Misfire/hesitation On Full Throttle

[Pugwebgeek 0]

I've been pulling my hair out on this one.

For the last few months my 1.9 8v has been misfiring or hiccuping on full throttle.

 

If I rev the car up in second gear on medium throttle then it will happily spin up to the rev limiter. However if I floor it then after about 4k revs it starts hiccuping and lacks power just like on most cars when you hit the rev limiter.

 

I've tried loads of things:

 

• Replacement Bosch Amp and Ducellier coil (worked on donor car)
  
• New spark plug leads
  
• New spark plugs
  
• New battery as previous one wasn't great at holding a charge for long
  
• New dizzy cap and rotor arm
  
• New fuel filter
  
• Tested the Throttle Position Switch with an electrical tester to make sure the idle, normal and load conditions are reading correctly across the connectors
  
• I also fitted a brand new AFM about a year ago and had the car CO levels set by a garage.
  
• I've also checked the big earth cable on top of the gearbox
  

 

Any ideas guys? I was thinking it could be fuel-related as full throttle condition would require more fuel and therefore it could start to run too lean and cough. Alternatively I was thinking that even if the TPS was working correctly maybe the wiring back to the ECU isn't perfect. I haven't messed with the injectors but maybe that's another possibility.

 

I am really stuck

[DrSarty 90 1 Cars]

Get the injectors cleaned, then perhaps try again.

 

Sometimes fault finding is like this.

 

You've really done most of what you can.

 

Have you tried looking for an inlet air leak? Spray some hairspray or EasyStart carefully around the inlet manifold when wiggling the inlet to see if the revs rise.

[pugpete1108 62 1 Cars]

Get the injectors cleaned, then perhaps try again.

 

Sometimes fault finding is like this.

 

You've really done most of what you can.

 

Have you tried looking for an inlet air leak? Spray some hairspray or EasyStart carefully around the inlet manifold when wiggling the inlet to see if the revs rise.

 

sorry to jump in but how does this help Rich? im sure i have an air leak on mine somewhere but cant find it?

[hothatch 2]

I don't thinkl an air leak would cause this to be honest. Have you checked the fuel pump pressure at the injector rail?

[MerlinGTI 3]

I had a missfire a while back at 4k, you could just about drive through it. Turned out to be a knackered dizzy.

 

Worth a try if you can swap one out for testing.

[S@m 156]

Sounds very much like an ignition amp problem to me, although you have said that you have a Bosch replacement one; I had this same issue with a brand new intermotor amp, albeit on an mi16, but still, might be worth checking again, and make sure it has a good contact with that heat transfer paste on the back.

Just a thought.

Sam

[Veero 1]

Don't get me started on Intermotor. Had a problem whereby it would get hot and just die. On replacing the amp it would start and run but die again once hot. Went to local factors, only thing they could get was an Intermotor one. I said it hadn't got the pin outs as the Bosch one. Was told that's the replacement from the OE spec. Guessed it might be OK.

 

Nothing but misfire under heavy load, ok ish on idle but popping and farting on anything above 2.5k. Took it back and got money off a genuine Bosch one. Triple checked part number. Part number same as stamp on my original 10 yr old Bosch one. Same pins as the Intermotor one. Feared the worst and explained my concerns. No surprise it did exactly the same as the Intermotor one. Took it back and had a right ballache to get my money back. Shop said they would only refund it if Bosch tested and found ti to be faulty. Didn't have to get the legaleese out fortunately and got money back.

 

It seems that even Bosch have changed the new part numbers so the Intermotor ones are actually copies of the Bosch one and that new Bosch ones are wrong.

 

So bought 3 second hand ones on here, so far no repeat of any symptoms. It was definitely the ignition amp causing all my grief.

[hothatch 2]

Don't get me started on Intermotor. Had a problem whereby it would get hot and just die. On replacing the amp it would start and run but die again once hot. Went to local factors, only thing they could get was an Intermotor one. I said it hadn't got the pin outs as the Bosch one. Was told that's the replacement from the OE spec. Guessed it might be OK.

 

Nothing but misfire under heavy load, ok ish on idle but popping and farting on anything above 2.5k. Took it back and got money off a genuine Bosch one. Triple checked part number. Part number same as stamp on my original 10 yr old Bosch one. Same pins as the Intermotor one. Feared the worst and explained my concerns. No surprise it did exactly the same as the Intermotor one. Took it back and had a right ballache to get my money back. Shop said they would only refund it if Bosch tested and found ti to be faulty. Didn't have to get the legaleese out fortunately and got money back.

 

It seems that even Bosch have changed the new part numbers so the Intermotor ones are actually copies of the Bosch one and that new Bosch ones are wrong.

 

So bought 3 second hand ones on here, so far no repeat of any symptoms. It was definitely the ignition amp causing all my grief.

 

Well thanks for that info ! New to me lol and I think you may have solved his problem

[Pugwebgeek 0]

Hey guys

Thanks for the helpful suggestions.

I am going to check over the main electrical connections to check for any unusual resistances down the wires including the amp. I'll have a go at cleaning up the contacts too.

 

If that doesn't work I'll give a new/replacement amp a try.

 

I'll let you know how I go

 

Cheers

[humanz 3]

An air leak can cause similar symptoms. If my afm isn't properly seated in the adaptor which joins it to the throttle, I get a similar problem. If u've exhausted all the other things suggested on here, another thing you can check are the grounding points. I was in your same position for the past few months. Replaced all the things you listed. Now that I've replaced some bad ground connections in the engine bay, and added a new ground, it seems all my issues have gone away.

[daveo 0]

this souns exatly like the problem i have, however i've found that once i've dragged the rev's through the problem spot i don't have an issues again.

 

all ignition conponents new bar the ign amp (replaced for know working one) and coil lead as i've had trubble finding once to suit. its femail to male ended. my coil is intermotor and cause me no isses as yet. there is no wondering of the rev counter which i'm told point towards a coil problem?

[Pugwebgeek 0]

I love my little 1.9 8V 205 but this problem is driving me insane

 

I've checked for air leaks and replaced the rubber tubing elbow between the AFM and TB as the end was a bit gnarled. Still no joy

I've found another amp and tried that but no luck

Tried a replacement TPS in case the one I had tested okay cold but when hot went bananas. Still no good.

 

Then randomly I took it for a spin and all was good

All sorted I thought but the next day back to the old problem and now with it idling at 1600 revs even when I blip the throttle. It will go back to 1300-1400 for a sec but rises back to 1600

I put the old amp back on but it's still the same i.e. high idle and misfiring at high revs (almost like the limiter is kicking in)

 

What I've noticed is that when it misfires at 5000ish the rev counter can drop like a stone and then leap back up again. Looking at the wiring diagrams (http://www.planete-205.com/forum/viewtopic-38583.php) it looks like connector 1 from the coil goes to the rev counter and ECU.

 

I have cleaned up the connectors to the coil and amp, tested the connections to the ECU etc and all seems okay. I am wondering if it might be the ECU or Tachymetric Relay

 

Anyone had any similar problems?

 

Colin

[daveo 0]

^^ that is almost exactly what my car is doing appart from the rev counter bit. one trip out the car is faultles and the next it cant go past 3.5 or 4k rpm. it sounds like its droping down to 3 cylinders almost!

[dodsworth_gti 11]

ive got a misfire and i cant damn find it and its getting really anooying now

 

same again,at about 4k,but mine gets really violent,and does it right to the limiter sometimes,and other times it will do it once or twice and between them it will pull like a mother from hell

 

my rev guage jumps about like a mad man all over the place when its in this misfire area

 

i need to find this as its getting annoying lol

[MerlinGTI 3]

I had a missfire a while back at 4k, you could just about drive through it. Turned out to be a knackered dizzy.

 

Worth a try if you can swap one out for testing.

 

F'ing dizzy!

 

Takes 5 mins to swap a dizzy out. Do it just to shut me the hell up

[The Arch Bishop 0]

Do it before he gets angry!!

[Pugwebgeek 0]

Yep, sounds like I better get cracking on that one

 

I might have a problem because I shipped my little GTi out with me to Oz a couple of years back and now realise that all the ones here have the cat convertor so have a different set up. It makes getting certain parts pretty difficult

 

Anyone ever tried to have a go at testing or repairing a dizzy before I start trying to hunt one down here?

[MerlinGTI 3]

Not a test as such, but my knackered one had visible swarf inside, and an awful lot of play in the shaft when compared to the good secondhand one I replaced it with.

[Pugwebgeek 0]

Finally some good news. MerlinGTi - I took your advice but didn't have a spare dizzy to swap in so found Damir's thread on dismantling the bugger because I'd spun the dizzy using an cordless drill and got some random readings

 

To cut a long story short, the dizzy had a fair bit of oil inside so I took the bearing off the top and pulled out the field coil bit.

 

So I cleaned it all up and put it back together. Back on the drill and the readings were higher and steady rather than showing 3 then 0 then 5, I got 10V AC at full drill speed.

 

If anyone is thinking of dismantling the Bosch dizzy, allow hours of fiddling about getting the springs back on!! You have been warned

 

Anyways, I have my 205 back. It's nice and responsive at low revs and goes all the way up to 6600 when the limiter kicks in.

 

Life is sweet again

 

Thanks for all your ideas guys. I've tried a fair few of them, spent a ton on new leads, amp module etc and in the end I think it was oil getting on the contacts between the field coil and the distributor pick up cable on the side.

 

 

 

I'm off to take it for a blast in the Blue Mountains

[MerlinGTI 3]

Great news!

 

Glad your sorted Well done on fixing a dizzy btw

[kyepan 291]

So I cleaned it all up and put it back together. Back on the drill and the readings were higher and steady rather than showing 3 then 0 then 5, I got 10V AC at full drill speed.

 

If anyone is thinking of dismantling the Bosch dizzy, allow hours of fiddling about getting the springs back on!! You have been warned

 

lol, i feel your pain, also took one apart to try and sort out a misfire.. glad it's working.