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Troubleshooting a revived 3800sc project by Ken_86gt
Started on: 09-23-2014 12:56 PM
Replies: 12 (234 views)
Last post by: nosrac on 09-27-2014 09:38 PM
Ken_86gt
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Report this Post09-23-2014 12:56 PM Click Here to See the Profile for Ken_86gtClick Here to Email Ken_86gtSend a Private Message to Ken_86gtEdit/Delete MessageReply w/QuoteDirect Link to This Post
Help me troubleshoot my engine swap project. I did the swap about 8-9 years ago but never actually completed it. Now I am back into it and having some trouble that seems to be misfire related.

The parts:
'99 GTP 3800SC
4T65HD that came with engine
VS cam
3.4 pulley
Evap delete
boost bypass delete
2nd (rear) O2 delete
FastFiero PCM
Suppertrapp muffler
fuel pump was replaced with aftermarket for more pressure, I dont recall which one.

Issue with car is it stumbles or misfires at idle, sometimes enough to set a P0300. While driving it there isn't much power above 1/4 throttle and misfire gets worse. When not driving the engine revs up great with no misfire.

I can scan the car with Carcode (Alex Pepper). I am currently getting -15 to -20 LTFT at idle. I had the injectors tested and cleaned, two failed. I replaced the bad ones and it runs better, but same issues persist. Actually the fuel trims went even more negative than previously. Changed plugs, swapped plug wires around, swapped ICM coil pack with used one.....no change

I cleaned the MAF. When I scan it the values change with RPM, about 2460HZ at idle.

I did not change the O2 sensor yet.

Fuel pressure regulator is not leaking. Pressure at idle is about 42. Car off around 50.

I changed the Crank Position Sensor, no change.

Did a compression test:
1 140
2 120
3 130
4 150
5 130
6 150


What is next?
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nosrac
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Report this Post09-23-2014 02:02 PM Click Here to See the Profile for nosracSend a Private Message to nosracEdit/Delete MessageReply w/QuoteDirect Link to This Post
Get your PCM reprogrammed. I don't think u R getting enough fuel.
PM me 4 details.

[This message has been edited by nosrac (edited 09-23-2014).]

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phonedawgz
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Report this Post09-23-2014 05:06 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
What does the tach do when the trouble happens?
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Ken_86gt
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Report this Post09-23-2014 05:08 PM Click Here to See the Profile for Ken_86gtClick Here to Email Ken_86gtSend a Private Message to Ken_86gtEdit/Delete MessageReply w/QuoteDirect Link to This Post
When driving and it starts to mis I see the tach RPMs drop and then come back
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phonedawgz
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Report this Post09-23-2014 06:52 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
You have an ignition problem.

Replace the spark plug wires if they are old. Then look at the coil packs.

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Ken_86gt
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Report this Post09-24-2014 10:29 AM Click Here to See the Profile for Ken_86gtClick Here to Email Ken_86gtSend a Private Message to Ken_86gtEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for the input. My plan:
Work with nosrac on the PCM
Get new plug wires, they are a few years old.
I also ordered a new Delphi ICM.

It will likely be a week or more before I can get these installed and tested
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darkhorizon
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Report this Post09-24-2014 01:09 PM Click Here to See the Profile for darkhorizonSend a Private Message to darkhorizonEdit/Delete MessageReply w/QuoteDirect Link to This Post
Pcm is probably fine.

Negative fuel trims will suggest you are somehow injecting too much fuel... and not much else will cause those readings. This typically will only mean you have too much fuel pressure or the wrong injectors. Can you confrim they are stock injectors? Have you attempted running without the o2 sensor to verify that you are indeed spraying too much fuel? It should run worse after you clear the fuel trims and remove the o2 sensor as it will be adding almost 20% more fuel at that point.
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Ken_86gt
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Report this Post09-24-2014 01:41 PM Click Here to See the Profile for Ken_86gtClick Here to Email Ken_86gtSend a Private Message to Ken_86gtEdit/Delete MessageReply w/QuoteDirect Link to This Post
The injectors came with the motor- I assume they are stock.... The part number is 24508208 on one side and 0280155811 on the other side. Which according to Google is probably 36lb at 42psi. The the injector service report indicate that they flow 38 lb/hr at 3 bar and 2500 rpm.

I just sent my PCM off, so I cant test the O2 response for a week or so. I can say that when I was driving it around the fuel trims always stayed negative. They would get close to 0, but never quite made it. It does seem that the PCM is trying to reduce the fuel at idle, and the rest of the band for that matter. It is possible the PCM had been programmed with the wrong injector flow rate- I should know that soon.

[This message has been edited by Ken_86gt (edited 09-24-2014).]

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Tweeder
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Report this Post09-24-2014 03:01 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have had this type of issue with spark plugs as well as spark plug wires being mixed up.

------------------
86 SE Convertible 3800sc 4t65e HD(2002), Gen V, 3.5 pulley, SD headers

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nosrac
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Report this Post09-24-2014 03:36 PM Click Here to See the Profile for nosracSend a Private Message to nosracEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Ken_86gt:

The injectors came with the motor- I assume they are stock.... The part number is 24508208 on one side and 0280155811 on the other side. Which according to Google is probably 36lb at 42psi. The the injector service report indicate that they flow 38 lb/hr at 3 bar and 2500 rpm.

I just sent my PCM off, so I cant test the O2 response for a week or so. I can say that when I was driving it around the fuel trims always stayed negative. They would get close to 0, but never quite made it. It does seem that the PCM is trying to reduce the fuel at idle, and the rest of the band for that matter. It is possible the PCM had been programmed with the wrong injector flow rate- I should know that soon.





If the trims are close to 0 like (-3) but never get there during cruise conditions then that is a good safe tune. They should lock at 0 during WOT. If they are negative double digits then u are getting too much fuel or poor spark. That is if the o2 is in good working order and u don't have a mechanical issue.
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nosrac
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Report this Post09-24-2014 03:40 PM Click Here to See the Profile for nosracSend a Private Message to nosracEdit/Delete MessageReply w/QuoteDirect Link to This Post

nosrac

3500 posts
Member since Jan 2005
 
quote
Originally posted by Tweeder:

I have had this type of issue with spark plugs as well as spark plug wires being mixed up.



X2 on crossing the plug wires. It is easy to do.
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Ken_86gt
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Report this Post09-24-2014 04:59 PM Click Here to See the Profile for Ken_86gtClick Here to Email Ken_86gtSend a Private Message to Ken_86gtEdit/Delete MessageReply w/QuoteDirect Link to This Post
I agree the plugs wires can be confusing at times. I think I have a good handle on it. But I am not ruling out anything.

[This message has been edited by Ken_86gt (edited 10-01-2014).]

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nosrac
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Report this Post09-27-2014 09:38 PM Click Here to See the Profile for nosracSend a Private Message to nosracEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by nosrac:
If the trims are close to 0 like (-3) but never get there during cruise conditions then that is a good safe tune. They should lock at 0 during WOT. If they are negative double digits then u are getting too much fuel or poor spark. That is if the o2 is in good working order and u don't have a mechanical issue.


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