Hi MC, When I started my Carrera this morning I heard a loud “pop” then the car would not run. It will start but it stalls right away. Chuck
Chuck, That pop you heard was probably due to an intake system backfire. On an early Carrera, a lean fuel mixture can cause parts to break or hoses to blow off. When this happens, the car will start (on the “cold start valve”) but as soon as you release the starter, the cold start valve shuts off and the engine stalls.
If you have the earlier CIS fuel injection used on normally aspirated cars up to 1983, this can indicate (or cause) a significantly expensive problem. On these models, a plastic plenum directs air flow from the air flow meter to the intake runners. If the car backfires, usually an “anti backfire” flapper valve opens and relieves pressure. This can prevent damage but the backfire can be violent enough to actually break the plenum. Sometimes, the plenum may be leaking air and the backfire is just the “straw that broke the camel’s back”. Some cars have the original plenum, the fuel/air mixture weakens the plastic and it can come apart or fractures. In a best case scenario, you find that the glue which secured the flapper valve has failed and it just needs to be re-glued. While you are checking this, see if all the screws are still tight which hold it together. If you find screws loose, tighten all those you can reach and plan to do a more thorough repair since the ones you can’t reach are probably also loose.
If yours is an 84 to 89 Carrera, there is a hose that usually pops off near the rear of the engine (where you can’t see it). It connects the main air flow meter to the intake throttle body. If you are fortunate, the only thing to do is reinstall the big air hose. The hose is located directly in the middle and top of the engine. Check the clamps that secure it and you may find one loose. If you do, loosen it more and try slipping the hose back on then tighten the clamp. Another source of intake leaks on the later cars involves the breather hoses. These rot due to age, heat, and oil. They are located where you cannot see them unless you remove the air flow meter assembly and If you are willing to go to that extent, plan to replace them since they are now over 20 years old.
On the Carrera 2 & 4, the latest problem that I have seen was an entire intake plenum assembly blown right off the top of the engine. The client said “I think the entire rear of the car lifted up when it happened”. This one was a little tricky. Turns out that when the car had been serviced four months earlier, two of the exhaust side spark plug wires were switched on the right bank. This ignited the intake charge while the intake valve was open. This “human induced” problem that was undetectable during driving the car but on that fateful day, BOOM. There were no apparent long term effects of this problem but it points out the need to mark the things that you remove when servicing your car. –MC