byrdman454

I am at a loss with my S4. Just recently it has been acting up. The problem is very intermittant, by like days at a time. The car was driving fine all week, then yesterday it started acting up. It was running so bad I could not even back out of the parking spot. The car fires right up, but idles very low and fluctuates by 2-300 rpm. It will rev at idle, but is very rough. It will finally not rev anymore after attempting to clear it and it dies. After this it will start right up, but it is still idling so bad the whole car shakes. I let it set about 30 minutes, having started it a couple times and drove it home without any issues. I just fired it up this afternoon and it ran fine. I let it warm up good and shut it off. I then went about 20 minutes later to pull it back into the garage and it did it again. As soon as you put it in gear with it idling that low, it dies. Even extra throttle will not help. The last time it did this was while I was driving. The car started losing revs and missing out, and extra throttle would not help. I had to pull on the side of the road. I sat for about 20 minutes looking things over and tried it again. It ran perfect since then. I just thought it was bad gas until it happened again yesterday.

I ran my Spanner on it and one time I got the fault "no hall signal". I cleared the code and checked the connector and it seemed fine unlike the posts I have been reading about. I did not get the fault again.

Does anyone have any idea on what this can be? I was reading some old posts and it does not sound like the Hall sensor would not let the car idle, it would just not have good performance. Does this sound like a MAF, temp sensor, what? I am running out of patience with this. It is frustrating that I cannot re-create the problem so I can solve it. The only similarity in all the times it has occurred is that the car was warmed up.

Anybody got any ideas?
Thanks
Mike

whitefox

Vacuum?

IcemanG17

Hmm
Only when the car is warm....that sounds like a bad temp II sensor...but the temp sensor usually is a rough-unstable idle? because the LH is running too rich (default if the sensor fails)..since it does so many things that are weird...my guess is the LH-EZK are bad...is there someone around you can swap a know good one with to see if it helps? There is another post about the temp sensor today...follow the link to Rich's page and test your sensor....if its normal (mine was)....I'm thinking LH?

Garth S

... it does sound a lot like the LH module.

docmirror

Does sound like the dreaded LH module slow death. Try a swap with any year LH and run it for a while to let the system learn the new module. See how it behaves. Vacuum is also a possiblility, but usually not related to cold/warm. Also possible is the MAF. Warm up and MAF is also symptomatic. The wire is heated, and can begin to change resistance as the heating degrades, working toward an open circuit.

Doc

byrdman454

The spanner did not show any faults when it ran through the LH and EZK tests. Wouldn't a failing LH show up?

I do not have access to another LH. I am quite alone here in STL....I think. I do have a '84 Euro, but it runs a open loop system without a O2 sensor, so that's not going to work.

i will check the resistance on the TempII tomorrow. I was going to pull the airbox and yank the MAF sensor connector, but by that time the car was running normal again. I can't seem to make the car have this problem, it just happens. Is there any way to check the LH without swapping it out?

Thanks
Mike

Bill Ball

When it happens again, unplug the MAF and restart. If it runs better, blame the MAF, but only if it runs worse when you plug the MAF back in (since you have an intermittent problem).

bd0nalds0n

Any way to check the air fuel ratio? Over-rich is a symptom of LH failure; maybe you have an extreme case. Black smoke out the tailpipe during the problems?

FeedNfrenZ

A very usefull and easy test that very few people seem to use is a ignition timing check with a timing light. This checks temp. 2, knock, hall effect and fly wheel position sensors all in one shot not to metion the coil, EZK, etc.. I had but didn't save the procedure on what numbers you look for and what sensors affect the timing in certain ways when I find it I'll post it but if someone has it handy can you post it? You can also use the timing light to check fire to each plug and you can KINDA judge it's strenght. NOW.............. one problem! Maybe someone can help me. How do you determine if the timing on the drivers side is correct? Since we run daul distributers using the timing light from the number one cylinder is only testing the pasernger side timing. It is some what unlikley but possible that cylinders 5 trough 8 are out of time. What is the relationship of say the number 5 cylinder to the timing marks?

heinrich

A car that runs fine when cold, but suffers when warm ... Brent ... ?

FeedNfrenZ

Don't EVEN use that 4 letter word at this point!

Mrmerlin

Hi just curious has the car been in any wet weather? If so I would get under the passenger side dashboard close the fuse panel and look up see if it looks like there is tell tale signs of a water leak, this will leak water onto the fuse panel and the EZK/LH connections I would then remove the EZK/LH connections disconnect the battery before removing the connections, and check for corrosion on the pins and connector, also to check is the 14 pin connector and the thick wire that are just in front of the passenger side cross brace under the hood these should also be checked for corrosion also with the battery disconnected, good luck, Stan

OrionKhan

That's my guess too.

I had a similar problem. I'd check out that MAF. That was the culprit on my car.

Rich9928p

Mike is lucky, his '84 Euro uses the same MAF as his S4, so he can do the swap and see if it helps.

John Speake

If temp sensor 2 fails, then the LH automatically senses this and defaults to "hot" setting of fuelling. So you can rule out Temp sensor 2 in this case.

A Hall sensor fault would not cause the issues you have with the car at present. In any case, sometimes spurious fault codes are stored incorrectly. This is why the LH and EZK periodically automaticallly erase their stored fault codes.

Let know how the MAF swap goes !