348 Engine repair thread

Right, but understand the screw behavior. You can do it with the car off, then put it back to the number before you messed with it. t's not as clean as turn left numbers go down guaranteed. It's why people say they turn it and see no difference. I can turn is 1/4 turn and see 0 difference. infavt the.resistance does not change. Other times touch it a hair and numbers jump.
Not as clear cut as left down right up like clock work with same increment turns.

There is a technique is all I'm saying.

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I was wondering what caused that slack, its excessive when changing direction. makes sense, thankyou. As I mentioned people try and measure it with the maf plugged in, make changes and say nothing happens.

Best to go back then forward once you see changes with meter then go in one direction only. If you have to go backward it's tricky without measuring when the slack is taken up given that it takes a few minutes for gases to calm after a change. Also best to blip the throttle and let it settle.

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Just remember it's open loop trim not closed. Let us know how it goes! Take pics!

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I balanced the throttles between banks today. You can do it with power applied and car not running it you use the harness type I employed. Difference between banks throttle position:
Idle - 4mv
20% - 3mv
40% - 0mv
60%- 30mv
90%- 10mv

To be fair I did not have to adjust anything it was dead nuts presumably because I set the TB's at .05 mm gap and set the TPS as exact as I could get prior. Your allowed 80mv difference I had 4mv difference at idle position. For the throttle open positions your allowed up to 100mv difference.

How about those shiny brand new OEM TPS sensors and MAF's.
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Here is the manual details for others who need it, the forum is shrinking the image.
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Made a couple of 02 harnesses to measure those when its warmer.
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I have the 2 factory ECU pinout boxes too, but the harness is just much easier.

 

Yeah if the tb gap is not right getting the air screws right for idle is really tough. I started with the max clearance of .05 mm but I can always go down if needed. Use 2 feelers one on each side.

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Just heard back from my friend with the SS he's owned for 20 years, the MAF's were set at the factory to:

• 379.5 drivers side and
• 384.1 the passenger side

Ok back to me....

It was still gurgling and surging and it seemed to coincide with the air injection coming on, although it never came on because it would bog so never really heard it. Everything is new so it has to be something simple. It also idles fine when warm. I sprayed starter fluid everywhere when cold, no leaks...

Went over vacuum hoses for the injection seemed fine. Looked up some pics I took. Turns out the depression tank has a check valve in it. The manifold vacuum hose I'm pointing to was plugged into the wrong port according to my pre dis-assembly pictures. So I swapped those 2 hoses. Fired it up, idled great and air injection came on with the familiar growl and no bog or surge. Air injection went off and it idled fine. I assumed it was just an empty basin so I did not mark which hose was for what. There is only 2 of them and 3 ports. I assumed it made no difference. It does..

Found 2 coolant hose leaks where the band clamps were not quite tight enough, quick 1/4 turn and that solved that. I set the MAF's to 378 for now. Will measure voltage etc at a later time.

Bled the cooling system again, fans come on at 190 on the button, prior it was a bit over that with the air in the system. Will likely bleed again it every time I start it for a few times.

Set the banks vacuum the same, idles a bit high so I may redo the TB's down to .03mm air screws are 1/2 turn out. Boy it sounds good though, deep and smooth.

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Yep few folks said vacum, issue is there was no leak so I could not figure it out. The injection not coming on and surging when it was supposed to, you could hear the solenoids so it was related to that which led to check and compare lines to prior pics. Prob won't t take it put till spring as I still have to button it up, bleed hydraulics then put on new front springs. Dreading that.

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Last time I did it I had to pop the tie rod and ball joint. Removing and replacing the springs is trivial once out, its getting them out that I hate, at least the fronts.
But I'm putting ss lines in the front to match the rears so the brakes will not in the way at least. Getting the shick back is is a bit of a pain getting the bottom bolts in. Done it before when I did the shock bushings, I'd rather do cv joints.

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The behavior prior was surging when cold yes, the MAF adjustment helped that condition quite a bit, once the cats were up to temp its was fine prior it would hunt a longer for sure. But the air injection issue was different, the conditions were similar so the got co-mingled until I realized there was 2 issues. I assumed it was the cold idle condition. You never hear the injection at all post reassembly instead the car bogs and surges. Once up to temp it stops but it takes a long time since its idling almost to a bog and engine shakes. The MAF adjustment made it better and it idled better but as soon as air injection came on it would be back.

Now if I stopped the car and heat soaked a bit the cats when turned back on were warm enough the injection never came on and it idled fine so I assumed the MAF adjustment fixed it. If you just let it run the difference is you never hear the air injection growl, you hear solenoids click, no injection grown but engine immediately wants to die but ECU fights.

Definitely not the air temps because I started it yesterday and the injection issue and it happened 20 seconds after start. So I knew it was something there as there was no injection growl. So air injection related... so I went back over the injection stuff and traced the lines and compared to the pics. I actually did find a post out there where someone confirmed if those hoses were wrong, and to mark them properly, or the system would not work right.

I went and started it today, no issue. As a test I set the MAF's back to 383 and had the funky idle hunt when injection came on that you could hear the growl, but its just a hunt not a shaking bogging like the vacuum issue with no air injection growl which is a much worse form of it. Put MAF's back to 387 and it was fine.

I think something funky happens when those hoses are reversed like air goes into the manifold from the exhaust or something, it sounds odd and holds no meaningful idle until the car goes into closed loop. Again takes a long time to it was hard to diagnose and I hated running the car like that.

Most definitely sounds and feels like a vacuum issue to everyone's point but the issue is not a leak which was frustrating. In the end it was traced to something with air injection and the only thing it could be was vacuum leak (which I checked) or hoses routed wrong. It was the latter. Good thing I had pics. You know a good shop with 348 experience would have solved it and charged me 2K for watching the world cup and saying how hard it was to find.

Miroljub may have an understanding of the issue if hoses are reversed, I can't explain the physics of it.