Gutless 1.6 - Any Ideas?

[Rob Thomson 6]

Before the Cadwell track day I took the 1.6 GTi to Mech Repairs in Cheltenham to make sure it was in good health, more than anything so I'd be sure it wouldn't detonate itself to death flat-out on track. The chap spent some time running the engine on the diagnostics and declared the ignition system to be working correctly (always good to know when you've got a mechanical dizzy) before checking the fuelling at different revs and then giving it a power run.

 

On the first run it managed 84bhp, the problem being running lean at the top-end. Playing around with the AFM spring improved matters a bit (but only by making the bottom-end very rich) and we ended up with 93bhp at the flywheel, still leaning off towards the top but better (and safer) at the top end for Cadwell. In its current state there's no way it'll pass an MOT.

 

I guess the factory 115bhp is a bit optimistic, and it has done 128k miles, but what's causing it to lean off? The AFM's reconditioned, but I guess that doesn't necessarily mean it's any good. I'd assumed that fuel pumps either work or they don't, but Baz and Anthony reckoned that was worth a look. The injectors could probably do with a clean too. Any other ideas what could be wrong with the little bastard?

 

Thanks, Rob.

[Ethos 0]

Tooth out?

[Rob Thomson 6]

Tooth out?

 

I'd be amazed if it was, the belt was changed fairly recently and I'm usually alright at that sort of thing. Mechanically it seems fine and it's very willing to rev.

 

And anyway, that wouldn't explain why it's so lean at the top-end.

[Tesstuff 222]

I guess the factory 115bhp is a bit optimistic, and it has done 128k miles, but what's causing it to lean off? The AFM's reconditioned, but I guess that doesn't necessarily mean it's any good. I'd assumed that fuel pumps either work or they don't, but Baz and Anthony reckoned that was worth a look. The injectors could probably do with a clean too. Any other ideas what could be wrong with the little bastard?

 

Thanks, Rob.

 

 

Our 1.6 Gti has every single one of its 115 bhp, it is a 60k original example. So it is possible

[welshpug 1,666]

my 1.9 had 129 bhp last time it was on the rollers, so perfectly feasible (its on 145k!)

 

what exhaust and downpipe does it have?

[DrSarty 90 1 Cars]

Sorry to hear about this Rob.

 

You know it's lean, so that does point to fuel surely? I think you're going about it the right way. Is an easy swap the AFM?

 

After that I'd say injectors, FPR, fuel filter and pump - not necessarily in that order. Injector cleaning could be up to £80 though!

 

EDIT: And just thinking about this in a logical 'Spock' fashion - is another alternative a weakening being caused by extra air getting in higher up the rev range, e.g. a slight leak in the inlet manifold? What about a loss of compression and the HG being on its way out? A comp test is free.

Edited September 12, 2009 by DrSarty

[Rob Thomson 6]

what exhaust and downpipe does it have?

It had a new Bosal system when I bought it and that's still on there. When it falls apart I plan to replace it with a genuine system from Peugeot, but I have wondered whether what's on there is restrictive.

 

Is an easy swap the AFM?

Yep - but try finding a known good one. The power and torque curves are actually very smooth (which I guess implies that some elements of the system - perhaps including the AFM - are working well) but it all tails off very early at the top-end. I think that suggests a fuel delivery problem, but I'm often wrong about these things!!

 

After that I'd say injectors, FPR, fuel filter and pump - not necessarily in that order. Injector cleaning could be up to £80 though!

Yep, I am quite tempted to replace all of those bits (and the AFM). The problem is that it's very easy to spend a lot of money and be no closer to finding why it's lacking power (apart from eliminating the replaced parts).

[Rob Thomson 6]

EDIT: And just thinking about this in a logical 'Spock' fashion - is another alternative a weakening being caused by extra air getting in higher up the rev range, e.g. a slight leak in the inlet manifold? What about a loss of compression and the HG being on its way out? A comp test is free.

I might dig out the compression tester tomorrow and have a play with that. I really don't think there's anything wrong with the engine mechanically (it did 120 miles more-or-less on the limiter around Cadwell on Wednesday without using a drop of oil or water), but it's a check I can do free so I might as well.

 

For what it's worth, the rolling road man was convinced it was an ancillary issue.

[welshpug 1,666]

fuel pressure you can get tested to eliminate the FPR and fuel pump, the AFM itself can be tested too with an Ohmmeter.

 

not sure if the Bosal downpipe has the split section, I know a friends rally car recently spat out a section and did not like to rev as cleanly at all, since replaced with a Magnex manifold and its back to its usual 1.6 revviness and pulls very hard to the limiter in each gear inc 5th.

[Rob Thomson 6]

fuel pressure you can get tested to eliminate the FPR and fuel pump, the AFM itself can be tested too with an Ohmmeter.

 

not sure if the Bosal downpipe has the split section, I know a friends rally car recently spat out a section and did not like to rev as cleanly at all, since replaced with a Magnex manifold and its back to its usual 1.6 revviness and pulls very hard to the limiter in each gear inc 5th.

 

Testing stuff? I much prefer guesswork!! That's a good plan actually; I'll get my friendly local garage to do a pressure test and get the multi-meter out to test the AFM.

 

The Bosal does have the split section, but it has had a very annoying exhaust rattle for a while and I did wonder whether it might be the baffle coming loose. Strangely thrashing it around Cadwell seems to have fixed the rattle... I mentioned that to the RR man who again dismissed it and said he was certain it was a fuelling issue.

[kyepan 291]

Testing stuff? I much prefer guesswork!! That's a good plan actually; I'll get my friendly local garage to do a pressure test and get the multi-meter out to test the AFM.

 

The Bosal does have the split section, but it has had a very annoying exhaust rattle for a while and I did wonder whether it might be the baffle coming loose. Strangely thrashing it around Cadwell seems to have fixed the rattle... I mentioned that to the RR man who again dismissed it and said he was certain it was a fuelling issue.

 

I second this advice from my experiences recently.. the mi was feeling very flat, a new fuel pump, and its like ... well its fast. we also put a gauge inline to check this and at idle it was showing a good 3 bar/45psi, so it was only leaning out under load, which is hard to test without a the bonnet off, or on a rolling road.

 

 

testing the afm is pretty easy, you just need to get the ignition on poke something down it to move the flap, pull the rubber boot off the connector and back probe it until you find the 0-5v reading. Then make sure the voltage is within range ( which is probably somewhere in the Bosch engine management book) or caps will have the MI voltages. But if it starts runs idles and revs it should be within tolerance.

 

hope this helps.

 

J

Edited September 12, 2009 by kyepan

[welshpug 1,666]

details for the AFM testing are in the Haynes manual

[ALEX 98 1 Cars]

The Bosal does have the split section,

 

Are you sure? My last 2 were Bosal and they didn't have one.

I changed it only today for a Walker one mainly for this reason.

The first thing I said after specifying what car its was for "And I don't want one of those crappy Bosal exhausts without the split downpipe!"

I even drew him a little diagram and everything!

[Rob Thomson 6]

I second this advice from my experiences recently.. the mi was feeling very flat, a new fuel pump, and its like ... well its fast. we also put a gauge inline to check this and at idle it was showing a good 3 bar/45psi, so it was only leaning out under load, which is hard to test without a the bonnet off, or on a rolling road.

Yep, pressure's only half the story isn't it, you also need flow. Still, I guess a pressure test might be worth a try.

 

testing the afm is pretty easy, you just need to get the ignition on poke something down it to move the flap, pull the rubber boot off the connector and back probe it until you find the 0-5v reading. Then make sure the voltage is within range ( which is probably somewhere in the Bosch engine management book) or caps will have the MI voltages. But if it starts runs idles and revs it should be within tolerance.

 

hope this helps.

That does help, thanks very much.

 

details for the AFM testing are in the Haynes manual

That'll be my bed-time reading!

 

Are you sure? My last 2 were Bosal and they didn't have one.

Yep, it's definitely split. However it possible that the front pipe isn't Bosal... the back box definitely is and they were replaced together.

 

 

Anyway, thanks for all the suggestions. The poor little thing's doing an autotest in the morning but I'll have a poke around in the afternoon and see what I can find.

 

Cheers, Rob.

[steve@cornwall 100]

Isn't it the job of the TPS to enrich the fuel at full throttle?

[Rob Thomson 6]

Isn't it the job of the TPS to enrich the fuel at full throttle?

Yep, and we confirmed that it's functioning when it was on the rollers.

 

Thanks for the idea though!

[Galifrey 1]

Yep, and we confirmed that it's functioning when it was on the rollers.

 

Thanks for the idea though!

 

When did you last have the injectors cleaned? Mine were shocking at 116k had them cleaned at local bosch FI specialist and the difference was amazing!

Edited September 12, 2009 by Porsche911r101

[Rob Thomson 6]

When did you last have the injectors cleaned? Mine were shocking at 116k had them cleaned at local bosch FI specialist and the difference was amazing!

I doubt they've ever been cleaned. Don't know why I didn't get them done while it was all in bits but you live and learn!

[Miles 331 1 Cars]

It's not that bad, Don;t forget all rollers will show different result's.

I know from having the odd 205, That you can get some real dog slow one's, I had one like that back in 1990 and the car was only 4 years then and everthing checked out OK but was just one of those engine's

[Baz 421]

+1, as a thought.

 

I still think it's worth checking the FP etc though, just to rule anything out etc.

 

Sometimes they're just not all that i'm afraid, there's quite some differences in the port castings it seems, which amounts to quite drastic differences between a good and bad example.

 

I'm lucky and seem to have one of the good ones, i wouldn't be at all surprised if mine's still kicking out around/nearly all of it's 115 horses, and that's now on c160k. I love it!

[Galifrey 1]

I doubt they've ever been cleaned. Don't know why I didn't get them done while it was all in bits but you live and learn!

 

Mine were coroded in badly, when I managed to pull them out, the caps came off and dropped inside the inlet ports!

 

Luckily the valves were closed enough for them not to drop inside the engine, so after removing the inlet manifold, a length of pvc pipe was inserted into the inlet, blown into, and out they popped!

 

All my plugs were looking like brand new until I had the injectors cleaned, now they look healthier, some slight sooting on the metal, and a nice light biege deposit elsewhere.

 

Prior to the cleaning, getting it over 4.5k rpm was a struggle!

 

[sideways danny 0]

was it Dave or Brian? I'd take what either says as gospel. Try a new pump and fuel filter it's quite feasable that the pump has got lazy and the filter if blocked

[Rob Thomson 6]

Thanks for all the ideas, chaps. I didn't have time to look at it at the weekend but will muster up soon.

 

I should have said it's definitely been a lot slower since it's all been rebuilt so I don't think it's a 'bad one'. Hopefully a bit of TLC should see it back to its old self.

 

Cheers, Rob.