Problem starting when cold or damp.. Help

[abulloch]

I'd be very grateful for any advice or pointers...

* 240 1991 (not diesel), 159,000 miles.

[I know if I take this in for servicing they'll go through throwing out parts and replacing with new till the problem disappears, and as I'm in California this'll cost $1,000 or more...]

The basic problem: when starting in cold or damp weather the engine either won't catch, or it barely does, then falters and dies. Result: flooded (wet) plugs, which I take out, dry off, then get started by flooring the gas - we then judder into action, painfully.

Further symptoms: once started, the engine is sensitive for 20 mins or so. Flat spot at idle (dies occasionally); runs better with gear (auto) in 2nd instead of Drive.

After 20 mins everything's fine: runs smoothly, no more hesitation etc.

What I've done so far: new plugs (Bosch), new distributor cap and arm; fuel injector cleaner (in gas). result: improved but not cured.

OK: What are the top candidates in order of probability?

?? - idle setting? idle throttle? fuel injectors? air mass metre ? other settings?

What would you do first? and then next?

Many thanks for your comments and suggestions.

Anthony

[Patrick Garland]

Before I say anything I must point out I'm not an expert !! However, I didn't see on your list that you had changed the HT leads. I have had similar problems in the past and although they looked ok there was a breakdown in the HT leads from the distributor to the plugs. Some rub across the top of the rocker cover or the bracket for lifting the engine out and allow a discharge thus reducing spark power. Also the damp gets in and whilst a squirt of WD40 over the leads helps it doesn't cure the problem which comes back. If you get someone to try starting the engine while you've got your head under the bonnet on a moonless night sometimes you can see a small spark shorting across to the engine. So my suggestion would be a new set of leads.

[Clifford Pope]

When mine did that it was the Crankshaft Position Sensor, on top of the clutch bellhousing. The wiring insulation degrades with time.
It's fiddly but straightforward to replace, but don't force it if stuck. The bracket is a bit fragile, and if it breaks it is a gearbox-off job.

[Citizen.Agfa]

Wotcher. I'll second the bit about the leads; silicon leads break up with time/use, a good indicator of condition is the flexibility (or lack of same) of the leads. If, when you hold a lead horizontally it sticks out straight then now is a good time to change them!

Good luck and all the best, Nick H.

[abulloch]

Thanks for the suggestions - I'm taking your advice. Meanwhile there's an additional question I meant to ask:

The Service Engine Light comes on, of course, and the diagnostic code that comes up consistently is 1-2-1, which points to the Mass Airflow Sensor.

How reliable are these service codes? Should I just go for replacing the Mass Airflow, which is a very expensive part? or could the diagnostic unit throw up a 1-2-1 if it was some part earlier up the chain (as it were)? So, if the plug wires are bad, or if the Idle Throttle is gummed up, could this cause the Mass Airflow to malfunction and the diagnostic unit to point to that?

Anthony

[PAZ3154]

usually code 1-2-1 can be ignored. even the healthiest of cars bring up this code. it's a fault within the on-board diagostic system. however mass air flow sensors do give trouble on these cars and could cause the fault you're having. dealers retail is now about £175.00 exchange although you may be able to find a cheaper supplier these days. if you're lucky you may be able to pick up a decent used one

[Clifford Pope]

Wouldn't the first test be to clear the code, and then see if it re-appeared? If not, you could safely assume it was spurious.
I get 1.4.4 about once every 6 months, clear it, and it stays clear until I have almost forgotten about it.

[PAZ3154]

>Wouldn't the first test be to clear the code, and then see if
>it re-appeared? If not, you could safely assume it was
>spurious.
>I get 1.4.4 about once every 6 months, clear it, and it stays
>clear until I have almost forgotten about it.


yes fair point. the only reason i say ignore 1-2-1 is because i was told this on a volvo course years and years ago. it crops up apparently because of a design fault in the communication between the maf sensor and ecu. he basicly told us to ignore it completely as in theory all cars would display this code. of course that makes it difficult to tell whether the code is genuinly showing or because of the fault. that's why i've found the only real way to check this is by substituting a known good unit and seeing if it cures the fault. there's every likelyhood the code will reappear straight away regardless

[Peter D]

This could be an AMM fault but lets dot go there yet. Remove the HT leads and carfully measure the resistance from the metal plug to the metal socket, do not probe the inner core of the cable. These and the king lead should be below 3.5K ohms. I assume you have the blue silicon rubber type plug caps. If any are high resistance then either replace or repair by inserting a satinless steel dress making pin down the centre core with a wrap if copper wire round it and solder it to the outside of the metal. Fiddly but effective. To remove the silicon outer squirt with WD40 then use a compressed air line and inflate the rubber, this will lube the cable and allow you to feed the cable through the cap to affect the repair. If all leads are ok then come back with the part muber form your AMM it might be 0280-212-016 Regards Peter

Hi

Have you checked your fuses? I have a 1990 240 which would refuse to start on some cold or damp mornings or sometimes fire but feel as if running on only two cylinders for 10 minutes. After much searching and replacing of leads etc it turned out to be the fuse for the fuel pump not contacting properly.

Worth a check