Quote:
Originally Posted by cyberpine
Guys - I do really appreciate all your valuable feedback.
I'll preface this by saying I'm clearly no mechanic. So it's going to seem like I'm wasting my time, money and space a bit.
Update: I got the truck back. The guy that helped me out with it is a good guy, but I'm not sure he had everything he needed to really solve the problem. Honestly, not sure he did much but to take wild stabs in the dark frankly.
He replaced a Holley Throttle Body with some factory TBI he found. He says the model number matches the OEM for my truck. He also told me the temp sensor (which is brand new and you guys pointed for me) is disconnected now and I learned so is the Map Sensor (which is a swap). He said and (I confirmed) , the truck will not run with either connected at this point.  I have a bag with all my old parts.
The truck is running, but clearly things are not entirely right. That said, the truck has never run l or idled as well since I've had it this past year.
I'd like to also go back and append to my original question, Would it be a terrible idea to mount a Carb on top of existing intake? I have a 3704 EdelBrock TBI intake. Even possible? Is there an adapter? too restrictive? What carb? This guy agreed to do the install cheap.  I understand I can get rid of all that electrical/sensory and mysterious crap, but I will need to add an external fuel pump.
Many Thanks again for any ideas or suggestions! |
JC
1) That 'mechanic' is a hack at best, but least he installed some different parts to see what works, what does not. Stay away from him - he has no clue how TBI operates.
2) By disconnecting coolant temperature sensor (CTS) ECM sees high CTS voltage which is equivalent to very cold temperature -40C. At -40C ECM will call for very rich mixture - this why you feel the power from engine.
3) By disconnecting MAP sensor ECM is forced into a limp mode (SES light is on continuously) Without MAP sensor input ECM uses TPS as its only source of engine load information available. It's ability to control fuel delivery is very limited.
4) TBI camaros were equipped with similar LO3 engines. So, if he really pooled TB unit from camaro it should have correct size injectors -2x 50lb-Hr which is adequate for a stock 305. (I would verify this soon, but its ok for now)
5) The hissing noise you are hearing is probably (It tough to be certain without being there) from a fully open, stuck IAC. This would explain very high idle 1100 to 1200 RPM.
6) I am also guessing that your 'mechanic' also screwed around with base timing by moving from 0 deg to 20. In limp mode ECM fixes timing to a constant value. He probably over advanced timing to get it to run without MAP and the moment MAP is reconnected ECM tries to control timing by advancing as it normally would which way too much - ECM has no idea that base timing is way off - killing engine in the process.
Analysis
a) Fuel system appears to deliver enough fuel.
b) Sensors MAP, TPS, CTS - remain questionable, but appear functional
c) IAC - operational - should be verified.
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Things to do
1) Reconnect all sensors plug CTS back in, reconnect MAP, make sure all other hoses, plugs are fully plugged in.
2) Perform POST = Power on self test. Move ignition key from Off to Acc to Run position - SES light should go from Solid ON - blink off - solid ON (do not start engine) Fuel pump should turn on for about 2-3 seconds and shut off. This would indicate that ECM is operating normally by being able to read EPROM contents. - Turn off ignition
3) Locate ALDL connector - it is located just under steering column. It looks like this:
4) Pulling DTC codes with a simple paper clip. Insert paper clip into socket pins A & B (usually upper right corner) shorting the two togther. Turn ignition into run position, but do not start engine.
Observe SES light. If there are no DTC codes set SES will blink code 12 three times. If there are DTC codes set each will be flashed 3 times in ascending order, pause followed by the same sequence again. So, for example of CTS and MAP are disconnected DTC 15 and 33 will be set:
12...12...12....15...15...15....33...33...33 12 12 12 15 15 15 33 33 33 and so on.
At the same time ECM will command IAC to fully closed position, which you can verify by observing IAC pentacle closing idle air passage - from the top looking down (sorry, I do not have photo handy right now - will post tomorrow)
Perform this simple test and post what you see (and please stay away from that 'mechanic') .
//RF