PHIL928

This is for a '95 5 speed.

A little history first;
The car was resprayed and it is known that the body shop did not connect things back up correctly. However everything has been connected back up and I can't find any other loose wires, or anything dodgy.

The problem;
The car will idle steady at about 800rpm for a few seconds, then it is as if the idle control valve shuts and the idle drops very low to around 350-400rpm. Then the idle controller opens and you can hear a surge of air go through, at this point the idle jumps to 1200 rpm before settling down at 800rpm for about 30 seconds then it starts all over again. It is intermittent, however when it does occur the idle cycles consistently from 800, to 400, to 1200rpm.
Sometimes it will stall.

Things that have been checked/changed;
New Idle control valve
New 6 pin TPS
New MAF
New Temp 2
Rebuilt fuel injectors
O2 checked and functioning fine
Changed both LH and EZK but problem continued
No vacuum leaks

So what should be checked next because I'm all out of ideas

FredR

Phil,

You may have fitted a new idle control valve new idle control valve but that does not guarantee it is functioning correctly. There is a test procedure for the idle valve but whether that can be performed accurately in situ not sure- have a look in the manual- if you do not have a copy let me know and I'll scan the relevant bit for you this evening if you send an SMS/mail.

As I know/understand the idle valve only responds to rpm's other than during warm up when it initially runs faster so I assume when that map is controlling the system is looking for higher rpm's for initial stability. To my mind a faulty control input would not explain what you are experiencing but maybe a sticky shuttle in the isv would however unlikely it may seem.

The other thing you might look for is false air- I dare say this could cause wild swings. It is very easy to miss cracks in the rubber pipes, vents in there especially if you are not looking for them in the first place. For the various stub in connections I fit them using a smear of silicon RTV such that when engaged you can just see a smidgeon of compound oozing out of the joint and then use a jubilee clip with very mild compression to provide a more positive engagement.

You can also try disengaging/blocking off the recycle from the filler tank temporarily and blank off the small bore connection on the driver's side of the filler neck to test if that modulates the symptoms at all.

False air would explain the engine racing a bit but not the dipping sad to say.To check the idle valve with a known good one [obviously] requires removal of the entire inlet system sad to say but it can be done in about 4 hours.

Regards

Fred

PHIL928

Hi Fred,

Well I'm certain it is something to do with the idle controller. I already had the intake off to check the idle control valve was new as the garage said. I then proceeded to check it's operation using Theo's tool and it cycles from open to closed without getting stuck at all. It's a real head scratcher!

Dictys

Phil,

With the o2 sensor disconnected all together does it still do this?

davek9

When was the last time the battery was unpluged? You may want to reset the computers by unplugging the battery for 10 min. And start fresh.
Access to a shark tunner / spanner / hammer could narrow down if all sensors are working correctly.

Kevin in Atlanta

Assuming there are no vacuum leaks and given the fact that the post paint respray re-assembly was less than optimal, I would be looking for a break or short in the injection or engine harnesses.

Mrmerlin

with the engine off can you hear the TPS clicking on and off by moving the throttle assembly?

Were the two plastic fittings replaced that go into the MAF boot?,
have you checked the intake manifold at the RF to see if its sitting on its gasket sometimes this can hit the edge of the water bridge and not be fully seated

When did the engine start running like this?
What was the last thing you fixed?

SeanR

Sounds to me like there is a split on one of the two ISV hoses under the intake. Most likely the one facing forward that loops back to the MAF boot.

jcorenman

^^^ This. The surging sounds like a fueling issue, and if the O2-sensor is no good then it will throw the fuel way off. If it has more than 50-60K miles, just replace it. (Rated life is 60K but they often get funky before that).

PHIL928

So took the manifold off again to look for cracks in hoses that I missed, but no leaks. However I did not find a new ICV like I was supposed to. The garage lied to me. ARM
However you could not tell from looking at it between the 2 halves of the manifold, it only became apparent when the halves were separated and corrosion/dirt build up on the metal parts was visible.
Bench tested the ICV and it's pretty slow and a bit sticky at times. I think I have found the problem.

Thankyou for your input guys!

FredR

Phil,

Doesn't it please you when your friends know what they are talking about?

There are a lot of scams going on in our part of the world and some of the less scrupulous look at the punter who comes to the garage and work out the bill based on their perception of his apparent means to pay rather than the job at hand.

Whereas I would not dismiss any possibility, the most likely is not a scam by the owner of the business but rather a crooked employee from the sub continent. Remember these chaps do not make much so temptation has to be rife. It is not too difficult to concoct faults when there is no problem with the kit fitted. They deal regularly with other like minded souls in franchises that stock the OEM parts. They can probably get a dummy parts invoice for a few dollars of bakhsheesh and claim they fitted a new part. Most punters would not know what happened until double jeopordy strikes and the kit that was scammed actually fails. Given there are not too many 928's, this is what may have happened even though a fault was never reported by the owner- just soemthing "they found" while it was in. It thus falls apart when the allegedly replaced part fails suddenly.

On popular cars they typically tell the owner something failed, replace the "failed part" with a new one and then pocket the duff one to sell to a back street garage. They will even give you your old one back but in fact it was never on your car. I think this happened on my wife's Mitsubishi 4WD Pajero many years ago. It was running poorly, they told me it was the alternator, charged me about $400 for a new one and then when they handed it back to me I did about 200m before turning it around and going back to them. The crook who owned the garage [a fellow Brit would you believe] then promptly adjusted the distributor and hey presto all was OK. I then asked him why, if that was all the problem was, did he replace the alternator. He shrugged his shoulders and I asked him if I could use his phone- he said "who do you want to call" I said " The Royal Oman Police". He tore up the bill, gave me the money back and told me to keep the new alternator.

The Mitsubishi main dealer, again many years ago when the car was 1 year old and just out of warranty, had a little shimmy on the front brakes- the main dealer told me on th ephone after a outine lube service it needed new disc pads, new front discs, new rear shoe pads and the rear brake drum skimming at a total cost of about $600. I asked him if he and his colleagues had Company health insurance becasue when I got there in 15 minutes time I was going to break something on someone. When I arrived they had good news for me- the rear brake "problem" could wait until the next service and in fact the front disc only needed a light skim and the pads re-faced and the cost- $30! Oh goody said I.

I must have saved myself a fortune with similar interventions over the last 23 years.

Tell our friend the owner to take the dealer to task. There is only one place in Dubai they could have got the ISV from- a check with their parts department should reveal [if the date is known] whether such an item was supplied. No problem given his automotive assets I suspect. The repair garage should have a supply invoice on file that he can cross check against. if that is what happened someone could have made $200 or so out of our friend and that pisses me off.

Regards

Fred

Mrmerlin

take a picture of the old ISV with todays paper so it shows the date

Dictys

ARM get all their parts from the Owners father's company in Germany.

Most of us have had issues with them in the past.