I have a 1993 Toyota MR2 Tubo with about 150,000 miles on it. For the past several years on a cold start (it doesn’t seem to matter what the outside temperature is, just that the car has sat for a long time, like overnight), if I try to drive away immediately the car will chug. It almost feels like the car is choking or is not firing. It happens mostly on acceleration above 2500 rpm and in 2nd and 3rd gears, getting worse as you go higher in the gears.
After a few minutes the problem goes away and the car will run fine. Also, if I start the car and let it idle for 5-6 minutes it seems like the car will run fine without the chugging.
Could anyone point me in the right direction on what might be the problem and how I would fix it? The car is in great shape and I hope to keep it for a long time, but I’d like to get rid of this annoyance.
I had a similar problem with my 2000 Ford Explorer. A rough start that would smooth out after a minute or two. I checked the fuel pressure at cold start and checked the coilpak before cold start to rule out those as issues. The CEL finally lit up after a really rough cold start on a cold day this past winter indicating a lean condition on the passenger side of the engine. After some research in some Ford forums, it turns out the problem was the upper intake manifold gaskets just beginning to leak in my case.
I know the ODB-I system in your car will not give you that kind of help. But if you rule out fuel and ignition as part of the problem, maybe a leaking seal? One method to checking intake seal leaks is to use throttle body cleaner to spray around the gasket areas around the intake and see if the engine smooths out.
The problem might be with a defective coolant temp sensor for the computer. If the defective sensor is telling the computer that the engine is already at operating temperature when started cold it will run too lean for the condition. This can cause the engine to misfire or chug and lack power. Then once the engine has a chance to warm up it runs normally.