87 911 - coughs and burps during warm up

[kylekmcc]

My 87 has an intermittent problem that I could use some advise on diagnosing. It runs great EXCEPT for after it starts (about 2 minutes) and for the next 5 minutes until it is fully warm - but not all of the time. The problem originally happened only when it was damp or wet outside - now it is more frequent. During that time it severely hesitates from 1,500 RPM to 3,500 RPM. Feels like it is misfiring and produces clouds out of the exhaust. Over 3,500 RPM is runs fine. It has 60,500 miles and has just had a major service; valves adjusted, carbon cleaned and injectors cleaned, replaced: ignition wires, rotor, cap, idle stabilizer, idle stop switch, cyl head sensor, plugs, fuel filter, belts, ignition coil, O2 sensor. Have also checked for vacuum leaks and found none and checked the fuel injector wiring connectors. Mechanics have advised that the valve guides are OK and are also stumpted.

Other than letting the car sit and warm up for 15 minutes before I drive it, anyone have any ideas of what to check or replace next ?

[Rick Lee]

When all else fails, replace the DME relay.

[Milu]

How much mileage do you do? As you've checked all the usual suspects for a 3.2 except DME relay, I'd suspect the car has been stored or used little and you've got a lot of condensation in your fuel or contaminated fuel. I had similar symptoms from a car that had been stored that also had experts stumped.
Another possibility is that something in the system is sending a strange signal to your DME brain. Is your cyl head temp sensor new, properly connected?
Are all plugs and connections properly connected and DRY?
Good luck.