You shouldn't run a cheap injector.

First of all, a 91 turbo? Hmm. Have you done a VIN search?

You must have an s4 swap in your car. It's the only logical explanation for a code 07. Or someone put an S4 ECU in your car. What does the wiring look like at the ECU?

Is your BAC valve connector oval? If your are indeed S5 then it should be oval.

 

Re-check the trouble code. Those ECU's aren't too smart, but if it says something is wrong, there probably is. I've never seen it throw a random code, but maybe the Euro version is different.
The stock ecu has a few settings that run for a set time after startup and may override the error signal. Once it sees the error, it will go into safe/limp mode.


Have you measured the boost pressure to make sure it's not hitting the overboost fuel cut? Any exhaust modifications?

 

Guys it was running fine before he did all of the modifications.

 

Thank you all for your replies. The car is a 91 S5 convertible turbo. In Europe we had an official turbo convertible from 1989 to 1991. As I said all your explanations seem valid but the thing that I really cannot understand is why the car pulls great for 3-4 pulls every time that I turn of the engine. That's why I don't think that the problem is the new injectors. If the injectors were the problem then it should not run good at all times, right?

I have a turbo back aftermarket exhaust: 80mm downpipe, 76mm cat-back.

The idle is perfect and the car pulls really good most of the times. I bought a pressure test kit and a multimeter and I will try to measure the properties of the boost sensor, AFM and intake temperature sensor. Any suggestion for other sensors to check is welcome.

 

Swap your old injectors back in. Test your fuel pressure. Change the 30 year old fuel filter.

 

The old injectors are ruined beyond repair. I will change the fuel filter and test the pressure. Thanks.

 

I'm not understanding this. If the car was running before, how can the injectors be ruined beyond repair? Did they get damaged during removal?

 

I agree. Get rid of the eBay crap injectors. If you wanna cheap out then be prepared to deal with the consequences.
Not to mention many guys on here will simply ignore your posts if you ignore the advice.

 

Well the car had hot start issues because the injectors were leaking. The rubber seals of the injectors were ruined and the cost to repair and clean them would be half the cost to buy new ones from ebay.

 

Ok, I will try to buy new ones but could anyone explain to me why the car pulls just fine for 3-4 pulls and then starts to bulk? Why do the injectors work fine for these 3-4 WOT pulls and what happens next in order to initiate the bulking? and why the whole problem resets when I turn off the engine and then back on?

 

This is typical limp/safe mode behavior. Is there a check engine light after it bucks?
The ECU doesn't have a memory for codes so turning off the power clears them. Once it sees enough faults, it throws a code and shuts down the party.

Your exhaust is likely causing the car to overboost and cut fuel. It's a built-in safety feature of the stock ecu. Measure your max turbo boost pressure with a gauge and confirm it isn't over 8.5 psi.
The fix is to port the wastegate or add an extra exhaust flange for some restriction.

 

European... now your code 07 makes sense.

 

Whats code 07? I tried to look it up. Cant find it.

 

I have thought about the fuel cut but the car does not seem to hit it. It boosts fine and the aftermarket boost gauge does not exceed the stock boost. And I have ported the wastegate years ago when I installed the aftermarket exhaust. Also before the injector change the boost was also in proper levels.

No check engine light...

 

This is going to be something as dumb (not that you're dumb OP, just that its a stupid problem) as a charge pipe is manifesting a leak when it gets hot-ish then that cascades in to some odd limp behavior hence the key switch 'fix'.

 

I totally agree with that...that's why I am trying to collect opinions about it. Seems like it will be a really minor tweak that I have to discover...

Any more help or ideas are welcome of course.

 

Wouldn't it throw a code if it was going into limp mode?

Just out of curiosity, can you post the part numbers of the injectors you removed? Should be like a 19550-XXXX number. Then can you check resistance of the new injectors and report back those two things? I know the Ebay add stated high impedance, but its probably good to check and see what you have exactly.

 

I mean, maybe? These are ECUs that were designed in the mid to late 80s in a car with harnesses that're 28+ years old, from a specific year where there were some suspect wiring issues.

 

The European spec is hard to diagnose with the FSM. Their FCs were made with left over parts lol. He's probably running an ECU that we would consider an s4. It's the only logical explanation for a code 07.

Which reminds me, you didn't get back to us about the BAC valve connector being oval or not. Man, the Euro FC is always full of surprises.

EDIT: I wanted to point out that you should be using the s4 and s5 manuals. Also, if you are throwing a code 07 then I would be focusing on getting rid of the code. Check wiring and test boost sensor.

 

If it was my car I would change the fuel filter. You might surprise yourself.

 

Ok, I will try to find them in the chaos of my garage and also take some photos to see the mess...
How can I check the resistance of the new ones? They are already installed on the engine.

 

You are probably right, the diagnostic machine looked like really old and I don't think that it works properly. I am waiting for the multi-meter to check the boost sensor.
I am always reading the S5 FSM.

Also I have forgot to mention that my engine block was bought brand new 12 years ago from a fellow forum member. When I installed it, the mechanic told me that it had some minor differences compared to the old one. I have only 27.000 km.

 

Yeah I know. Its the first thing that I will replace when I have the time.

 

Yesterday I took the car for a quick spin and I noticed that when the car reaches the normal temperature then the problem appears. As I said before the problem is temporarily gone when I turn the engine off and on again.

I have removed the emissions but I wonder if there are any emission control system that is related to my problem.

Also I noticed that the bulking starts when the car starts to boost. Are there any sensors that control the boost level according to temperature?

 

You might find the problem if you did some actual troubleshooting.