My brother's car has started acting up lately, according to him it happened gradually. The engine is a B21F with K-jet and Lambda, idles very rough and doesn't have much power (not that it was ever a hotrod but I've driven it before and it used to be quite perky compared to now), and the fuel economy has dropped dramatically. Just put new plug wires on since the old ones were pretty ratty, no change. Hoses look ok, air cleaner is clean, cap and rotor are fine, frequency valve is buzzing, timing belt appears to be ok though it's hard to see the crank pully mark without really tearing into things. What should I do next? Compression test? Check the fuel pressure?
Check for air leaks, particularly at the injector seats. Trickle water over them while the engine is running and listen for a change in speed, or even for it to stall.
Does a car of that age have points ignition? If so and they are pitted change them. If you see much of a spark between them if you open them manually (ignition on) change the condenser. Set the points gap (or dwell angle) and check the timing. Also replace the spark plugs if here is any doubt about them.
It's unlikely to be a slipped timing belt if this has come on gradually.
A compression test may tell you something.
If all that checks out OK, move to the fuel system. Make sure the cold start injector isn't leaking. Check the spray patterns of the injectors into a jam jar (be aware that the fuel pressure is several bar).
Check the air flow meter flap is unobstructed, and check the spray patterns change when you move it.
We didn't get K-Jet with the lambda upgrade in the UK, but this could be a likely candidate, too. I'd say that a failed lambda probe is more likely than any other part of the system, but don't know what symptoms it would produce.
The warm up regulator can go bad. Check for a voltage at the connector, and make sure the internal heater coil has not gone open circuit.
Similarly, the thermo-time switch (looks like a temperature sensor at the rear of the engine, under the last leg of the inlet maniforld). This should be open circuit if the engine is warm, or if the starter has been operated for more than a few seconds. There should also be a voltage at the connector.
After this, you need to think of pressure testing the system.
Obviously, if the engine is in poor shape (compression) then the following will probably be a waste of time.
The number one problem with K-Jet is vacuum leaks. Assuming that there are none, then the next step is to measure the fuel pressures - line pressure and control pressure. Control pressure is controlled by the Control Pressure Regulator, aka Warm Up regulator. It's the pressure on the center fuel line connected to the fuel distributor, and greatly affects the mixture. It should be about 25 psi at cold start, and about
55 psi when the engine is fully warm. Also water in the fuel can cause rust and sticking inside the fuel distributor.
If the car is fitted with a catalytic converter make sure it's not plugged. I was having this problem until the we bored-out the cat and then she flew. If there is no cat then still consider the possibility of a partial blockage in the exhaust and check this out.
Your solution (and your cost) may be surprisingly low-tech.
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On Mon, 15 Nov 2004 08:52:52 -0500, the illustrious Mike F favored us with the following prose:
I tried spraying some WD-40 around the injectors and on hoses, didn't seem to make a change, I'll try water though so I can get in more places without making such a mess.
Nope, it's fully electronic with a pickup coil in the distributor. Timing is adjustable but no points to mess with.
That was my thought too, though knowing my brother it's hard to say exactly how/what happened, I seem to have gotten all the mechanical aptitude and he got the art/music ability.
I guess I may as well do this since I have access to the equipment, the engine has around 230k miles on it but it doesn't make any nasty mechanical sounds and ran strong well past 200k.
The Lambda system doesn't kick in until the O2 sensor has warmed up anyway and it idles very poorly even when cold so I'm thinking this is probably ok or at least not the cause of all the problems.
The warmup regulator has been a source of trouble on my 240 Turbo as well, it's a bit of a black box, nobody seems to know how to diagnose or repair them. I'm hoping it's ok but another thing to check I suppose.
I've got a list of things to check, now to find some time to deal with it. Thanks.
I know it is a long shot, but I had a 145 that started running very badly in the winter. It turned out the thermostat was sticking partly open - maybe only a mm, but it prevented the engine from warming up. If you have a temperature guage you can rule that out, but if not....
I remember another fault that can *apparently* occur with these units. The underside of the unit has a hole in it (some versions vary) so that it is open to atmospheric pressure, and somewhere between the unit and the mounting bracket, it gets blocked.
Inside is a bi-metallic strip that is heated by an electric coil as well as by ambient temperature. The purpose of this strip is to push against a spring, countering the effect it has upon a fuel valve port, restricting the flow, and consequently affecting the system's control pressure. When the strip is cold, the spring is restrained, and a richer mixture results for cold running. As the strip warms up, it moves away from the spring, which can then bear harder upon the valve, reducing the mixture for normal running. Have a look here for diagrams and further detail about K-Jet
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If the strip doesn't lift off the spring retainer (for example, if the heater coil has failed), the car will start normally from cold, and then gradually behave as if the mixture was over rich. If the strip is damaged, and is permanently away from the spring, it will be hard to start, but behave normally when warm. If the valve port is blocked it will be harder to start, and may show signs of a weak mixture when warm. If the spring is weakened, then a permanently enriched mixture will result.
In practice, the bimetallic strip doesn't move more than a few millimeters, and this can be checked on the bench by opening the unit and connecting the heater coil to a 12v battery.
I have repaired a warm-up regulator, but other than re-solder a broken wire to the heater, you are very limited with what you can do. It is possible to alter the position of the bimetallic strip inside by whacking it's mounting post with a hammer (I've done it), but this is hardly precision adjustment. Easier by far to replace.
Well the compression test told us just about all we needed to know. The plug on #3 was siezed so we couldn't check, but the compression on 1, 2, and 4 was 8 (yes, 8), 120, 120. Leakdown test on 1 and 4 revealed badly leaking exhaust valves, spark plug in #1 was gummed up black and #4 was white with bubbles in the insulator, #2 looked pretty normal. I'm guessing either the injectors partially clogged or the whole system was running too lean. At any rate it looks as though it's time for an engine swap, might be a good excuse to drop in a B23E for a bit more kick. Thanks all for the tips.
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