My car is a 1985 325e coupe, 5 speed, 206,000 miles. It has a problem where it bucks heavily under load at around 1500-2500 RPM. It literally cuts out as if it's starved for fuel or spark, and then kicks back in right at the previous speed. It's severe enough to give you whiplash if it happens in 1st or 2nd gear under acceleration! When the problem is really bad, cruising around in 5th gear at 40-45 mph feels like you're driving a machine gun if you try to give it any gas.
The problem is intermittent; I have tried many things to fix the problem. First I tried replacing a grounding strap (the one that comes off the back of the valve cover). It ran PERFECTLY for 300 miles, and then the problem started again. Next I added to that strap, giving it a dual ground, and it drove fine, again, for about 200 miles. Next tried plugs. Replaced them all. Replaced the ignition coil. Opened the distributor cap and cleaned all the carbon deposits. Cleaned the spark plug wires.
The injectors are all ok--they passed the test of holding a screwdriver to your ear and holding it against the injector and listening for the clicking to vary with RPM. They are all fine.
I've ruled out air/vacuum, and all the engine electricals seem in tact. I brought it in and had the fuel pump relays replaced and the car drove perfectly for 150 miles, and even seemed like it had more power. I've let the mechanic drive it home from work and back so he can really get an idea/feel of what's happening and he said he always thought it seemed like it wasn't getting enough fuel, even when it ran right. It sort of bogs a little between 1000-2500 rpm, but I figured that was normal because of the engine's economy design and flat cam profile.
Now we're thinking: oK. it drives fine and then starts turning to crap after about 150 miles. Perhaps one of the 2 fuel pumps is failed. Let's speculate it's the transfer pump (the one in the tank). Is it possible, you think, that if it's failed, then the main pump is overworking enough that after a certain amount of time, it's overheating and burning out the relays?
Anyone else experience this before???
Thanks! Send ideas to agraff@student.umass.edu.
-=Rob
The problem is intermittent; I have tried many things to fix the problem. First I tried replacing a grounding strap (the one that comes off the back of the valve cover). It ran PERFECTLY for 300 miles, and then the problem started again. Next I added to that strap, giving it a dual ground, and it drove fine, again, for about 200 miles. Next tried plugs. Replaced them all. Replaced the ignition coil. Opened the distributor cap and cleaned all the carbon deposits. Cleaned the spark plug wires.
The injectors are all ok--they passed the test of holding a screwdriver to your ear and holding it against the injector and listening for the clicking to vary with RPM. They are all fine.
I've ruled out air/vacuum, and all the engine electricals seem in tact. I brought it in and had the fuel pump relays replaced and the car drove perfectly for 150 miles, and even seemed like it had more power. I've let the mechanic drive it home from work and back so he can really get an idea/feel of what's happening and he said he always thought it seemed like it wasn't getting enough fuel, even when it ran right. It sort of bogs a little between 1000-2500 rpm, but I figured that was normal because of the engine's economy design and flat cam profile.
Now we're thinking: oK. it drives fine and then starts turning to crap after about 150 miles. Perhaps one of the 2 fuel pumps is failed. Let's speculate it's the transfer pump (the one in the tank). Is it possible, you think, that if it's failed, then the main pump is overworking enough that after a certain amount of time, it's overheating and burning out the relays?
Anyone else experience this before???
Thanks! Send ideas to agraff@student.umass.edu.
-=Rob
