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Newbie, so perhaps this has been asked and answered. 88 C4 Auto 100k miles. Previous owner put Pro Charger P-600B on it 15 years ago. I bought it 7 years ago and it never ran right. Tried everything I could do myself (swapped MAF sensors trying to rid of 036,replaced relays, sensors, etc). Engine builder here in Tucson diag'ed it and it had two blown head gaskets and #4 broken piston and ring (blow-by when you hit the boost blew the dipstick out of the tube). So he put in new pistons (skirts were in the oil pan), rings, bearings and new gasket set. All traces of emissions are gone. Capped off the EGR as well. Capped off all vacuum ports. Fired it up and idle was fine for 30 seconds, then loaded up and quit. Found out the Pro Charger was leaking oil thus pushing oil into the intake. $5,000 later I said 'Thanks' and got the car back in my garage. I removed the Pro Charger because I just wanted to go back to Stock. Who needs that blower anyway? I was able to find a used air box and have figured out the Alternator bracket. Fired it up. Barely ran. Set initial timing to 4 degrees adv. Swapped out (5th time) MAF with a BOSCH. Fired up and runs great, lots of HP, but Idle is rough. So here is the delima: The Pro Charger conversion required the chip to be re-burnt and 42lb injectors installed. My question is: Do I need to go back to the 24lb injectors and the stock EPROM? I finally have the right MAF and thought the ECM would adjust to NOT seeing that blower. But I can't get the Idle miss out of it, no matter what I do. Any help, comments, suggestions are greatly appreciated. Thank you, Craig.
At minimum you are going to retune the chip. 42's are too big for the stock engine, but someone might be able to get it to work with a really good tune?
42 lb injectors are huge for a stock engine.
I'm guessing you have an aftermarket chip adapter so that you could run a custom tune, you could always request a mail order tune for $100ish dollars, which would be a lot cheaper and less labor intensive than changing out injectors.
On the plus side i'm pretty sure you could run E85 with that much injector if you wanted to.
Also do you know any more about the internals? Did the builder put stock replacement pistons in (need to know the displacement of them. Flat tops? Dished?) Are they running heads with a larger combustion chamber to keep compression down? All of these are going to be large factors in what the engine is going to do since its not on a blower anymore. There is a high possibility that something else is wrong with the engine - cracked head/blown gasket/ etc if it never ran right. If you are looking to go back to stock the easiest thing to do might find a low mileage used L98 and put it in
Last edited by Pwnage1337; 11-14-2018 at 12:24 PM.
At minimum you are going to retune the chip. 42's are too big for the stock engine, but someone might be able to get it to work with a really good tune?
42 lb injectors are huge for a stock engine.
I'm guessing you have an aftermarket chip adapter so that you could run a custom tune, you could always request a mail order tune for $100ish dollars, which would be a lot cheaper and less labor intensive than changing out injectors.
On the plus side i'm pretty sure you could run E85 with that much injector if you wanted to.
Also do you know any more about the internals? Did the builder put stock replacement pistons in (need to know the displacement of them. Flat tops? Dished?) Are they running heads with a larger combustion chamber to keep compression down? All of these are going to be large factors in what the engine is going to do since its not on a blower anymore. There is a high possibility that something else is wrong with the engine - cracked head/blown gasket/ etc if it never ran right. If you are looking to go back to stock the easiest thing to do might find a low mileage used L98 and put it in
I'm told the heads are original, since this engine builder could tell by the gasket. The intake had been off however, and that makes sense since the injectors had be be changed. The pistons he put in are Power Seals, but that's all I know. Yes, the original head gaskets were cracked/leaking and # 4 Piston and a collapsed ring. The car ran great right after the Pro Charger build, I remember when it was done for my friend who then sold me the car after it started having problems. All the piston skirts were in the bottom of the pan, and when I asked him if ran the PI_SS out of it, he said 'YES'. So, I'm guessing it was all stock when they did the conversion.
The main issue I'm facing now is where do I get an OEM PROM that matches that ECM? Better yet, who can burn a new one? Changing out the injectors is no biggie, if that makes it less hassle. The only mod is that the EGR is out and I'm told that with the OEM PROM, the check engine light will always be on.
Great. Thank you for that referral. Even though Tucson is only 1 mil population, you'd think someone here would know how do this. In retrospect, it might have been cheaper and tons easier to send the P-600 back to Pro Charger and have them put in new seals.
The main issue I'm facing now is where do I get an OEM PROM that matches that ECM? Better yet, who can burn a new one? Changing out the injectors is no biggie, if that makes it less hassle. The only mod is that the EGR is out and I'm told that with the OEM PROM, the check engine light will always be on.
If you go back to a stock prom (can also be stock calibration burned onto aftermarket adapter like moates, etc.), you'll need to go back to all stock hardware - injectors, EGR, cam, etc. 42lb injectors shouldn't be a problem for you as long as the chip is programmed for them. And, even with a tune for the procharger, your idle and part-throttle should be stock-like. They usually just take out some timing under heavy load and add fuel in power-enrichment mode (basically full throttle, higher rpm where the MAF pegs out). So, you may have some other things going on here.
Also, a 'standard' procharger installation uses an FMU; it basically just ups the fuel pressure with boost. If you have this setup, you'll want to ditch that as well - though it's unlikely you have the FMU since that's usually done in lieu of larger injectors.
If you get a prom adapter and chip, I'm happy to program it for you as it's a piece of cake if you're just looking for basically stock with a few things turned off.
Best I could do. No clue if you are familiar with this Prom, as I was not around when who ever put this in did the work, or how they got it to work at all.
Here is what I can say about what is NO LONGER on that engine. 1. Blocked off and threw out the EGR. 2. Remove and toss out the Smog Pump. 3. Remove and toss the Cold Start Gizmo. 4. Remove and toss the charcoal canister. 5. Remove all vacuum hoses and anything electrical connected to them. Capped off several Vac ports under the throttle body, leaving only the PCV and Brake booster hoses. 6.There is a vac hose that was connected to the Cruise control that is still there capped off. I would like to put that back on. Can't think of anything else right now.
In one pic you'll see that Fuel Pressure Regulator that was installed with the Pro Charger. Notice it's capped off, but there is a thumb-screw adjustment that is about 1/4" away from tight. My plan is to union those lines and do away with it.
Check fuel pressure on the rail last night. Key on, motor off, 43 lbs. At startup, and running RPM to 3k showed low of 22 then back over 43 for a brief moment.
Just tell me what to do next. I can ship this PROM to you so you can see the tune on it now, or if you think that this should work, then let me know (as you stated above, minus a few quirks). I just ordered an ODB1 scanner as I have the check engine light bulb out due it constantly being on. As I have stated, once you are rolling, the motor runs great. Very responsive, very good acceleration. It's only when you come to a stop does is start to idle rough. Base timing set to 4 degrees with the wire from the ECM un-plugged. Idle about 700. Connect the ECM wire, Idle goes to 900. In drive with brakes on, idle dances from 6 to 7 sometimes 8, then repeats. No smoke from the tailpipe, and no stalling. Take-off from light normal. Here are the pics. Let me know what you suggest since I'm clueless at this point.
Perhaps. A little surprised by the label that it’s Remanufactured for GM. And ‘may be used as a core’. Who knows what happened as I have no reference on what a real OEM ECM looks like.
I’m wondering if just buying a complete used ECM is a crapshoot or not. It might not even work now that I’ve removed all emissions. Could be a code that messes up another functions. But those EPROMS (like I have shown) are really cheap. I guess a person could burn 5 or so configurations and wing it.
Looks like you have a hodge-podge of stuff there. You do have a FMU, but it looks like it's disconnected. Again, I'm not sure why you'd have the FMU as well as 42# injectors - usually, it's one or the other and not both. I can't tell from looking what kind of chip you have, but it doesn't look good with it's messy solder joints.
What I like to use is a hypertech chip, any for 86-89 TPI will do. I pop out the hypertech EPROM chip (the memory chip inside the case) and replace it with an amtel AT29C256. The nice thing about this setup is it preserves limp-home mode (many aftermarket adapter don't), and the AT29C256 chip is programmable (you can just re-write it many times without having to mess with a UV eraser to blank it). The hypertech units have a memory chip plug-in socket in them so nothing needs to be soldered. If you can't find a hypertech for cheap (I pick them up when I see them for ~$30 or so), the moates adapter or similar also works just fine.
Also, see if you can pull a part # off your injectors. You'll want to verify exactly what they are in case they're not 42's. If they were done 15 years ago, I'd expect to see Ford/Bosch green-tops, and seeing that FMU there leads me to think you may still have stockers. But, then again, those green rings look like they might be Buick GN 30#'ers...
89onlyZ51: This is a pic of the injector I took this morning. I can barely make out the numbers. But the guy who did the engine said they were 42 lbs. Of course, he could have been wrong.
Yes, I would be happy to order whatever is necessary and ship it to you. Looking at that current config, there is the EPROM on the left, and two chips on the right. Doe the chip you refer to replace both of those?
Hard to read that number, maybe you'll have better luck.
89onlyZ51: Stock? Huh. I was told they were 'Oversized' 42's. Oh well. The mechanic charged me $150 to ultrasonically clean and test them at 42 LBS. Of course I have my doubts about him now.
If those injectors are OK, that's a bonus.
I'm told I need the rear-end ratio as well, and that is located in a code next to a 'G" someplace on an official looking sticker on the car someplace. The plot thickens.
Also told I need the '89 chip (burn?) to accounts for me removing Cold Start Valve. '89 was the first year they (GM) scrapped that idea, but it was indeed there in '88
Yeah, we can drop the '$6e' code on the chip, which will have the cold-start enrichment without the need for the cold start valve. It's easy since you have an automatic, and nothing else really changed between '88 and '89.
89onlyZ51: Stock? Huh. I was told they were 'Oversized' 42's. Oh well. The mechanic charged me $150 to ultrasonically clean and test them at 42 LBS. Of course I have my doubts about him now.
If those injectors are OK, that's a bonus.
I'm told I need the rear-end ratio as well, and that is located in a code next to a 'G" someplace on an official looking sticker on the car someplace. The plot thickens.
Also told I need the '89 chip (burn?) to accounts for me removing Cold Start Valve. '89 was the first year they (GM) scrapped that idea, but it was indeed there in '88
I suspect you misinterpreted something, he probably cleaned/tested them at 42 lbs of fuel pressure. A 22 pound injector will flow 22 pounds at a given PSI. (I think the standard psi for rating them is 43.5?) At 50 psi it's going to flow more, at 100% duty cycle.
Last edited by Pwnage1337; 11-16-2018 at 12:01 AM.
Reason: I fucked up
I suspect you misinterpreted something, he probably cleaned/tested them at 42 lbs of fuel pressure. A 22 pound injector will flow 22 pounds at a given PSI. (I think the standard psi for rating them is 43.5?) At 50 psi it's going to flow more, at 100% duty cycle.
I can't believe anyone would run a supercharger with stock injectors.
11-14-2018, 10:49 AM
88 Conversion back to Stock from Supercharger
