James96

Hi Everyone,

I have recently purchased a 93 3.6. The following is occurring upon start-up, driving etc.

• Cold Start is perfect, doesn't smell overly rich considering has an aftermarket exhaust
• Upon normal driving everything feels fairly normal (under 4k rpm, little throttle input)
• As car begins to warm up still feels completely normal, also sounds healthy
• Coming onto boost is when the car becomes unsettled (potentially heat related?), little bit of smoke but car doesn't react well (only just coming onto boost)
• Once attempting to pull through boost once, rpms lowering the car immediately begins to want to die out and stall
• Have to keep revs up to stop from stalling
• Car also easy overly easy to start after, only with accelerator input
• Once car cools down again cold start is perfect

The below was apparently recently be changed by previous owner:

• Fuel pumps
• Injectors
• Fuel filter
• Intercooler Pressure sensor
• Spark Plugs

We have currently started with:

• Fresh tank of fuel
• Fresh Fuel Filter

Issue still remains so further diagnosing has begun, would appreciate diagnosis ideas.

Thanks

fritz k.

Hi,
since it seems that some parts have already been (uselessly) replaced a systematic diagnosis would start with determining what exactly is installed or deviates from stock equipment. The part numbers of the original Bosch CIS components are all known and e.g. injectors for the 3.6 are not easy available anymore.

One of the main problems of the CIS is false air and on our turbos are many possibilities for this. It makes sense to follow the entire intake path and check all hoses, pipes and connections and e.g. the correct fit of the intercooler.

After false air can be ruled out with sufficient certainty the system and control pressure of the CIS should be measured. This requires a manometer and suitable fittings as well as a hand pump.

Sounds more complicated than it is and once its done the solution for your problem should be on hand.

Fritz

PS: A few pics of the vehicle with engine compartment and exhaust would be nice.

James96

Thanks for the input Fritz, my mechanic has also removed and refitter intercooler and airbox to take a look at wear and also clean any contacts.

He is very well experienced but just seeking guidance for our next steps.

Car seems to be 100% stock besides exhaust and turbo timer




Thanks
J

Black_Hat

check your Turbo Control Unit - under the drivers seat .

I replaced the onboard relay due to inconsistent running/ idle/ onset of boost issues

this post helped me:

https://rennlist.com/forums/964-turb...trol-unit.html

fritz k.

Has the car sat for a long time under high humid conditions? What is the mileage?

The exhaust system is largely the same as the original, so it looks like there is no catalytic converter and no lambda sond. If the sond is missing, the connector should be jumpered.
Correct intercooler mounting is a bit tricky, it is done if the exhaust pipe rests without gap on the bridge of the throttle body, visible underneath the intercooler from the left side.

Fritz

heliolps2

Welcome to the group, Check your blow-off valve. fairly easy to replace. if it's sticking could cause some of the same issues you're having. you could also have a boost leak from your intercooler charge pipe or vacuum hoses.

Scott Dunavant

Sounds like the coil is failing under load. Easy to replace at a cheap cost. Also Check your route of the fuel hoses to the fuel accumulator.
That can be mis-routed.
next would be the WUR and Frequency injector valve that is not made anymore.
I can send a photo of the fuel hose route if needed.
Oh and make sure you have two quiet good running fuel pumps.

fritz k.

Above all, you should not get bogged down. With the above mentioned symptoms, a systematic diagnosis begins with the exclusion of false air. Then check the system and control pressure at the WUR. If the values are OK, it continous with checking the cold-start valve, auxiliary air valve and injectors. After that, the fuel side can be largely ruled out and it comes to the distributor, ignition coil, ignition cable, ignition control unit etc.

By going this way you come somehow to all of the mentioned possible causes sooner or later.

Regarding false air you should pay attention to the nuts of the intake air manifold. The manifold is temperature wise disconnected from the cylinder heads by spacers made of plastic. These spacers tend to shrink over the years what leads to loose nuts.

Fritz

Metal Guru

Quickest way to know if you have a leak of un-metered air is to see if the idle speed can be adjusted. If it can't then you have a leak.

James96

Thanks for the input everyone, issues have now been resolved, it was a mixture of the rear fuel pump needing replacing, a cracked fuel line, low quality fuel. Going go run some mileage to clean the pipes out, car is running well for time being and pulling through boost smoothly.

Next stop new suspension, shocks definitely need replacing aswell as bushes etc.

J

Scott Dunavant

We would love to see more photos and updates on this car.

James96

Hi Everyone,

Quick update, after driving the car for a while it still was incredibly rich and wasnt running 100%, we went ahead and got the WUR rebuilt aswell as the Fuel Distribution Head and now everything is running great. Currently onto some wiring loom repairs to remove all heavily corroded wires that have gone brittle over the years to remove the chance of any future failures.

Have also installed the following whilst in the shop:
-KW V3 Coilovers ( Yet to set up alignment, definitely going to run a substantially more aggressive stance)
- Lh + Rh Rear Cross Arms
- New Oem Front & Rear Top Mounts
- Porsche Classic Radio + All brand new oem speaker covers and aftermarket speakers
- Front & Rear Discs & Pads
- New Tailight Centre + Rh & Lh
- New Headlights
- New Side Skirt Rubber Seals Front to Back
- New Engine Bay Insulation
- New Belts Front to Back
- Complete Dry Ice Blast of Engine whilst removed

Does anyone have any recommendations if i should run spacers ? I am concerned depending on how aggressive the car sits we will run into rubbing issues.

Also what are mods / enhancements does everyone recommend? My goal is to have a fun streeter that sounds amazing + handles well without being incredibly stiff.

Exhaust that currently is on the car looks like it is from a not so great manufacturer so potentially thinking of replacing the full system incl headers. What is everyone's thoughts on plumbing the wastegate externally? Also adding a 1 bar spring? Can anybody suggest the ultimate sounding setup?

Will do my best to get some pics soon.

Thanks
J