The shop that installed my new GM HT383E engine (1996-up OBD-II) in my 1995 Chevy K2500 (OBD-I) is having trouble getting it to run correctly. I did a lot of research on the HT383E swap into my truck, including ultimate TBI mods etc. We are using the original stock TBI with an 18 psi fuel pressure regulator spring, custom TBIChips EPROM, EP381 60psi 155LPH fuel pump, and GM performance Vortec TBI intake manifold. The injectors are stock 5.7L injectors. I bought a wide-band AFR for tuning, but have not yet installed it. I was able to answer most questions on the swap through research, but now I need advice on diagnosing and resolving this issue.

BACKGROUND

1. Original engine was the stock 1995 OBD-I 5.7L engine (VIN K). I measured the fuel pressure at the fuel filter (output line) as 13.5 psi, with about 21 psi deadhead when I pinched off the return line. I had previously checked the base timing and it was at the correct stock setting of 0° with the timing advance wire disconnected from the PCM.

2. I installed the custom EPROM and 18 psi regulator spring before taking the truck to the shop. The adjusting screw of the fuel pressure regulator was accessible and I set it so that it applied no extra pressure on the spring. E.g., the spring hat was touching the regulator base. I did not check the fuel pressure at that point, and I did not install the new fuel pump at that time.

3. Prior to the engine swap the truck was running on roughly five cylinders due to very used-up valves. After installing the TBIChips EPROM and 18 psi regulator spring the truck started and ran fine (i.e., no worse than before). No hesitation pulling away from a stop sign. I drove about 15 minutes at highway speed in 3rd gear (because the tired engine was not happy in Drive) to the shop. I don't know the RPMs offhand but I think at least 3000 rpm or so. Truck ran fine at that RPM, no coughing or backfiring.

ENGINE INSTALLATION

4. The shop installed the high-pressure fuel pump, GM HT383E engine, new Monster Transmissions 4L60E transmission with 1650 RPM stall converter, and mid-length headers.

5. Parts I supplied included a new stock coil (ACDelco D503A), new oxygen sensor, and custom EGR tube as I am retaining the EGR system.

6. I made sure the shop knew to install the new in-tank fuel hose that came with the high-pressure fuel pump.

7. We re-used the old OBD-I distributor, and swapped the distributor gear with the one on the new OBD-II distributor for compatibility with the roller cam. The crank sensor that came with the new engine is not being used, as there is no provision for it on an OBD-I vehicle.

CURRENT SITUATION & PROBLEM DESCRIPTION

8. The shop says the engine will barely run with the timing advance wire disconnected from the PCM and base timing set to 0° per 1995 factory spec. They did not try connecting the timing advance wire at this base setting. The check engine light is off, no flash codes.

9. The engine idles OK with base timing set at 4° and the timing advance wire disconnected. When the timing advance wire is connected the timing is 22° at idle. While the engine runs well at light throttle up to about 2500 RPM, but when pulling away from a stop sign the engine will cough, backfire, and lose power at roughly 2500 RPM. The mechanic says this seems like a timing issue.

ADDITIONAL INFORMATION

10. I asked the mechanic to check the fuel pressure and he said that he could not as that would require tapping into the fuel return line after the regulator and there is no fitting to do so. I am not sure I believe this, as I previously checked the fuel pressure on the pressure line by removing the fuel filter and inserting a TBI pressure gauge. I thought we could check it and see if it is at 18 psi as the regulator would pass though any overpressure, but the mechanic says no. Is this correct?

11. The fact that the old engine ran fine at 3000+ RPM with the new EPROM and 18psi spring indicates to me that the EPROM is fine. I have a call in to Brian at TBIChips to get his thoughts on the issue.

Any thoughts on how to diagnose and resolve this problem?

Many thanks,

Fred

 

The problem is likely not the engine or any of the hardware at all. Just the guy named Brian who does not know what he is doing. Or rather knows exactly what he is doing to fake his way through a crappy program. I have helped fix multiple vehicles that had the Brian treatment.

Check your fuel pressure as well, seen those "18 psi" springs coil bind and drive the pressure up into the 30s on a stock TBI unit as well. Your mechanic either does not own the gauge or is too lazy to check the pressure. I have a TBI pressure test kit as well as a GM TBI adapter in my larger kit.

The timing issue is Brians reluctance to change the timing map, claiming the TBI map works well with vortec heads.

The cough on acceleration is the 100% more acceleration enrichment fuel that vortec heads like that.

Finally it would not surprise me at all if Brian slipped in his "Perfect BLM" formula into your tuning....That's right he sets the BLM limits to ~118/130 to make it look like a good tune in the datalogs, but in reality it is pig rich or worse LEAN because the PCM can no longer control the fuel delivery past a few %.

It would also not surprise me at all if he gave you a V6 memcal with the wrong knock filter and limp home mode settings.

 

Fred,

I would not make these allegations if I did not see them with my own eyes in chips that were created for other vehicles by Brian.

If you want to learn more about the tuning of these engines, check out the DIY Prom board here as well as the website Gearhead-efi.com

Chris

 

problms in yuor chip, tbi chips cant do crap. contact eagle mark on gearhead efi or any of the tbi guys on here for a base tune, and then datalog your engine.

the 18 psi springs are iffy like stated. id definitely check what your pressure is really at. on my tbi 383 in my old 88 stepside i had to run a tpi pump with adjustable pressure control and alot of datalogging.

check your fuel pressure and get a different chip

 

this! i can back up everything he just said 10 fold. i struggled with mine for quite awhile until i found mark on gearhead and he got my truck running right again.

 

Thanks for the quick responses. It is tough being new to this as in my research I read many review on mail order chips, with ratings from great to good to bad. I rolled the dice and perhaps it did not go my way this time. I just spent an hour reading on gearhead-efi.com, looks like the right info. I will follow up with learning how to burn my own chips, but right now I just need it to run well enough to get it home and put those first critical few miles on the brand-new engine. I am tempted to go to the shop with the stock MEMCAL, pop it in and see if it runs well enough to drive the 15 miles home. Then I can check fuel pressure myself and install my AFR gauge. Worst case I flatbed it home and deal with it there. What do folks suggest?

And just to be clear on checking fuel pressure, removing the fuel filter and inserting a TBI pressure gauge will measure the pressure the injectors are seeing, correct? And thanks for the tip on spring bind, I had not come across that before. --Fred

 

Fred,

Chances are if you advance the timing to about 8* at the distributor with the EST disconnected and pop the stock memcal in it it will be a lot better than it is now. Just stay off the throttle. The vortec heads need more timing than the TBI heads.

That being said, the engine + labor etc I would probably just spend the $100 and get a flatbed and bring it home and address it correctly.

Like you said the first miles are pretty critical and I would hate to have too much fuel pressure wash the rings and cause the bores to glaze before the rings can seat.

 

just trailer it home and get it done right without the risk of screwing anything up. theres alot of guys good enough to get you to a base tune that you can save and build off of from there as well. and thats what i did to see what was tweaked and to get an understanding of what needed to be done.

 

UPDATE: So after all this and my mechanic swearing up and down that the distributor was installed correctly and he checked it three times, he comes in this morning and finds that he was one tooth off on the distributor placement. He says the truck runs great now, but I won't really know until I break it in and am able to go to higher throttle settings.

I do appreciate all the quick and helpful replies here, and will look into doing my own chips and tuning. But at least now I can drive the truck and take my time doing research on chip programming. Thanks again--Fred