Hi Guy’s,
Ok so the story. Last year over a period of months my car’s idle crept upwards until she started to throw code 35. I always suspected an air leak somewhere but I just couldn’t find it even using the tried and tested carb cleaner around the inlet manifold trick.
Apart from the high idle the car ran fine so I decided to replace the MAP sensor, the IAC valve, the TPS and the purge valve for the charcoal canister, as well as a few hoses that hadn’t been changed since new just to make sure it wasn’t them. None of these replacements made any difference to the idle so I decided that I’d strip down the upper, middle and lower inlet manifolds over the winter while the car was in storage.
Cut to May this year and I’ve done the gasket change and the car’s idling smack between 650-700rpm once she’s warmed up. I’ve used the car well during the (brief!) British summer with no problems at all. Then a few weeks back I was going to a friend’s house who lives down a long gravel and pot holed track, so I slowed her way down to just above walking pace. All of a sudden, SES light comes on. Because the engine was basically idling I thought IAC valve code 35 again, so I stopped and sure enough she was ticking over at around 800-900rpm. Brilliant, I’ve got another air leak again and continued on down the track. About a minute later the light went off as soon as I started to accelerate. As I pulled up to my friends house I noticed the rpm’s were back at 650, strange I thought must be an intermittent or something. I’ve been using the car since and the idle has been fine, 650-700rpm and no running issues at all. Then last week after I parked the car up it popped into my head what had happened a few weeks before so I decided out of interest to see if it was a code 35 that I’d got at the time.
I bridged the B,A, terminals at the ALDL and I got the usual 3 code 12 flashes followed then by a code 35! Still not thinking anything of it I switched the car off and pulled the jumper. A week passed before I went to the car again, I jumped in turned the key and the engine stumbled briefly and stopped. It always fires first turn and I never have to crank it. So try again, turned the key she fired almost but stopped, it was like something was turning the car off as soon as it tried to start.
Ok so I checked the fuses, all ok, checked the fuel pressure, 41psi with the key at start and the fuel pump working as far as I could hear. Next I checked for spark at the distributor by earthing the coil on the engine, yep spark there too. Seeing how so many guys have had suspect ICM’s I have a spare at hand so I put that in to see if it was that. Same problem a no start.
Then I thought, right the car was working fine up until the last time I used it so it’s got to be something I did then. Thinking back to pulling the code 35 from the system I though sh*t I’ve bridged the wrong wires and fried the ECM! So I re-connected my jumper wires to the ALDL and got code 12 with no problems at all. I thought right the only other thing connected with that ECM interrogation was the IAC valve. So I took the top off the throttle body with the IAC in situ to see where the pintle was. As far as I could see it was way out completely blocking the passageway! I’m thinking if that’s been stuck there all this time would that starve the engine of air and cause a no start? So I pulled the IAC, measured the pintle length and found it to be at 32mm. I pushed it back in to 28mm, disconnected the battery reconnected the IAC and then reconnected the battery. I went to start the car fully expecting nothing but to my complete and utter amazement she started the second I turned the key, she coughed and spluttered a little while she obviously cleared all the fuel from the cylinders but settled into a nice steady idle!
I took it out for a run to let the computer get it’s head around stuff and she’s back to her old self!
Obviously I don’t know what’s going to happen tomorrow when I start her from cold as I want to see if I’ve really solved my problem. But can anyone tell me what’s going off here? Have I found another reason why our cars sometimes won’t start? Have I actually fix it? And can anyone explain why the IAC could caused a no start??

All the best,
Speed.

 

hey, have you checked round all the wires in that area and made sure the cases havnt worn through over the years and occasionally / grounding or shorting ?
this would cause wierd problems that would be fixed everytime you were fettling and knocked the wires without even knowing.....

 

Hi zs&tas, yeah I checked all the wires and i'm lucky in the fact that they're all fine. With the car only used during dry day's in the summer and dry stored in winter I've not had any electrical problems. (touch wood!) I'm still stumped at what the actual problem was, but seeing how it occured after I pulled the code 35 from the ECM I'm pretty sure it was something to do with not re setting the IAC after i did this. Whatever, the car starts/run's just fine again now which is just as well as i didn't want to put her away for the winter without getting her back to her old self!

Speed.

 

The reason the IAC was closed is due to the jumper across A & B. When you jump A & B and do a key-on, engine-off the IAC is continuously stepped closed. Key-off and the IAC is left in the closed position.

Need to remember to hold the go-pedal down some when trying to start the engine after doing this.

RBob.

 

thats real interesting to know thanks ! dont ever remember having a problem here but thats gd to know for future fettling.

Speed, where did you get your parts from and who made them ?
could be a faulty new IAC ? also

 

It is interesting because I've pulled codes from the ECM before in exactly the same manner but the car's started fine afterwards I've not even had to press the gas pedal.

Do you think that's why the car wouldn't start RBob, or does the IAC close everytime you jump A&B? The more I think about it, it's got to be something to do with what I did because like I said the car's just fine now.

I've got all my parts from Rock Auto zs&tas, only had one problem with them so far after 12 years and that was when they sent me the wrong spark plugs for my car (Too long!) then tried to tell me that the europe engined V6's were different from the state side ones Always try to buy Denso, Bosch, or AC Delco stuff if possible.

Speed.

 

sounds like you have a pretty good supplier there mate, i use USautomotive in bedford and the customer service so far has been ace. ( just in case Rock Auto dosnt have something ! )

 

Yeah used USAuto a few times, but most of the thing's I've changed on the bird were either not available or cost just as much to import myself. I've put the car away again for this year and I'm planning to do a rear drum to disc conversion over the winter, so I'll be using Summit for that. They're excellent if you want to upgrade your car in any way whilst RockAuto just cater for the OEM stuff.

Speed.

 

oh yeah, how are you going to attack this job then ? usually people dropin the 4th gen axle ?

personally im happy with the drums, engine braking gives me everything i need
however i will need some new front discs, i have fitted some mtec grooved/drilled to my daily and they bite real nice for no actuall 'real' mods.

 

Not heard of the 4th Gen mod, but I'm looking at either the Right Stuff, or SSBC conversion kit. My rear axle's just fine and I wouldn't want to put one on that I didn't know the history of. Knowing my luck I'd then end up with great brakes and a shot axle!!

Never been able to get park brake to work properly with drums, and over the years I've changed everything on them - I mean EVERYTHING!

So I'm ditching them and going for something totally new. I replaced the front one's years ago for Wilwood super dynalite cross drilled and slotted discs and never looked back! Should keep me busy over the winter!

Speed.