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Bad ecms or gremlins 89 TBI 350

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Old 06-05-2017, 12:55 AM   #1
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Bad ecms or gremlins 89 TBI 350

89 camaro TBI Vin E been fighting gremlins with intermittent stalling when clutch is pressed and off throttle also honestly just gutless here's what's known ...

No codes Fresh engine 250miles since overhaul new plugs wires cap button pcv all stock with new gm stock cam etc
on start the idle raises and come 1100 then 700 ish then after warm up where closed loop should be but not going into closed loop the engine drops to around 500-550 with an IAC count of 0-14
CTS of 199 ,
tps .46 ,
blm 120 ,
integrater 128
iat ranges from -21- 388
Timing set at 0 and at idle with advance hooked up is 17 ,
O2 .410-.470v,
map 1.0-1.2 ,
idle vac is 17 hg
Oil pressure [email protected]
all vacuum lines have been replaced ether spray makes no change anywhere around tbi-manifold
And thats all with ecm#1 stock ecm with hypertec chip .

Ecm#2 is from a 90 caprice all values are the same except it will go into closed loop
IAC count of 12-23
blm 150
and the idle is around 600 is but still intermittently stalls when slowing

Tested the iat replaced it with new
I've removed c12 tan iat wire, made a test terminal using OE female pin and installed in connector and grounded the wire and no change with on reading still ranged with either ecm.

ESC appears normal off idle it climbs to 30ish advance

Cts reads 10 of my manual guage

map is constant and vac is steady

Timing steady and smooth

Inj spray pattern looks great

Driving the car does good mid range it really pulls and if you start the car it'll idle all day but off idle to 1100 is crap and coming to a stop the car sometimes goes from a gradual fall from 1200 to idle and sometimes its sudden to 0 rpm . 1 out of about 5 times it'll stall

besides the stalling would a faulty Ecm cause the stall and weird iat range and why would the blm be different between the two ecm and both have the same iat issue?

What am I missing?
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Old 06-11-2017, 02:46 PM   #2
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Re: Bad ecms or gremlins 89 TBI 350

The iac logic is different from manual to automatic transmission.
This can cause bucking and engine shut down coming to a stop.
Looks as if you need to do a custom tune and add fuel to lower the blm.
An afpr would help but tuning is the best answer. You can convert from the older 2732 prom to the newer eeprom at moates.net as well as getting a burn 2 programmer. You can do a starter tune using a 305 manual transmission tune and incorporate the timing and fueling from the caprice anlu tune.the Iat maybe a definition data stream issue.you might want to bump the warm iac count to 20-25.

Last edited by Tuned Performance; 06-11-2017 at 03:11 PM.
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Old 06-13-2017, 11:21 PM   #3
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Re: Bad ecms or gremlins 89 TBI 350

The only issue with the tune is not many guys local I'd trust with that... The other issue is the OEM ecm is the manual tranny ecm so I would think it shouldn't have that issue. On top it does it with both ecms the caprice and the oem . The blm counts I agree need to be lower, I assumed the 350 injectors would have made some difference in closed loop blm counts. But appears not to.
As the IAC counts go , with the "magic" brown wire disconnected base timing at 0 and idle barely at 500 closer to 475 I can't go lower manually to get the counts up to the 20-25 range any lower it becomes so unreliable in driveability. And if I set base idle at 550-600 the IAC counts are 5-15. Theres been a pile of discussion on what "normal" idle vacuum is and per google it should be 20-25" and I'm only pulling 17". But I'm not sure if this is ecm related or something else... Compression is great , cam is stock for 350 91-93 engine.
The car sat dormant with a blown engine a few years but at the time of engine failure had a new gm fuel pump freshly installed. The injector pattern is crisp and clean no streaking or puddling/droplets so I wouldn't think its fuel delivery the tower was swapped from OEM to the 350 caprice tower and no change made.
All parameters look normal driving and slowing no changes in tach reference the IAC doesn't drop instantly actual IAC counts driving are in the 15-20 range.. Air divert cycles normally, egr comes in and o2 responds accordingly, map seems right as compared to my other obd1 car (93 cavalier) the only parameter that is an odd ball is the iat .... and blm / IAC count (on one ecm only)

I'd love a good tune on it but with it acting up driving far is out of the question

​​​​​The data stream issue... Would that be board driver circuit related or interpretation of the scan tool... I suppose the easy way to phrase it do you think the ecms have bad or not correct circuits or its just not sending good dialogue to the scan tool...
Note it works fine for every other car I've used it on

Last edited by expedition2166; 06-13-2017 at 11:30 PM. Reason: Additions
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Old 06-14-2017, 01:24 PM   #4
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Re: Bad ecms or gremlins 89 TBI 350

Appears to be a lot more going on here then stated in the first post. For one is the swap from the 305 to a 350. What heads are on the 350?

Quote:
with the "magic" brown wire disconnected base timing at 0
Should be tan with a black stripe. Was the correct connector opened for setting the timing? If not the spark timing is going to be very low.

Quote:
The data stream issue... Would that be...
Tested the iat replaced it with new
I've removed c12 tan iat wire, made a test terminal using OE female pin and installed in connector and grounded the wire and no change with on reading still ranged with either ecm.
The only time I've seen the IAT value roll down and around is when using a truck ECM with the scan tool set for a car. The reason is that the trucks didn't get an IAT, so that byte in the data stream is the O2 cross counts.

This is in ECMs such as the '7747.

The car systems have an IAT, so GM placed the IAT value in the data stream instead of the O2 cross counts. This is on ECMs such as the '8746 which is the stock factory ECM for your car.

RBob.

Last edited by RBob; 06-14-2017 at 01:34 PM.
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Old 06-14-2017, 01:34 PM   #5
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Re: Bad ecms or gremlins 89 TBI 350

Ecm 1 is a 1227747 AK ah
Ecm 2 is a 16136965 awaj
The 350 is a gm crate for a 92 tbi truck
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Old 06-14-2017, 01:39 PM   #6
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Re: Bad ecms or gremlins 89 TBI 350

And the base timing with wire disconnected is 0 and base idle is 550 ... 16 and 650 rpm ish per the tach 600 per scan tool wire connected
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Old 06-14-2017, 03:49 PM   #7
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Re: Bad ecms or gremlins 89 TBI 350

Try a 1228746
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Old 06-14-2017, 04:01 PM   #8
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Re: Bad ecms or gremlins 89 TBI 350

What about the current cal pak and prom .... Or try to find a salvage unit?
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Old 06-14-2017, 04:05 PM   #9
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Re: Bad ecms or gremlins 89 TBI 350

The proms would not be interchangeable, you might want to try the classifieds section or eBay and lookup the bcc. As stated above you should do a custom tune. I don't know if the caprice 965 uses a iat I'd think not. You can also post the bcc here. The closest to your setup but automatic would be anlu or atjp.
The 1228063 would work too but the 746 is a better ecm.

Last edited by Tuned Performance; 06-14-2017 at 04:40 PM.
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Old 06-14-2017, 04:27 PM   #10
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Re: Bad ecms or gremlins 89 TBI 350

Is that ecm one thats easily tweeked I've seen a few numbers tossed out there on ecms to stay away from because of difficulty working with them
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Old 06-14-2017, 04:30 PM   #11
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Re: Bad ecms or gremlins 89 TBI 350

And the 695 was the bastard year caprice and had an identical setup to my camaro had a salvage yard part compatibility sheet and there was only one or two compatible years
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Old 06-14-2017, 04:30 PM   #12
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Re: Bad ecms or gremlins 89 TBI 350

$61 mask is easy to work with, another option would be dynamic efi ebl.
http://www.dynamicefi.com/EBL_Flash.php
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Old 06-15-2017, 10:04 AM   #13
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Re: Bad ecms or gremlins 89 TBI 350

Quote:
Originally Posted by expedition2166 View Post
Ecm 1 is a 1227747 AK ah
Ecm 2 is a 16136965 awaj
The 350 is a gm crate for a 92 tbi truck
The '7747 with AKAH is a decent choice for that engine. It is for an '88 truck 350. However, it is for an auto, not a stick shift. This is likely why there is stalling and idling issues.

Of course the Caprice AWAJ is the same, for an auto. And it is for a 305, not a 350. Note that is has an IAT, but it also has both the IAT and O2 x-cnts in the data stream.

There are PROMs (stock GM) for stick shift trucks available for the '7747. But not for the '6965 ECM, they will all be for an auto trans.

RBob.
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Old 06-15-2017, 10:37 AM   #14
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Re: Bad ecms or gremlins 89 TBI 350

Ah ha .... So in short disregard the iat because both are essentially useless one not having that circuit and the other driven over... Good makes me feel better on that note... Now I suppose I must ask this.. If I dumped the $$ into something like the burn2/ostrich2 stuff from moates the 7747 would be the better or should I find the actual OEM ecm and tune it... With a generic chip or find a good prom...
Because right now the whole system is gutless this car was quick off the line and strong but with either ecm with this engine its lagging which is the other confusing part because aside the new engine which has all the same parts as the previous engine thats why I started trying different combos that were bolt on to try .... What's the board difference between an auto and manual or could a prom be written and either ecm work?
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Old 06-15-2017, 06:24 PM   #15
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Re: Bad ecms or gremlins 89 TBI 350

A prom could be written for either ecm. There are .bin files at gearhead efi to do the stock 747 ($42) mask. The caprice would be a custom tune.
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Old 06-15-2017, 06:33 PM   #16
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Re: Bad ecms or gremlins 89 TBI 350

http://www.gearhead-efi.com/Fuel-Inj...Information-42

I do have a akwh prom (350 manual trans) if your interested

Last edited by Tuned Performance; 06-15-2017 at 06:48 PM.
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Old 06-15-2017, 07:21 PM   #17
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Re: Bad ecms or gremlins 89 TBI 350

Which ecm would that prom work best in .... The caprice ecm is super clean pin wise and the 7747 is not as pretty but still works and how much... And I'd need to change the cal pak too wouldn't i
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Old 06-15-2017, 07:52 PM   #18
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Re: Bad ecms or gremlins 89 TBI 350

The akwh is for the 747, you use the same calpak.
Does $15 shipped sound fair ?
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Old 06-15-2017, 08:03 PM   #19
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Re: Bad ecms or gremlins 89 TBI 350

Yea I could give it a go it should at least tell me if the driveability is indeed ecm/prom related.... Of course I have to as if its in good to go shape or is it questionable in operations.... I'll pm you
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Old 06-19-2017, 10:59 AM   #20
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Re: Bad ecms or gremlins 89 TBI 350

Ses flashes and stays in limp home mode
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Old 06-19-2017, 05:45 PM   #21
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Re: Bad ecms or gremlins 89 TBI 350

I guess it's not seated in the 747 all the way or it's a faulty prom. Refunded funds .
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Old 06-19-2017, 05:59 PM   #22
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Re: Bad ecms or gremlins 89 TBI 350

It was, I was hoping it would work too
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