I keep getting Code 22, low TPS voltage signal, replaced the TPS, same problem. If I take a reading with the car stopped, it reads between 340mv at closed to 4.9v at WOT which is spec according to the Haynes for the 1993 Caprice. My Caprice throttle body has a non adjustable TPS BTW.

I've examined the Holley TB and it adjustable truck TPS, and it goes from 1.2v (at closed) to 3.7 (at WOT). I bought a new TPS for the Holley Truck TBI, and the range was a LITTLE wider, 1.1 to 3.9. Is this some sort of function of the 1227747 ecm? Does it only work in the 1.1 to 4.0v range? Something seems wierd.

Kelly 'GhoSSt' Rosato

 

I think my non-adjustable one at idle is at 0.66 volts. I thought the proper idle RANGE was like 0.5 - 1.1 at idle, but not sure...

 

.34v is really too low, reguardless of wht the book says. I'd try moving it up some.

Depending on the style of TPS you might be able to *slot* the mounting holes so that it is adjustable.

At 4.9v surprised you haven't tripped a high TPS.

 

Well, here's the story to date. I was having such a hard time getting the car to idle correctly with the 29ln injectors, that Ed @ Fastchip and I pow-wowed and decided to get a set of 19's just to get me thru emissions until I drop the 406ci in. So he sends me a new chip for the Edelbrock MPFI and 19lb'ers. I swap out the injectors, plug in the chip and get a code 51, bad EEPROM . Then in an unrelated event, I am testing the TPS just to make sure its in spec, which it wasn't (1.3 - 3.7). So I stuck a stock TB from my collection on there with the new round type tps (non adjustable).

It was a little off (.390 - 4.9) so I whipped out the dremel and opened up the holes to adjust it between .490 and 4.5. But I start getting the code 22 out on the road. It might be the TPS on that stock TB is bad, since it was one from my pile of used FI stuff. So I went down and pulled about 5 various TPS's off of junk engines at a buddy's Caddy yard. plugged one back on the Holley TB and adjusted it to spec. So I'm going to remount the Holley in the morning and see if that gets rid of this nagging code 22.

Short version:

1) I'm running with an EEPROM that thinks that the car has 29lb injectors. They're really 19's.

2) I also think that I swapped a bad (high/narrow) TPS on the Holley TB for a buggy TPS on the stock TB.

Theory: IPW's are too narrow, system is running lean, ECM blames it on the TPS not reporting a throttle thats open more. Could that cause the code 22 without setting a lean condition code???

Kelly 'GhoSSt' Rosato

 

Are you running MPI on the 747?

 

Sounds like I should wait to do my custom MPFI??? I hope you get this all worked out!!!

Keep us informed. Have nice weekend.

 

Yes, its the Edelbrock TBI to MPFI conversion. Howell, et al, give you a custom prom, Edelbrock give you the prom AND a piggy back board that, I suspect, cuts the injector pulse cycle to compensate for the differences between how a MPFI/TPI type system batch fires as opposed to a TBI type system. A lot of my problems were related to various bugs that no one had experience with. Edelbrock supplies 19lb injectors for EVERY application, including big block conversions, except the 502ci swap, and for that they provide 29lbers.

I talked Edelbrock into sending me the 29's because I'm going to a very strong 400. But with those, Ed Wright at FastChip and I had a hard time getting the idle to behave because the injector pulse widths were SO thin, the car would surge wildly at idle and die often.
Add that to the bad TPS on the Holley (which I should have looked at months ago), and I'm begining to suspect a buggy ecm and its a joy to behold . If I had been smart(er), I would have repinned the harness for a 730 and called it good.

Oh well, live and learn. The Edelbrock MPFI is a much more capable system out of the box than a stock TPI (imnsho), its single plane, capable of good HP numbers at a decent inital cost. But running it off of a TBI computer, any of them, 7747 or otherwise, is not worth the trouble. I'll probably screw in a MAT, repin the harness and run it off of a 730 in the future at some point.

Its worthwhile definatly, but there were some bugs, even with all my planning, I did not anticipate.

Kelly 'GhoSSt' Rosato

 

I have almost the same setup and have done the 7747 to 7730 ecm swap, but the code ($8D) doesn't seem to like anything bigger than 24 lb injectors. I burned a chip for the 24's and modified the VE tables and it idles smooth as glass, but I'm wondering if it's me or does anybody elses 7730 go nuts when you tell it you have bigger than 24's?

 

It also depends on the displacement. There was a recent post about this and a fix. The problem was the pulse width getting limited no matter what RPM and it was inverse to the displacement.

As for the 7747 and edelbrock's mpfi kit, I hate it. I was SO pissed that the owner of the truck told my friends that he got the correct sized injectors for the zz4 yet for 3 weeks tuning on the weekends I couldn't get enough fuel to her above 3600rpm. Pulled the spark plugs, yup, white ash lean... . Truck finally started getting REALLY low on power so I came over to check it out. Pulled the spark plugs and the drivers side was all dry, turns out the number 1 cylinder injector was internally grouned out shutting down the injector driver. This is how I found out how smooth a MPFI setup will run on only 4 cylinders! So when we went to order a 2 new injectors (another injector was measuring 10ohms) we called up Edelbrock and asked for the size from the part number... I was furious it was only 19lbs. So we ordered 2 to get the truck back into running condition and the following week I had the owner buy a 7730, memcal, and "yellow" harness plug. We're going to get the truck started with the 7730 when it warms up, then 29# injectors are getting ordered.
A lean engine damage from Edelbrock, nah, they wouldn't be that stupid... or would they? You'd think they would have covered their butts but this is asking for some form of legal action.
I'll keep you all posted with the results, should be fun having a peaky horsepower curve instead of one that looks like the torque curve .

 

I've got the Edelbrock kit, got the 29lb injectors for it, on a Vortec headed 350 with the LT4 Hot Cam. I got it to run fairly good with the 7747, but decided to go with the 7730 for the MAT and fan controls, not to mention the 8192 baud rate. With displacement set at 713 cc/cyl and flow rate at 24 lb/hr and adjusting the VE tables, it runs very well and has very good power. My problem comes in when I program for an injector larger than 24, the service engine light stays on, it pukes out black smoke, idles stays at about 1200 rpm, and it won't even talk to my Autoxray scanner. I also see that in Tunerpro the slider for injector size stops at 24.02.

 

The ecu file is wrong. It doesn't have the ability to process the raw bytes (it's 16-bit) into a real world unit (lb/hr). This is a limitation of the ecu file format which is being corrected with TunerPro v4 where the xdf file will be used. This will correct this problem. In the mean-time I say do the calculations by hand and use the built in hex editor to edit the injector constant. I'm suprised nobody else has pointed this out, or if they have it go through my radar.

 

the service engine light stays on, it pukes out black smoke, idles stays at about 1200 rpm, and it won't even talk to my Autoxray scanner. This sounds like an EPROM programming problem. With the solid SES, black smoke, and no ALDL the ECM is running off of the redundent fuel device (RFD). With the RFD calibrated for smaller injectors is will be overly rich. I would first look into a PROM burning issue. Unless the ECU file you are using to so messed up that it is editing the code and not the proper calibration location. . .

As for the injector flow term:

The fuel flow conversion from #/hr to seconds/gram is:

sec/gm = 10158.8 / #hr

So a 22#/hr injector gives 462 and a 29 #/hr injector gives a value of 350. Both double byte values.

RBob.

 

haha, wow my brain isn't working this morning.
So yeah, TunerPro's "resolution" when moving the slide bar is rather course with 16-bit values. Sorry, did I say course, I mean you might as well not even use it. Just enter in the correct size the old fashioned key in way . Works fine. And to think, I thought it might have been a limitation to the ecu file format. My bad for jumping the gun on that one.

 

I've tried typing the injector size into Tunerpro directly and still get the same results. As long as I stay at 24lb or smaller it works just fine.

 

I just opened the hex editor in Tunerpro and checked address 41C-->41D and the value is 015E (350) which appears to be correct, but it still does the same thing.

 

While we're on this subject do any of you guys/gals use any tuning software and/or mask that lets me use larger than 24's for sure? I was thinking of getting TunerCats and their $8D tdf file but I'd really like to know that it would work for me before I buy it.

 

That's odd, do you have the latest version of TunerPro?
I just double checked my work and if you enter in your injector flow rate (I entered 28) and click save, then reopen it's saved at 28. Shown as hex is also working so I don't know what you're doing but I got it to work. Don't touch the sliding bar at all, just enter the new value and click save, just did it with 36 and it worked.

 

Oh yeah, Tunerpro saves the value just fine. It's just tha a bin file with injector sizes won't work in the car.

 

Sounds like you just haven't adjusted the VE tables accordingly. Move the injector size constant means you have to move the VE!

 

Sorry gents, VE tables got readjusted with changing the flow rate. 24lb and less with the according VE tables runs good, but setting any size larger than that, even with adjusting the VE tables and it ignores the chip and runs on the redundant fuel device and refuses to talk to the scanner or the scanning software (Datamaster). That's why I was asking about Tunercat before I buy it and give that a whack, because I thought maybe a lot of the $8D ecu files had a limit on injector size, and I tried a few,believe me.

 

You're the first person to have this problem. It sounds like a checksum problem, might want to double check that you've got TunerPro automatically calculating the checksum.

 

Did that first, even tried WinBin, and calculating it myself. which is sort ofa PITA.

 

If you want me to check it out send me you're bin that works and the one that doesn't. I'll look at them and see if I can figure out a why.

 

Thanks sooo much for the help, I really appreciate it. I'll get the files together in the next day or so because I just burned another chip so I may send this one along with the bad one and if it will help I'll send a DataMaster log too.Once again I send my thanks for helping a noob like me.