Darkshot

iTrader: (4)

First I want to give a little background, yesterday I just bought a 91 RS with a 350 TBI (my first thirdgen, I love it! ). I'm pretty sure this was a stock L05 replacement motor put in two owners ago. I did take a peek behind the motor and saw "GM 5.7", so I know its a 350. I've been searching for a couple hours now and have found a bunch of information regarding the chip that I should start running, and I want to confirm some of this because when searching you find lots of helpful info, but never something that answers your questions 100%, ya know what I mean?

Right now its running what I THINK are 55# injectors with the stock 305 ECM. It runs good most of the time, however it shows various computer-related symptoms such as minor surging while driving, sometimes it will hickup at idle, occasionally it will stall at idle or low close-to-idle RPMs, and it has some cold starting issues. A search revealed that these are all problems directly related to running the 305 ECM on a 350, so i'm not alarmed I just know I need to get the right 350 chip in there before I can really trust it to daily use.

Now, I would like whatever input you can give me on the above, however here is my real question. It seems from reading other posts that the closest match for this engine and this car would be a chip from an 1989 Caprice 9C1 cop car, correct? Is this the best year, or are there others that will suffice? I've done a bit of reading over on the DIY PROM board, however i'm still at the "confused and clueless" stage and need to do more reading before I start writing my own flat out. I would like to get this thing running the best I can ASAP. Is this Caprice chip something that I can purchase that will plug right into my stock computer making my car instantly run a little bit better? I know that custom tuning is the only real way to go, but I need to at least get something better in there for now (until I can learn custom tuning) and i'm sure that even a remotely close 350 chip will make this thing run 100 times better.

Thanks!
Andy

RBob

iTrader: (1)

First thing to do is to check the injectors to find out exactly which ones are in there. If the color paint codes are stilll on them it will be easy. If they are no longer visable you will need to read the numbers off the top of the injectors.

The color codes are on the center post. There are not the connector pin colors.

There are two sets of numbers. The 4 digit number is a data code, we don't care about that one. It is the other number that is required. If they are GM injectors the number will look like this:

GM5235206*RPD

That is the number found on the 61#/hr 350 injectors with the ORG/BLK color code.

Once the injectors are known then a better recomendation can be made on which chip to get. Should be able to purchase it at any GM parts counter.

Probably a good idea to pull the ECM down and get the service# off of it. Just to be sure it is the correct one for a 3rd gen. Should be 1228746.

RBob.

Darkshot

iTrader: (4)

Alright, the center post (NOT the terminals, the mushroom shaped thing) had a little bit of paint left on it, and im 99% sure that it is orange. I searched and found that this was 55#, but you're saying its 61#? Im certain they are orange. I'll get a pic up in a sec. I can also just see the numbers, i'll clean them off a bit and post those to be sure.

Darkshot

iTrader: (4)

Okay, I have all the numbers:

Driver side:
5235206-ACR
3200-GM

Passenger Side (The numbers are reversed, can these things be put in backwards?)
GM17084327RPD
5221 GM

And I checked out the ECM, the service number is 1228746 so I'm good.

How much can I expect to pay for a chip at a GM dealer?

RBob

iTrader: (1)

Can never be easy, can it

Looks like two different but close flowing injectors. The 5235206-ACR is a 61#/hr standard 350 truck injector. Good possibility it is a replacement as the ACR is most likely AC Rochester(?).

The GM17084327RPD number comes up as an '89-'91 LO5 9C1 65#/hr injector. I had forgotten they even made these (In '92 & '93 a 68#/hr injector was used for those vehicles).

The RPD is a typical stock injector from Rochestor Products Division.

The injectors are keyed to the housing which is why one faces one direction and the other the opposite direction.

I guess the best bet is to get a '91 Caprice with a LO5 engine PROM.

And, if at all possible it would be best to get 2 of the same injectors. See if you can find another of the GM17084327RPD injector and go with the above MY for a PROM.

RBob.

Darkshot

iTrader: (4)

Thanks for the great info. What are the negative effects of running one 65 and one 61 pounder? If I get that chip and stick with the current injectors will it be a hinderance to my low-end around town low RPM daily driving? Or is the problem only at high RPMs, with one of them hitting their peak before the other making 4 cylinders run lean? Or is that not even how TBI works?

Fast355

iTrader: (2)

I have seen stock GM pods with two different sized injectors in them. Take the 4.3 HO(used before the CPI came out) in the Astro/Safari for example. The left injector is a 55 lb/hr 305 injector and the right is a 61 lb/hr 350 injector. It was for emissions purposes. I have pulled many sets of them out over the years in the same pairing.

I do agree with RBob though. This pairing was most likely done in error and it will be easier to tune with 2 of the same injectors, preferably the larger size.

Darkshot

iTrader: (4)

I've done some calling around, and there was a guy at one local auto parts store tell me that I have a few problems, he said there was two different sized chips (a larger one and a smaller one) for that year Caprice 350 and he doesnt know which one I need. He also said that even if I do get the right one he thinks I will have problems running that chip in a 91 Camaro that I would need to get the computer from the Caprice.

I also talked to a guy at a local Chevy dealer and just said I needed a chip for a 91 Caprice 350 TBI. He quoted me $92 and 3-5 day wait.

Another Chevy dealer said I needed a PROM # before I can order it - is there somebody here who can supply me with correct PROM number for a 91 Caprice 350 TBI?

Would I be better off just having somebody custom tune my TBI until I can gather the parts and skills needed to do it myself?

83 Crossfire TA

iTrader: (2)

Huh, could you clue the rest of us in where you’re looking this up? Between my old crossfire stuff and my newer normal TBI stuff I probably have a dozen of these injectors floating around that I don’t know what they actually are besides by what they’re supposed to be.

Huh, never thought about this before, but why are they keyed to the housing?

The crossfire setups used staggered injector sizes also since one had the regulator hanging off of it and one had an inline accumulator, and I guess GM figured that they would be seeing different pressures.

For emissions purposes? I’m not sure that that makes any sense to me… how would running half the engine richer or leaner help emissions wise?

Darkshot

iTrader: (4)

I'll be driving along, and the engine will start to do its own thing, randomly start revving itself or slowing down to almost stall. These problems are less noticable at mid/higher RPMs, they are most noticable at idle. They are not very pronounced, my tach doesnt work but it cant be revving itself more than 300 RPMs up or down from idle when it does this, it just randomly fluctuates. The car is totally driveable, I just sometime have to pop it into nuetral at a stop light to let it do its thing. After it does this it flashes an SES light for a few seconds. I've pulled the codes, its throwing a code 22, 23, and 42. I do realize that these could be old, and I also realize that the ECM is likely confused because of the stock 305 PROM and these codes may be invalid to begin with. I am currently working on getting a better chip. Any more input for me?

83 Crossfire TA

iTrader: (2)

Huh, just thinking out loud… does the Caprice LO5 use a ‘8746?

kdrolt

The 89-90 models did.
The 91-93 models did not.

RBob

iTrader: (1)

IAT low, TPS low, and EST. The EST can be left over from setting the timing.

IAT and TPS low could be from have the sensor disconnected with the engine running. OTOH, either one being true would cause the issues you are seeing. I second the recommendation to clear the codes (disconnect - bat cable for about a minute and reconnect). And go from there.

And, as kdolt mentioned with the '8746 ECM, you'll want to get a '90 MY PROM.

RBob.

Gunny Highway

iTrader: (1)

The chips themselves are not different sizes. There's a LO3 chip and a LO5 chip, and a LO5 Cop Car chips (which came with the 65# injectors). And for the love of G0d, please don't spend $92 on a stock chip. Go look at EBay or on here somewhere. I sold my Cop Car chip for like $30 about a year ago.

TierAngst

I picked up a whole ecm for $10 on ebay

Darkshot

iTrader: (4)

Thanks for all the help everybody, sorry if I am being a nuisance with these questions, I'm doing the best I can, constantly searching and calling and trying to figure things out. I've been scouring eBay, I cant find 65# injectors anywhere but I keep finding these:

eBay Motors: CHEVY / GMC TRUCK / VAN CAPRICE 350 TBI INJECTORS (item 8052481166 end time May-30-06 01:44:28 PDT)

Its the same part number as the one I have, however acording to another auction that part number is for 55#, not 61#.

Also, will other ECM's plug right into my harness? Such as the 1227747?

83 Crossfire TA

iTrader: (2)

So Rbob's previous recommendation to run a '91 caprice chip won't work...

RBob

iTrader: (1)

That is correct. Same as I mentioned in my previous to this post.

RBob.

RBob

iTrader: (1)

Yes, the '7747 will plug right in and run. It is the truck version of the '8746, so it has slightly different code.

RBob.

xjcamaro89

Take from a person like me that has just been through the basics of chip burning. Its not as hard as you think it is. I was in your same boat about a month ago, now my car runs a whole lot better (but still not done tuning), i put a L05 in to replace my 305 and was in the same situation as you. Check out this thread and read through it, there is a lot of step by step info to get you started, and what all you need (for harware) to get started, check it out, and good luck!

https://www.thirdgen.org/forums/tbi/...free-tune.html

RBob

iTrader: (1)

OK, checked my chips and none for the '8746 L05. Did come up with this info:

AKNA9640 part# 16089638

FED, auto, BB platform, L05, 3.08 rear.

Released in '89, listed for '89-'91(?!) Caprice, etc. (don't know why '91 is listed, maybe carry over?).

HTH's,

RBob.

83 Crossfire TA

iTrader: (2)

Huh, I thought that there were some actual sensor differences, like one had a CTS and ATS and the other only uses a CTS…

(not trying to be a pain in the butt, just trying to point out where he or someone else reading this might end up running into hassles taking everything in this thread literally and or trying to figure out what I don’t know about the TBI setups…)

fullsize fun

just send this guy over at TBI CHIPS a email and let him know what you got and he can hook you up prolly a lot cheaper than gm ,plus it will be what you need, i had him do a chip for me in my 90 9C1 caprice when i swapped a set of 305 heads on my LO5.

RBob

iTrader: (1)

It's part of that 'slightly different code.' It is directly pin for pin compatable, and other then being calibrated for trucks will run the L03 or L05 just fine. It doesn't use an IAT, but that won't matter. Unplug the '8746, plug in the '7747, turn the key and go.

RBob.

fullsize fun

all TBI engines have a IAT sensor or ATS if thats what you wan t to call it , in the aircleaner ,all F.I. engines need to know the temp of the incoming air.

RBob

iTrader: (1)

Not sure of why you would post this. As it is a false statement.

RBob.

Fast355

iTrader: (2)

Early TBI trucks did not use IAT sensors! Some of the later PCM model ones did, but not the early ones.

RBob

iTrader: (1)

Hey, ouch. . . you quoted the wrong guy

RBob.

Fast355

iTrader: (2)

I was agreeing with you.

RBob

iTrader: (1)

My fault, I didn't see the little guy with the sign. Had images turned off in Firefox and with that it doesn't even show the placeholder for the image.

RBob.

83 Crossfire TA

iTrader: (2)

Yea, my ’92 LO5 powered truck doesn’t have an air temp sensor