Re: LT-1 issue
 

Thanks Alan. That is on the agenda.

Re: LT-1 issue
 

Following up on Alan's advise to track down the voltage loss at the TPS, I contacted a guy that Accel advised as a service rep for their product. I spoke to him several time last year when I was experiencing a no start condition and he was helpful
As I explained my low voltage to the TPS, he suggested unplugging the MAP sensor (which was getting a 5v input) and then checking the TPS input. Well, with both connectors disconnected (TPS and MAP), both input voltages from the ECM read 4.97 volts. When I installed the MAP sensor connector, the voltage to the TPS dropped back to 4.24V.
I checked the ECM ground which is directly to the battery and the ground from the rear of the cyl. head and all were clean and tight.
Would a defective MAP sensor cause excessive current draw and subsequently weaken the TPS input?? Not certain how that stuff works. The accel guy indicated the two circuits , although different pins in the ECM connector, have the same voltage reference source.
He indicated a ground problem or possibly a bad MAP sensor.

All input/experience appreciated.

John

Re: LT-1 issue
 

Update: The above tests were run with the battery at 17V.

Here's a matrix to clarify test results:

Both connectors attached: 3.75V TPS 3.75V MAP

TPS connected/MAP disconnected: 5.0V TPS 5.0V MAP

TPS disconnected/MAP connected: 4.2V TPS 4.2V MAP

Both disconnected : 5.0V TPS 5.0V MAP

Hopefully someone can make some sense out of this. The MAP sensor appears to be having the negative influence on the system.
Help!!

Thanks,

John

Re: LT-1 issue
 

Simply substitute another MAP sensor and re-test.

Re: LT-1 issue
 

John,
Do you have some sort of step down transformer/transistor reducing the voltage to your ECU to somewhere around 13.5 vdc, or is it happy with being supplied with 17 vdc? The reason I ask is that some ECU's do not like excessive voltage, and their internal regulators are not designed to deal with more than 14 vdc or so.

Re: LT-1 issue
 

Alan, The ECU is seeing direct voltage from 16volt battery.....typically 16.8 - 17 volts.
This set-up was in the car when I got it. The Accel support guy and I did not discuss this...but I will follow up and ask him.

John

Re: LT-1 issue
 

Installed new MAP sensor and the previous voltage of 3.75 dropped to 1.54 volts at the input side on both the MAP and TPS connectors.
For info purposes, I measured the resistance between the B and C terminals (volts in /signal out) on both MAP sensors with the following result:
Old sensor : 343
New sensor: 24 (is this a reject?) INFO CORRECTED FROM ORIGINAL POST. Had the numbers switched

Anyone have a reference number for this resistance??
Thanks,

John

Re: LT-1 issue
 

Umm ..... just a thought. The wire's didn't get mixed up did they ?

Re: LT-1 issue
 

No they did not,

Re: LT-1 issue
 

When MAP sensors were common place and needed replacement we went with OEM. I had quit a few MAP and ECT sensors that weren't even close to specs. Like Ed said you need a good DVO meter to check for some problems. I use a Fluke 88 I have had for about 20 years. Not all MAP sensors have the same BAR specs as the vacume changes.

Kirk