Bouncy Idle after new head gasket.I give up!

Car is a 93 J Spec NA manual. Iridium plugs thats done about 15k and the 02 sensors were replaced about 5 months ago and were fine. One HT lead clip is broken but it does run lumpy when I pull it out of the distro cap. I am happy to test the o2 sensors if this is possible.

I'm sorry guys, it seems like I always only ask. I've been searching on here and google for a few hours, tried a few things but no luck. The car drove fine from Friday night until yesterday. It started misfiring and I found that it was the waterpipe coming from the y piece over the middle plug.It wasn't on properly so dripped water down onto the lead. Wasn't very wet but after cleaning the plug and sticking it all back together it was fine. Drove it to work and back last night with no problems.

However, this morning I drove about 2 miles, when the revs jumped up to about 1200 and keeps jumping up and down between 1200 and 1300 very fast. There was a strong fuel smell too, so I expected a vac hose to be off. I got home and had a look, couldn't see anything and took the positive battery terminal off to reset the ecu. It worked fine when started, went for a drive and it was all good. I'm obviously going very slow due to the HG replacement. Parked up for a few hours and started it up again to go get some fuel and what do you know, it's back. Car also sounds very tappidy but it could also be the distributor clicking? I don't know.

Reset the ECU again with no luck. I then found one of the vac hoses underneath the y piece was disconnected, connected it but no fix. If I pull the vac hoses from the intake manifold, the revs jump up but when I pull the one from the top of the y piece CLICK ME nothing happens. Is this normal? I'm really fed up with this car now so any help would be appreciated. I've also used about 20 quid to do 30 miles very slowly which is very odd as I have no smoke from the exhaust.

Think I might have bogged up the vac lines. The 4 pipes of which one connects to the bottom of the butterfly and the other on top of the throttle body. Will this cause the idling problem if I put them in wrong order? I've found a vac line diagram but it makes little sense as it shows an EGR.

Why did it need the head gasket replacing? The tappety comment worries me.... There's absolutely nbo need to run in, go slowly blah blah after a head gasket change, no new moving parts are involved.

From what you say, with the caveat that diagnosing by e-mail is rife with potential mistakes, I would say you might be best looking for a vacuum leak. Were all new manifold, plenum and TB gaskets used. Who did the job, a hose leak suggests it may not be by professionals?

Was done by my mechanic. All new gaskets used. I think it's down to me though because I took the throttle body off and forgot to connect the vacuum hose underneath the butterfly. Started it this morning no tapidy noise and idles fine after 10 minutes of warming up. I also pulled the hoses from the four pipes instead of the throttle body and intake so might've mixed them up causing the problem. On top of that my ac light started flashing too and not blowing cold anymore.

Oh and HG went after halfords replaced the waterpump and radiator.

So checked and rerouted all vac pipes and they're all good but still having problems. Unplugged and replugged egr1 solenoid and the car idled fine, only started revving higher and bouncing when AC turned on but back to normal when off. Drove a few miles, turned the car on and off with no issues. Drove 15 miles and then started doing it again but this time I noticed that idling does not respond when I turn the AC on. Also the engine check light does not illuminate when the ignition is on.

Is the charging system working properly, and are all engine and ECU grounds OK? Needs expert attention IMHO. You could fiddle about with until the cows come home without good diagnostic skills.

Going through earth continuity and so far so good bridged e1 and te1 but my engine management light still won't come on but now a new thing which worries me about a short, the ac is turning itself on and speeding itself upto max when the ignition is on. Wtf

Going through earth continuity and so far so good bridged e1 and te1 but my engine management light still won't come on but now a new thing which worries me about a short, the ac is turning itself on and speeding itself upto max when the ignition is on. Wtf

Mine used to do that every now and then. My guess is just some wiring issue that connects to the AC switch. Hasn't done it in a while though.

Mine used to do that every now and then. My guess is just some wiring issue that connects to the AC switch. Hasn't done it in a while though.

Did you have any idling problems though?

If you have no engine management light on key on look to the ecu ground wires. DavidP mentioned them, and he showed photos of them. You need a decent sparkie to check it out. Sounds like ecu grounding issues to me, especially as the head's been off. Check ecu connector plug to engine ground continuity. Simple multimeter with shop manual wiring diagram job for a sparkie. Ground loops can cause all that you speak of. I am but 50 miles from south Manchester....

My engine management light doesn't work 100% of the time but it's caused by a bad connection or dry solder? But works if I give it a gentle smack or wobble the loom connector. Worth a try so you can check for codes.

I am assuming the PCB connector behind the light panel is good, they suffer dry joints and give intermittent warning light operation. It would not affect engine operation though. Re-soldering the connector pins sorts that.

I am assuming the PCB connector behind the light panel is good, they suffer dry joints and give intermittent warning light operation. It would not affect engine operation though. Re-soldering the connector pins sorts that.

As for the ecu grounds see post #11 here:

http://www.mkivsupra.net/vbb/showthread.php?314641-fuel-not-getting-into-engine

I am assuming the PCB connector behind the light panel is good, they suffer dry joints and give intermittent warning light operation. It would not affect engine operation though. Re-soldering the connector pins sorts that.

 

 

As for the ecu grounds see post #11 here:

 

http://www.mkivsupra.net/vbb/showthread.php?314641-fuel-not-getting-into-engine

Yes I think it is a case of dry solder as my EM light did come on going over bumps or randomly in the past. The mechanic who did the work is going to have a look tomorrow. I'm putting my money on the AC. I get a metallic noise when idling and the revs do not change whether the AC is on or off. Gonna take the belt off and start it for a few seconds to see if it is true. If the guy can't sort it tomorrow, I'll have to make the trip Chris.

It's grounded at them two points and I'm getting continuity throughout the whole manifold when I check it with the battery earth.

The A/C system has an electronic pressure valve in it. if the gas is low or empty the A/C clutch will not engage at all. Hence the revs won't go up when the A/C is turned on.

The A/C system has an electronic pressure valve in it. if the gas is low or empty the A/C clutch will not engage at all. Hence the revs won't go up when the A/C is turned on.

That's what I mean, sometimes it does and sometimes it doesn't.

Disconnect the wires to the compressor's electromagnetic clutch, there's a connector near the compressor. It's just conceivable the clutch is sometimes engaging if the gas charge is on the cusp of being enough to allow it to engage from time to time. I have never seen it myself, but it seems possible in theory.

Have you considered petrol and a match?

Disconnect the wires to the compressor's electromagnetic clutch, there's a connector near the compressor. It's just conceivable the clutch is sometimes engaging if the gas charge is on the cusp of being enough to allow it to engage from time to time. I have never seen it myself, but it seems possible in theory.

 

 

Have you considered petrol and a match?

My matches are ready!! Is it this plug under the green ring?

Yes, it's awkward to get your hands to, but that's the one.

Yes, it's awkward to get your hands to, but that's the one.

Ok so got it off and reset the ecu. Was idling the same but then after 6 miles it was normal idling just under 900 for another mile at every stop. Stopped at home and still good. Turned the engine on and off and after the 3rd time it started doing it again. I did however notice a very noticable squeaking though. Sounded like just before my mates alternator died. Voltage seems fine though. Even 13.8V -14V and the car pulls fine still. Going to redo the earths tomorrow and on Thursday I'll plug my mates ECU in and see if anything changes just before my mechanic takes over and retrace his steps. Chris I do appreciate all your input though.

All sorted guys it was down to a dying Ecu messing with the aircon an idling. Thanks for all the support though!

Good to hear it's been solved now put the matches away

I love seeing cars getting fixed.

Nice one dude