A Few Questions - 1.6 Running Problems

[Pie 0]

Hi

 

I have a 1991 1.6 CTi, when it is on the move it runs fine but it as soon as it starts to idle it runs poorly. If the idle goes down to 1000 revs it will run very lumpy and then stall.

 

Anyway, a few questions. If I disconnect the throttle position sensor, it starts and runs exactly the same as if it were plugged in - it appears to do nothing. Is this normal?! I have it set up so that as soon as the throttle is touched, it clicks. If I disconnect other things like the ECU temp sensor and AFM then the engine stalls and won't start up again, so they appear to be working.

 

Secondly, am I right in thinking that all air going into the engine goes through the AFM? Because if I cover the AFM with my hand while the engine is running, the engine doesn't cut out - indicating to me that there is an air leak somewhere?

 

Finally, whilst looking for air leaks I came across a small pipe coming out of the bottom of the throttle body (directly under where the throttle cable is attached) and it isn't linked to anything. My thoughts are that it is the vacuum advance pipe? I looked on the distributor and the vacuum advance didn't have anything attached to it, could this cause idle problems or is it unimportant?

 

Thanks, I hope I was clear enough, that is all!

[welshpug 1,626]

quite common for the Throttle switch to be faulty, you need to check it with a multimeter.

 

does sound like an air leak, the oil filler pot bolt is a common one as it is not a blind hole and will cause an air leak if missing.

 

vacuum advance wont cause idling issues on its own.

[Pie 0]

OK, I'll get a multimeter and check it

 

I have checked the oil filler pot and all the breather hoses, can't seem to find any gaps

 

I'll leave the vacuum advance for now then, thanks!

[205kenny 7]

The bolt welshpug is refering to bolts the oil filler to the inlet manifold.

 

You said you used your hand to cover the afm? You wont get an air tight seal doing it that way, use something flat that will seal. A good way to find an air leak is to spray brake cleaner(or similar) on the inlet pipes and see if theres any change in engine rpm.

 

As for the vacuum advance pipe, you may aswel fit it. Its just a case a running the pipe from the dizzy to throttle body.

[Pie 0]

Thanks for the reply!

 

I am 100% sure that bolt is in place and tightened up

 

It seems as though the previous owner tightened up the jubilee clip on the AFM a bit too much so the edge isn't straight and my palm just fits over the top of it! It's the fact that it doesn't make the engine struggle much at all.. The revs drop a bit (maybe 100 rpm) but I can't stall it.

 

Tried spraying carb cleaner on the inlet pipes I can see, not much happened. Are there any other inlet/vacuum pipes other than the ones between the throttle body/AFM/oil filler?

 

I have ordered some pipe for the vacuum advance, the bit left on the throttle body isn't long enough! Also I think the vacuum advance itself is knackered cause if I put some pipe on it and suck, there seems to be no resistance.. I have got a multimeter ordered too, couldn't find anyone that had one and it seems like an essential tool!

[Pie 0]

OK, the situation has changed.. I bought some pipe to connect up the vacuum advance, and also bought a new vacuum advance unit. Started it up with the new bits, and it idles a lot better at low revs now. However now, the revs slowly creep up, and up, on their own. It got to 2.2k revs and then I cut the engine. What could be causing this?

 

I have checked for air leaks, taken all the breather hoses on the throttle body off and checked them. The two bolts on the side of the manifold are definitely in and I have even sealed them. I took the SAD off earlier and cleaned that, and then sealed the pipes up with silicone.

 

With the multimeter, I have tested the throttle position sensor, this works, tested the AFM, this works and finally tested the ECU temperature sensor, this also appears to work.

 

On a side note, the car takes a fair few attempts to start. However, once it has started, even if it is just for a few seconds, if you turn it off, then turn it back on, the engine will start first time, even though it is still cold. Someone said that the fuel must be feeding back into the tank and to put a one-way valve in the system somewhere. Would this be the right thing to do?

 

Any advice appreciated!

[Pie 0]

Solved the mystery rising revs, cleaned the SAD terminals and the revs seem OK now. In fact it is running quite well!

 

Now, if I just blip the throttle up to like 1500 revs, sometimes it will stick on 1500, sometimes it will stick at 1500 then slowly come down to idle? If I kick the throttle again it will go back down. Won't stick on higher revs.

 

Also, first time starting takes a fair few attempts, eg if it is left for a day it might take 5 or 6 attempts before it catches and keeps running.. Once it has been running, even for a just a few seconds, if you cut the engine then start it again(up to about an hour later), it will start first time?

[Slo 283 1 Cars]

check your spark plugs for colour and condition could be a mixture problem

[Tom Fenton 1,526]

The hanging on to revs thing sounds like the throttle body needs to come off and have a good clean out to me.