload once you pull the flap/shaft out .

 

 

Sadly , Bosch AFM's are riveted from the bottom , but you can grind off the rivets and clean up the sealant and pop open the bottom cover to access the flap door .. later re-assembly with some sealant around the edges and fit Phillips screws instead of rivets , that'll do , i've opened and closed a few of them like so and , no complains .  Same years Nippondenso AFM's (basically copy of the Bosch AFM's , but much better designed , made by Japanese) had screw on bottom cover so you could've dismantle clean them and re-assemble easily . 

 

D

 

 

Edited September 7, 2021 by DamirGTI

[ACJJ619 1]

Okay, an update. Thanks for the help so far all.

 

I unplugged each injector one by one and the engine was worse each time, so I'm confident they're all firing.

 

I then tried running it with the throttle position sensor unplugged and found it actually runs better. The idle doesn't suddenly change dramatically when you unplug it, but if you blip the throttle or put the clutch in with the TPS plugged in as it has been, the revs plummet to almost stalling and then come back up to a lumpy idle. With the sensor unplugged, the revs drop more gradually down to the appropriate idle speed and you don't get the near-stall-recovery behaviour.

 

I just had a short drive with it unplugged and it seems a little more spritely too, but difficult to tell on a short drive. Certainly no worse though.

 

In terms of adjustment, I've got it set so that when the throttle is at the stop, the TPS clicks. It then clicks again as soon as you apply any throttle and finally once again at WOT. I believe this is the correct adjustment but it seems to be causing issues even still.

 

 

[Richard309Sri XU5JA 205GTi 8]

14 hours ago, ACJJ619 said:

I then tried running it with the throttle position sensor unplugged and found it actually runs better. The idle doesn't suddenly change dramatically when you unplug it, but if you blip the throttle or put the clutch in with the TPS plugged in as it has been, the revs plummet to almost stalling and then come back up to a lumpy idle. With the sensor unplugged, the revs drop more gradually down to the appropriate idle speed and you don't get the near-stall-recovery behaviour

that means you are running on throttle open all the time as far as I know. Ill check maybe someone else knows also. 

 

The fuel mapping is different in throttle open and throttle closed/idle "mode" as far as I know - seems to be supported by what you describe 

[ACJJ619 1]

Just had a 30 minute drive to work with the sensor unplugged and it definitely feels better. Idle is smoother (though is now slightly too high at 1500rpm, needs the screw winding in a bit) and performance, particularly when warm, seems smoother.

 

Given that performance seems better (though could be placebo) I was thinking maybe it's running throttle closed the whole time. I'll see if I can source a replacement.

[ACJJ619 1]

Update: Just did back to back 2nd gear pulls, 30 to 55mph with the TPS plugged and unplugged. 6.3s with the sensor plugged in, 8.1s with the sensor unplugged, or about 1.8s difference!

 

So the car idles better with it unplugged, but performs better (WOT anyway) with it plugged in. So my guess is that it's broken and signalling WOT at all times. Got a new replacement on the way 

[opticaltrigger 52]

I'm honestly not 100% here, and someone might well correct me. But I was under the impression that the throttle switch's function is for injector cut when on the overrun.

You could just check the switches operation with a meter.

So I'm kind of struggling a bit...

Although I seem to have some vague feeling that the ecu add's or subtracts a few percent of fuel if the switch drops out. i.e. unplugged. I could have that wrong, hopefully Damir or one of the other guy's might read this and have an opinion on that, coz I'm not certain.

However, if that is the case it might be why you notice a difference by unplugging it. But I think that your problem is more related to the AFM and general engine condition, rather than that little switch. I'd like to know though so please keep us posted.

 

All the best O.T.

[welshpug 1,661]

sounds like unplugging the throttle switch is masking a fuelling issue.

 

its for over run fuel cutoff and idle fuelling, and also WOT.

 

if unplugging makes a difference it sounds like the afm is making it run lean/rich and the disconnection of the switch brings the fuel closer to what it needs.

 

 

they are easy enough to set up/test, Haynes workshop manual details it quite well.

[ACJJ619 1]

Thanks for the info.

 

So it performs better plugged in, but idles worse. So I'd assume the mixture is okay for normal running but wrong for idle. Would that not point to a TPS refusing to tell the ECU when the car is idling and therefore the mixture being incorrect and it being lumpy?

 

I could smooth it out by raising the idle RPM to something like 1200 but it still has the behaviour of revs dropping dramatically to near-stalling when I press the clutch in.

[ACJJ619 1]

UPDATE:

 

Just done a bunch of back to back 2nd gear pulls, measuring 30mph to 55mph (rev limiter). I was testing a combo of a new (2nd hand) TPS, the original TPS, and a new Mann air filter (previous one was foam - unknown brand). Results below:

 

Foam filter, original TPS:

Run #1 - 6.1s

Run #2 - 6.0s

Run #3 - 6.3s

 

Foam filter, new TPS:

Run #1 - 7.7s

Run #2 - 7.1s

 

Mann filter, new TPS:

Run #1 - 7.2s

Run #2 - 7.1s

Run #3 - 7.1s

 

Foam filter, no TPS:

Run #1 - 8.0s

 

I'm kinda confused at the results. There doesn't seem to be any difference between the foam and Mann filter (as I expected) but there's a definite difference between the two throttle sensors. I'm of the understanding that it's a simple open/closed switch so as long as it knows I'm not idling, it shouldn't make any difference. But these tests show quite a clear difference in performance??

 

Also, the new TPS didn't change the idle. Revs still plummet to near-stall when the clutch is depressed. I'm going to tweak the AFM as per Haynes.

Edited September 15, 2021 by ACJJ619

[309SRiguy 15]

Are you thinking of altering the spring tension for the AFM flap? Unless it has been tweaked already and you want to tweak it back to standard you will likely end up worse than when you started. What exactly does Haynes suggest you do? I thought my 309 manual told me to leave the flap tension alone. If you do touch it make sure you mark positions carefully so that the spring will be somewhere near the tension you started with. I found that when all else was close to correct that one notch in either direction upset the fuel ratio too much.

The AFM looks as though it has seen better days.

The flap should not be out of line with the casing as it appears to be in a photo above. What about that sensor? It doesn't look like it has had an easy life.

Does the flap move smoothly? 

If the AFM hasn't been tweaked too much most of the mixture adjustment is by turning the hex head screw which adjusts the flow of air in the AFM air bypass channel. It bypasses the flap and adjusts the mixture by letting more or less air through.

If you remove the cover have a good close look at the carbon track that the contacts sweep over. There are ways of cleaning up the track and relocating the contacts to a fresh tracking position.

 

There are many articles on the peculiarities of the LE2 Jetronic. They were used in many vehicles at the time so lots of people have experienced the problems. Searching the web will certainly bring some hits. This site is well worth searching for knowledge of the LE2.

 

If the rest of the induction system is checked and sorted then a stuffed AFM will be more obvious. 

The leaks that can occur in the system can give bad mixture. Have you worked through the check list? Some of the common leaks might surprise you.

Is your timing correct? Is the vacuum advance working? or is the diaphragm damaged and leaking air into the manifold vacuum tube. 

Any extra air entering the intake will quickly lean the mixture to the point where there is too little adjustment within the system to correct the air/fuel ratio. 

 

 

[DamirGTI 342]

The allen screw on the AFM is for idle mixture adjusting , while driving and on all the rest of the rev range the mixture is governed by the AFM spring preload , state of the potentiometer-carbon track .

 

You can usually tweak the spring/cog wheel around 4 tooth in either direction rich-lean , and around "maxi" 7 tooth if it's on the lean settings already .. really depends from where you're starting off , if someone before you wound it up tight , midway or loose .

Then , there's certain spot close to ideal where 2 tooth on either side makes noticeable difference , and also an spot where while loosing the cog wheel the mixture starts to go lean !! (when should actually be rich , quite a bit rich) .

 

Also one needs to drive the car and monitor what happens with the mixture trough the entire rev range , only then you'll be able to adjust the AFM perfectly/spot on .. but needs an WB sensor and gauge as an setup/adjusting aid , otherwise it'll be guessing game , no way you can set it up by feel/ear/nose ..

Even ordinary 4 wire (with heater) narrow band lambda sensor hooked up to the multimeter stuffed into the exhaust is better than anything , it'll help you out seeing what happens with the mixture .. it'll be pretty precise on how lean it runs , but not so accurate on the rich side (though not as much/drastically imprecise)

 

And absolutely , need to fix all the other issue on the engine first before attempt to adjust the AFM ... vacuum leaks especially , cracked hoses , leaky gaskets and such .

 

D

Edited September 16, 2021 by DamirGTI