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Discussion Starter · #1 ·
I may be just imagining all this, but my car seems to run better before it gets into closed loop. I know that it might run a little better with the engine cool before it warms up fully, but it seems like a big difference. It feels like I get faster spool and more power/better drivability before it goes into closed loop. Any ideas why this might be so? When in closed loop, doesn't it just run using the stored BLM's, so fuel delivery should be basically the same? TIA.

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Rob Andersen
86 GN, Stock turbo and intercooler, Alchohol Injection, 43# Bosch injectors, MM Translator Plus w/3" MAF and extender chip, Hotwired Walbro 307, Hooker 2 1/2" duals, 3" THDP, Test pipe
12.39 @ 106.9 MPH
 

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First thing to suspect would be the O2 sensor. After that would probably be the particular chip you are running.

I believe it runs a bit richer in open loop until the ecm takes over.

Makes me appreciate the MaxEffort even more.
 
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Mine seems to idle better before it goes into closed loop, but when in gear, runs like crap (hesitates, bogs) until warm.. any ideas?

Ken

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87 GN - 52K, 30# green stripe injectors, adj. regulator, adj. wastegate, 3" Up-pipe, Tomka cold-air induction, XP pump hotwired, Hooker exhaust, Hi-Flow cat, Scanmaster, KYB Shocks, Eibach springs, Optima battery, Full power, Broken antenna.
 

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Discussion Starter · #5 ·
Thanks for the ideas. I'm running a MM extender chip which I can set to run open loop only. I'll have to set it to that and see if it runs better for the long term.

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Rob Andersen
86 GN, Stock turbo and intercooler, Alchohol Injection, 43# Bosch injectors, MM Translator Plus w/3" MAF and extender chip, Hotwired Walbro 307, Hooker 2 1/2" duals, 3" THDP, Test pipe
12.39 @ 106.9 MPH
 

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Oh, in closed loop, the ecm is running off feedback from the o2 sensor and others so it is not running off the stored blm values but is/should be continually adjusting values dependant upon current readings.

Should say it is still using blm values but updated ones.

As far as running badly in closed loop, clean and set the iac, reset the tps, be sure the o2 is cross counting sufficiently and still ranges widely from high to low.


[This message has been edited by Steve Wood (edited July 31, 2001).]
 

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Shaker X
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OK my car is doing all of that Steve. I have a new O2 sensor. My car really flattens out at 10# boost and I get KR numbers anywhere from 10-31* If I put in 100 octane the car hauls a55 again. I think it is the chip but I dunno for sure. The chip is set for 22* advance on the timing. I have put in another chip that was set at 18* timing and the same result.

Thanks
 

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Wot ignores the o2 so flattening out there is often the result of timing beng pulled for detonation. As you point out, you are having a lot of retard, and as higher octane makes it go away, it seems to be true detonation rather than false.

At that level of boost, I guess there are several avenues to explore.

1. fuel pump putting out enough flow? (weak pump, low voltage, dirty filter, weak regulator) Does the pressure rise properly when you get into boost?

2. Too much timing in the chip? 22 degs is a bit much on most of today's 93 octane. 18-19 normally works much better. If this were the only problem. I would have thought the 18 deg chip would have fixed it. I suspect it is part of the problem.

3. Carbon build up in the heads and on the valves....hot spots or artificially high compression. I kinda doubt it in your case.

4. One or two bad injectors that are not flowing enough. Will idle fine but not flow enough at higher pulse widths. Plugs may look lean on those cylinders if you put a new set in and then go do some wide open blasts and then check them. More common than you may imagine. Higher octane covers the problem as the mixture can go much leaner without seeing detonation.

I would not discount the injectors...



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Steve Wood

Growing old is mandatory; growing up is optional.


86 GN bought new, 87 T-type-81 El Camino with GN drive train-basically stock 86, 94 Caprice 9C1, 69 SS396 Camaro Convertible
 

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Hey guys, sorry to butt in. But I've got a similar knock retard problem with my 84, althought it *might* be false knock.

Steve, I was reading your thoughts about injectors, and that seems likely, but if some injectors weren't flowing well at WOT, wouldn't that result in a lean mixture, and thus show-up on a scantool?

Just wondering becuase I get anywhere from 10 to 18 degrees retard at WOT but my O2s are showing low to mid 800s (running rich if anything).

Thx!

Dave
 

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No, when using a conventional o2 as a reference, it is not accurate enough or relative enough to rely upon. The problem just gets masked in the overall reading of the total six cylinders.

Richness will not suppress detonation alone. Otherwise we would just pour the fuel to it and say to heck with high octane.

Once the detonation limit has been reached, there is very little cushion to be had from richness-particulary on 93 octane. You can make it detonate by going too lean but you cannot prevent it by going too rich.

Some say you can actually cause detonation by being too rich but I don't know if this is a fact or a belief.

If you are at 850 and detonating, only thing you can do is turn the boost down and you can probably turn the fp way down to get back to 760-800 without incurring detonation again.
 

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Shaker X
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1. I have a new pump (XP), Filter, Injectors, and regulator. Although, it is NOT hot wired.

2. I think so also.

3. I have only 4-5K on the new motor. I just recently rebuilt the entire engine from top to bottom so I know it's not the heads being dirty.

4. Injectors are new as well. I have put the plugs in gapped at .035 and run them and they looked normal. I then also replaced the plugs gapped at .030 just to see if the ignition system was good or bad and there was no difference. I also have a brand new coil pack and the TPS is set good. At WOT I am getting 850-890 on the 02mv.

How do I go about getting the injectors checked for flow?

Thanks Steve
 

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Have to pulled them and have them checked. I had a similar problem on my son's T a few months ago. The injectors were less than a year old. Seemed like the problem got worse as the engine warmed up.

Pulled the injectors and went out to Conleys and got them checked...One was badly stopped up....I don't know how...fixed the problem anyway.

You might look for another chip first as I know that has to be contributing to the problem. Might check your fp under boost too altho a scan tool ought to show up leanness like that.
 

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Hmm, thx for the response Steve.

If I am detonating, I doubt it's because of low octane. I'm running 92 octane and only 12# of boost (due to cracked headers I believe). But what I'm thinking now based on what you've said is I could be leaning out in one or more cylinder because of a bad injector. I'm still betting on false knock, but I'd like to check out this injector thing... so the only way to test em is to take em out and get a shop to test em for you? How hard are they to get out (what would I need to do?)?

Also, would cracked headers affect my O2 readings, or anything else for that matter?

Thx,

Dave
 

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If a header is cracked enough, it can, and probably will, affect the O2 readings which will then screw up your ecm behavior.

there is a good write up on the gnttype.org page under the tech articles on changing injectors. I am not familar with hot air cars so I don't know if there is anything in the way of changing them or not. Innercooled cars are easy.

I would fix the cracked header before proceeding.
 
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