Mk1 1.6 Silvertop Surging/Hanging Revs

[JimboJim]

Hey all.

I'm hoping some knowledgeable people around will be able to help.

I have a '99 MK1 1.6 16v (Silvertop Zetec). Long story short, had the car 18mnths with endless problems (Has circa 200k on it). ECU went, replaced 14mths ago along with a new MAP/MAF sensor. Also at that time I did a full service, with HT leads, Coil pack, new Idle control valve and TPS. All to cure a bad hunting problem which turned out after all that to be the ECU which got replaced. VSS is still a prob as speedo has picks and chooses when it wants to display indicated speed. Not a big issue in the grand scheme.

Recently on a 25 mile trip to work, I felt as though my car WASNT pulling as well as it should up a mild incline, didnt think much of it, poked the throttle harder and forgot about it. Issue hasnt come abck since, BUT on another trip recently, I noticed that car pulling itself when off throttle, dropped the clutch and revs surged to 3k. By the time I got to work the problem went away. Came and went a few times, now its stuck. On cold startup, or fully run in at temperature still hangs at 3k. Sometimes wants to idle at 1200 or so, but poke the throttle and its back to a steady 3k.

It drives ok, aside from it slipping the clutch (which is low) and burning all my dinosaur juice.

I've also had it on my OBDII reader, which shows NO CODES. after playing with the fixes below it did flash codes up (TPS), but after a reset was all ok again.

Attempts to fix:

Removed Idle valve, which was crystal clean inside, cleaned anyways and replaced. Problem persisted.

Removed TPS, again crystal clean, cleaned and replaced, problem persisted.

Removed pipe to throttle body, cleaned butterfly, problem persists.

Attempted to look at what I believe is a breather pipe under the inake manifold with the T piece. All looks ok. Checked all other hoses I can get to, no splits or leaks, all seem fine. Tried to look for a hose collapsing under vaccum too, couldnt find one.

The only way I have had it running semi-correctly, was on startup this evening, idled at 3k-ish, unplugged the MAF, and the revs instantly dropped to around normal, about 1k.

Gave it a rev and it revved fine and back down to a lumpy idle. Put the MAF back on, went for a drive, still hanging at 3k.

Back to the garage, de-MAF'd it again, the idle was very lumpy and hunting. After switch off, did another read of the ECU and baught up P0113. IAT sensor. Not familiar with these, is this another name for MAF?

In short guys I'm totally lost. I dont know a great deal, and would really appriciate any help. I'm pretty sure its not the usual culprit of ICV or TPS. I'm on a very low income and cant afford to take it to a garage, so as usual its running repairs in the man cave lol.

 

 

[JimboJim]

FIXED!

Just a note to help anyone else who has this problem. (Which is the point of forums don't forget!)

Been out in the garage tinkering with it. Stripped off the Plenum pipe (large diamiter hose from air box to throttle body), and inspected the butterfly valve again. Seemed to be fully closed.

Played around with the throttle cable linkage at the throttle body end and found it was leaving the butterfly valve open by around 1mm to 2mm max. Negligable to the eye. Sprayed with spring/linkage with penetrating fluid, gave the linkage a good work in and out, started the car and back to normal! - Idling at 750-800 as it should, revs fine up and down.

Mine does momenteraly hang on the way back down, but needs a full service, and its a knackard POS :p

NOTE: I'm expecting this problem to return at some point, WD40 and penetrating fluid wont last forever, but it gets me out of trouble for a while. On the next strip down, i'll get some proper grease, or failing that change the throttle body itself. (Not worth it for me on a half dead 200k mk1 focus)

But still, hope that helps anyone who has tried the usual suspects of ICV, TPS and MAF.

Jim