BadSS

I'm really sorry this is so long, but please help if you can. I've got a 86 IROC, fairly hot 355 (see sig) that I bought,, not running. The previous owner had a custom Jet "chip" (stock chip piggy backs it) that was burned for a near identical set up (mine should flow more air if anything),,, but now that I've put an engine in,, the JET "chip" (stock chip piggy backs it) is way richer at idle than just the stock "chip" (this is not a "bugged" 86 chip). The pulse width at idle is like 1.6 - 1.8 for the stock chip and 1.8 - 2.0 with the Jet (makes no sense because it was supposed to have been burned for the 24# injectors). You can tell the idle starts to clean up as the pulse width reaches 1.6 and degrades as it goes up to 1.8. I have no vacuum leaks or exhaust leaks, nearly all new sensors and relays, INT 130 -132, BLM at 130, IAC is 3-5, idles at 650 rpm, O2 reading flipping back and forth rich/lean, TPS .56 (can't remember MAF rate,, but my ASE friend with the scanner said it was O.K. - I hope), fuel pressure is as low as it can go - 34# w/vacuum. Judging by previous posts I'd guess it's running way to rich at idle because the computer still thinks it has 19# injectors and the O2 sensor can only do so much. I'm not to thrilled that I have this $500 Jet chip (I paid for it in a sense) and it's not working for me (Jet can't help,, they only hold info on the custom chips for 6 months),, and I'm in no hurry to spend that kind of money for another "custom" chip.

Since based on previous threads I now know I can swap different year model chips,,, do you think a 350 chip that used 22# injectors would work with the 24# SVO injectors (more like 27# ?) injectors? Believe it or not,, I'm not that worried about how fast it is,, right now I just want it to idle clean. Any suggestions,,, or recommendation on a stock chip,, or aftermarket if I just "have to have it".

This will probably indicate I'm clueless concerning the ECU,,, but is there any way to "intercept" the voltage reading from the O2 and send a higher voltage reading to the ECM to trick it,,, making it reduce pulse width at idle? I'd try anything right now to keep from buying another high dollar "chip" just to find it ain't right. I'd like to burn my own PROM,, but I'm a little impatient at this time,, plus my time is getting limited to what I can continue to spend on the car.

Any help you could give would be greatly appreciated. Thanks for your time.

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86 IROC - 9.8:1 - 355, TFS twisted wedge heads, 218/228-110, fully ported GM base, SLP runners, fully ported plenum, 52mm BBK, 24# FMS, 1 5/8" headers, single 3" Dyno-max, Jet Custom "chip", B&M Megashifter, 245/45ZR17s on Budnik Mercury 5s (ok they're 212 Eagles)

[This message has been edited by BadSS (edited October 11, 2000).]

Mark_ZZ3

How do you know it is running rich? The learn values seem fine, although the pulse width is up a bit. If it was running rich, then the lean values should be below 128.

Does it not idle well? Have you checked all the park plugs to see how they read?

I had all sorts of bugs to work out when I got my tpi running the first time. I had recently sonically cleaned injectors that were stuck (rap with screw driver handle fixed that), I had some difficulty seting the minimum air flow due to slight leak at MAF connection. I recall that during this time, my pulse width was 1.8-2.0. After I got all the bugs out, the pulse width dropped off to 1.6.

Just some suggestions. Look for things that should not be a problem. It does not sound like the PROM is the problem. Was the 52mm TB new? Have you adjusted the minimum air flow? What is the timing? I don't know what you have checked todate, so just some ideas.

MArk.

BadSS

Thanks for the reply. Yep,, it's running rich all right,, strong unburnt gas spell,, like a carb with the power valve blown. It's running fairly smooth though, however the idle gets smoother as the pulse width gets to 1.6. Appearently the computer thinks it's running a little lean,, and it adding more fuel. Runs great part throttle and WOT. Timing is at 8 degrees, followed the procedures posted (and from Chiltons) on setting the IAC, plugs look a little rich also (dark,, but not wet). Going to regap them at .035 (they're at .045 now - 53,000 volt coil though). It has "new" injectors, but I checked them when I changed the fuel pressure reg,, no leakage,, cold start was fine as well. O2 sensor looked good too, Just can't figure it out.

[This message has been edited by BadSS (edited October 11, 2000).]

Mark_ZZ3

You have headers right? Are you sure it is going into close loop?

An oxygen sensor may look good, but still be bad. I run a heated version, much nicer. AC Delco part # AFS-74. It's from a 91 S10 i think. The cheapest I could find.

I recall on an air/fuel meter project, i was testing with a non heated unit. IT seemed to work fine, but it was rather sluggish. I put a heated one in and what a difference. Quick readings, and they were different from the other one.

Just a thought.

Mark.

BadSS

Thanks Mark,, I appreciate your help.

Yep,, running headers,, not running a heated O2,, but they're shorty headers. I could see how it might help mixture before the car was at full temp,, or with long tube headers, and I do understand they react faster,,, but would the heated O2 sensor really make any difference once the car was at full operating temp? It's rich at idle whether you first crank it,, or when it goes into closed loop,,, and if I drive it for 10 - 15 minutes,, it still idles rich. I'm pleased with the way it runs,, really strong with the stock 305 chip. However, I've accepted the fact I'll have to get a "chip" burned to clean up the idle with these 24# injectors and the 218/228 - 110 cam (still pulls 18" vacuum though).

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86 IROC - 9.8:1 - 355, TFS twisted wedge heads, 218/228-110, fully ported GM base, SLP runners, fully ported plenum, 52mm BBK, 24# FMS, 1 5/8" headers, single 3" Dyno-max, B&M Megashifter, 245/45ZR17s on 212 Eagles

[This message has been edited by BadSS (edited October 12, 2000).]

BOWTYE8

Are you running a cat. If not that will explain the richness smell at idle. I can barly stand a stop light in my setup. idle fumes are strong. 130 BLM and int value are actually show a slightly lean condition. BUT I definately go for a heated O2 sensor with headers and a MUSt if your running no cat . The o2 sensor will not get hot enough. the O2 will fluctuate all the time except when in open loop or PE (wot) the is should go to rich.

Dennis

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85 vette,383,miniram,ZF6,4.10's..best ET 11.81@117.00 60' 1.65
w/100HP nirous 11.05@127
http://geocities.com/bowtie8

BadSS

Thanks BOWTYE8. I do not have a cat on the car, I did pick up a heated 02 from Autozone tonight coming from work - #13077 - $47.99. I figured it would be worth a try. So,, BOWTYE8 you're saying you run rich at idle also, right? Are you running a heated 02 and still runnning rich at idle? Nice page and ride(s),, if you're still running rich what are you going to do,, if anything,,, you're running 11's,, don't know if I would care if mine was rich at idle or not if I had a EFI car running that fast. Believe it or not I'm setting this IROC up for my wife as our 2nd car and our "grocery getter". I want it to idle at least as clean as I can get the carb on my race car to idle,,, you know? Any help as always is appreciated.

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86 IROC - 9.8:1 - 355, TFS twisted wedge heads, 218/228-110, fully ported GM base and plenum, SLP runners, 52mm BBK, 24# SVO, 1 5/8" Headman headers, 3" Dyno-max, TH350, B&M Megashifter, 245/45ZR17s on 212 Eagles