What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Thinking of doing the unthinkable... *Rotor to cap gap. Normal?*

If i remember right, with the est wire un plugged i had to time it all the way up to like 8* just to get it to run as good as it does. But i will double check. the minimum air is set by jumpering the a+b on the data connector, turn the ign on for about 30 seconds, disconnect est wire and IAC, start it and get it to idle around 750. Then set the tps about .55v and re connect everything. the throttle boddy has been cleaned alot and completely rebuilt so i would have to say the passages would be clean.
 
Well, you're close with the minimum air bit, but there are a few changes I'd make.

When you set it, you're wanting to set the minimum amount of air that the engine will run on with the IAC completely closed. After the truck is at operating temperature jumper the ALDL then wait the 30 seconds or so until the IAC is completely seated. Unplug it and remove your jumper, then start the truck back up. You want the EST connected during this procedure. Set the idle screw so that the truck is running as slowly as possible -- Somewhere between 400 and 500 rpm. If the TPS is not exactly .55 volts, don't worry about it too much, but set it as close as you can (if you can, not all are adjustable).

Shut the truck back down and remove a battery cable then plug the IAC back in. Wait a couple minutes for the ECM to clear itself then start it back up. It'll probably run funny for the few couple miles until the self learn kicks in, then it'll clear up. The IAC should be open between 30 - 40 counts at idle and should keep your truck running at about 750 - 800 rpm both in park and in drive.
 
Check, Double Check, then Tripple Check that you have absolutely every ground wire hooked up. I fought a similar problem for over a year only to find a ground pig-tail behind the motor that I missed. I hooked up the ground and it has been great ever since.
I program my own chips, data log, have a wide band O2 etc. so I was able to observe a lot of variances of the surging. For the most part, the motor rand around 12:1 AFR. If I turned the A/C on it dropped to around 10.5:1 AFR and ran like crap. The motor was strong but with poor MPG at cruise. Idle and just off Idle would surge quite a bit. All these problems went away after I hooked up the ground wire.

Look over and around every bit of your motor. I found my wires behind the distributor sitting on top of the tranny - by accident as I dropped a nut back there working on the EGR.

Good luck,
 
Just got back in from messing with it, Maybe i didnt let it warm up enough but i let it run about 5 min, then jumped a+b, and turned the key on for at least 30 sec, disconnected the IAC then started it. It idled so high that i was able to back the "idle screw" off all the way. Also, it runs about the same with the est wire connected and disconnected, and will run but idle higher with the ESC module disconnected. Then, I plugged the IAC back up and started it.The idle steadily came back down and bacame rough again.

Keitha;
I think i know what set of wires you are talking about. And i believe they are hooked up. I bolted them to one of the coil bracket bolts. I also have another set of grounds at the front of the motor bolted to the bottom of the a/c support bracket. Is there more somewhere that im missing?
 
I think there are 3 sets of pig-tails. I don't like the idea of using the coil bracket as a ground location just due the the high current fluxuations through the coil - it could present some funky results. I have mine grounded to the stud that holds the EGR solenoid to the mainfold.

On setting your idle and the IAC: visually make sure that the pintle is seated after you bridge the A/B and disconect the IAC. Did you un-jump A/B before you started the motor?
 
I did un jump a-b. Are you supposed to be able to see the pintle from the little passage way threw the top the TB? cause i couldnt see it.
 
You should be able to see the tip of the pintle. When you have the jumper in you should be able to hear the IAC motor "clicking" as it is fully extended. The tip of the pintle should plug a hole that leads to the air passages under the throttle body. In effect, the IAC creates a vacume by-pass and the ECM will add an increase of fuel to compensate.
 
If you run out of adjustment even with the iac fully closed, you have a vaccum leak on your hands. It may potentially be the intake gaskets on the lifter valley side if you cannot find one on top. Also, don't count out the brake booster as a vac leak source.
 
I couldnt see the end of the pintle from the top. So im going to try it again. I have messed so much with all that i couldn't imagine it just being out of adjustment. But hey, who knows. I'll let ya know what happens. I have often been curious about the booster. I think im going to try capping off the line to it and see what happens.
 
LIGHT BULB!!!

So, I did a compression check. They were all decent. Like 130 or so but they were all almost exactly the same. So, I then had a thought, a few times i have noticed the motor smoking. I kinda figured one of the cylinders had low compression so i said **** it. THEN, I thought, wait, they all have "good" compression but it smokes... Maybe that could confirm my suspicion of an internal intake manifold gasket leak! meaning it would sometimes suck up oil from the lifter valley and there for smoke despite the good compression. This would explain the crappy idle, the occasional smoke, and the reason the old carb cleaner trick came up with nothing. SO i think im going to go ahead and bite the bullet and do the intake gasket this weekend. Im sure it wont fix it... but hey, i gotta try.
 
Just read the whole thread.... good luck, sounds like you heve several guys on this one that know their stuff! My opinion is that you have found it with the internal intake leak!
 
Got the intake pulled. Nothing jumps out as bad, but some of it seems questionable. So im just going to get new gaskets and put it back together and see what happens.
 
I would of did a leakdown test before I did the intake. I have had engines with bad head gaskets have consistent compression, but then the leakdown was 50% on a couple cylinders.
 
interesting. Guess i should give that a shot... This may be a shocker but, the intake gaskets did nothing. I did however determine that i have less vacuum then the comp then the comp would like. Im only getting in the 15in range. If i take a vacuum pump and bring it up to about 19-20 while hooked to the map sensor it snaps right out of it. I had my buddy over with a 91 burb and his has 19-20 minimum. We couldn't get his DOWN to 15... We took and plugged off every vacuum line on mine and even moved the timing around and could never get mine as high as his lowest vacuum reading... So, if you ask me, i have too low of vacuum likely caused by too large of a cam/a cam with not enough LSA. I think im going to then go ahead and do the leak down test, and if it comes up good, im just going to bite the bullet and swap the cam for a stock one.
 
So as another question, being as it seems to me the problem lies in the the comp not seeing enough vacuum, can a custom chip be burned to compensate for that? less fuel at this map reading etc,
 
I would get a chip burned before I would swap the cam, yes.
 
You must log in or register to reply here.

Latest Posts

Top Bottom