Aftermarket fuel injection for Chevy V8 swap (Page 2/3)
RCR SEP 24, 08:14 PM
Hopefully you hit on the issue. A number of peolple threw out some good advice, but no one actually asked you what the issue was. You mentioned driveability, but that could mean different things to different people.

Anyway, it's been some years, but I had a built 350 that initially ran a port/polished TPI with original, then siamesed runners. Ported lower intake and Twisted Wedge heads. I was using an Accell DFI. Eventually switched to an LT1 intake (yes, I did the custom conversion) with LT4 hot cam. Never had issues with vacuum leaks or anything like that. Miss that car...

Curious if you solved your issue.

Bob
RWB 87 GT SEP 24, 08:36 PM
FWB my ECM # is 1227730. RCR the drivability issues are hesitation when cold (below 180F), intermittent error codes for IAT and exhaust backfires when shifting gears under hard acceleration. My Fiero's exhaust does not have any crossover between the pipes. It has Ram Horns to mufflers to tailpipes, that's it. DP
pmbrunelle SEP 24, 08:44 PM

quote
Originally posted by RWB 87 GT:
the drivability issues are hesitation when cold (below 180F), intermittent error codes for IAT and exhaust backfires when shifting gears under hard acceleration.



Is that the fault of the ECM hardware, or the tune that's contained within?

If the tune just needs adjusting, it seems bizarre to replace the entire computer with a new one; which itself will need to be tuned.
darkhorizon SEP 24, 10:56 PM
Tuning the one you have or fixing whatever is making it run poorly is going to be your best action here. If you wanted to run another ECU, something like a microsquirt or other cheap ecu would be ok. You dont really need an entire new system of harness, intake, injectors etc.
Blacktree SEP 24, 11:12 PM
Sounds to me like you just need to fine-tune the tune. And luckily, there is some aftermarket tuning support for the GM 7730 ECM.
RWB 87 GT SEP 25, 08:27 AM
Yes I may just need a retune, however that will be somewhat of a crapshoot without the cam specs. I bought the car in June this year and the PO just says it's a mild cam but has no more information. I don't really want to pull the engine to put a degree wheel & dial indicator on it. I am now thinking I need to have my fuel injectors cleaned and serviced, this could be contributing to the exhaust backfire. DP
Blacktree SEP 25, 10:31 AM
You don't need the cam specs. What you do need (to get a decent tune) is a data log.
darbysan SEP 25, 10:52 AM
Also, make sure your timing is set properly. On the TPI, you must unplug a single brown wire/blk stripe at the distributor, and then set the timing to 6 BTDC. Unplugging the wire will set a code, so remove the fuse for the ECM or disconnect the battery for 45 seconds to clear it.

Also, try spraying a bit of starter fluid around all of the gasket areas / vacuum hoses with the engine running. Any vacuum leaks will cause the engine to speed up. I thought I had done a perfect job on the runner gaskets, only to find a pretty good leak there.

Clean the MAF and the IAC with MAF Cleaner. Be careful with the MAF - don't break the small internal wire- just clean it off. Setting the IAC may also help. Procedures on Thirdgen, or PM me.

As stated, a data log via ALDL will help to fine tune your ride. I had to change my MAF factors to account for a higher flowing intake, but finally got my BLM and INT numbers in good shape. All pretty easy to do, and is definitely a DIY with a Moates Burn1 device and their add on ZIF socket. The CAM won't really matter unless it is one that is so far out of normal range that the computer can't react to it (Valve Overlap should be at least 110 to keep vacuum high enough)

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'87 GT , '00 3800 Series II SC, 4t65e, Vue Power Steering. (SOLD)

RWB 87 GT SEP 25, 12:18 PM
Yes Darby I know how to set the timing, although it is quite difficult since the frame rail blocks my view of the harmonic balancer. My car has MAP controlled TPI. It sounds like data-logging and continuous incremental tweaks is the way get the car tuned perfectly.

Anyway I took the car out for my standard 44 mile test loop this morning and now it runs pretty good. It has a minor vibration above 70 mph so I may have lost a wheel weight. It still hesitates once in a while in 3rd gear when accelerating and it still has minor exhaust backfires when I lift off abruptly. With those symptoms I am still leaning towards having the fuel injectors cleaned and serviced next week. I will keep you posted.

Thanks guys for all the input, this forum has been a huge help so far. DP
Johns 4.9 SEP 25, 01:15 PM
FAST makes a self tuning retrofit kit for GM TPI systems. I'm using it on my 4.9 Cadillac engine and it works great. Simple and user friendly.
Cheers