Check Engine light still on...
#1
Intermediate
Thread Starter
Check Engine light still on...
I finally got a chance to work on the car again!! I put a fuel pressure gauge in line between the two throttle bodies and get between 15-17 Lbs of pressure with the car running....
So now I still have the "Check Engine Light" and it is hard starting sometimes I have to pour a small dash of fuel into the throttle bodies but then it starts right up?
So its not fuel pressure, no codes with a Snap On MT2000 Scanner, no codes with the "Paper Clip method"?
So now Im wondering if it could be my MAP sensor or the IAC valves?
Any help you can provide would be great as Im at a loss as to what to do next?
Thanks,
Steve
So now I still have the "Check Engine Light" and it is hard starting sometimes I have to pour a small dash of fuel into the throttle bodies but then it starts right up?
So its not fuel pressure, no codes with a Snap On MT2000 Scanner, no codes with the "Paper Clip method"?
So now Im wondering if it could be my MAP sensor or the IAC valves?
Any help you can provide would be great as Im at a loss as to what to do next?
Thanks,
Steve
#4
Zen Vet Master Level VII
With the XFire check your Throttle Position First. The setting should be at .525.
The fact that you can pour gas and fire it off tells me the (first) step is check your TPS setting. After that, IAC, MAP sensor...etc.
The fact that you can pour gas and fire it off tells me the (first) step is check your TPS setting. After that, IAC, MAP sensor...etc.
#5
Pro
Not clear why the Check Engine Light would be "ON" with no codes set. However, your hard start issue could be the fuel pump relay. If you have an extended cranking period prior to the engine firing off, does the fuel pump run when you turn the engine "ON" prior to cranking it? Check the fuel pressure with your gauge on a cold start, ignition "ON" without cranking. It should rise to 13 psi and then drop back to 0 psi when the pump stops after about 5 secs. Then turn engine "OFF" and attempt to start it. Pressure should rise immediately to 13 PSI and stay there while engine runs. If you have to crank the engine for a long time prior to seeing a fuel pressure increase the pump relay is suspect. The L83 engine uses an oil pressure switch as a backup to the fuel pump relay to turn on the pump but, it takes a bit of cranking to work. Sorry about the windy answer... it just takes a bit to go thru the workings!
#6
Intermediate
Thread Starter
Where is the fuel pump relay located?
How do I test my or measure my Throttle position Sensor?
Will either of these cause the "Check Engine Light" to come on?
Thanks for all your help..
Steve
How do I test my or measure my Throttle position Sensor?
Will either of these cause the "Check Engine Light" to come on?
Thanks for all your help..
Steve
#7
Pro
To test the TPS you need a digital multi-meter and a jumper harness or you can probe the connector from the back side. Initial reading should be 0.525 volts between terminal A and B (A is bottom, B is middle on the TPS, ignition on not running). Then slowly open throttle and ensure that readings move smoothly throughout the range. A jump, dead spot or plateau is a bad TPS.
A bad TPS circuit could set trouble codes 21 or 22 and turn on the Check Engine Light.
Hope this helps, I'm going from memory as I no longer have an 84 FSM. When I still had my 84 I did a lot of this however! I recommend a real 1984 GM service manual as there are a lot of unique things about a Cross-Fire.
#8
Zen Vet Master Level VII
#9
Pro
#10
Intermediate
Thread Starter
I forot to mention I already replaced the ECU with a "rebuilt" one...
Check engine light still on...
I ordered a TPS test harness and new TPS Module.... So we will see... Still a bit unclear as to how to adjust it?
Thanks for all the help..
Steve
Check engine light still on...
I ordered a TPS test harness and new TPS Module.... So we will see... Still a bit unclear as to how to adjust it?
Thanks for all the help..
Steve
#11
Pro
The TPS turns on its mounting screws. With the ignition "ON" and not running twist it until the multi-meter shows 0.525 volts between terminals A and B and tighten it up.
#13
Drifting
Member Since: Nov 2015
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Finalist 2020 C4 of the Year - Unmodified
After disconnecting battery, press brake for 10 seconds, reconnect battery, is the Check light still on? That would also point to ECM.
(guys, don't go off about pressing brake, I know. Worth doing with a big problem, it's 10 seconds. And, ya know.)
Last edited by kael; 01-23-2018 at 10:55 PM. Reason: cables, right
#14
Intermediate
Thread Starter
The "Check Engine Light" was on with the original ECU.. I thought that maybe the ECU was bad and causing the Check Engine Light. So I replaced it with a Reman ECU and still have the Check Engine Light....
I will try the "Press brake for 10 seconds" before reconnecting battery and see if that does anything and I will disconnect and reconnect the ECU and cables... And try re-seating the EPROM too...
At this point Im lost... But I cant work on the car for at least a week, hopefully the TPS Tester will show up and I can check that too...
My plan is to use the tester first to take a reading on the current TPS then if adjustment is needed try that...
If I need to replace the TPS I will...
If none of that changes the "Check Engine Light" situation then I will try the ECU re-seating, brake pedal thing...
Thanks so much for everyone's help... This Check Engine Light thing is crazy...LOL
Steve
I will try the "Press brake for 10 seconds" before reconnecting battery and see if that does anything and I will disconnect and reconnect the ECU and cables... And try re-seating the EPROM too...
At this point Im lost... But I cant work on the car for at least a week, hopefully the TPS Tester will show up and I can check that too...
My plan is to use the tester first to take a reading on the current TPS then if adjustment is needed try that...
If I need to replace the TPS I will...
If none of that changes the "Check Engine Light" situation then I will try the ECU re-seating, brake pedal thing...
Thanks so much for everyone's help... This Check Engine Light thing is crazy...LOL
Steve
#15
Pro
The "Check Engine Light" was on with the original ECU.. I thought that maybe the ECU was bad and causing the Check Engine Light. So I replaced it with a Reman ECU and still have the Check Engine Light....
I will try the "Press brake for 10 seconds" before reconnecting battery and see if that does anything and I will disconnect and reconnect the ECU and cables... And try re-seating the EPROM too...
At this point Im lost... But I cant work on the car for at least a week, hopefully the TPS Tester will show up and I can check that too...
My plan is to use the tester first to take a reading on the current TPS then if adjustment is needed try that...
If I need to replace the TPS I will...
If none of that changes the "Check Engine Light" situation then I will try the ECU re-seating, brake pedal thing...
Thanks so much for everyone's help... This Check Engine Light thing is crazy...LOL
Steve
I will try the "Press brake for 10 seconds" before reconnecting battery and see if that does anything and I will disconnect and reconnect the ECU and cables... And try re-seating the EPROM too...
At this point Im lost... But I cant work on the car for at least a week, hopefully the TPS Tester will show up and I can check that too...
My plan is to use the tester first to take a reading on the current TPS then if adjustment is needed try that...
If I need to replace the TPS I will...
If none of that changes the "Check Engine Light" situation then I will try the ECU re-seating, brake pedal thing...
Thanks so much for everyone's help... This Check Engine Light thing is crazy...LOL
Steve
#16
Intermediate
Thread Starter
It runs fine... has a slight miss but I think I need to set the timing...
And trust me I havent ruled out pulling the bulb... Just want to exhaust all the options first...
Thanks,
Steve
And trust me I havent ruled out pulling the bulb... Just want to exhaust all the options first...
Thanks,
Steve
#18
Intermediate
Thread Starter
TPS Testing Harness showed up today!! I wont be able to work on the car until later in the week, but have the tester a new MAP sensor and new TPS.... My plan is to run a test on the existing TPS depending on results replace the TPS if needed... IF Check Engine Light goes away... We are good...
If not replace MAP sensor... If Check Engine Light is still on after all this...
I will pull both TBI units and have them rebuilt... They need it anyway, the rebuilder says he can test my existing IAC motors... If they need replacement then so be it...
Hopefully through all this the Check Engine Light goes away... IF NOT...Im pulling the bulb... Since I have to send the Digital Dash in for repair, it should be easy..LOL
I appreciate everyones help and advice through everything... This group is great!!
Steve
If not replace MAP sensor... If Check Engine Light is still on after all this...
I will pull both TBI units and have them rebuilt... They need it anyway, the rebuilder says he can test my existing IAC motors... If they need replacement then so be it...
Hopefully through all this the Check Engine Light goes away... IF NOT...Im pulling the bulb... Since I have to send the Digital Dash in for repair, it should be easy..LOL
I appreciate everyones help and advice through everything... This group is great!!
Steve
#19
Pro
TPS Testing Harness showed up today!! I wont be able to work on the car until later in the week, but have the tester a new MAP sensor and new TPS.... My plan is to run a test on the existing TPS depending on results replace the TPS if needed... IF Check Engine Light goes away... We are good...
If not replace MAP sensor... If Check Engine Light is still on after all this...
I will pull both TBI units and have them rebuilt... They need it anyway, the rebuilder says he can test my existing IAC motors... If they need replacement then so be it...
Hopefully through all this the Check Engine Light goes away... IF NOT...Im pulling the bulb... Since I have to send the Digital Dash in for repair, it should be easy..LOL
I appreciate everyones help and advice through everything... This group is great!!
Steve
If not replace MAP sensor... If Check Engine Light is still on after all this...
I will pull both TBI units and have them rebuilt... They need it anyway, the rebuilder says he can test my existing IAC motors... If they need replacement then so be it...
Hopefully through all this the Check Engine Light goes away... IF NOT...Im pulling the bulb... Since I have to send the Digital Dash in for repair, it should be easy..LOL
I appreciate everyones help and advice through everything... This group is great!!
Steve