First off guys, let me tell you I realize there's a search function on these boards. I'm a member of a motorcycle board and am familiar with these types of boards. However, I don't really know what topics I would search for my questions, so I 'll just post my problem here and hopefully you guys can educate me ( I am ignorant ) on my car problems.

I bought my son a 1987 TPI 5.0 Iroc. The engine was on it's last legs so we had a 350 (5.7) built and put in the car. Before the 5.7, he was running mid 16's at the local drag strip here. Once we put the 5.7 in, his times dropped to mid 15's. (no slicks - regular street tires) This is nearly all stock. We added the 350 with just a very slightly larger cam (supposedly still small enough no adjustments to the computer would need to be made) , then he has K&N filters and Flowmaster exhaust. We still have the old stock (from the 5.0) MAF, injectors, intake, fuel pump, etc... Timing is set at 6 degrees...transmission is 700r4 with professionally installed shift kit. The car does shift hard (a good thing)

Everyone we talk to says even with this basic setup, we should be getting better times at the track.

When my son runs at the track (running w.o.t.), he says he gets some slight ping up to about 60mph, then the ping stops and he gets a surge of power. He also then gets the "check engine" light. That's the ONLY time this comes on...when he's getting on it hard at the track. This generates the error code "43". I have no idea what that is. I was told to disconnect the knock sensor, which we did - but it made no difference...still get the pinging and the surge of power at about 60mph (w.o.t.) Let me add...he is running at 6 degrees timing, and runs 90 octane all the time.

I have talked to a dozen local "mechanics" who have given me a dozen differing opinions - anywhere from needing a different MAF to needing larger injectors, larger fuel pump, different chip, etc...since all of this stuff was on the 305 and we now have it on the 350.

Basically, if I did everything these guys told me to do, I feel I'd just be running in circles since they all have a different "fix" for my problems.

One outside source I contacted, is a fellow in Oklahoma who makes custom chips http://www.fastchip.com He told me I needed 24lb injectors and his custom made (based on our intake, exhaust, cam, etc...) $350.00 chip to cure these problems.

I figure there are some true experts here (or at least I hope there are) that can steer me in the right direction. I don't want to spend big $$$ on boring, pistons, etc.... but if I can just get this (what seems to be possibly computer problems) worked out, I'd certainly be willing to buy whatever I need.

Thanks in advance!
Larry Davis
"Irocdad"

 

The 5.0 TPI uses 19 lb/hr injectors while the 5.7 TPI uses 22 lb/hr injectors. If you are using the 19's on the 350, I would consider the larger - I would look for AT LEAST the 22's. Fuel pump will be alright for now, but a fuel pressure check would be a good idea - just as maintainance if anything.

The actual intake is the exact same between the 305 and 350.

Obviously the PROM is different between the 2 engines to accomodate the knock sensor and the 350, as well as the fuel injectors.

The knock sensor is also different. This could be the source of the ping as the KS is tied into the electronic spark timing system. The sensor may be picking up false knock and pulling the timing some. I would look into getting this swapped out.

Exactly what cam was installed?

I would work on getting to the engine running correctly (so to speak), then work in getting it faster.

 

Okay...the cam is a Melling 22-110 cam

Degrees .050" Dur Int. 204 Exh. 214
Degrees ADV Dur Int. 278 Exh. 288
Inches Valve Lift Int. .420 Exh. .443
Degrees Lobe Cntr Int. 110 Exh. 110

I know nothing about those numbers. This "mild" cam is what the engine builder recommended.

Also..forgot...we have the Edelbrock 68722 Ceramic Headers.

As for the fuel pump, we just had a new one installed. However, this was before I started getting advice, so it is a stock one, not a high performance one. But the pressure should still be fine?? But you say I should go ahead and get larger fuel injectors and the chip, as well as a knock sensor. I'm assuming I just go down and ask for a 350 knock sensor? (I'm new to this, so be patient with my ignorance. ) I guess the big deal would be the injectors (I've found 24lb ones on Ebay for $50 - $100) and then the chip. Should I go with http://www.fastchip.com and buy his $350.00 custom chip? Or do you recommend otherwise? Would that chip even address these problems?

Thanks!
Larry

 

On my recommendation, just go and find 8 factory L98 (factory 350 TPI) injectors, PROM, and knock sensor. That should get you on the right track as far as that is concerned. But, that's my recommendation. Those 3 things are the only differences between the factory 305 and 350 TPI engines.

You could probably search eBay for some L98 injectors to begin with. Or, you could search for LT1 injectors, which are a direct bolt-in, but are rated at 24 lb/hr. However, with those, you would have to tune - which might not be such a bad idea, especially since you have a slightly upgraded cam.

For the most part, I'm against just buying a chip off the shelf that you put into your car that doesn't require datalogging, tuning, etc. Those, to me, are generic and don't really solve the issue that calls for the new chip in the first place.

The pressure on the fuel pump should be fine. If it can supply a 305 TPI, it should be alright for a 350 TPI. One thing you might want to look into, if not for now, at least so you have it in case you want to do future upgrades is an adjustable fuel pressure regulator (pretty much does as it's name implies).

Any cam to begin with, idealy, could use tuning. Just a good basic rule of thumb. However, I agree, that cam is fairly small, and probably small enough that it can escape heavy tuning. Though it has a fairly large adv. duration. If you want to dig in and take it 1 step further, you could go with the 24 lb/hr and tune it so that everything is designed to work - tune your spark tables, your fuel tables, etc all around the injectors and cam.

 

Man I sure appreciate your help. I've been doing a lot of research this evening. Apparently (tell me if I'm wrong) I need to replace the ESC module also. I've found through auto parts web sites that knock sensors AND ESC modules have differing part numbers between the 305's and 350's.

Now as for the chip, I understand what you're saying. Please just let me verify this, though. Supposedly the chip I'd be buying is not an "off the shelf" chip. He sells those for $150.00 This more expensive chip is one that he would burn according to my injector size, cam specs, exhaust, etc... My vast mechanical knowledge would probably fit in the palm of your hand, so he may be selling me "snake oil", but as I said...he claims (and seems to have a good reputation in our tri-state area) that these $350.00 chips are custom burned for each individual setup - not just a generic chip - which he also sells.

So, do you still feel that would be a $350.00 waste? I obviously am going to need a new PROM, and I can't do my own....just not knowledgeable enough.

Thanks again.
Larry

 

Just for getting it running in a basically correct fashion, the stock 350 TPI PROM should get you going. You can likely get one through a dealership for about $60, or a salvage yard for ???. If you go the salvage yard route, be certain the donor car has the same type transmission, 16" wheels, and of course is from a 350. If it's a pull-your-own yard, you might find the detonation sensor, injectors, and whatever else you may think is of value.

Your cam specs reveal just a bit more duration, but negligible differences in lifts over a decent stock cam. The LSA is also close enough to prevent problems. Stock 305 TPIs used LSAs as low as 108°. Do we know how the cam was degreed when installed? Straight up? -4°, perhaps?

 

You are correct on the module. It, too, is part of the ESC system (electronic spark control) -which is adapted for each engine specifically.

I didn't really look around the site that much, I just saw that there were cars and engines listed, and then a price ($159) for it, and sort of drew my own conclusions...

From my experiece, the kind that I am thinking of is you have to datalog (a program called WinALDL or other form of datalogger), submit your findings, and you get one custom burnt for your application. EDIT - I just now see the Custom Chip area, and see where you got the $350 tag from - my mistake. I am not too up to date on the custom burning stuff, what's good, what isn't, that kind of deal, so that is probably something best left for someone who is. I just clicked on the link where you look at the custom form and it LOOKS decent...again, my personal experience isn't THAT vast in this area...

Do you have a laptop? You could fabricate an ALDL cable and download WinALDL. That, for beginners, would at least give you an idea of what's going on with your engine.

 

This part doesn't make sense. There should've been at least a change one way or the other. Are you 100% sure it was the knock sensor that you unplugged?

The only other possibilities I can think of at the moment would be a problem in the distributor or ESC module. If the knock sensor was taken out of the loop, yet it still has the problem, that suggests to me something else in the ignition.

Just by chance there could be knock but it isn't ignition related, have you ohm tested your injectors to eliminate a failing injector?


FYI you do not have to swap to larger injectors, or get a custom chip. The factory system has a range of adjustment and your 350 will fall inside that range.

________________________________________

Code 43 Electronic Spark Control (ESC) system

Faulty or loose wiring and/or connections to ECM terminal L.

Faulty or loose wiring and/or connections from the ESC controller to the ECM.

Faulty or loose wiring and/or connections from the knock sensor to ESC controller.

Voltage at ECM A-B connector terminal B7 should be over 6 volts unless the system is sensing detonation.

Faulty ESC sensor and/or module.
__________________________________________

Another FYI for troubleshooting, you should be able to unhook or remove the actual knock sensor from the system without ever generating any kind of error code. Replacing the sensor will likely have no effect on your problem or code.

 

I have no idea how the cam was degreed when it was installed. The builder did that and it was never discussed. Besides, I'm not knowledgeable enough to turn that into useful information anyway.

As for the knock sensor, yes I'm positive we unplugged it...it's right there in front of the starter...no mistaking it. So, yea, I was kind of puzzled also when it made no difference when we unplugged it.

I guess at this point, I'm going to replace the knock sensor and the ESC module, and have my wiring checked to make sure there are no shorts in those connections. It looks like to change the knock sensor, I'm going to need to drain as much coolant out as I can....correct? Do I need to put anything on it's threads (tape, etc...)
And, I really have no idea where the ESC module goes...is all that stuff behind the glove compartment? Is that hard to access?

Keep the information coming...you guys are a wealth of knowledge.
Thanks
Larry

 

The esc module on my 87 TPI eng is located on the drivers side near the firewall (just outboard of the brake master cyl). There's also some relays in the area for the fuel pump, MAF, and MAF burn-off.

Later years have the ESC module in the ECM (eng computer), but I believe yours will be under the hood.

I use a little liquid teflon thread sealant on the knock sensor threads. I've heard using too much tape on the threads can isolate the sensor (a bad thing).

Definately drain the coolant first!!

The knock sensor is basically just a microphone tuned to listen at a specific frequency (frequency is dependent on the bore size).
Disconnecting it simply keeps the ESC from hearing any distress signals sent from the knock sensor. Kind of a "no news is good news" situation.

I've had a code 43 a couple of times when it was really hot under the hood. Eng would barely stay running while the ESC was throwing codes.

 

We'll have to presume the cam was installed straight up (which ia actually 4° advanced, which is actually straight up, but it's a long story). Regardless, it isn't off the map for "normal" insofar as the factory tuning would have trouble with it. TPIs have use 109° LSA cams for years and .415/.430 lifts for years, both from the factory.

Stekman is correct that any setup can benefit from some program tuning, but if your goal is to get running in stock form, a factory MEMCAL should suit your setup.



That image is only for reference, and I believe the P/N you would actually be using is 16068654 or 16068672.

Unplugging the detonation sensor should eventually set an error code. Something there is strange. Perhaps the Electronic Spark Control module or its connections are faulty. The module doesn't matter, since you'll need to change that WITH the sensor to P/N 16128261. Your '87 model year car should have the ESC module located on the firewall, adjacent to the brake booster:



As for changing the sensor, you will have to drain the coolant as much as possible before removing the sensor, otherwise removing the sensor will accomplish that for you. Unless you live in San Francisco or Duluth and can park sideways on about a 60° hill, you'll lose some coolant, since the sensor IS the block drain. Plan to deal with the coolant accordingly, and to use a thread sealant on the replacement sensor when installing.

The "secret module" in front of the dash where you might normally expect to find a glove box would be the ECM - Where you'll need to change the PROM/MEMCAL.

 

Thanks a bunch. The photo will really help me with the ESC module. We've had snow today, so my next day off that the weather is decent, I will start replacing some of these parts. ( don't have an "indoor" place to do this )

Thanks a bunch guys. I'll be back on the board in a few days with more questions.

Larry